Elsevier

Ophthalmology

Volume 114, Issue 3, March 2007, Pages 525-536
Ophthalmology

Original Article
Relationship between Optical Coherence Tomography–Measured Central Retinal Thickness and Visual Acuity in Diabetic Macular Edema

https://doi.org/10.1016/j.ophtha.2006.06.052Get rights and content

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.

Section snippets

Patients and Methods

This study analyzed data collected from a multicenter randomized clinical trial comparing modified Early Treatment of Diabetic Retinopathy (ETDRS) laser photocoagulation with a modified macular grid approach for the treatment of DME (protocol available at http://public.drcr.net; accession date, May 13, 2006). The study, funded by the National Eye Institute of the National Institutes of Health, U.S. Department of Health and Human Services, was conducted by the Diabetic Retinopathy Clinical

Results

The study included 210 participants, of whom 41 (20%) had 2 study eyes and 169 (80%) had 1 study eye, for a total of 251 eyes. Baseline characteristics of the participants and of the study eyes are provided in Table 1.

Discussion

Although it has long been appreciated that central macular thickening can be associated with a decrease in visual acuity and that treatments that reduce such retinal thickening can improve vision, quantitative evaluation of these relationships and the effect of laser photocoagulation are scarce. In this study, we documented a modest correlation between best-corrected visual acuity and OCT center point thickness before focal laser photocoagulation, as well as a modest correlation between change

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    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.”

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