Evaluation of Retinal Nerve Fiber Layer and Ganglion Cell Layer Thickness in Alzheimer’s Disease Using Optical Coherence Tomography

Objective To evaluate the feasibility of using optical coherence tomography (OCT) for the detection of Alzheimer's disease (AD), by measuring the thickness of the retinal nerve fiber layer (RNFL) and the ganglion cell layer and inner plexiform layer (GCL-IPL). Material and Methods This was a single-center, cross-sectional study. The study included 29 patients with AD (mean age ± standard deviation: 75.61 ± 6.24 years) and 29 healthy age- and sex-matched controls. All participants underwent cognitive evaluations using the Montreal Cognitive Assessment test. Measurements of the RNFL thickness, as well as GCL-IPL thickness, were obtained for all participants using OCT. Both RNFL and GCL-IPL parameters were adjusted for best-corrected visual acuity, hypertension, diabetes and dyslipidemia. Results The mean RNFL thickness was significantly thinner in the AD group than in the control group (85.24 and 90.68 µm, respectively, adjusted P=0.014). The superior quadrant was thinner in the AD group (adjusted P=0.033). The thicknesses did not differ significantly between groups for the other quadrants. The mean GCL-IPL thickness in the AD (68.81 µm) was significantly thinner than that in the controls (76.42 µm) (adjusted P=0.014). Overall, there was a negative correlation between age and mean RNFL; and between age and GCL-IPL thickness (r=-0.338, P=0.010 and r=-0.346, P=0.008, respectively). Conclusion The mean RNFL and GCL-IPL thicknesses were thinner in the AD group than in the control group. These findings suggest that RNFL and GCL-IPL thickness may be biological markers for AD.