No one has to sell eye doctors on how cool the human eye is. One interesting area of the eye that is being researched is the retinal pigment epithelium (RPE). This is the layer of cells that is next to the retina. It acts as a conduit between the photoreceptors of the retina and the choroid, which is a layer of blood vessels are between the retina and sclera. The role of RPE is to nourish the retinal tissue and maintain its health by bring molecules in and out, disposing of dead cells and secreting hormones.
Things go wrong with the RPE when it is a victim of inflammation. Inflammation confuses the RPE cells, and that can impair the cell’s ability to clear away debris and damaged parts. This can lead to further inflammation, cell death, and age related macular degeneration.
Researchers at the University of Wisconsin are studying this very thing to learn what are the processes that lead to the RPE to stop doing its job and as a result, cellular trash, such as drusen, builds up. They found that vitamin A molecules form clumps in the RPE that trap cholesterol. While vitamin A is important for good vision, it can go through a change and form clumps. This can lead to deposits that can build up over the years. The researchers showed that in both inherited and age-related macular degeneration, the vitamin A molecule clumps and the cholesterol that builds up disrupts the work of the cells responsible for cleaning and recycling cellular material and that can lead to inflammation.
Of course, that isn’t the end of the RPE story. Like fingerprints, RPE cells form a unique pattern. Yet unlike fingerprints, the pattern can be used to track changes in the RPE. Researchers at the National Eye Institute (NEI) used a combination of adaptive optics imaging and fluorescent dye to track patterns in the RPE of both healthy volunteers and volunteers with retinal disease.
At first, researchers weren’t sure how the dye was going to look in the RPE. Once the dye did its work, they saw that a pattern appeared. They then designed software which recognizes the patterns and computes the changes from one imaging session to the next. As you can guess, healthy volunteers saw little change in the RPE patterns. The patterns of volunteers with late onset retinal degeneration (L-ORD) were slightly less stable than healthy volunteers. One volunteer had Bietti crystalline dystrophy. This is a disease that causes a loss of RPE cells. The RPE cells of this patient were larger, less organized and there were drastic changes in the cell pattern over time.
Researchers feel that being able to visualize patterns in the RPE over time will help them to understand how it changes and this can lead to the development of treatments to either repair or prevent damage to the RPE.
These are just two examples of how research is adding more knowledge about the eye and showing just how cool the eye is.