Alzheimer’s disease (AD) is a neurodegenerative illness characterised by progressive decline in cognitive function. AD is the main cause of dementia worldwide. Over recent years researchers have strived to find biomarkers to diagnose AD, particularly in the early stages of cognitive decline. To achieve this early diagnosis, optical coherence tomography (OCT) has been used by the authors to measure macular thickness in patients with known mild cognitive impairment (MCI) and subjective memory complaints (SMC). Results showed a statistically significant difference in the macular thickness of the control group and both those with MCI and SMC. These findings suggest that in the future, OCT could become a reliable biomarker and a useful tool for the screening as well as for the monitoring of cognitive impairment associated with AD. This is an important finding due to the rapid demographic ageing worldwide, and the subsequent increase in age related cerebral disease.