Relevance of contrast sensitivity for the diagnosis and monitoring of early stages of Alzheimer's disease

Purpose Several visual tests can be used to determine the behavior of neurons, including the contrast‐sensitivity test (CST), which analyzes the actions of retinal ganglion cells and their cortical processes. Brain atrophy, one of the characteristic signs of Alzheimer’s Disease (AD), is caused by severe loss of neurons in the brain, including several areas known to be involved in visual processing. Our aim was to analyze CST changes in early AD in order to ascertain whether or not CST could be used for AD diagnosis and progression control of the disease. Methods Twenty GDS 4 AD patients, and 25 controls were examined at the Hospital Clínico San Carlos in Madrid (Spain) and underwent a complete ophthalmologic exam (visual acuity, refraction, CST, color test, biomicroscopy, IOP, and fundoscopy). The CST used was CSV‐1000 E chart test, providing for four rows of sine‐wave gratings, which test the spatial frequencies of 3, 6, 12, and 18 cycles/degree. The chart was presented at 2.5 m. Results In AD patients, the CST proved lower in all spatial frequencies, the greatest decrease affecting the highest frequency. Conclusion In early AD, the CST registered a decline in the function of both magnocellular and parvocellular retinal ganglion cells. The CST could be a useful tool for early diagnosis and follow‐up of AD patients.