en Clinical Neuroscience Clinical Neuroscience Original Original <strong>Introduction: </strong>Alzheimer disease (AD) is the most common form of dementia worldwide. The modalities to diagnose AD are generally expensive and limited. Both the central nervous system (CNS) and the retina are derived from the cranial neural crest; therefore, changes in retinal layers may reflect changes in the CNS tissue. Optical coherence tomography (OCT) machine can show delicate retinal layers and is widely used for retinal disorders. This study aims to find a new biomarker to help clinicians diagnose AD via retinal OCT examination.&nbsp;<br> <strong>Methods:</strong> After considering the inclusion and exclusion criteria, 25 patients with mild and moderate AD and 25 healthy subjects were enrolled in the study. OCT was done for all eyes. The central macular thickness (CMT) and the ganglion cell complex (GCC) thickness were calculated. The groups were compared using the SPSS software, v. 22.<br> <strong>Results:</strong> Both GCC thickness and CMT were significantly decreased in patients with AD when compared to healthy age- and sex-matched individuals.<br> <strong>Conclusion: </strong>Retinal changes, specifically CMT and GCC thickness, may reflect the AD process in the brain. OCT can be considered a non-invasive and inexpensive method to help diagnose AD.&nbsp;<br> <span style="font-family:Times New Roman;"><span style="font-size:11pt"><span style="line-height:normal"><span style="font-size:16.0pt"><span style="color:black"></span></span></span></span></span> Alzheimer disease, Optical coherence tomography, Ganglion cell complex, Central macular thickness 675 684 http://bcn.iums.ac.ir/browse.php?a_code=A-10-2040-1&slc_lang=en&sid=1 Zahra Farzinvash zahra1142000@yahoo.com 13700319475328460042860 13700319475328460042860 Yes Department of Ophthalmology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Marzie Abutorabi-Zarchi 13700319475328460042861 13700319475328460042861 No Department of Neurology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Masoudreza Manaviat 13700319475328460042862 13700319475328460042862 No Department of Ophthalmology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Habib Zare Mehrjerdi 13700319475328460042863 13700319475328460042863 No Department of Ophthalmology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.