One is the inability to replace the function of cells in the retina with a digital camera. (scientificamerican.com)
-LSB-...] work by protecting tiny blood vessels in the retina of the eye and the inner ear. (liveinthenow.com)
The second, intermediate layer of the retinal blood vessels seems to activate during periods of low oxygen and acts as a «reserve» of blood vessels in the retina. (sciencedaily.com)