Relationship of Visual Acuity to Macular Thickness and Duration of Macular Edema in Diabetic Retinopathy and Irvine-Gass Syndrome

Abstract

Purpose:: To examine the relationship between optical coherence tomography (OCT) measured central macular thickness (CMT) and visual acuity in patients with clinically significant diabetic macular edema (CSDME) before and after treatment and according to duration of macular edema (ME) prior to argon laser treatment. Also, to compare this relationship to that in patients with pseudophakic macular edema (Irvine-Gass syndrome; IGS) before and after topical anti-inflammatory drug treatment.

Methods:: The medical charts and computerized OCT records of 144 patients with CSDME and 27 patients with pseudophakic macular edema were studied retrospectively. CMT as measured by OCT mapping software was correlated with Snellen best-corrected visual acuity (BCVA) in the various patient groups. Snellen visual acuities were converted to decimal equivalents for statistical analysis.

Results:: CMT correlated with BCVA before (R = -0.639, p < 0.0005, n = 61) and after (R = -0.510, p < 0.0005, n = 125) treatment of patients with CSDME. This correlation did not differ significantly among patients treated within 8 days of diagnosis (1^st quartile of duration, R = -0.605, p < 0.0005, n = 32), between 8 and 19 days (2^nd quartile, R = -0.525, p < 0.005, n = 29), between 19 and 46 days (3rd quartile, R = -0.437, p < 0.01, n = 33), or between 46 and 911 days (4^th quartile, R = -0.516, p < 0.0025, n = 31). CMT did not correlate with BCVA in patients with IGS before (R = -0.121, p > 0.25, n = 21) or after (R = -0.215, p >0 .20, n = 20) treatment.

Conclusions:: This study agrees with recent findings by the Diabetic Retinopathy Clinical Research Network, that CMT as measured by OCT correlates modestly with BCVA in patients with CSDME. Our study found a much poorer relationship between these two variables in IGS. Our results also suggest that the relationship between CMT and BCVA is not dependent on duration of ME prior to treatment. OCT remains a powerful tool in measurement of CMT. However, its correlation with visual acuity is modest in CSDME and even poorer in IGS.

Keywords: macula/fovea • edema • retina