Patients with type 2 diabetes (T2D) have an increased risk of developing serious eye conditions such as retinopathy, glaucoma, and cataracts.1 Researchers have hypothesized that uncontrolled glycemic levels cause damage to the blood vessels in the eye, that can eventually advance to more serious conditions.
According to the 2025 American Diabetes Association Standards of Care in Diabetes, people with T2D should have a comprehensive eye exam with dilation at the time of diagnosis.2 If there is no evidence of retinopathy, continued screening is recommended every 1-2 years. If any evidence of retinopathy is present, screenings are recommended at least annually. The American Academy of Ophthalmology recommends that patients with T2D have an eye exam at diagnosis and at least yearly thereafter.3 Both organizations emphasize that a dilated eye exam is preferred, but digital imaging methods are becoming more popular and are also acceptable.2,3
Individuals with diabetes can help to prevent complications including eye conditions by managing their blood sugar through a combination of healthy eating, regular exercise, and prescribed medications.4-6
Diabetic Retinopathy
Diabetic retinopathy is a progressive disorder affecting the small blood vessels of the retina caused by the prolonged impact of diabetes mellitus.4 Diabetic retinopathy occurs when high blood sugar damages the blood vessels in the retina, leading to increased vascular permeability and/or vessel occlusion leading to retinal ischemia.7 These physiological changes can cause swelling or reduced oxygen supply that if left untreated, can cause vision damage or loss. Diabetic retinopathy is both preventable and treatable, with successful prevention and treatment depending heavily on early detection.
Diabetic retinopathy is common; a 2021 study estimated that approximately 9.6 million people in the United States have diabetic retinopathy, accounting for more than 26% of those with diabetes.8 This study estimates that 1.84 million people with diabetes (5.06% of those with diabetes) have vision-threatening diabetic retinopathy. This study does not differentiate between Type 1 and Type 2 diabetes mellitus.
A seminal study from 1998 in the United Kingdom found that in patients (n=3,867) with newly diagnosed T2D, intensive glycemic control reduced the risk of microvascular events such as diabetic retinopathy by 25% (11.4 vs. 8.6 events per 1,000 person-years).9 Additionally, an analysis from the same UK cohort found that a 1% reduction in hemoglobin A1c was associated with a 37% decrease in risk for microvascular complications (adjusted incidence 6.1 per 1,000 person-years for <6% A1c, 9.3 for 6-7% A1c, 14.2 for 7-8% A1c, 22.8 for 8-9% A1c, 40.4 for 9-10%, and 57.8 for >10% A1c).10
The prevalence of diabetic retinopathy increases with duration of T2D, underscoring the importance of early screening and sustained follow-up. A retrospective cohort study of 2,272 patients with T2D found that only 1.1% of patients had diabetic retinopathy at the time of diagnosis, jumping to 6.6% after 0-5 years, 12% after 5-10 years, 24% after 10-15 years, all the way up to 63% 30 years or more after diagnosis of T2D.11
Glaucoma and Cataracts
In addition to diabetic retinopathy, patients with T2D are at an increased risk of developing glaucoma and cataracts, the two leading causes of vision loss worldwide (15.2 million and 3.6 million cases, respectively).12
Glaucoma is a disease characterized by damage to the optic nerve, generally caused by increased intraocular pressure as fluid does not drain out of the eye normally.13,14 A 2015 meta-analysis (n=2,445,203) found that the prevalence of glaucoma was 9.5% in participants with diabetes compared to 2.6% in participants without diabetes or pre-diabetes (Relative Risk [RR] 1.48, 95% CI [1.29-1.71], p<0.001).15 The pathophysiology behind the increased incidence of glaucoma in those with T2D is not entirely understood, although it is thought to be connected to intraocular pressure increases linked to elevated serum glucose levels or microvascular damage leading to increased susceptibility.15,16 Ensuring that patients with diabetes have regular eye exams with intraocular pressure measurement can potentially help catch glaucoma early and preserve vision.
