Welcome to CAO’s Online Continuing Education program for Optometric Assistants. The courses we offer are approved for CE credit for CAO Certified Optometric Assistants and AOA Certified Para-Optometrics (CPO), Para-Optometric Assistants (CPOA), and Para-Optometric Technicians (CPOT). It is important to check with your respective certifying bodies to determine the acceptability of these courses, should credits be required on a provincial or state level. We also welcome non-certified optometric personnel to utilize these courses for your own training and education, in the hope that you will make the decision to become certified in the future.

 

Course List

Course Code	Course Title	Credit	Cost*
OAC-001	Dry Eye Syndrome – Causes & Treatments	2 hours	$40.00
OAC-002	Diagnostic Pharmaceutical Agents (DPAs)	2 hours	$40.00
OAC-003	Ultraviolet Light And The Human Eye	1.5 hours	$30.00
OAC-004	Soft Contact Lens Parameters	1 hour	$20.00
OAC-005	Treatment Options for Age Related Macular Degeneration	1 hour	$20.00

* Plus applicable taxes.

How to Proceed

1. Click on the Course Code above to review the course content.
2. After reviewing the course material, please complete the test questions as follows:
   • Use the online form: click to the test questions and click the appropriate answers and then print the web page.
3. After completing and printing the test question form, mail or fax it to the CAO for review. (Note: answers to the test questions cannot be submitted online.)
4. Contact CAO if you have any questions at 1-888-263-4676 ext. 210 or 216, or email catherine@opto.ca.
5. After submitting your course registration and answers, you will receive an acknowledgement from CAO. Those individuals who achieve a passing grade (70% or higher), will receive a verification slip. All registered respondents will receive test results. Please allow three weeks for processing.

Course OAC-001
Dry Eye Syndrome – Causes & Treatments

Acknowledgements: Many thanks are extended to ALCON Canada Inc. for contributing illustrations 1 and 3, to Michael T. Kellam, OD, FAAO of Nanaimo, BC for contributing illustrations 4, 5, 6, 7, 8, and 10, and to, Oddysey Medical, Inc., Memphis, TN for contributing illustration 9.
Special thanks to Dr Alphonse Carew for technical assistance.
Author: Terry Theiss, CPOT, ABOC

What Is Dry Eye Syndrome?

The condition commonly called dry eye syndrome is formally known as keratoconjunctivitis sicca (KCS) and is sometimes referred to as Ocular Surface disease (OSD). Dry eyes are caused by a major deficiency of the tears, that is, the quantity or the quality of the tears is inadequate. If one of the three layers of the tears isn’t formed properly, dry eyes may result. Without sufficient lubrication, the cornea becomes less hydrated than normal and the surface may erode or develop pits, as a result of the dryness. It’s a far more serious condition than having too many tears (known as epiphora). Not only is the condition irritating and uncomfortable for patients, it may threaten their vision over the long-term.

The tear film is a key line of defense in maintaining the health of the eye. In fact, tears act as a barrier to infection. The danger with untreated KCS is that it can lead to serious corneal disease, damage to eye tissue, and potential scarring of the cornea and impairment of vision. Dry-eyed contact lens wearers will experience increased irritation and may run a greater risk of eye infection than other contact lens wearers.

A Brief Review of Tear Composition

Tears have three distinct layers. The outermost or top layer is oily and thus prevents evaporation of the tears. Its fatty composition also keeps the surface of the tear layer smooth. The oily layer is produced primarily by the Meibomian glands, which are located along the margins of the eyelids.

The middle watery layer provides most of the volume of the tears. It is produced primarily by the lacrimal glands, which sit above the temporal side of each eye. The aqueous layer lubricates, cleanses the eye of debris, carries oxygen to the cornea, and provides an optically clear surface. In addition, the aqueous layer contains its own natural antibiotic, called lysozyme, which inhibits bacterial growth.

The innermost layer is composed of mucous, which is produced by the goblet cells in the conjunctiva. The mucin layer provides stability to the tear film and spreads the tears evenly over the uneven corneal surface. Because the cornea tends to be un-wettable (hydrophobic), this layer helps to provide continuous moisture and causes it to be more “water-loving” get (hydrophilic). The mucin layer actually binds the aqueous layer to the hydrophobic corneal surface. The condition that occurs due to disruptions of the oily or mucin layer is known as evaporative dry eye. The condition caused by an inadequate of amount of the aqueous layer is known as tear deficient dry eye.

Why Do Assistants Need to Know About Dry Eye Syndrome?

Optometric assistants are in constant contact with patients. It is important to understand what dry eye syndrome is, what typical complaints a patient might have, and what the treatment options are. For adequate appointment scheduling, assistants at the reception desk must understand how long a dry eye exam takes and how long to wait between follow-up appointments. They will also need to know the instructions to give a patient prior to evaluation, how to answer questions, and how to reinforce the doctor’s instructions to the patient. Assistants in the preliminary testing setting have to know how to ask pertinent questions during a case history. They may also be involved in setting up the clinical exam room. Assistants with administrative responsibilities must understand all of the procedures to ensure that accurate reports to referring practitioners are issued and that correct diagnostic and billing codes are used. There’s no question that understanding and knowledge are fundamental tools for providing better patient care.

What Are the Causes of Dry Eye Syndrome?

So, who gets KCS? Primarily older adults experience dry Eye Syndrome, because the production of tears and their components naturally decrease with age. Often the mucin layer does not cover the cornea adequately. A large majority of the people affected are women aged 40-60 due to menopausal hormonal changes, but pregnancy and the use of birth control pills may also cause hormonal changes that affect tear production. The causes of KCS are many and people other than the elderly experience dry eyes, too.

A number of medical conditions may cause KCS. The following are some of the main culprits:

• Diabetes;
• Rheumatoid arthritis (the autoimmune disease, not the degenerative joint disease called osteoarthritis);
• Lupus (another autoimmune disease);
• Asthma;
• Sjogren’s syndrome (a systemic disorder that includes a variety of arthritic joint and skin problems);
• Rosacea (chronic acne);
• Scleroderma (a disease in which all the layers of the skin become hardened and rigid);
• HIV.

Chronic blepharitis can interrupt the production of the oily layer of tears by the Meibomian glands in the lids. The eyelid tissue becomes inflamed and thickened, thus preventing the oily component of the tears from leaving the glands. The tears then dry up too quickly, thus causing an evaporative dry eye.

Injury to the eyes may damage tear-producing glands. Likewise chemical burns or thermal burns to the eye can damage glands involved in tear production. If glands malfunction, they are unable to contribute to the proper formation of the tear film.

Environmental factors play a role in dry eye syndrome. A dry climate, exposure to wind, air conditioning, air pollution, and cigarette smoke add to the problem. Simply sitting in front of a fan may be a contributing factor.

Some medications cause dry eyes. Some of the more common ones implicated in KCS are:

• Antihistamines (used for allergies or motion sickness);
• Decongestants;
• Diuretics;
• Some types of antidepressants;
• Oral contraceptives;
• Arthritis medications;
• Anesthetics;
• Anti-cholinergics (a type of anti-spasmodic);
• Acutane (acne treatment);
• Beta-blockers (often used for hypertension and migraines);
• Muscle relaxants;
• Sleeping medications.

Patient behaviour can sometimes be the culprit. Someone who sits for long hours staring at a computer or television may notice dry eye problems. Contact lens patients who over wear their lenses may experience KCS. Patients who wear dirty contact lenses are also at risk. Any time the contact lens prevents the tear layer from adequately supplying the cornea with moisture and nutrients, a dry eye condition can result. Dry eye syndrome is actually one of the leading causes of patient intolerance to contact lenses.

Some types of kerato-refractive surgery lead to dry eye syndrome. In particular LASIK-induced dry eye (sometimes called LNE, LASIK-induced neurotrophic epitheliopathy) is a known potential side effect of the surgery. Recent studies indicate that this may be due to damage done to the nerve layer of the cornea during surgery. The condition seems to reverse itself about six months after surgery as the corneal nerves complete their regeneration into the flap and corneal sensitivity returns. Patients with dry eye syndrome before the surgery tend to have more difficulty with LNE. Patients who experience LNE may likely notice a return of dry eye symptoms following enhancement surgery.

What Are the Common Complaints of Patients with Dry Eye Syndrome?

Patients’ complaints fall into three main categories: different types of discomfort, appearance of the eyes, and visual problems. Depending upon the individual and the severity of the condition, a patient may mention a few or many of these symptoms.

