Role of optical coherence tomography in diagnosis of Alzheimer's disease

Purpose: To evaluate changes in visual function and anatomical structures in the neuroretina of patients diagnosed with Alzheimer's disease (AD) in comparison with healthy controls. Methods: A total of 25 eyes of 13 AD patients and 80 eyes of 40 healthy subjects were analysed. Best corrected visual acuity (BCVA) was assessed in different contrast situations (100%, 2.5%, 1.25%) with ETDRS chart (Early Treatment Diabetic Retinopathy Study). Also, retinal nerve fibre layer (RNFL) and ganglion cell layer (GCL) thickness were analysed using Spectralis and Triton optical coherence tomography (OCT), globally and by sectors, both in peripapillary and macular area. Results: A statistically significant decrease was found in BCVA in AD patients in comparison with controls ( p < 0.001), specifically in 100% and 1.25% contrast charts. Regarding structural analysis, a significant reduction in retinal thickness was found in AD patients in comparison with controls. Global thickness was found to be significantly thinner in peripapillary retina in Triton OCT ( p < 0.001). In a similar way, macular GCL, both in Triton and Spectralis OCT, showed a significant thinning ( p < 0.001) in global and sectorial analysis. RNFL showed a significant tendency towards thinning, but specifically in infero‐temporal sector of macular area in Spectralis OCT ( p < 0.001). Conclusions: The neurodegeneration that AD produces to the brain affects the retina in a parallel way, and that can be objectified by measuring BCVA parameters and thickness measurements in OCT. Compared to healthy controls, AD has a significant thinning in several neuroretinal layers, which can be considered a potential diagnostic tool considering that OCT is a quick, reproducible, non‐invasive test.