Correlation Between Ganglion Cell Layer Thinning and Poor Visual Function After Resolution of Diabetic Macular Edema

PURPOSE. To assess the thickness of the ganglion cell-inner plexiform layer (GCIPL) in eyes with resolved diabetic macular edema (DME), using spectral-domain optical coherence tomography (SD-OCT), and its relationship with the visual function. METHODS. This retrospective observational case-control cohort study included eyes of diabetic patients with resolved DME (r-DME eyes), that is, normal central macular thickness (CMT) after treatment of DME, and eyes of aged-matched diabetic patients without maculopathy (no-DME eyes). The GCIPL thickness was measured on a macular cube SD-OCT scan using a specific automatic segmentation algorithm. Linear regression analyses were performed to determine the association between the GCIPL thickness and the visual acuity (VA) measured at the time of the OCT measurement. RESULTS. Average GCIPL thickness was reduced in r-DME eyes compared with no-DME eyes (74 +/- 14 mu m versus 83.2 +/- 6 mu m, P = 0.0189), whereas no significant difference in mean CMT was observed (260.0 +/- 34 mu m versus 265.7 +/- 22 mu m, P = 0.847). Visual acuity significantly correlated with the average GCIPL thickness (r = 0.8, P < 0.0001) and minimum GCIPL thickness (r = 0.84, P < 0.0001) in r-DME eyes. CONCLUSIONS. Despite favorable anatomic response and restoration of a CMT in the range of normal values after resolution of DME, the GCIPL thickness in r-DME eyes was lower than that in no-DME eyes and correlated with the VA. These results suggest that inner retinal alterations occurring in patients with DME and diabetic retinopathy may lead to visual deficiency persisting after treatment.