Discomfort to the patient can range from minor irritation to major pain. Some may describe a pulling or pressure sensation. Others experience a burning or stinging sensation, which is worse indoors. A sandy, gritty, dry feeling, as if something is in the eyes is not uncommon. Severe pain will occur if ulcers have formed as a result of dry eyes that have been left untreated for a long period of time. (An ulcer is an infection into the deeper layers of the cornea, which is caused by a disturbance or erosion of the corneal surface.)

Eye appearance may be affected in two ways. The eyes may appear red, because blood vessels in the conjunctiva send an increased blood supply to try to deal with the problem. Very dry eyes lose their glassy appearance and lack the normal lustre of a healthy, wet eye.

Patients will complain of blurred vision. If the cornea doesn’t have an even film of moisture covering it, the dry areas will not refract light properly. When the cornea is less hydrated than normal, it won’t refract light in its usual manner. Patients may also complain of sensitivity to bright light.

Occasionally patients take it upon themselves to purchase over-the-counter eye drops. Unfortunately they purchase drops that “get the red out,” which only makes matters worse. The drops temporarily constrict the blood vessels in the eye, causing the eye to look less red. Once the effect of the drops wears off, the redness returns, and is often worse than before. This rebound effect then causes the patient to think that more drops are necessary. It becomes a vicious cycle, which does nothing to determine the underlying cause of the problem and only aggravates the eye further.

How Does the Optometrist Test for Dry Eyes?

An optometrist uses several different tests to evaluate a patient’s tears. Some tests determine how long the tears remain stable in the eye. Others evaluate the amount of tears produced by the eye. And another looks at the condition of the cornea itself. To diagnose KCS more than one test is often required.

To evaluate the volume of tears produced, two different tests may be used. The first one is called the Schirmer test. A strip of filter paper is used, which is 5 mm. wide and 20-30 mm. long. The top 5 mm. is folded over and tucked inside the middle section of the lower lid. The slight irritation of the paper causes the lacrimal gland to secrete tears. After 5 minutes, the length of moistened area is measured from the fold line. If 10 mm. or more of the filter paper is wet, tear production is considered normal. Less than 10 mm. indicates dryness and an inadequate aqueous layer. Some doctors believe that a more accurate assessment of tear secretion is gained by using an anesthetic drop prior to insertion of the filter paper. In this case, excess wetting of the strip does not occur, because the eye is less irritated, and the result is a more accurate baseline reading.

The second test, the Quick Zone/Phenol Red Cotton Thread test is newer and like the Schirmer test, also evaluates tear production. This test uses a 70-mm. cotton thread, which has been soaked in a pH sensitive red dye. The dry portion of the thread remains yellow, while the tear-soaked portion turns red. The top 3 mm. of the thread is placed inside the temporal 1/3 of the lower lid, with the remaining portion hanging down onto the cheek. The thread is left in the eye for only 15 seconds and is much less irritating to the patient, even without an anesthetic. Upon removal, the red portion is measured (including the top 3 mm.). Normal results measure 10-20 mm. It is believed that the results of the Phenol Red Cotton Thread test are more valid than those of the Schirmer test.

 

By using fluorescein (a dye which appears green under the cobalt blue filter of a slit lamp) and a slit lamp, the doctor can observe the pool of tears, called the meniscus, along the lower lid. A normal tear meniscus varies from 0.5 to 1.0 mm above the lid and is usually highest on the nasal side.

A device also exists, that tests for the presence of a specific lacrimal protein in a patient’s tears. If there are sufficient amounts, it indicates an adequate aqueous layer. Decreases in the enzyme occur even in the earliest stages of lacrimal gland dysfunction. If the problem is detected in its initial stages, treatment for tear deficient dry eye can be provided before complications arise. If the protein is present and the aqueous layer is healthy, then the patient is experiencing an evaporative dry eye.

One of the most commonly used tests to evaluate tear stability, the BUT (break up time), uses fluorescein. Fluorescein is applied to the eye (using a fluorescein-impregnated strip moistened with sterile saline), and the eye is immediately examined under the slit lamp. The patient is instructed to blink once and then to hold the eye open. The doctor times the interval from the blink to the appearance of the first dry spot on the cornea (areas that appear black, i.e., fluorescein has dissipated). If the tears “break up” in less than 10 seconds an abnormal or unstable tear film exists due to a problem with the mucin layer of the tears.

Rose bengal, a red dye that stains damaged, dying, and dead cells, is used to determine the health of the conjunctiva and the cornea. Rose bengal does not have any toxic effect on the eye, however it stings slightly upon instillation. If the conjunctiva or the cornea is unhealthy due to dry eye syndrome, the devitalized cells will appear bright red when viewed under the cobalt filter. Usually staining of the cornea indicates a more advanced condition than staining of the conjunctiva, and larger areas of staining also indicate more advanced disease. Some patients with symptoms may not show any signs of staining, so it’s an imperfect test in that respect.

Lissamine green is an alternative to rose bengal, which doesn’t require the use of an anesthetic. In mild KCS, blue staining appears on the nasal bulbar conjunctiva. In more advanced cases, the cornea and the temporal bulbar conjunctiva may also be involved.

What Are the Options for Treatment?

Treatment for dry eyes takes many different forms. Some treatments are temporary. Some treatments are more costly. Some treatments work for specific types of dry eye problems and not for others. The following is a description of the major types of treatments currently available.

The first treatment category targets the behaviour of the patient. These methods aim at conserving tears in the early stages of KCS. Sometimes they are the only treatment necessary, if the patient complies as instructed. The following is a list of do’s for those patients:

• Blink more often and blink fully (be sure your eye closes fully when you blink);
• Take visual breaks from computers and near work or even from watching television for long periods of time;
• Drink more water (six glasses a day);
• Cut down on caffeine consumption, caffeine dehydrates the body;
• Avoid fans and wind;
• Use a humidifier in dry environments;
• Use moisture-retaining eyewear in dry environments or during activities that increase your exposure to wind (wrap around sunglasses, fitovers, goggles, etc.);
• Practice proper lid hygiene and reduce blepharitis;
• Re-hydrate contact lenses mid-afternoon;
• Reduce cigarette smoking and avoid secondhand smoke.

Doctors may also refit contact lens patients into lens materials with enhanced wettability. Some doctors may advise that a patient take vitamin A, as there is evidence that it may have a regenerating effect on the production of the mucin layer. And some patients may be given strict regimens for treating blepharitis, including medication.

The second treatment category is the use of ocular lubricants. Over-the-counter artificial tears are usually recommended for daytime use. Sometimes the patient will have to try two or three different brands, as the preservatives vary and may or may not cause irritation. Initially these drops are to be used four times a day, however the preservatives can be toxic to a compromised ocular surface. If sensitivity to preservatives is a problem, non-preserved lubricants in single dose containers can be used as an alternative. Over-the-counter ointments may be recommended for use at bedtime. Tear gels require the instillation of a single drop to form a long-lasting tear film. And doctor-prescribed disks or strips that are impregnated with time-release moisturizers are another option, however due to the discomfort caused, they are used very infrequently.

Often the use of lubricants is a short-term solution, because the continued use of artificial tears can worsen the irritation and interfere with the eye’s own ability to produce tears. It may be more important to determine the underlying problem and resolve it. For example, treat an allergy with appropriate medication or prescribe an anti-inflammatory agent for inflammation of ocular tissues, eyelids, etc.

The third treatment category is the use of punctal plugs. The plugs are inserted into the canaliculi through the puncta. They prevent tears from draining into the lacrimal canals and can reduce tear outflow by as much as 88%. By decreasing outflow, the tears stay in contact with the cornea for a longer time, which helps to reverse the disease process. Plugs are most successful for patients with tear deficient dry eye.

 

 

Punctal plugs take two forms: temporary, dissolvable ones made of collagen and permanent ones made of soft silicone. Usually collagen plugs are inserted into the lower puncta in a simple, fast painless procedure in the office, as a test. Some patients are advised to continue using lubricating drops four times a day. After four to seven days the plugs dissolve, but that gives patients plenty of time to evaluate their comfort and any changes in vision. If the collagen plugs bring no relief, then permanent ones won’t work either.

There are two types of permanent silicone plugs. One variety is implanted completely into the canaliculus. The apex of the other type rests on the lid margin. Plugs vary in length and diameter. They are inserted with the use of anesthetic drops and an insertion instrument. Again the procedure is quick and painless; the patient may only feel some pressure from the doctor’s finger. Plugs may be used only in the lower lid, or in extreme cases in the upper lid as well. Many people opt to do one eye first and see how it goes, before doing the other eye. Again, some doctors advise patients to continue using artificial tears until their first follow-up visit. All patients should be reminded not to rub their lids in the punctal area for the first few weeks. After the first few days, the patient shouldn’t be aware of the plugs. If for any reason the plugs must be removed, it is easy to do so.

