Retinal Thickness and Visual Acuity in Diabetic Macular Edema: An Optical Coherence Tomography-Based Study

Objective: To determine the relationship between foveal (retinal) thickness and visual acuity in diabetic macular edema through optical coherence tomography (OCT) mapping software. Study Design: Cross-sectional descriptive study. Place and Duration of Study: The Retina Clinic of Al-Shifa Trust Eye Hospital, Rawalpindi, from August 2011 to August 2012. Methodology: Eighty eyes of 68 patients with clinical diagnosis of diabetic macular edema, based on complete ophthalmic examination, were enrolled. The best-corrected visual acuity was recorded on logMar scale. OCT imaging was performed through dilated pupil by experienced operator. Foveal thickness was determined. OCT parameters of macular thickness were analysed with baseline variables including age, duration since diagnosed with diabetes, and visual acuity. Results: The mean visual acuity was 0.81 (0.2 - 1.8) logMar units. The average foveal thickness was 395.09 +/- 142.26 (183 - 825 pm). There was moderate correlation between foveal thickness and visual acuity (r(s) = 0.574, p < 0.001), absent in those who had visual acuity worse than 1 logMar. There was a weak positive association between foveal thickness and the duration of diabetes (r(s) = 0.249, p < 0.05). There was, however, no correlation between foveal thickness and age (r(s) = 0.012, p=0.919). Conclusion: There is a moderate correlation between visual acuity and degree of foveal thickening in diabetic macular edema, hence two cannot be used interchangeably in clinical practice.