Eye Dork - Eye Have the Answer

For vision to be a continuous process the photoreceptors (rods and cones) must continually regenerate 11-cis retinal. Rods and cones have slightly different ways of doing this. WARNING: this is only for the extremely nerdy. If you aren't very interested in the biochemical processing of vitamin A in the retina, this entry probably isn't for you. For rods: A photon (light ray) is absorbed by pigment within the opsin in the outer segment of the photoreceptor cell. Inside the activated opsin, 11-cis retinal is converted to all-trans retinal and released to the disc of the inner segment of the photoreceptor. Within the disc, all-trans retinal binds phosphatidylethanolamine. This produces N-retinylidine-phosphatidyl-ethanolamine (NRPE). ATP binding cassette transporter carries the NRPE complex to the cell membrane of the disc. At the cell membrane the all-trans retinal portion of the NRPE complex is transported to the cytoplasm within the cell body of the photoreceptor. Insi...

Light rays from an image are focused onto the retina by glasses or contacts and the anterior structures of the eye. Light rays are converted from a physical wave into a chemical and electrical message to be interpreted by the brain. This process is called phototransduction. In the sensory retina, there five main cell types and nine layers involved in this process. The sensory retina is an optically clear structure. For phototransduction to begin, an image must pass through the anterior blood supply and every layer of the sensory retina until the image finally reaches the photoreceptor layer. The photoreceptor layer is composed of rods and cones. There are roughly 120 million rods in the adult retina. These cells allow us to see the difference between light and dark. Rods are utilized for night vision and low lighting conditions. There are 6 to 7 million cones in the adult eye. Cones are only utilized for day or brighter conditions. These cells are specialize for color detection. ...