Diabetes, Eye Health, and Vision Care: The Impact and Importance of Early Intervention

Diabetes

Diabetes is a global health crisis, affecting more than 588 million adults worldwide, with projections indicating a rise to 852 million by 2050.¹ In Canada, approximately 3.7 million individuals live with diagnosed diabetes. The prevalence of diabetes increases with age; among those aged 65+, the prevalence of diagnosed diabetes is 27%.² 

The impact of diabetes on vision

One of the most significant but often overlooked complications of diabetes is its impact on vision. Diabetes affects vision primarily through prolonged hyperglycemia, which damages blood vessels in the retina, leading to diabetic retinopathy (DR). Diabetic retinopathy is a leading cause of vision loss both worldwide and in Canada. DR progresses in stages, starting with mild non-proliferative DR and advancing to proliferative DR, which can cause severe vision impairment if untreated. 

Diabetic Retinopathy

DR is currently the fifth leading cause of avoidable blindness in North America.³ Based on a report from 2021, an estimated 1,037,000 Canadians live with diabetic retinopathy.⁴ Early intervention through regular eye examinations can play an important role in detecting not only diabetic retinopathy, but in detecting diabetes altogether. Studies show that ocular manifestations are already present in a significant portion of patients at the time of diabetes diagnosis. Creuzot reports that 20% of individuals with type 2 diabetes already have diabetic retinopathy upon diagnosis⁵, while older research estimates this range to be between 10% to 47%.^6-8 This indicates that a substantial number of individuals with undiagnosed diabetes may already exhibit ocular changes before systemic symptoms prompt them to seek medical attention. Ocular complications often develop within five years of the onset of type 2 diabetes, suggesting that many patients identified through optometric screening may have already been living with undiagnosed diabetes for several years. As such, regular comprehensive eye exams provide a critical opportunity for optometrists to detect early clinical signs of diabetes, enabling timely referral and intervention, and potentially mitigating long-term complications.

Diabetic retinopathy is often asymptomatic in its early stages, making it a silent yet progressive threat to vision health. As Fung, Patel et al. note, patients may not experience any noticeable symptoms until significant retinal damage has occurred.⁹ This underscores the critical importance of regular comprehensive eye examinations for individuals with diabetes. Early detection and timely treatment can prevent vision complications that may otherwise go unnoticed until they are advanced and potentially irreversible. Diabetic eye screening programs have been proven to significantly reduce the risk of vision loss by facilitating earlier intervention. 

For example, systematic screening for diabetic retinopathy done as part of the National Health Services Diabetic Eye Screening Program in the United Kingdom was able to significantly reduce rates of blindness. By 2010, diabetic retinopathy was no longer the leading cause of blindness among the working-age group in the U.K.¹⁰ 

Despite these benefits, access to regular screening remains uneven, often due to cost-related barriers and insufficient insurance coverage for essential services such as retinal imaging.

The Importance of Regular Comprehensive Eye Exams

Routine eye exams are essential for early detection to prevent diabetes-related vision loss. The CAO recommends that adults aged 20 to 64 receive an eye exam every two years, and those aged 65 years or older receive an annual eye exam.  Diabetes Canada recommends that individuals with type 1 diabetes undergo an eye exam within five years of diagnosis and are then rescreened annually. Those with type 2 diabetes should have an exam at diagnosis and be rescreened every 1 to 2 years thereafter.¹¹ 

In addition to retinopathy, optometrists can detect other ocular signs that may indicate undiagnosed diabetes. Fluctuating vision, loss of accommodation, and sudden diplopia are among the non-retinal complications that can raise suspicion of diabetes in otherwise asymptomatic individuals.¹² Regular preventive eye visits allow optometrists to notice these changes early, facilitating prompt referrals for medical evaluation and diagnosis. This highlights the vital role optometry plays in systemic health monitoring and the importance of routine vision care in the early detection of chronic diseases like diabetes.

