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OCT changes minimally related to visual acuity variation
Changes in central subfield thickness may account for only a low percentage of total variations in visual acuity changes, according to findings published in JAMA Ophthalmology.
Neil M. Bressler, MD, and colleagues determined that changes in OCT central subfield thickness (OCT CST) do not accurately indicate changes in visual acuity in patients undergoing anti-VEGF treatment.
The researchers examined the data of 652 participants (median age, 61 years; 46.6% women) receiving six monthly intravitreal anti-VEGF injections over 3 years. The main outcomes were the association between changes in visual acuity letter score with changes in CST at intervals of 12 weeks, 1 year and 2 years after randomization to aflibercept, bevacizumab or ranibizumab.
Bressler and colleagues identified the correlation between CST and visual acuity at the follow-ups at 12 weeks in 616 patients (0.24; 95% CI, 0.16-0.31) and 609 patients in 1 year (0.31; 95% CI, 0.24-0.38). At the 2-year follow-up mark, the CST-visual acuity correlation in 566 patients was 0.23 (95% CI; 0.15-0.31).
In the same follow-up periods, the correlation coefficients of change in visual acuity vs. change in OCT CST was 0.36 (95% CI; 0.29-0.43) at 12 weeks and 1 year and 0.33 (95% CI; 0.26-0.41) at 2 years, the researchers wrote.
“These findings do not support using changes in OCT CST in lieu of changes in visual acuity in phase 3 clinical trials evaluating anti-VEGF treatments for diabetic macular edema and suggest that OCT CST changes are not typically a reliable guide to informing a physician or patient about changes in visual acuity with anti-VEGF treatment for an individual eye,” Bressler and colleagues wrote. – by Earl Holland Jr.
Disclosures: Bressler reports receiving grants from the National Eye Institute during the study as well as grants from Bayer, Genentech/Roche, Novartis and Samsung Bioepis. Please see the study for all other authors’ relevant financial disclosures.
Perspective
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The clinical take-home from this study is that SD-OCT CST changes are not a reliable surrogate for visual outcomes after anti-VEGF therapy for diabetic macular edema (DME). This is not entirely surprising. It is well known that macular ischemia is a major contributor to poor central vision in diabetics and it does not respond to anti-VEGF treatment. Eyes with greater macular ischemia will experience less vision improvement after anti-VEGF therapy than eyes with less macular nonperfusion.
The study has limitations, for example, the lack of consideration of potential influences from other SD-OCT measurements and retinal findings when additional macular pathologies are present. Furthermore, the results of the study are only applicable to the Diabetic Retinopathy Clinical Research Network treatment protocol and may not reflect the same results of other treatment populations or other treatment protocols for DME. The study failed to provide a reason why there was only mild-moderate correlation between change in visual acuity and CST.
Clinicians should be aware that delayed treatment for DME is positively associated with worse visual outcomes. In general, BCVA at the time of the initial treatment tends to be the strongest determinant of final VA. Other studies have demonstrated that increased age and degree of baseline diabetic retinopathy were associated with less improvement in BCVA with anti-VEGF therapy. This should be taken into consideration when educating patients prior to referral. However, making direct correlations between OCT morphological findings and potential visual outcomes should be guarded.
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