New research published in JAMA Ophthalmology assessing the link between common eye diseases and diabetes revealed that in a population of European ethnicity, diabetes was associated with cataract development, but diabetes medication was not.

Furthermore, treatment with metformin was associated with a lower risk of open-angle glaucoma (OAG) while other diabetes medications were associated with a lower risk of age-related macular degeneration (AMD), authors wrote.

However, interventional clinical trials are required to determine proof of benefit for these medications.

Together, OAG, AMD, and cataracts are the leading causes of blindness around the world and account for about 65% of blindness in adults over the age of 50. Over the next 2 decades, prevalence of OAG and AMD is expected to increase alongside gains in life expectancy, researchers explained.

Previous research has suggested a potential protective effect of metformin on OAG and AMD with mechanisms appearing independent of glucose-lowering effects.

To better elucidate the association between metformin, insulin, and sulfonylurea derivatives with OAG, AMD and cataracts, investigators assessed data from the prospective Rotterdam Study. To investigate potential comorbidity, they also looked at links between untreated type 2 diabetes (T2D) and the 3 eye conditions.

Rotterdam study enrollment took place between April 1990 and June 2014 and participants underwent both baseline examinations and 5-year follow-up visits. Of the 14,926 participants, a total of 11,260 were included in the current analysis, all of whom underwent ophthalmologic examinations, had measurements of serum-glucose performed at baseline, continuous medication monitoring, and completed at least 1 follow-up visit.

“Medication data were obtained from 7 fully automated pharmacies using a centralized computer network in the study district from January 1, 1991, onward,” authors wrote.

Mean (SD) patient age was 65.1 (9.8) years while 58.7% of the cohort were women. The Rotterdam study was based in The Netherlands and 98% of participants were of European ancestry. Nearly 30% of participants were diagnosed with T2D (28.4%), 4.4% were diagnosed with OAG, 17.6% with AMD, and 37.3% with cataract.

Analyses revealed:

• Untreated T2D was associated with a higher risk of OAG (odds ratio [OR], 1.50; 95% CI, 1.06-2.13; P  =  .02), AMD (OR, 1.35; 95% CI, 1.11-1.64; P  =  .003), and cataract (OR, 1.63; 95% CI, 1.39-1.92; P  < .001)
• T2D treated with metformin was associated with a lower risk of OAG (OR, 0.18; 95% CI, 0.08-0.41; P  < .001)
• Other diabetes medication (ie, insulin, sulfonylurea derivates) was associated with a lower risk of AMD (combined OR, 0.32; 95% CI, 0.18 to 0.55; P  < .001)
• The cumulative lifetime risk of OAG was lower for individuals taking metformin (1.5%; 95% CI, 0.01%-3.1%) than for individuals without T2D (7.2%; 95% CI, 5.7%-8.7%)
• The lifetime risk of AMD was lower for individuals taking other diabetes medication (17.0%; 95% CI, 5.8%-26.8% vs 33.1%; 95% CI, 30.6%-35.6%)

Overall, “metformin had the strongest inverse association with OAG followed by AMD but was not associated with cataract,” authors wrote.

While the study’s prospective population-based design and large sample population mark strengths, residual confounding may have been present and a low number of patients with OAG was assessed.

However, the magnitude of associations seen warrants interventional clinical trials, researchers concluded.

Reference

Vergroesen JE, Thee EF, Ahmadizar F, et al. Association of diabetes medication with open-angle glaucoma, age-related macular degeneration, and cataract in the Rotterdam study. JAMA Ophthalmol. Published online May 19, 2022. doi: 10.1001/jamaophthalmol.2022.1435