| Description |
Fovea centralis is a depression located in the back of the primate retina. This region is crucial for sharp central vision. Age Related Macular Degeneration (AMD) is a debilitating disease that affects several million people in the world. In this disease, the retina and RPE surrounding the fovea undergoes degeneration, thereby compromising visual acuity. The fovea contains significant amounts of three carotenoids - lutein, zeaxanthin, and meso-zeaxanthin. Carotenoids are plant-derived pigment molecules. Vertebrates are unable to synthesize these compounds de novo, and have to obtain these through the diet. Carotenoids protect the foveal region from oxidative stress, light damage, and improves vision. Carotenoid supplementation is shown to alter the course of AMD. Hundreds of carotenoids are present in nature, and the regular human diet consumes about 50 of these. Among these, only 15 are absorbed by the gut and present in the serum. However, only lutein, zeaxanthin, and meso-zeaxanthin are present in the retina. Retinal concentrations of these carotenoids are 5000 times greater than observed levels in the serum, suggesting a very specific transport mechanism into the retina. There are gaps in our knowledge of the mechanisms involved in carotenoid transport into the eye. meso-Zeaxanthin is a retina-specific carotenoid that is rarely encountered in nature. No dietary sources of meso-zeaxanthin are identified. At the foveal pit, there are equal amounts of lutein, zeaxanthin, and meso-zeaxanthin. However, meso-zeaxanthin is absent in the peripheral retina. The mechanism by which meso-zeaxanthin is produced in the eye and the physiological significance of its presence is not understood . |