The final treatment category includes less common options. Medications may be prescribed for a variety of reasons. Tetracycline may be necessary for blepharitis that isn’t controllable with lid scrubs or topical ointments. Antibiotics or corticosteroids may be used for infection or inflammation of ocular tissue caused by KCS. Currently an oral medication, called Theralife Eye, is undergoing clinical trials, which is reputed to increase tear secretion. It could become another useful tool and a common treatment option, if it lives up to its reputation.

Other less common treatments include a therapeutic soft lens being used as a bandage. And in a few cases laser or cauterization may be used to permanently occlude the puncta. Severe dry eye is sometimes treated in a procedure called tarsorrhaphy. This rarely used procedure involves temporarily or permanently sewing the eyelids fully or partially together. Obviously, some of these treatments will necessitate referral to an ophthalmologist.

The treatment option selected for patients will take into account all of their health history, as well as their lifestyles, and their unique needs. What works for one person, may not work for another. Its takes a knowledgeable, experienced optometrist, who listens carefully to patients and evaluates their conditions accurately to successfully manage KCS.

As an informed assistant you play a key role in patient care. You can take note of any typical dry eye complaints, when listening to patients. You can answer patients’ questions about what to expect from specific procedures. You can emphasize the doctor’s orders to the patient. In every optometric office, a well-educated assistant is an integral part of the health care team and a valuable contributor to the successful treatment of dry eye syndrome.

Click to View the Test Questions

Course OAC-002 Diagnostic Pharmaceutical Agents (DPAs)
A Primer for Optometric Assistants

Acknowledgements: Special thanks to the following for their technical advice: Alphonse Carew, OD; Joan Hansen, OD; Michael Kellam, OD.
Author: Terry Theiss, CPOT, ABOC.

What Are DPAs?

Diagnostic Pharmaceutical Agents (DPA’s) are ophthalmic drugs that are used by optometrists to diagnose ocular diseases and conditions. They are used during the eye examination to make it easier to evaluate the eye or to perform other procedures. Although some of the DPA’s discussed below are sometimes used therapeutically (to treat disease, abnormal conditions, or injury), this article will only address the diagnostic uses, i.e., for assessing the health of the eye. DPA’s fall into four basic categories: anesthetics, mydriatics, cycloplegics, and ophthalmic dyes. Anesthetics numb tissue and provide patient comfort. Mydriatics dilate the pupil and allow the optometrist greater visibility inside the eye. Cycloplegics temporarily paralyze the ciliary muscle (thus interfering with accommodation) so that a more accurate refraction may be determined. Ophthalmic dyes stain ocular tissue for easier evaluation by the optometrist.

Why Do OAs Need to Know About DPAs?

The use of DPA’s in an optometric practice involves assistants in several ways. The first is in taking case histories. During the preliminary testing phase, when patient histories are taken, information is gathered about the patient’s current medical condition and use of medications. The data gathered is crucial knowledge for the optometrist, especially if DPA’s must be used. Some medical conditions are contraindications for certain DPA’s; for example, patients with heart disease may need to avoid several types of dilation drops. Patients who take medication on a regular basis may be contra-indicated for a specific DPA; for example, the optometrist may select an alternate DPA for an insulin-dependent diabetic. During the case history it is also very important to note patient allergies to medications and eyedrops.

The second area of involvement for optometric assistants is in administering DPA’s, usually in the form of drops. Never administer ocular medications without a doctor’s order!Familiarity with the specific medication being administered is required. The assistant must be aware of the appropriate technique for drop instillation, the proper storage of the medication, the immediate sensation the patient will experience, the effect of the drop and how long it will last, and any limitations to the patient’s activities while the drug is working. Eye drops enter the eye and ultimately circulate throughout the entire body of the patient, so post-instillation monitoring of the patient for adverse reactions is another important responsibility for the assistant who administers drops. This course does not include a detailed discussion of drop instillation techniques; it focuses rather on the medications themselves.

The third area of involvement for assistants with DPA’s is documentation. The following must be recorded permanently on the patient’s chart:

• During the case history in the preliminary exam,

• Current medical conditions;
• Medication list, including drug name, dosage and frequency of use;
• Allergies to medication.

• After drop instillation,

• Which eye received the drops;
• The number of drops administered;
• The time of administration;
• The assistant’s name or initials;
• Any reactions the patient had.

Optometric assistants can be particularly helpful in maintaining patient’s records. Sometimes the doctor will require written consent from a patient to perform a diagnostic test. Likewise, there are other times when patients refuse certain diagnostic tests that use pharmaceuticals. It is of the utmost importance that consent forms and documentation of patient refusal become permanent parts of the patient’s records. Not only the patient’s refusal, but also the doctor’s attempt to inform the patient of the health risks of refusal must be documented. Before the chart is filed away, the assistant should ensure that the optometrist has recorded all pertinent information and that any consent forms are included.

Topical Anesthetics

Purpose

Topical anesthetics, sometimes called local (not injected) anesthetics or “freezing drops”, stop nerve fibers from sending messages without putting the patient to sleep. The result is a numbing or deadening of the affected tissue, while the patient is fully conscious. In an optometric practice ophthalmic anesthetics are used diagnostically for reducing corneal sensitivity prior to instillation of other drops (which may cause greater discomfort), performance of applanation tonometry (in which the tonometer tip actually touches the cornea) and to increase the action of other ocular drugs.

The following chart provides specific information about the most commonly used anesthetics.

Generic Name	Trade Name
Proparacaine hydrochloride	Ak-TaineAlcaineOphthaine*Ophthetic*
Tetracaine	Pontocaine / Tetracaine
Concentration Dosage Action Duration 0.5% 1-2 drops prior to procedure 10-20 seconds 15-20 minutes
Storage: Protect from light. *These brands require refrigeration after opening.Comments:Discard discoloured and expired products.Adverse Reations:Temporary stinging, burning, and conjunctival redness may occur. Prolonged use is not recommended.Warnings: Blink reflex is temporarily eliminated. Use with caution in patients with known allergic hypersensitivity, cardiac disease, hyperthyroidism (e.g., Graves disease), or reduced levels of plasma enzymes (e.g., some liver diseases).

Patient Management

Topical anesthetics have relatively few side effects. Patients must be cautioned, however, not to rub their eyes while the medication is in effect. Damage could be done inadvertently to the cornea while it is anesthetized. When anesthetics are used to bring comfort to a patient with a foreign body (and so that the eye can be examined), they are never used for lengthy periods of time, because they inhibit healing.

Mydriatics

Purpose

Mydriatics cause the dilator muscle in the iris to contract, thus opening the pupil wider than normal. Pupillary dilation is used diagnostically for better viewing of the crystalline lens, vitreous, retina, and optic nerve.

Binocular indirect ophthalmoscopy, in particular, requires dilation of the pupil for full viewing from the ciliary body to the optic nerve. This enables the optometrist to identify and diagnose abnormalities that might not be detected using other methods.

Mydriatics are less commonly used to help in the diagnosis of scleritis, iritis, and narrow-angle glaucoma.

The following chart provides specific information about some commonly used mydriatics.

Generic Name	Trade Name
Proparacaine hydrochloride	AK-Dilate Mydfrin
Concentration Dosage Action Duration 2.5% & 10% 1-2 drops prior to procedure 15-30 minutes 4-6 hours
Storage:Oxidizes when exposed to light, air, and heat.Comments:Do not use past expiry date or if solution is discoloured or has precipitate. Also causes eyelid to open further. Light-coloured irides require lower dosage. Prior use of a topical anesthetic increases mydriatic action.Adverse Reactions:Temporary pain, tearing, keratitis. An increase in blood pressure in 10% of patients. Rebound miosis (constricted pupils) the next day in patients over 50 (and sometimes in younger patients, also). Possible increase in intraocular pressure in insulin-dependent diabetics. Heart arrhythmia. Tachycardia (rapid heartbeat). Occipital headache (back of head, base of skull).Warnings: Administer with caution to patients with narrow angles. Only the 2.5% solution is recommended for children and the elderly. Administer the 10% solution with caution to patients with hypertension, heart disease, and advanced arteriosclerosis. 10% is contra-indicated for patients taking MAO inhibitors, tricyclic antidepressants, reserpine, guanethidine, methyldopa, and beta-adrenergic blocking agents.

