Thickness mapping of the inner retina by spectral-domain optical coherence tomography in an N-methyl-D-aspartate-induced retinal damage model.

Spectral-domain optical coherence tomography (SD-OCT) is an interferometric optical tomography technique and provides high resolution and noninvasive visualization of retinal morphology. The purpose of this study was to assess the utility of thickness maps and quantitative thickness measurements of the ganglion cell complex (GCC: retinal nerve fiber layer, ganglion cell layer, and inner plexiform layer) obtained by SD-OCT of a mouse model of N-methyl-d-aspartate (NMDA)-induced retinal damage. SD-OCT imaging was performed in ddY mice at 1, 3, and 7 days and 1 month after intravitreal injection of NMDA. GCC thickness maps and circle cross-sectional OCT images were made from volumetric OCT images. The GCC thickness was measured on a cross-sectional OCT image on a circle with a radius 300 μm from the center of the optic nerve disc. Histological analysis was conducted by measuring the GCC thickness at the same time intervals. The thickness maps and the quantitative thickness values of GCC showed thickness changes at each time point in the NMDA-treated mice when compared with normal and vehicle-treated mice. Both the OCT sectional images and the histological images revealed increases in GCC thickness at 1 day, followed by decreases from 3 days to 1 month after NMDA injection. The GCC thickness measured using OCT sectional images correlated with the thickness measured using histological images. In conclusion, GCC thickness mapping is a useful method for evaluating NMDA-induced retinal degeneration in mice.