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Tina Ristau, Jessica Voegeler, Gabriele Lang, Sandra Liakopoulos, RELATION study group; Relevance of inner versus outer retinal thickness in diabetic macular edema in the RELATION study. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2376. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze the correlation between inner and outer retinal thickness on Optical Coherence Tomography (OCT) with visual acuity (VA) and fluorescein angiography (FA) parameters, and the response to treatment in diabetic macular edema (DME).
OCT volume scans and FA images from the RELATION study were analyzed by certified reading center graders. In the multicenter, double masked clinical trial 128 patients with visual impairment due to DME were randomized 2:1 to ranibizumab in combination with focal/grid laser photocoagulation (combined group) or focal/grid laser photocoagulation combined with sham injections (laser group) with a follow-up of up to 12 months. Manual quantitative OCT analysis was performed and mean central retinal thickness (CRT) was calculated for the neurosensory retina, the outer retina (outer nuclear layer and photoreceptors) and the inner retina (inner limiting membrane to outer retina). Thickness values were correlated with ETDRS VA, severity of macular ischemia and type of DME on FA.
OCT volume scans of 109 patients were available for analysis (spectral and time domain OCT). At baseline, VA showed significant correlations with CRT for neurosensory retina (R=-0.44, p<0.0001), inner retina (R=-0.22, p<0.05) and outer retina (R=-0.28, p<0.01). Eyes with greater inner retinal thickness values at baseline had lower VA values at last follow-up (R=-0.32, p<0.001), whereas outer retinal thickness appeared to have no significant prognostic value. Eyes with fluorescein leakage predominantly due to telangiectasia showed greater inner retinal thickness values than eyes with leakage predominantly due to microaneurysms (p<0.01). Outer retinal thickness values showed no difference between groups. There was no difference regarding severity of macular ischemia. Eyes in the combination group showed significantly stronger decrease in inner retinal thickness than eyes in the laser group (R=0.34, p<0.001), but no significant difference in reduction of outer retinal thickness values.
CRT values for the inner and the outer retina show differences regarding the type of DME on FA, VA outcome as well as the response to treatment. Subanalysis of various retinal layers on OCT may be relevant as outcome parameters in DME clinical trials.
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