Inner and Outer Retinal Volumetric and Morphologic Analysis of the Macula with Spectral Domain Optical Coherence Tomography in Retinitis Pigmentosa

PURPOSE: To use spectral domain optical coherence tomography (OCT) to assess the features of the inner and outer layers of the macula in subjects with retinitis pigmentosa (RP). DESIGN: Prospective observational comparative study. MATERIALS AND METHODS: Subjects with RP with reduced central visual acuity and central macular thinning (RP group) underwent spectral domain OCT evaluation along with age-matched healthy control subjects (control group). Using the E-MM5 raster protocol, a 5 × 5 mm central macular cut was acquired with inner and outer macular volumes serving as the primary outcome measures. A structural analysis of the inner and outer retinal layers at the macula in the RP group was also performed using the HD cross-line protocol. RESULTS: The RP group comprised six eyes of six RP subjects and control group comprised six eyes of six control subjects. The outer macular volume was significantly lower (P<0.05) in the RP group (2.01±0.44 mm(3)) compared to the control group (4.68±0.16 mm(3)). There was no difference in the mean inner macular volume between the RP group (2.46±0.24 mm(3)) and the control group (2.55±0.22 mm(3)). No significant structural alteration was noted in the inner retinal layers of the RP group. There was no significant correlation (r = -0.04, P>0.05) between best-corrected visual acuity and outer macular volume in the RP group. CONCLUSIONS: Spectral domain OCT findings confirm that RP preferentially affects the outer retinal layers in the macula. Although the number of patients included in this study was small, it demonstrated relatively well-preserved volume and morphology of the inner retinal layers using spectral domain OCT.