Correlation of outer retinal microstucture and foveal thickness with visual acuity after pars plana vitrectomy for complications of proliferative diabetic retinopathy.

PURPOSE: To compare spectral domain optical coherence tomography (SDOCT)-measured macular thickness, outer retinal layers architecture, and best-corrected visual acuity (BCVA) in eyes with proliferative diabetic retinopathy after pars plana vitrectomy. METHODS: In this retrospective case study, consecutive eyes operated by single surgeon were included. Retinal thickness was measured with SDOCT (Cirrus OCT; Carl Zeiss Meditec, Inc) as follows: automated central 1-mm subfield thickness (CFT), manually measured central foveal point thickness (CPT), integrity of external limiting membrane (ELM), and photoreceptor inner and outer segments (IS/OS). Three vitreoretinal-trained masked experts independently graded ELM and IS/OS layers. RESULTS: Of the 36 eyes included, 50% were those of women whose mean age was 49 years (range, 24-66 years). Mean preoperative BCVA was 20/600 (range, light perception to 20/80) and mean postoperative follow-up was 19 months (range, 4-43 months). Mean postoperative BCVA improved to 20/80 (range, counting fingers to 20/25; P < 0.0001) with mean SDOCT 1 mm CFT of 260 μm and manual CPT of 236 μm. Mean ELM integrity grade was 1.9 (range, 0-5), while the mean grade of IS/OS integrity was 2.2 (range, 0-5). The correlation coefficients (r) were 0.17 (P = 0.32) for logarithm of the minimum angle of resolution BCVA versus SDOCT automated CFT, 0.192 (P = 0.26) for BCVA versus SDOCT CPT, 0.52 (P = 0.012) for BCVA versus ELM, and 0.55 (P = 0.006) for BCVA versus IS/OS. CONCLUSION: SDOCT-measured CFT and CPT correlate weakly with BCVA, while ELM and IS/OS integrity correlates well with BCVA. Outer retinal microstructure may represent anatomically better level of postoperative visual function than retinal thickness after pars plana vitrectomy for complications of proliferative diabetic retinopathy.