Determinants of Optical Coherence Tomography Parameters in a Population-based Study

To study the effects of age, sex, intraocular pressure (IOP), corneal thickness, axial length (AXL), disc area, and the signal strength of the scan on optical coherence tomography (OCT) parameters of normal subjects in the L V Prasad Eye Institute-Glaucoma Epidemiological and Molecular Genetic Study (LVPEI-GLEAMS), a population-based study. Cross-sectional study. A total of 1,100 eyes (1,100 subjects) of normal adults aged between 40 and 80 years from LVPEI-GLEAMS underwent macular and optic nerve head imaging with spectral-domain OCT (SDOCT). Effect of age, sex, IOP, central corneal thickness (CCT) and AXL, disc area, and signal strength of the OCT scan on retinal nerve fiber layer (RNFL) thickness, rim area, and ganglion cell–inner plexiform layer (GC-IPL) thickness measurements were evaluated using univariate and multivariate regression models. Mean rim area, RNFL, and GC-IPL thickness were 1.31 mm2 (standard deviation [SD] = 0.22), 93.7 μm (SD = 9.3) and 79.6 μm (SD = 8.7), respectively. Age had a negative association with RNFL thickness (coefficient: −0.18, P < .001) and GC-IPL thickness (−0.18, P < .001). GC-IPL thickness was significantly less in women than in men (−1.05, P < .001). AXL had a negative association with rim area (−0.05, P < .001). Disc area was positively associated with RNFL thickness (4.90, P < .001) and rim area (0.15, P < .001). Signal strength of OCT scan was positively associated with RNFL thickness (1.6, P < .001) and negatively associated with rim area (−0.02, P < .001). Age, sex, AXL, disc area, and signal strength of the scan were significantly associated with OCT measurements. These factors may need to be considered while interpreting the OCT parameters in pathologic conditions such as glaucoma.