Choroideremia is a rare genetic condition that causes the eye to lose all layers of the retina, the thin layer of tissue on the back of the eye. Because the retina helps the eye focus light and turn that light into information the brain can process as images, the eventual loss of retinal layers caused by choroideremia can lead to blindness.
In an attempt to better understand choroideremia on a cellular level, researchers have studied the use of new imaging techniques to look more closely at this rare condition. A team of researchers with the National Institutes of Health and the National Eye Institute have explored a new way to better understand choroideremia using adaptive optics combined with traditional eye imaging tools. Their study is published in a recent issue of Communications Biology.
Specifically, the research team combined adaptive optics, a technology that allows researchers to take imaging scans and produce cleaner images of an affected area of the body, and indocyanine green dye. This combination allowed researchers to view three types of live cells in the retina: light-sensing photoreceptors, retinal pigment epithelium (RPE), and choroidal blood vessels. RPEs, in particular, play an important role in helping photoreceptors survive.
The ability to look with such detail at retinal cells allows researchers to better understand exactly how choroideremia affects the retina, which could inform future treatment options for this patient population.
The study included both men and women to help researchers explore how this rare condition affects them differently. Choroideremia is more common in men than women, as is severe disease. The gene that causes choroideremia is located on the X gene, so women, who have two X genes, at least have a working copy present. As a result, they experience less severe disease.
This fact was evident in images of male retinal cells produced in the study. Researchers noted that while both men and women had enlarged RPE cells, women had more of a balance of enlarged and healthy RPE cells, indicating they would experience less severe symptoms. The other two cell types were less affected by choroideremia, suggesting that RPE cells play an important role in understanding this disease.
While adaptive optics are not widely used, researchers found that more standard, available equipment (i.e., a laser ophthalmoscope) with green dye could still detect enlarged RPEs.