Effect of Carotenoid Supplementation on Retinal Health: An Evaluation of Macular Structure and Function in Healthy Adults

The purpose of this research is to evaluate the effect of oral dietary carotenoid supplements on various aspects of retinal health. This includes assessing its impact on macular pigment optical density (MPOD), which is a protective feature of retinal health in reducing lipofuscin (retinal waste) accumulation in the retina.

Our goal is to investigate the protective role of this oral carotenoid supplement on the macular structure, measured as retinal thickness, macular blood vessel density, choriocapillaris density and ocular perfusion pressure (defined as the difference between blood pressure and eye pressure) as well as evaluating visual functions such as contrast sensitivity (the ability to perceive less bold objects ) and photostress recovery time (the minimum time for a person to read the lowest level on an eye chart after shining a light in front of the eye for several seconds). This study will also investigate the relationship between skin carotenoid level and ocular carotenoid level, using a non-invasive finger measurement. Also, we want to explore the effect of carotenoid supplementation on cognitive function in terms of working memory. Understanding how this supplementation impacts all these markers is crucial for enhancing our knowledge of the potential health benefits of carotenoids in improving dietary assessment methods.

This study takes 3 visits. Participants will provide written informed consent on the first visit after reviewing the study procedures, potential risks, benefits, confidentiality measures, and their right to withdraw. Then they will undergo a comprehensive history-taking and complete a validated questionnaire to screen for sensitivity to light, as well as a diet questionnaire. Following this, participant will have non-invasive testing, requiring no eye drops or dyes. This involves measurement of contrast sensitivity (CS), photostress recovery, MPOD, blood pressure (BP), intraocular pressure (IOP), skin carotenoid level, retinal thickness and vascular measures using an optical coherence tomographer (OCT), lipofuscin levels using fundus autofluorescence (FAF) pictures and cognitive function assessment of working memory using a computerized 2- back test. Each participant will then be provided with a commercially-made softgel capsule (either carotenoid supplement or placebo containing only the inactive ingredients) in unmarked bottles and instructed to take one softgel capsule daily with a meal for 3 months. Follow-up visits will take place for 1 month and 3 months, during which the same measurements mentioned above will be repeated.