Research has suggested that myopia may be associated with less severe diabetic retinopathy (DR), but this hypothesis, supported with small case series, has never been tested in larger prospective studies—until recently. A new clinical trial assessed the relationship between refractive error and DR and included a cohort of patients in the Diabetes Control and Complications Trial and its follow-up study Epidemiology of Diabetes Interventions and Complications.

The patient cohort consisted of those with Type I diabetes, followed for more than 30 years with serial refractive error and DR stage measurements. The study measured DR stage with fundus photographs taken every six months and measured refractive error at regular intervals throughout the two studies.

The researchers found that hyperopia was associated with higher risk of two-step progression, three-step progression and proliferative DR, compared with emmetropia in unadjusted models. These associations were still significant after adjusting for diabetes-related factors such as smoking status, age, sex, blood pressure, albumin excretion rate and triglycerides. Most importantly, myopia was not associated with any of the five DR outcomes in unadjusted models, and only marginally associated with two-step progression in adjusted models.

The researchers concluded that myopia is not associated with DR progression risk, but that hyperopia is an independent risk factor for two- and three-step DR progression and proliferative DR.

Hainsworth DP, Gao X, Lachin JM, et al. Refractive error and retinopathy outcomes in type 1 diabetes: The DCCT/EDIC Study. Ophthalmology. September 13, 2020. [Epub ahead of print].