Age-related macular degeneration (AMD)

What is age-related macular degeneration (AMD)?

Age-related macular degeneration is an eye disease that affects central vision. As the name suggests, age it is a major risk factor for this disease and it is the leading cause of blindness in North American adults over the age of 50.^1,2,3 The central vision is affected as a result of waste build up at the center part of the back of the eye called the macula.⁴ The macula is responsible for detailed vision necessary for activities such as reading, driving, and recognizing people’s faces.⁴ AMD can progress slowly in some individuals and rapidly in others.⁴ Therefore, it is important to get routine eye exams to detect it early on.

What are the symptoms of AMD?⁴

AMD is a progressive disease, often accompanied by worsening symptoms over time. In the early stages, AMD may be symptom-free and can only be detected in an eye exam. As the disease progresses, the most common initial symptoms include blurred central vision, particularly noticeable while performing tasks that require seeing detail, such as reading. Glasses cannot correct for this blurred spot. In the intermediate stages, the blurred area may increase in size and interfere with various daily activities such as driving. Other symptoms of AMD include straight lines appearing wavy or distorted, and dark spots or missing areas in vision. In its later stages, there is a complete loss of central detailed vision. Patients experience no pain with AMD.

What are the types of AMD?⁴

There are two types of AMD, dry and wet. Dry AMD is the most common form of AMD accounting for 90% of all cases. It is the milder form resulting in degeneration of the central macular tissue that generally develops slowly over time. Dry AMD can develop into wet AMD at any time. Wet AMD is less common and accounts for 10% of all cases. It is characterized by leakage and bleeding of weak blood vessels under the macula and symptoms progress rapidly.

Who is at risk of developing AMD?^4,5

Individuals with an increased age are at an elevated risk for developing AMD. Other risk factors include smoking, extensive UV light exposure, family history of AMD, and cardiovascular disease. 

How can I prevent and treat AMD?^6-8

• Lifelong UV protection by wearing UV protective glasses and smoking cessation can reduce the risk of developing AMD.
• Living a healthy lifestyle with healthy diet and routine exercise will reduce the risk of AMD.
• Keep your blood pressure in control and reduce your intake of fatty foods.
• A diet rich in antioxidants such as vitamins C, vitamin E, zinc, copper, lutein, zeaxanthin, and omega 3 fatty acids may help prevent AMD. These antioxidants can be found in fruits and leafy green vegetables.
• Routine eye exams are important in the early detection and prevention of AMD. Early signs of AMD can be found during an eye exam even if no symptoms are noticed. Upon detection, the optometrist will discuss ways to minimize the possibility of vision loss.

In the early stages of AMD, treatment options include dietary supplements with the AREDS2 formula, self-monitoring of vision at home with an Amsler grid, and routine eye exams to monitor for progression. An Amsler grid is a test provided by the optometrist that allows you to monitor for vision changes at home between routine eye exams. AMD is an eye disease that can cause sudden changes in vision when it turns into the wet form. If changes in vision are noticed, contact your optometrist, as timely treatment can limit the extent of vision loss. 

In the later stages of AMD, treatment options include eye injections to prevent further leakage of blood vessels in order to minimize vision loss. Patients with vision loss due AMD can benefit from low vision aids. Your optometrist can prescribe magnifying devices to enhance your distance and near vision. These aids will not restore sight, but will allow people to maximize their remaining vision and provide improved functional vision to help people go about their daily activities.

References

1. Cruess A et al. The cost of vision loss in Canada. 2. Results. Can J Opthalmol. 2011;46:315-318.
2. Cruess A et al. Burden of illness of neovascular age-related macular degeneration in Canada. Can J Opthalmol. 2007;42(6):836-843.
3. Pascolini D et al. 2002 global update on available data on visual impairment: a compilation of population-based prevalence studies. Ophthalmic Epidemiol. 2004;11(2):67-115.
4. Jager RD et al. Age-related macular degeneration. N Engl J Med. 2008;358:2606-2617.
5. Chakravarthy U et al. Clinical risk factors for age-related macular degeneration: a systematic review and meta-analysis. BMC Ophthalmol. 2010;10(1):1-13.
6. Nowak JZ. Age-related macular degeneration (AMD): pathogenesis and therapy. Pharmacol Rep. 2006;58(3):353-363.
7. Mares JA et al. Health lifestyles related to subsequent prevalence of age-related macular degeneration. Arch Ophthalmol. 2011;129(4):470-480.
8. Chew EY et al. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the age-related eye disease study 2 (AREDS2) randomized clinical trial. Jama. 2013;309(19):2005-2015.