 

Generic Name	Trade Name
Hydroxy-amphetamine-hydrobromide	Paradrine
Concentration Dosage Action Duration 1% 1-2 drops prior to procedure 45-60 minutes 4-6 hours
Comments:May be a safe mydriatic to use for patients with shallow anterior chambers. Also used in diagnosis of Horner’s syndrome.Adverse Reactions:Causes little if any ocular irritation and elevates intraocular pressure minimally. Some patients experience a mild increase in blood pressure.Warnings: May be a safer mydriatic for patients with insulin-dependent diabetes and for those taking reserpine, guanethidine, and methyldopa. Less strongly contra-indicated in certain high risk patients.

 

Generic Name	Trade Name
Tropicamide	Mydriacyl Tropicacyl
Concentration Dosage Action Duration 0.5% & 1% 1-2 drops 30-40 minutes prior to refraction 20-30 minutes 4-6 hours
Comments:Primarily used for mydriatic effect for ophthalmoscopy. It is probably the safest mydriatic to use for patients with hypertension, angina and heart disease.Adverse Reactions:Stinging, increased intraocular pressure, dry mouth, blurred vision, photophobia, tachycardia, headache or allergic hypersensitivity.Warnings: Contra-indicated in patients with narrow-angle glaucoma. Use with caution in children due to possible association with psychotic reactions and behavioural disturbances.

Note that one of the above-named drugs, Tropicamide, also has mild cycloplegic effects. Consequently, it is sometimes classified as a cycloplegic, depending upon the source.

Patient Management

Mydriatics containing phenylephrine must be used carefully and with full knowledge of the potential harmful effects. If you have been asked to administer a drop and notice that it is contraindicated for the patient, due to a medical condition or regularly taken medication, it never hurts to double check with the doctor prior to instillation. It is always safer to err on the side of caution.

Individual patients experience different effects from mydriatics. The eyes of blue-eyed people dilate more quickly and return to normal more quickly than those of brown-eyed people. People who weigh more require a higher dosage of medication to achieve the required effect. Thus, lighter weight people, including children, need a lower dosage.

Because pupillary dilation lasts for four to six hours, patients must be cautioned about two activities. Protective sunglasses must be worn when outside. If a patient has no sunglasses, the office will usually provide a disposable pair, which can be worn alone or over the top of a pair of eyeglasses. Patients must also be warned that their vision may be blurred. If distance vision is blurred, they may need someone to drive them home. If near vision is blurred, it may be difficult to return to work, if their jobs require reading and computers. Once the effects of the drops wear off, sensitivity to sunlight and clarity of vision will return to normal.

Cycloplegics

Purpose

Cycloplegics are used primarily for children and young adults. Because young people often have an amazing ability to focus at near (accommodate), it can be important to temporarily eliminate their ability to do so.

A cycloplegic inactivates the ciliary muscle and the sphincter muscle in the iris and allows the optometrist to more accurately assess the patient’s refraction. Pupillary dilation is a side effect of cycloplegia, so the optometrist will also have a better view inside the eye of a cyclopleged patient.

The following chart provides specific information about one cycloplegic.

 

Generic Name	Trade Name
Cyclopentolate hydrochloride	AK-Pentolate Cyclogyl
Concentration Dosage Action Duration 0.5%, 1%, 2% 1 drop followed by a 2nd drop in 5-10 minutes 30-60 minutes 6-24 hours
Comments:Drug of choice for cycloplegic refraction. In infants 0.5% solution should be used with digital pressure on nasolacrimal sac. Causes mydriasis and cycloplegia.Adverse Reactions:Stinging, increased intraocular pressure, blurred vision, photophobia. May be associated with psychotic reactions and behavioural disturbances in children.Warnings: Monitor signs of toxicity in children with Down’s syndrome, spastic paralysis, and lightly pigmented skin. Precipitation of narrow-angle glaucoma. May interfere with anti-glaucoma action of carbachol or pilocarpine.

Sometimes you will encounter drugs in the office that combine a mydriatic with a cycloplegic. For example, Cyclomydril is Phenylephrine hydrochloride (described on mydriatic chart) combined with Cyclopentolate hydrochloride (described on cycloplegic chart). The combination of two drugs produces greater dilation than either drug used alone, and dilation occurs more quickly.

Patient Management

Advice to patients is similar to that when using mydriatics. Sensitivity to the effect of a cycloplegic varies according to the person’s eye colour and body weight. Patients should also be counseled about sensitivity to light and blurred vision. Depending on the cycloplegic used, the blurred vision may last up to 24 hours.

Ophthalmic Dyes

A variety of ophthalmic dyes are used for diagnosing several different eye diseases and conditions. Dyes aid optometrists in assessing the health of corneal and conjunctival tissue and in evaluating how well the lacrimal system functions. Other uses of ocular stains are for contact lens fitting and management, applanation tonometry and diagnosing dry eye syndrome.

Fluorescein

Purpose

Fluorescein is the most commonly used diagnostic dye. If the front surface of the cornea is damaged, fluorescein in the compromised areas appears bright fluorescent green when it is exposed to ultraviolet or bright yellow green if exposed to a cobalt blue light. In other words, fluorescein only stains damaged cells, not healthy tissue. Fluorescein has several uses. In the examination of ocular tissue it is used to detect the following:

• Abrasions and ulcers of the cornea and conjunctiva;
• Corneal edema (swelling of corneal tissue);
• Foreign bodies.

Fluorescein is also used to make the tear layer visible when fitting contact lenses, as well as in assessing the health of corneal tissue. Patients suspected of having dry eye syndrome are examined with fluorescein in the tear breakup time test (see Course #OAC-001) and the presence or absence of the dye in the nose helps to assess any obstruction to the lacrimal drainage system. Goldmann applanation tonometry utilizes fluorescein for assessing intraocular pressure.

Application

Fluorescein is applied in the form of drops or by impregnated filter paper strips that are moistened with sterile saline prior to application. Because fluorescein solution is highly susceptible to contamination by Pseudomonas aeruginosa and other types of bacteria, the paper strips are most commonly used. The following two solutions, which combine fluorescein with an anesthetic and a preservative, are also resistant to contamination:

• Fluoracaine (Proparacaine HCl and fluorescein) by Akorn;
• Fluress (Benoxinate HCl and fluorescein) by Pilkington/Barnes Hind.

The following chart illustrates some of the more commonly used fluorescein products:

Fluorescein Solutions	Fluorescein Strips
Fluress (Pilkington/Barnes-Hind)	Ful-Glo (Pilkington/Barnes-Hind)
Fluorocaine (Akorn)	Fluor-I-Strip (Wyeth-Ayerst)
Proparacaine Fluorescein (Bausch & Lomb)	Fluorets (Akorn)

Patient Management

Fluorescein may cause temporary irritation of the cornea or conjunctiva. Patients may notice that their tears or fluid in the nose appear yellow for a short time after this dye is used. Because it stains soft contact lenses, the eye should be thoroughly irrigated after fluorescein use or lenses should not be worn for one to two hours after instillation.

One product, Flurosoft by Holles, uses a larger molecule of fluorescein. This will not adversely affect soft contact lenses with a water content under 55%, as long as they are thoroughly rinsed with saline within three to five minutes of exposure to Flurosoft. It is important to note that soft lenses exposed to Fluorosoft should not be disinfected with a hydrogen peroxide based system until all traces of the dye are removed.

Rose Bengal

Purpose

Rose bengal is the other most commonly used diagnostic dye in optometric offices. When dead or damaged ocular tissue is stained with this dye it appears bright pink or magenta when viewed with white light. Similar to fluorescein, rose bengal is available in solution or in dye-impregnated filter paper strips.

Rose bengal is most frequently used for the diagnosis of keratoconjunctivitis sicca (KCS), which is also known as dry eye syndrome. It is less commonly used in the evaluation of corneal and conjunctival abrasions, ulcers, and foreign bodies. Rose bengal stains devitalized (damaged) corneal and conjunctival cells and mucous strands in the tear film.

Patient Management

Be forewarned that it can cause mild stinging and irritation, which may be relieved with topical anesthetics. Some patients have a hypersensitivity to rose bengal. Rose bengal stains skin, clothing, and soft contact lenses, so it should be used with caution. Contact lens wearers’ eyes should be well irrigated prior to lens insertion. Rinse any spills on clothing or skin thoroughly.

Lissamine Green

Lissamine green is a diagnostic ocular dye that is occasionally used in optometric practices in very much the same way as rose bengal. It has no side effects, but the staining seems to last longer than that of rose bengal.

