Aims: To evaluate the relationship between best corrected visual acuity (BCVA), age, type of diabetes, sight threatening diabetic retinopathy (STDR) and ocular co-morbidity.
Methods: 1,549 randomly selected people with diabetes mellitus (DM) from a county-wide digital photographic screening programme had standardised logMAR BCVA measurement, followed by slit lamp biomicroscopy examination by an experienced ophthalmologist.
Results: Subnormal vision (logMAR ≥ 0.3, Snellen ≤ 6/12) and blindness (logMAR > 1.3, Snellen < 3/60) in the better-seeing eye were found in 9.0% and 0.45%. The sensitivity, specificity and positive and negative predictive values of using subnormal vision to screen for STDR in an individual eye was 33.4%, 85.9%, 18.6% and 93.0% respectively. Important contributory causes of moderate visual loss (LogMAR 0.50 to 0.98, Snellen 6/18 or worse but better than 6/60) and of Acuity Blindness (LogMar ≥ 1.0, Snellen 6/60 or worse) in an individual eye were lenticular opacity (including capsular opacification) 49%, macular degeneration (including myopic degeneration) 29%, diabetic maculopathy 15%, other media causes (including corneal opacity) 13% and amblyopia 10%.
Conclusion: The majority of visual loss in a population with diabetes is due to causes other than DR. BCVA alone is not a reliable criterion in predicting STDR.