To identify factors associated with variability in measures obtained by spectral domain optical coherence tomography (SD-OCT).

One hundred ninety-six subjects (370 eyes) with no ophthalmic evidence of retinopathy and with corrected visual acuities better than 0.6 were included. Macular thickness and retinal nerve fiber layer (RNFL) thickness were measured using SD-OCT and were analyzed according to sex, laterality, age, spherical equivalent and signal strength.

The central subfield thickness was significantly lower in the female subjects (r = -0.260, p = 0.000). As age increased, average inner and outer macular thickness increased significantly (r = 0.153, p = 0.010; r = 0.193, p = 0.001). Spherical equivalent correlated negatively with central subfield thickness (r = -0.352, p = 0.000) but correlated positively with average inner macular thickness, average outer macular thickness, overall average thickness, overall macular volume, and average RNFL thickness (r = 0.181, p = 0.002; r = 0.287, p = 0.000; r = 0.346, p = 0.000; r = 0.341, p = 0.000; and r = 0.261, p = 0.000, respectively). Signal strength correlated negatively with average inner macular thickness (r = -0.136, p = 0.023).

SD-OCT shows that retinal thickness is related to age, sex, spherical equivalent and signal strength. Analysis of retinal thickness by SD-OCT should be interpreted in the context of these findings.