Legal Issues

Optometrists have been granted the right to use diagnostic pharmaceuticals either at the time they received their licenses to practice or through an additional post-graduate certification process.

The optometrist is required to fulfill certain legal obligations, which are intended to protect patients from the risk of injury. One of the main concerns is that of informing patients of the risks and hazards of the use of a medication, so that they may make informed decisions about whether to consent to a drug’s use.

Fortunately, there are very few circumstances when DPA’s require the informed consent of the patient. Most of the DPA’s used are fairly benign. If, however, a patient has narrow anterior chamber angles (and thus is more likely to experience dilation-induced glaucoma), the decision to dilate must be made jointly with the patient. Children may sometimes have toxic reactions to cycloplegics, so parental consent is advised.

Every patient has the right to refuse any test; no one can coerce a patient against his or her will. Sometimes, patients simply don’t want to receive an ophthalmic drug. Other times they are frightened that the results of the test may indicate a disease, so they would rather avoid the bad news. Whatever the case, an optometrist is obliged to explain the potential ramifications of a patient’s decision to refuse a test. Documentation in the chart of a patient’s refusal and the doctor’s explanation of the possible consequences is mandatory. Optometric assistants play an important role in ensuring that proper documentation occurs.

Conclusion

Remember, any assistant who instills drops in a patient’s eyes does so only on the doctor’s orders. The assistant is operating under the legal umbrella of the doctor’s license. If at any time an assistant is unsure of a procedure or an instruction, it is of the utmost importance to seek clarification from the optometrist before proceeding. It is always wise to fully understand the nature of any medication before administering it to a patient.

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Course OAC-003
Ultraviolet Light and the Human Eye

Acknowledgements: Special thanks to the following:
Michael Kellam, OD, FAAO for his technical advice
Author: Terry Theiss, CPOT, ABOC

The Nature of Ultraviolet Light

It is a known fact that too much ultraviolet (UV) light can damage the human eye. To better understand the effects of UV and the methods of preventing injury to delicate ocular tissues, we must first discuss what ultraviolet light is. Basically it is a type of energy that radiates from the sun and is often known as ultraviolet radiation (UVR). The electromagnetic spectrum is the total collection of energy radiating from the sun, both visible and invisible to the human eye. It includes everything from radio waves and microwaves to visible light to x-rays and gamma rays. UV is one part of the invisible portion of the electromagnetic spectrum and accounts for only 5% of the radiation from the sun.

Two key theories exist about the nature of light. One of them describes light as occurring in waves, and it is this theory which we will examine in relationship to ultraviolet light. What makes light rays visible or invisible is their wavelength. The wavelength is the distance from the peak of one wave to the peak of the next one. You may find it easier to understand by viewing the illustration below:

The light that we experience as “white” is actually composed of many different colours. If a beam of white light is passed through a prism, the beam is separated into its component colours. Each colour is a different wavelength. They are what we recognize as the colours of the rainbow: red, orange, yellow, green, blue, indigo, and violet. Wavelengths are measured in nanometers (nm), which are billionths of a meter. The visible spectrum is made up of light rays whose wavelengths vary from about 400-750 nm. And ultraviolet light is made of light waves that range from about 100-400 nm.

Ultraviolet waves can be further categorized by their wavelengths:

UV-C (100-280nm)
UV-B (280-315nm)
UV-A (315-400nm)

Therefore, the distance from the peak of one wave of UV-C to the peak of another will measure between 100nm and 280nm. As the distance between wave peaks lengthens, the light energy takes on different characteristics and is thus given a different name. The characteristics of each type of UVR will be discussed later.

A narrow band of gases surrounds the earth in the stratosphere, between 15-40km from the earth’s surface. Ozone, an unstable form of oxygen, is distributed sparsely throughout the band, thus giving it the name “ozone layer”. Normally the ozone layer acts as a shield by blocking most of the harmful UV radiation, i.e., the UV with shorter wavelengths. However, the ozone layer is thinning due to man’s use of industrial chemicals. As a result, the ecosystems of the world have been affected and our health is at risk. People experience more sunburns, skin cancer, cataracts, as well as other eye diseases.

Natural UVR Protection

The human body has built-in protective devices to prevent damage to delicate retinal tissue. While they are not fully effective against all UVR, they do provide a certain level of defense. Eyebrows and eyelids act as screens from damaging rays. Squinting and the constriction of the pupil are automatic reflexes that also protect. The cornea itself acts as a filter; it absorbs 100% of UV-C. The anterior layers of the cornea absorb much of the UV-B that we are exposed to. The crystalline lens absorbs most UVR up to 370nm; that is the balance of the UV-B that is not absorbed by the cornea, as well as most of the UV-A. The aqueous and vitreous humours may also absorb a small amount of UVR.

The Effects of UVR on the Eye

UV-C, because of its very short wavelengths, is absorbed by the upper atmosphere. This is very good news, since it is the most damaging of UV radiation. At this time, UV-C from the sun does not reach the earth’s surface. It is important to know, however, that there are some man-made sources of UV-C. Suntan lamps, germicidal lamps, carbon arc lamps and arc welding equipment emit UV-C and can cause serious corneal tissue damage. Welder’s flash is a corneal burn caused by welding without protective lenses.

UVR received at the earth’s surface is UV-B. The skin and cornea have become the second line of defense, absorbing the UV-B that passesthrough the ozone layer. High level exposure to UV-B can also cause corneal damage. Snow blindness is a burn of this type. Long-term or frequent exposure contributes to the development of pingueculae (wedge-shaped, yellowish thickenings of conjunctival tissue, usually between the inner canthus and the nasal limbus) and pterygia (growths of vascular and connective tissue that invade the cornea). Long-term overexposure can also lead to cataract formation and damage to deeper layers of the cornea (stroma, Descemet’s membrane, and endothelium). UV-B may also be implicated in skin cancers around the eye, as well as ocular melanomas.

UV-A is what tans our skin. It comprises 90% of the UVR received at the earth’s surface. While the direct evidence is less clear, one-time, high level exposure and chronic low-level exposure are thought to cause ocular damage in the form of cataracts and macular degeneration. In fact, UVR is increasingly believed to be the cause of age-related brown cataracts that occur in the nucleus of the crystalline lens. (Increasing evidence suggests that short wavelength blue light in the range 400 to 475 nm can also lead to macular degeneration.)

Symptoms, Evaluation & Treatment of UV Keratitis

When the cornea is burned by exposure to UV-C or UV-B, the condition is called UV keratitis or photokeratitis. Usually the patient does not experience any symptoms for 30 minutes to 24 hours. Among the first symptoms to appear are excessive tears and sandy or gritty sensations in both eyes. As time passes, the foreign body sensation increases, and the patient experiences significant pain. More tearing, photophobia, blurring of vision, ocular redness, and blepharospasm (continually squeezing the lids closed) occur. Sensitivity to light and blurring of vision can remain for a week after the exposure, however permanent of the cornea damage rarely occurs.

To evaluate the extent of the damage, the first procedure is to obtain visual acuities. Once acuities are recorded an anesthetic drop is often used to relieve the patient’s pain during the examination. When examined under a biomicroscope, the fluorescein-stained cornea will probably appear pitted, due to the damage suffered by the corneal epithelium; this condition is called punctate keratitis. This may be classified as acute or superficial. Anterior uveitis (inflammation of Descemet’s membrane, the corneal endothelium, the iris, and even the crystalline lens) may also result temporarily.

Once the effect of the anesthetic drops wears off, the patient will re-experience the symptoms previously described. Because frequent use of anesthetic drops will prevent proper healing, patients are rarely allowed to take them home. Treatment may include the use of antibiotic drops or ointment to prevent infection, patching, and pain medication. Patients are advised to rest with both eyes closed as much as possible for the first 24 hours. Follow-up visits may be scheduled to ensure the cornea is healing as expected, depending upon the severity of the damage. Patients should be advised to wear protective eyewear in the future.

Patients at Greatest Risk

Several categories of people are at greater risk of UV damage. Children are more at risk than adults, because from birth to the age of six their crystalline lenses do not absorb as much UVR. For the first year, a child’s crystalline lens is practically transparent and lets in far more UVR than an adult’s lens. Just as people with fair skin are more at risk of sunburn, blue-eyed people are more at risk because their irides do not absorb as much light as darker irides. And patients who have had cataract surgery are at more risk of UV-A damage due to the removal of the crystalline lens. While many of today’s intraocular lenses incorporate UV-absorbing qualities, they are still not as effective as the natural lens. It is important to note that UV damage is cumulative over one’s lifetime, so protection at all times is important.

