Quantitative Assessment of Outer Retinal Layer and Photoreceptor Outer Segment Layer and Their Relation to Visual Acuity in Diabetic Macular Edema

PURPOSE: To compare outer retinal layer (ORL) thickness and photoreceptor outer segment (PROS) length between normal eyes and eyes with diabetic macular edema (DME), and also, to study the correlation between central macular thicknesses (CMT), ORL, and PROS length with best corrected visual acuity (BCVA) in DME. METHODS: 80 eyes were included in the study; they were divided into two groups, group Ι (40 normal eyes) and group ΙΙ (40 eyes) with DME. Complete ophthalmic examination and OCT were done for all eyes. Comparison between ORL and PROS was done between both groups; also, correlation between ORL thickness, PROS length, and CMT with BCVA in group ΙΙ was studied. RESULTS: CMT was greater in group ΙΙ than group Ι (392.70 ± 62.91 and 265.73 ± 17.17, respectively) (SS, p < 0.001). ORL thickness was statistically significantly greater in group Ι than group ΙΙ (104.80 ± 4.94, 93.68 ± 6.34, p < 0.001). Regarding PROS length, it was statistically significantly greater in group Ι than group ΙΙ (31.38 ± 3.4 and 26.65 ± 3.39, respectively, p < 0.001). There was moderate correlation between BCVA and ORL thickness (r = −0.440, p=0.004) and strong correlation between BCVA and PROS length in group ΙΙ (r = − 0.690, p < 0.001), while there was weak correlation between BCVA and CMT (r = 0.198, p=0.220). CONCLUSION: Both ORL thickness and PROS length were greater in healthy normal eyes than eyes with DME. BCVA was correlated better with PROS length and ORL thickness than CMT.