Relationship between Optical Coherence Tomography–Measured Central Retinal Thickness and Visual Acuity in Diabetic Macular Edema
Received 28 March 2006; accepted 17 June 2006. published online 21 November 2006.
Objective
To compare optical coherence tomography (OCT)-measured retinal thickness and visual acuity in eyes with diabetic macular edema (DME) both before and after macular laser photocoagulation.
Design
Cross-sectional and longitudinal study.
Participants
Two hundred ten patients (251 eyes) with DME enrolled in a randomized clinical trial of laser techniques.
Methods
Retinal thickness was measured with OCT and visual acuity was measured with the electronic Early Treatment of Diabetic Retinopathy procedure.
Main Outcome Measures
Optical coherence tomography-measured center point thickness and visual acuity.
Results
The correlation coefficients for visual acuity versus OCT center point thickness were 0.52 at baseline and 0.49, 0.36, and 0.38 at 3.5, 8, and 12 months after laser photocoagulation. The slope of the best fit line to the baseline data was approximately 4.4 letters (95% confidence interval, 3.5–5.3) of better of visual acuity for every 100-μm decrease in center point thickness at baseline with no important difference at follow-up visits. Approximately one third of the variation in visual acuity could be predicted by a linear regression model that incorporated OCT center point thickness, age, hemoglobin A1C, and severity of fluorescein leakage. The correlation between change in visual acuity and change in OCT center point thickening 3.5 months after laser treatment was 0.44, with no important difference at the other follow-up times. A subset of eyes showed paradoxical improvements in visual acuity with increased center point thickening (7%–17% at the 3 time points) or paradoxical worsening of visual acuity with a decrease in center point thickening (18%–26% at the 3 time points).
Conclusions
There is modest correlation between OCT-measured center point thickness and visual acuity, and modest correlation of changes in retinal thickening and visual acuity after focal laser treatment for DME. However, a wide range of visual acuity may be observed for a given degree of retinal edema. Thus, although OCT measurements of retinal thickness represent an important tool in clinical evaluation, they cannot substitute reliably as a surrogate for visual acuity at a given point in time. This study does not address whether short-term changes on OCT are predictive of long-term effects on visual acuity.
Correspondence to David J. Browning, MD, c/o Jaeb Center for Health Research, 15310 Amberly Drive, Suite 350, Tampa, FL 33647. E-mail: drcrnet@jaeb.org.
Manuscript no. 2006-373.
Supported by a cooperative agreement from the National Eye Institute, Bethesda, Maryland, and National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland (grant nos.: EY14231, EY14269, EY14229).
⁎ The members of the Writing Committee and a list of the members of the Diabetic Retinopathy Clinical Research Network (DRCR.net) participating in the trial appear in “Appendix.”
ABSTRACT