T2D also increases the risk for developing cataracts, which occur when the lens of the eye becomes clouded, causing visual impairments.17,18 A 2018 population-based study (n=56,510) in the United Kingdom found that the incidence rate of cataracts was 20.4 per 1,000 person-years in those with diabetes compared to 10.8 in the general population.19 Proposed mechanisms for the formation of cataracts in diabetic patients include osmotic stress as a result of swelling in the cortical lens fibers, oxidative stress from the high blood sugar levels, or the accumulation of sorbitol in the lens.17,20
References
- Solomon SD, Chew E, Duh EJ, et al. Diabetic Retinopathy: A Position Statement by the American Diabetes Association. Diabetes Care. 2017-03-01 2017;40(3):412-418. doi:10.2337/dc16-2641
- Elsayed NA, Mccoy RG, Aleppo G, et al. Retinopathy, Neuropathy, and Foot Care: Standards of Care in Diabetes—2025. Diabetes Care. 2025-01-01 2025;48(Supplement_1):S252-S265. doi:10.2337/dc25-s012
- Lim JI, Kim SJ, Bailey ST, et al. Diabetic Retinopathy Preferred Practice Pattern®. Ophthalmology. 2025:S0161-6420 (24) 00784-X.
- 12. Retinopathy, Neuropathy, and Foot Care: Standards of Care in Diabetes-2024. Diabetes Care. Jan 1 2024;47(Suppl 1):S231-s243. doi:10.2337/dc24-S012
- Fong DS, Aiello L, Gardner TW, et al. Retinopathy in Diabetes. Diabetes Care. 2004;27(suppl_1):s84-s87. doi:10.2337/diacare.27.2007.S84
- 3. Prevention or Delay of Diabetes and Associated Comorbidities: Standards of Care in Diabetes-2024. Diabetes Care. Jan 1 2024;47(Suppl 1):S43-s51. doi:10.2337/dc24-S003
- Jampol LM, Glassman AR, Sun J. Evaluation and care of patients with diabetic retinopathy. New England Journal of Medicine. 2020;382(17):1629-1637.
- Lundeen EA, Burke-Conte Z, Rein DB, et al. Prevalence of Diabetic Retinopathy in the US in 2021. JAMA Ophthalmology. 2023/08/01;141(8)doi:10.1001/jamaophthalmol.2023.2289
- Group UPDS. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). The lancet. 1998;352(9131):837-853.
- Stratton IM, Adler AI, Neil HAW, et al. Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): prospective observational study. BMJ : British Medical Journal. 2000 Aug 12;321(7258)doi:10.1136/bmj.321.7258.405
- Voigt M, Schmidt S, Lehmann T, et al. Prevalence and progression rate of diabetic retinopathy in type 2 diabetes patients in correlation with the duration of diabetes. Experimental and Clinical Endocrinology & Diabetes. 2018;126(09):570-576.
- Steinmetz JD, Bourne RR, Briant PS, et al. Causes of blindness and vision impairment in 2020 and trends over 30 years, and prevalence of avoidable blindness in relation to VISION 2020: the Right to Sight: an analysis for the Global Burden of Disease Study. The Lancet Global Health. 2021;9(2):e144-e160.
- Schuster AK, Erb C, Hoffmann EM, Dietlein T, Pfeiffer N. The Diagnosis and Treatment of Glaucoma. Dtsch Arztebl Int. Mar 27 2020;117(13):225-234. doi:10.3238/arztebl.2020.0225
- Boyd K. Understanding Glaucoma: Symptoms, Causes, Diagnosis, Treatment. American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/what-is-glaucoma
- Zhao D, Cho J, Kim MH, Friedman DS, Guallar E. Diabetes, Fasting Glucose, and the Risk of Glaucoma. Ophthalmology. 2015/01/01;122(1)doi:10.1016/j.ophtha.2014.07.051
- Zhao Y-X, Chen X-W. Diabetes and risk of glaucoma: systematic review and a Meta-analysis of prospective cohort studies. International Journal of Ophthalmology. 2017 Sep 18;10(9)doi:10.18240/ijo.2017.09.16
- Obrosova IG, Chung SS, Kador PF. Diabetic cataracts: mechanisms and management. Diabetes Metab Res Rev. Mar 2010;26(3):172-80. doi:10.1002/dmrr.1075
- Boyd K. What Are Cataracts? https://www.aao.org/eye-health/diseases/what-are-cataracts
- Becker C, Schneider C, Aballéa S, et al. Cataract in patients with diabetes mellitus-incidence rates in the UK and risk factors. Eye (Lond). Jun 2018;32(6):1028-1035. doi:10.1038/s41433-017-0003-1
- Kiziltoprak H, Tekin K, Inanc M, Goker YS. Cataract in diabetes mellitus. World journal of diabetes. 2019;10(3):140.