Timely diagnosis of diabetes is essential to minimizing the risk of complications. Delays in identifying diabetes are closely linked to a higher incidence of diabetes-related health issues, including retinopathy. Late diagnoses of ocular diseases are also linked to poorer quality of life, including physical, psychological, financial, and social aspects.¹³ Early detection through optometric screening enables healthcare providers to devise timely treatment plans, reducing the burden of advanced disease and improving patient outcomes.¹⁴

Conclusion

Diabetes-related vision complications are a significant but preventable cause of blindness. Strong evidence supports the role of regular eye exams in reducing the burden of diabetic eye disease. As the global diabetes prevalence continues to rise, prioritizing vision health through early intervention, education, and equitable access to care is crucial in preventing vision loss and improving quality of life for individuals with diabetes.
 

References

1. International Diabetes Federation. Diabetes Atlas 11^th Edition. https://diabetesatlas.org/resources/idf-diabetes-atlas-2025/. 2025.
2. Public Health Agency of Canada. Snapshot of Diabetes in Canada, 2023. Government of Canada; 2023.
3. Teo ZL, Tham YC, Yu M, et al. Global Prevalence of Diabetic Retinopathy and Projection of Burden through 2045: Systematic Review and Meta-analysis. Ophthalmology. 2021;128(11):1580-1591. doi:10.1016/j.ophtha.2021.04.027
4. Deloitte. The cost of vision loss and blindness in Canada. https://www.fightingblindness.ca/wp-content/uploads/2021/12/Deloitte-Cost-of-vision-loss-and-blindness-in-Canada-report-May-2021.pdf. 2021.
5. Creuzot C. Rétinopathie Diabétique. Collége des Ophtalmologistes Universitaires de France (COUF). 2021
6. Kohner EM, Aldington SJ, Stratton IM, et al. United Kingdom Prospective Diabetes Study, 30: diabetic retinopathy at diagnosis of non-insulin-dependent diabetes mellitus and associated risk factors. Arch Ophthalmol. 1998;116(3):297-303. doi:10.1001/archopht.116.3.297
7. Harris MI, Klein R, Welborn TA, Knuiman MW. Onset of NIDDM occurs at least 4-7 yr before clinical diagnosis. Diabetes Care. 1992;15(7):815-819. doi:10.2337/diacare.15.7.815
8. Ellis JD, Zvandasara T, Leese G, et al. Clues to duration of undiagnosed disease from retinopathy and maculopathy at diagnosis in type 2 diabetes: a cross-sectional study. Br J Ophthalmol. 2011;95(9):1229-1233. doi:10.1136/bjo.2010.196204
9. Fung TH, Patel B, Wilmot EG, Amoaku WM. Diabetic retinopathy for the non-ophthalmologist. Clin Med (Lond). 2022;22(2):112-116. doi:10.7861/clinmed.2021-0792
10. Scanlon PH. The contribution of the English NHS Diabetic Eye Screening Programme to reductions in diabetes-related blindness, comparisons within Europe, and future challenges. Acta Diabetol. 2021;58(4):521-530. doi:10.1007/s00592-021-01687-w
11. Altomere F, Kherani A, Lovshin J. 2018 Clinical Practice Guidelines Chapter 30: Retinopathy. Can J Diabetes. 2018; 42(1);S210-S216. doi:10.1016/j.jcjd.2017.10.027
12. Feldman-Billard S, Dupas B. Eye disorders other than diabetic retinopathy in patients with diabetes. Diabetes Metab. 2021;47(6):101279. doi:10.1016/j.diabet.2021.101279
13. Almazroa A, Almatar H, Alduhayan R, et al. The Patients' Perspective for the Impact of Late Detection of Ocular Diseases on Quality of Life: A Cross-Sectional Study. Clin Optom (Auckl). 2023;15:191-204. doi:10.2147/OPTO.S422451
14. Ghazal M, Al Khalil Y, Alhalabi M, Fraiwan L, El-Baz A. Early detection of diabetes using retinal OCT images. Diabetes and Retinopathy: Volume 2: Computer-Assisted Diagnosis. 2020;2:173-204. doi:https://doi.org/10.1016/B978-0-12-817438-8.00009-2