Mapping the thickness of retinal layers using Spectralis spectral domain optical coherence tomography in Indian eyes

Purpose: This study aimed at establishing the normative data for the thickness of macular layers on Spectralis Spectral-domain optical coherence tomography (SD-OCT) in healthy Indian eyes and testing the effects of age, gender, central corneal thickness (CCT), and intraocular pressure (IOP) on such values. Methods: This cross-sectional study was done on 308 eyes of 159 healthy subjects. OCT scans were obtained using the posterior pole asymmetry scan protocol. From the thickness map, data were grouped into nine Early Treatment Diabetic Retinopathy Study (ETDRS) macular sectors. Correlation between retinal thickness and age/IOP/CCT was done using Pearson correlation. Correcting for age as a covariate, multivariate regression analysis was done to know which retinal layers showed significant differences in thickness between males and females. Results: The mean age was 46.06 +/- 13.06 years (range: 20-75 years). Significant central subfield (CSF) thickening with age was noted in retinal nerve fiber layer (RNFL), inner nuclear layer (IPL), inner nudear layer (INL), outer plexiform layer (OPL), and outer nuclear layer (ONL) (P < 0.04). The average thickness of the outer ring reduced with age in the ganglion cell layer (GCL)/IPL/INL (P = 0.001). Women had thinner inner and outer retinal thickness than men in all ETDRS rings (P < 0.001). There was no interocular asymmetry (P > 0.05) and no correlation between IOP/CCT and retinal layer thickness. Conclusion: In CSF, age-related thickening was noted in RNFL, IPL, INL, OPL, and ONL. The average inner ring thickness decreased with age in GCL and IPL and increased in the RPE layer. The average outer ring thickness decreased with age in GCL, IPL, and INL layers and increased in OPL. The average IR and OR thickness was significantly less in women compared to men in all sub-fields. There was no correlation between IOP/CCT and retinal layer thickness.