Visual Acuity Measurement and Ocular Co-Morbidity in Diabetic Retinopathy Screening

¹ Cheltenham General Hospital, United Kingdom
² Gloucestershire Hospitals NHS Foundation Trust, United Kingdom

^* To whom correspondence should be addressed. E-mail: peter{at}p5sca.demon.co.uk.

Accepted 2 February 2008

	Abstract

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.