Other risk factors vary. Different types of prescription drugs can increase sensitivity to UVR. Some of the most common ones are certain anti-depressants, chemotherapy drugs, oral contraceptives, diuretics, and acne medications containing tetracycline. Even some artificial sweeteners and herbal remedies such as St. John’s Wort cause photosensitivity. Patients with a history of macular degeneration in their families should be encouraged to wear sun protection. Patients who work or play outdoors a lot, who use sunlamps or tanning salons, who live in the mountains or in particularly sunny climates, or who spend a lot of time skiing or at the beach all run a higher risk of exposure. And certain industries are more hazardous, such as welding, medical technology, dentistry, graphic arts, electronic circuit board manufacturing, and any activity that uses UV-emitting lights. Contrary to popular opinion, there is no proof that computer screens emit damaging amounts of UVR, however fluorescent lights and lasers do indeed pose threats.

More about UVR Protection

One of the first important factors is to pay attention to the time and place for outdoor activities. UVR intensity is greatest between the hours of 10:00am and 3:00pm. The surface of the ground also plays a role in the amount of exposure. Grass and soil absorb much of the UVR. Sand, concrete and water reflect up to about 20%. Snow and ice reflect up to about 85%. UVR is highest at locations near the equator and increases 2% for every 1,000 feet in elevation. It is a known fact that people who live in areas with greater sunlight duration have a higher incidence of cataracts than those living in areas with less sunlight. And remember, UVR passes through clouds, even when the day is relatively cool.

The UV Index by Environment Canada that is now published in newspapers and announced on radio and TV is an extremely helpful tool to use as a guideline. Become familiar with the chart below.

Figure 7. Environment Canada’s UV Index™ Last updated on: 23 September 2004

UV Index	Description	Sun Protection Actions
0 – 2	Low	Minimal sun protection required for normal activity. Wear sunglasses on bright days. If outside for more than one hour, cover up and use sunscreen. Reflection from snow can nearly double UV strength. Wear sunglasses and apply sunscreen.
3 – 5	Moderate	Take precautions – cover up, wear a hat, sunglasses and sunscreen – especially if you will be outside for 30 minutes or more. Look for shade near midday when the sun is strongest.
6 – 7	High	Protection required – UV damages the skin and can cause sunburn. Reduce time in the sun between 11 a.m. and 4 p.m. and take full precautions – seek shade, cover up, wear a hat, sunglasses and sunscreen.
8 – 10	Very High	Extra precautions required – unprotected skin will be damaged and can burn quickly. Avoid the sun between 11 a.m. and 4 p.m. and take full precautions – seek shade, cover up, wear a hat, sunglasses and sunscreen.
11+	Extreme	Values of 11 or more are very rare in Canada. However, the UV Index can reach 14 or more in the tropics and southern U.S. Take full precautions. Unprotected skin will be damaged and can burn in minutes. Avoid the sun between 11 a.m. and 4 p.m., cover up, wear a hat, sunglasses and sunscreen White sand and other bright surfaces reflect UV and increase UV exposure.

Note that sunglasses are recommended most of the time. Hats with wide brims can reduce UVR exposure to ocular tissue by 50%. Beach and patio umbrellas provide protection, as well.

UVR Protection from Optical Products

As optometric assistants, you have three types of products that can help to protect your patients from UVR exposure: frames, spectacle lenses, and contact lenses. Yes, both soft and gas permeable contact lenses can be ordered with UV-absorbing qualities, however they are not fully protective to all ocular tissue. Your contact lens patient should still be advised to have a protective pair of plano sunglasses to wear over their contacts. And the shape and position of the frames is very important. Frame should have larger lenses. It also helps if they fit closer to the face with more facial wrap or adjustable nosepads that bring the frame in closer to the eyes. Sideshields can also be helpful. However, the remainder of the protection comes from the lenses themselves.

Various optical associations agree that to be effective the lenses should block out 99-100% of UV-A and UV-B. In addition sunglasses should screen out 75-90% of visible light. The Canadian Standards Association (CSA) has adopted guidelines for four categories of sunglass lenses: cosmetic, general purpose, special purpose, and “robust” lenses (for certain types of outdoor workers).

Many options exist for providing UV in spectacle lenses. Standard CR-39 (plastic) filters out almost 100% of UV-B and 90% of UV-A. Crown glass filters out about 80% of UV-B but very little UV-A. Therefore, neither CR-39 nor crown glass are considered adequate UV protective. All mid and high index plastic lenses, including polycarbonate, incorporate UV-absorbing agents in their materials or coatings, so they are UV-absorbent to a fairly high degree. Some absorb up to 380nm, others to 400nm. High index glass lenses require additional treatment to be considered UV protective and are not adequate protection without it.

CR-39 can be made to absorb up to 400nm, if the lens is soaked in a specialized dye. This is often called “UV coating” or UV 400 and may have a slightly yellowish hue. It is important to note that its effectiveness diminishes with age. Glass lenses must be processed with an actual UV coating (not dye) to provide UV protection.

Lens tints can provide protection, as well. Good quality polarized and any photochromic lenses are considered protective for most patients. Photochromic lenses, either in glass or plastic, darken because special components of the lens material change colour when they absorb UVR. Some people, who are at higher risk of macular degeneration, require special glare-control or blue-blocker lenses, which have a brownish, amber, or orange hue. For full protection of the retina for these patients, we will likely find in the future that we are recommending sunglasses with a cut-off of 475 nm, not 400 nm, if blue light from 400-475 nm is truly proven to be a cause of macular degeneration. Tinted lenses alone (gray, brown, or green) are not fully protective. They will, however, provide some degree of protection, and they are excellent when combined with a UV dye.

Detecting UV protection in a lens with the naked eye is impossible. You can get a rough idea of the level of UV protection in a lens by holding a photochromic lens (preferably a plastic one) behind the lens in question while in full sun. If the photochromic lens darkens, the UVR passed through the lens in question. If the photochromic lens remains clear, then the lens in question effectively absorbed the UV. To get a more accurate assessment of the UV transmission of a lens, a s pectrophotometer or UV meter may be used. Some automated lensometers also analyze UV transmission and provide both on-screen displays or printouts.

As optometric assistants, we have a duty to discuss the dangers of UVR exposure with our patients and to offer solutions based on their lifestyle and needs. People must be given the choice to protect their eyes, especially because we now have the technology to provide full UV protection in all eyewear we dispense. When discussing the options available be sure to watch the language you use. The use of UV protective lenses will minimize the risk of later damage, but it cannot absolutely guarantee that no damage will occur. One added benefit is that UV protective eyewear also reduces discomfort from glare. So, encourage your patients to protect their eyes, and be a good role model by protecting your own eyes and those of your family members.

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Course OAC-004
Soft Contact Lens Parameters

Acknowledgements: Special thanks to the following:
Michael T. Kellam, OD, FAAO for his technical advice
Terry Theiss for the use of Figures 1 and 2.
Author: Terry Theiss, CPOT, ABOC

Parameters are the measurements, specifications, and/or characteristics of a contact lens. To achieve the best fitting relationship with the cornea, optometrists determine the ideal parameters of a contact lens for an individual patient. Whenever an optometric assistant orders or checks in a contact lens, the parameters must exactly match those prescribed by the doctor. Whenever contact lens inventory is organized, it is done in a methodical fashion by grouping according to parameters. Without a fundamental understanding of what the parameters represent, mistakes can be made that may cause delays, frustration for the optometrist, or even discomfort for the patient.

Interestingly, as the contact lens industry has evolved, the choice of parameters has changed much as in the garment industry. In the early days clothing was custom-made and tailored to the individual. Later in order to accommodate more people at more reasonable prices, clothing began to come in standard sizes. To further reduce price today we find small, medium and large sizes and sometimes one-size-fits-all. Soft contact lens manufacturing has moved in a similar direction. We used to be able to order custom-made soft lenses from local laboratories. These days we have to find the standard sized lens to fit the patient. There are still many parameters available, which accounts for the many different lenses on the market.

In this course we will explore all of the parameters associated with soft contact lenses. In later courses we will discuss gas permeable contact lens parameters and verification techniques to ensure that the parameters received are the same as those that were ordered. Because soft lenses and gas permeable lenses have some distinct differences, we will discuss the parameters of gas permeable lenses separately.

