© 2021, Geriatrics Society. All rights reserved.Introduction: Recent developments suggest that optical coherence tomography can play an important role in diagnosing and following-up neurodegenerative diseases, including Alzheimer’s disease. This study evaluates optical coherence tomography findings in mild cognitive impairment and middle-stage Alzheimer’s disease patients. Materials and Method: Seventy patients with amnestic type mild cognitive impairment, 54 patients with middle-stage Alzheimer’s disease, and 54 cognitively healthy individuals were included. All study participants were evaluated with neuropsychological tests, ophthalmological examination, and optical coherence tomography. Ganglion cell complex and retinal nerve fiber layer thicknesses were measured, and comparisons were made between groups. Results: Inferior temporal and inferior retinal nerve fiber layer thicknesses were thinner in the middle-stage Alzheimer’s disease group than in the control and mild cognitive impairment groups. After statistical corrections, the inferior and inferior temporal retinal nerve fiber layers were thinner in the middle-stage Alzheimer’s disease group compared to the control and mild cognitive impairment groups. Besides, the nasal and nasal lower retinal nerve fiber layers were thicker than the control group. No statistically significant difference was found between the groups in terms of mean, superior and inferior ganglion cell complex thickness. Conclusion: The results showed that retinal axon loss might develop in Alzheimer’s disease. This loss may be focal, and the inferior temporal region may have selective sensitivity. Optical coherence tomography might reflect the neuropathological process in Alzheimer’s disease, contribute to the diagnosis and follow-up. However, it is not helpful in the early diagnosis of Alzheimer’s disease because of the lack of difference between mild cognitive impairment and control groups.