Diabetic retinopathy not the primary cause of visual loss in diabetic patients, study finds

The majority of visual loss among patients with diabetes appears to be attributable to causes other than diabetic retinopathy, according to a large, randomized study by researchers in the United Kingdom.

"[Best corrected visual acuity] alone is not a reliable criterion in predicting [sight-threatening diabetic retinopathy]," the study authors said.

Peter H. Scanlon, MBBS, MD, FRCP, DCH, DRCOG, DO, MRCOphth, and colleagues at Cheltenham General Hospital obtained standardized logMAR BCVA measurements and slit-lamp biomicroscopy examinations for 1,549 patients with diabetes selected from a digital photographic screening program. The investigators evaluated the relationship between BCVA, age, diabetes type, sight-threatening diabetic retinopathy and ocular comorbidity. They published their results in the June issue of British Journal of Ophthalmology.

Subnormal vision of 0.3 logMAR or higher in the better-seeing eye was found in 9% of patients; blindness of 1.3 logMAR or higher in the better-seeing eye was found in 0.45% of patients.

"The sensitivity, specificity, and positive and negative predictive values of using subnormal vision to screen for [sight-threatening diabetic retinopathy] in an individual eye were 33.4%, 85.9%, 18.6% and 93%, respectively," the authors said.

Important contributory causes of moderate loss (logMAR visual acuity between 0.50 and 0.98) and of acuity blindness (logMAR higher than 1.0) in an individual eye were lenticular opacity in 49% of patients, macular degeneration in 29% of patients, diabetic maculopathy in 15% of patients, other media causes — including corneal opacity — in 13% of patients, and amblyopia in 10% of patients, according to the study.