Nauman Hashmani, Sharif Hashmani

To map and view the effects of age, gender, and axial length on seven individual retinal layers around the optic nerve head (ONH). We scanned 242 healthy patients using the Spectralis spectral domain optical coherence tomography in an outpatient setting. The layers were observed on the Early Treatment Diabetic Retinopathy Study sectors using the standard Spectralis Family Acquisition Module 6.0.11.0. The center was the ONH, the inner circle (IC) was 1-3 mm away, and the outer circle (OC) was 3-6 mm away. The seven layers were retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), and retinal pigment epithelium (RPE). Additionally, we calculated the mean thickness of two combined layers: inner retinal layer (IRL) and photoreceptor layer (PL). Finally, we measured the mean of the total retinal thickness (TRT). The TRT was highest at the inferior end in the IC and at the nasal end in the OC. The RPE (p<0.001) and PL (p<0.001) were thicker in males; however, the IRL (p=0.015) was thicker in females. We found that the RNFL (p<0.001, r=0.139), GCL (p<0.001, r=0.116), IPL (p=0.016, r=0.059), INL (p<0.001, r=0.104), OPL (p=0.009, r=0.064), ONL (p<0.001, r=0.157), RPE (p=0.001, r=0.079), IRL (p<0.001, r=0.190), PL (p=0.030, r=0.053), and TRT (p<0.001, r=0.191) correlated negatively with age. The axial length significantly and negatively correlated at the GCL (p=0.003, r=0.093), IPL (p=0.020, r=0.072), INL (p=0.018, r=0.073), ONL (p<0.001, r=0.110), IRL (p=0.003, r=0.092), and TRT (p=0.003, r=0.094). We found poor reproducibility in the IC; however, this was excellent in the OC. We found significant differences in layers according to age, gender, and axial length. Additionally, reproducibility can be improved by altering the algorithm to account for the ONH parameters.