Lens Name

The first specification of a soft contact lens is its manufacturer and the name of the lens. These are very important for several reasons. The name implies the manufacturing process used, the lens material, and the approved wearing period/lens life.

Manufacturing Process

Each contact lens manufacturer uses different processes to produce their lenses. Some lenses are spun cast, some are lathe cut, and others are cast-moulded. Each of these manufacturing methods is associated with different fitting techniques and characteristics, accuracy of reproduction, and cost of manufacturing.

Lens Material

A variety of materials are used to produce soft contact lenses. Different blends of plastics, called polymers, have different water contents, different abilities to repel deposits, and again different fitting characteristics. The brand name of a lens guarantees that the lens was made by a specific process with a specific polymer.

Low water content lenses contain less than 50% water. The lower the water content, generally the more resistant to damage a lens is. Some of the more commonly recognized names of these materials are crofilcon A (38.6%), polymacon (38.6%), and tetrafilcon A (43%).

High water content lenses contain more than 50% water, which increases the amount of oxygen transmitted through the material to the cornea. Oxygen transmission actually doubles when the water content of a lens is increased by 20%. Commonly recognized names of these materials are etafilcon A (58%), helfilcon C (57%), and methafilcon B (55%). Higher water content lenses are sometimes used therapeutically to protect the cornea while healing from corneal surgery or injury.

The newest soft lens materials also contain silicon, which further enhances the ability of the lens to transmit oxygen. And silicon increases transmissibility without increasing the water content of the lens. This better delivery of oxygen to the cornea allows lenses to be worn overnight more safely. You may recognize these lenses by the names Acuvue Advance with Hydraclear and Focus Night & Day.

Wearing Period/Lens Life

Each combination of material, thickness, and lens design will have a specific life expectancy. Since each combination of these parameters has a specific brand name, the brand name of a lens implies the recommended life of the lens and how it should be worn. Daily disposable lenses are to be worn for only one day and thrown out before bedtime. Frequent (or planned) replacement lenses are worn during waking hours and are thrown out at the end of the specified life span, e.g., two weeks, one month, three months, etc. Continuous (or extended) wear lenses are worn for one week or for as long as 30 days non-stop (at the recommendation of the optometrist) and then are replaced with a new, fresh lens. Flexible wear lenses are normally worn only during the day, but they can be worn occasionally overnight. Contact lenses also exist that may last a year, if cared for properly.

Thus, the lens manufacturer and brand name are an important parameter in contact lens fitting, because they imply appropriate uses and fitting characteristics determined by manufacturing method, lens material, and recommended life span of the lens.

Base Curve

The base curve determination is a significant part of the fitting process and is affected by other factors. Most commonly a keratometer is used to measure the cornea, though it actually measures only the central 3 millimeters (mm) in diopters. We call the results the “K-readings.” Simplistically the base curve of a contact lens approximates the curve of the patient’s cornea, though most soft lenses are fit flatter than the patient’s K-readings. If need be, the entire cornea’s geography can be mapped with a corneal topographer.

The base curves of soft lenses are designated by a number such as 8.4, 8.5, 8.6, etc., which indicates the length of the lens radius (distance from the center to one edge). They commonly range from 8.0 to 9.0, with more unusual curves sometimes available. The smaller the number, the steeper the lens or conversely the larger the number, the flatter the lens. In rough terms this can be understood by looking at circles. The curve of the surface on a smaller circle (with a shorter radius) is steeper (more curved) than that of a larger circle (with a longer radius) as illustrated in Figure 1.

Lens Diameter

Standard soft lens diameters most commonly range from 13.0mm to 15.0mm, although custom lenses are available in larger and smaller sizes. The optometrist selects the lens diameter that will fit the size of the patient’s cornea and iris and that provides the best fit. The base curve of a soft lens, combined with its diameter, affects its fitting characteristics. In other words, changing the diameter of the lens, but keeping the base curve the same, will change the vault of the lens. The vault of the lens is the distance measured from the central corneal surface to the highest peak of the contact lens as illustrated in Figure 2.

Lens Design & Power

Soft lenses come primarily in spherical, toric, multifocal, and aphakic designs. Spherical contact lenses, as with spherical spectacle lenses, have one corrective power and are to be used for a specific focal range. Toric contact lenses are designed for astigmatic patients and have sphere power, cylinder power and an axis designation. Toric lenses are usually weighted with prism or have special edge designs, so that the lens will orient on the eye to the required axis. Spherical and toric lenses are used primarily for distance correction, however in the fitting strategy called monovision, one eye may be fit with a correction for near and the other for distance.

Multifocal soft lenses include different viewing areas for distance and near, as well as the add power in their power specifications. Some provide alternating vision; in other words the patient uses different areas of the lens at different times depending upon the viewing distance required. Typical alternating designs have two concentric areas of power; sometimes the center is for distance and sometimes it is for near.

Other types of multifocal soft lenses provide what is known as simultaneous vision. In these lenses, both distance and near corrections are focused on the retina at all times and the patient learns to ignore one field of vision while using the other. Most are progressive and/or aspheric in nature very much like progressive and aspheric spectacle lenses.

Aphakic lens designs are for patients who have had cataract surgery but do not have intraocular lens implants (IOLs). These patients, having had their crystalline lenses removed, commonly require between +10.00 and +20.00 diopters of power. An aphakic lens is thicker than lenses of lower power because of the higher diopter value. They are often worn on an extended wear basis, because handling can be difficult for these predominantly elderly patients. Thanks to the success of IOLs this is not a commonly used lens design today.

When a specific brand name lens by a certain manufacturer is selected, the optometrist knows what design the lens has. The only parameters the prescribing doctor must supply are the base curve, lens power, (including cylinder and axis if a toric), add power (if a multifocal), and lens diameter. Multifocal toric, aphakic toric, and aphakic multifocal lenses are very rare.

Lens Tint

The final parameter needed for a soft lens is the lens tint. While the colour of the lens does not affect its fitting characteristics, it is nonetheless an important variable. Several different types of tints are available for different purposes. A handling tint or visibility tint is pale blue and is used to help the patient see the lens when it is off the eye.

Cosmetic tints are available in three basic categories. Enhancing tints simply turn a blue eye bluer or a green eye greener. The colours are transparent and are deeper in colour than a visibility tint. Opaque tints alter the colour of the wearer’s eye more significantly. These lenses can turn a brown eye into a blue eye. Novelty tints are usually used for theatrical or costume purposes. They are available in many wild and crazy designs such as cat’s eyes, alien eyes, hearts and shamrocks.

The final category of tints is used for prosthetic or therapeutic purposes. Prosthetic tints exist primarily to improve the look of an eye that is abnormal. Some have a handpainted iris to match the other eye. The iris may be painted off-center to cover an eye that is badly turned in or out. Others have different sized black pupils. A lens with an opaque black pupil can be used therapeutically to occlude vision.

Tint in a soft lens is usually specified using the manufacturer’s colour names. Sometimes #1, #2, or #3 is used to indicate the intensity of colour (#1 is the lightest). In the case of a handpainted prosthetic or therapeutic lens more specific information will be required, which will be described by the manufacturer during consultation and ordering.

Conclusion

In review, soft contact lens parameters include lens name, base curve, lens diameter, lens power, and tint. To accurately order a soft contact lens all of the above information must be provided. When the contact lens arrives, all of the parameters must be verified to ensure that the lens received is indeed the lens that was ordered. When taking a soft lens from an in-house stockroom, an optometric assistant must also pay attention to all of the required parameters. To supply a lens of the wrong base curve or diameter would cause potentially as much of a problem as supplying spectacle lenses in the wrong prescription. Attention to detail is critical.

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Course OAC-005
Treatment Options for Age Related Macular Degeneration

Acknowledgements: Special thanks to Carla D. Clarke, OD, for her technical advice.
Author: Kelly Antonation, CCOA

Glossary

Age related macular degeneration (ARMD) is an eye disease that affects the retina and causes loss of central vision, which can be devastating to a person’s ability to function in daily tasks. ARMD often becomes symptomatic around the age of 55 with progressive loss of vision. ¹

Types of ARMD

There are two types of ARMD: dry ARMD and wet ARMD. The dry form of this disease is also referred to as non-exudative or drusenoid macular degeneration. 90% of all those afflicted with ARMD have the dry form of the disease.² This form generally results in less pronounced changes that can be stable for a long period of time. Yellowish deposits, called drusen, accumulate in the retinal pigment epithelial tissue (RPE). The RPE is located beneath the macula located at the back of the eye.³ Photoreceptor cells located in the macula produce metabolic waste material which the RPE is unable to process. This waste or drusen interferes with the function of the photoreceptors. Over time there is a progressive loss of central vision which can impair almost every aspect of a person’s life.

In contrast to dry ARMD, the wet form of ARMD is referred to as choroidal or subretinal neovascularization or disciform degeneration. Wet ARMD progresses very rapidly from dry ARMD and can severely blur or distort central vision.⁴ Angiogenesis, which is new blood vessel growth, occurs under the macula. The new blood vessels are weak and tend to leak causing damage to the photoreceptor cells.⁵

Risk Factors for ARMD

The etiology of wet and dry ARMD is not well known; however, there are several risk factors associated with ARMD. Dr. Kassoff, an ophthalmologist with many years experience in research of ARMD, stated, “Oxidative damage to the retina may be involved.”⁶ Smoking has been identified as one of the main causes of this oxidation because of the free radicals it generates.⁷ A free radical molecule has only seven electrons, one less than a stable oxygen molecule. It will bombard the body seeking an additional electron to make it stable.⁸ These molecules will destroy or mutate cells. This makes smoking the highest risk factor for the development of ARMD. Additionally, smoking causes altered blood viscosity, depletion of antioxidants in the blood, altered blood flow mechanisms in the blood vessels, and lowered macular xanthophylls such as lutein.⁹ Other environmental risk factors include: ultraviolet light exposure and drugs that cause photosensitizing.

In addition to smoking, genetic predisposition has been examined as a risk factor. Women with fair skin and light coloured irises have been identified as having a higher risk for developing this disease. This genetic component seems to be related to the lower amounts of retinal pigment.¹⁰ Although there are indications that some races may be more susceptible to ARMD, the rising prevalence of this disease in Japan indicates that it is more closely related to diet than genetics,¹¹ due to those who have acquired a more westernized diet.

Research on ARMD

Research into ARMD is ongoing. Many studies are independent, such as the AREDS Study and the Veterans LAST Study, which have no proprietary interests in the supplements that were examined. The study on rheopheresis, which is a blood filtering process that removes high molecular weight proteins from the serum, is being conducted by the centers that perform this procedure for profit which may lead to research bias.¹²

One of the limitations of researching journal articles is bias. When research is biased, it can have the effect of distorting or skewing the results. When looking at studies that are funded by companies or individuals that stand to gain from the results of the study, it is prudent to see if there are other studies that corroborate the research.

Even in independent studies, the efficacy of treatments that are researched has to be examined in light of cohort size and population. For example, the Veterans LAST Study and the AREDS Study were both randomized double-masked, placebo-controlled trials. However, the AREDS study had a cohort size of “4,757 mixed gender patients enrolled in a seven year multicentre over 12 months.”¹³ The methodology of the LAST study is such that the results are promising; however, even the LAST researchers acknowledge the sample size and time frame for the experiment would lead the results to be called preliminary and inconclusive.¹⁴ Another concern with ARMD studies is the average age of the cohort. ARMD typically has a senile onset; therefore, the populations to which the results are applied have a high mortality rate.

Treatment Options for ARMD

Currently, allopathic medicine has not found a drug to halt the progression of dry ARMD. The only treatment outside of drug therapy is still in clinical trials. One such treatment is rheopheresis. This process may improve blood flow through the small vessels by reducing the viscosity of blood and plasma.¹⁵ Dr. Richard Davis, an ophthalmologist involved in the rheopheresis study, suggests, “Since impaired blood flow in vessels beneath the retina – in the choroid – is thought to contribute to the development of dry macular degeneration, rheopheresis was introduced as a possible treatment for this condition.”¹⁶ Rheopheresis has been used in Europe for many years to treat various age related disorders: however, there is a paucity of randomized, placebo-controlled clinical studies. This is now underway, but the results currently are not available. The preliminary results suggest that 4.9% of subjects have had adverse reactions to the treatment including paresthesia, which is numbness and tingling, and hypotension or low blood pressure.¹⁷

Other treatments for dry ARMD under investigation have had mixed success. RPE cell transplants had initial promising results; but, in human clinical studies, transplanted RPE cells caused damaged immune response.

There is also research ongoing into photoreceptor cell transplant and stem cell transplant; however, there has not been enough clinical evidence into these treatments to expect them to become mainstream medical intervention in the near future.¹⁸

As wet ARMD is more visually devastating and can be rapidly progressive, more research into possible treatments has been completed. Laser photocoagulation is currently the preferred treatment of extra-foveal choroidal neovascularization.¹⁹ Blood vessels that grow outside the fovea, which is the very center of vision, are treated with a concentrated laser. This destroys the blood vessels and aims to stabilize vision loss. Laser also works more effectively when wet ARMD is caught at the very earliest stages.²⁰ There may be some vision loss from the laser; though, it is often less severe than if there was no treatment. In contrast, when blood vessels grow beneath the fovea, photodynamic therapy (PDT) is the medical treatment of choice. With PDT, a light activated drug is administered. This drug targets new blood vessel growth and is activated by a cool laser. This destroys the leaky blood vessels without harming the healthy tissue; consequently, patients generally require repeat treatments which are costly and may have some health risks, such as an adverse reaction to the drug.²¹

Nutrition as Prevention of ARMD

Although traditional treatments aim to stabilize vision loss, the best treatment seems to be prevention. All current nutritional studies point to environmental factors as being correlated with ARMD. Many studies have shown that antioxidant vitamins such as A, C, E, beta-carotene, lutein and the mineral zinc slow the progression of vision loss, and in the case of lutein may actually improve the visual acuities of ARMD patients. The LAST Study found that it was more beneficial to take lutein and other carotenoids than beta-carotene.

The study postulates that because the AREDS study showed a decrease in serum concentration of other carotenoids when using isolated beta-carotene, it would be better to supplement with lutein and antioxidant vitamins than beta-carotene.²²

Current medical methods do not detect subclinical nutrition deficiencies that lead to ARMD and other diseases. Dr. Mark Payne who is a medical doctor with years of prescribing natural remedies says, ” Less than 80% of women and children meet the RDA (required daily allowance of a particular nutrient) for Vitamin E and zinc.”²³ This is particularly disturbing as Vitamin E is the antioxidant that removes dangerous free radicals that cause oxidative damage to the body. As stated earlier, it is oxidative changes that contribute to the progression of ARMD. The North American fast food diet is lacking in meeting even the minimum RDA of vitamins responsible for combating oxidative stressors and damage.²⁴

In light of the body of evidence that supports nutritional intervention for those afflicted with ARMD, it would be prudent to counsel patients in the following manner: eliminate or reduce your exposure to known environmental risk factors, quit smoking, wear UV blocking sunglasses, and adopt a nutrient dense diet. A diet that is plentiful in dark leafy greens and brightly coloured orange and yellow vegetables is high in lutein and other important carotenoids and antioxidant vitamins, coupled with an adequate intake of zinc and Vitamin E supplementation would be beneficial. Using the dosages recommended in the AREDs Study and the Veterans LAST Study, a patient would supplement with antioxidants in the following dosages: Vitamin C 500mg, Vitamin E 400IU, beta-carotene 15mg, 10mg lutein.^25&26

There are other recommended nutritional treatment options, such as bilberry, which has been extensively used in Europe because of its high flavonoid content. Flavonoids are high in disease-fighting antioxidants. Bilberry flavonoids are called anthocyanosides. A high quality supplement of bilberry will contain 25% anthocyanosides, and the dosage with this percentage of ingredients is 80-160mg three times daily. Bilberry supplements have no known adverse side effects.²⁷ Bilberry supplementation is occasionally accompanied by brownish coloured deposits in the retina. The deposits are thought to be from increased rhodopsin, which is a pigment that aids in night vision. Bilberry has a powerful flavonoid that helps replenish rhodopsin, and this flavonoid increases circulation to the blood vessels in the eyes.²⁸ As previously stated, increased blood circulation is thought to decrease the onset and progression of ARMD.²⁹

Additionally, ginkgo biloba is a powerful antioxidant that improves circulation in the eye and slows down deterioration of the macula. It increases blood flow by improving blood viscosity and keeping blood vessels elastic. This improves blood flow through major blood vessels and capillaries.³⁰ Thus, it would be beneficial for those with ARMD to add these supplements to their diet, as well.

In conclusion, research clearly indicates that decreasing risk factors prevents or reduces the impairment of this condition.³¹ Under the supervision and with the permission of an optometrist, an optometric assistant may recommend that patients try to prevent this devastating disease with proper supplementation, diet, and reduction of environmental risk factors.

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