A potential space exists in the retina as a vestige of the space between the apical surfaces of the two epithelial lay-ers of the optic cup. If this space expands, the neural retina separates from the retinal pigment epithelium (RPE), which remains attached to the choroid layer. This condition is called retinal detachment. As a result of retinal detach-ment, the photoreceptor cells are no longer supplied by nu-trients from the underlying vessels in the choriocapillary plexus of the choroid. Clinical symptoms of retinal detachment include visual sensations commonly described as a “shower of pepper” or floaters. These are caused by red blood cells extravasated from the capillary vessels that have been injured during the retinal tear or detachment. In addition, some individuals describe sudden flashes of light, as well as a “web” or “veil” in front of the eye in conjunction with the onset of floaters. A detached retina can be observed and diagnosed during ophthalmoscopic eye examination (Fig. F24.2.1). If not repositioned quickly, the detached area of the retina will undergo necrosis, resulting in blindness. More commonly, as the vitreous body ages (in the sixth and sev-enth decades of life), it tends to shrink and pull away from the neural retina, which causes single or multiple tears in the neural retina. An argon laser is often used to repair reti-nal detachment by photocoagulating the edges of the de-tachment and producing scar tissue. This method prevents the retina from further detachment and facilitates the repo-sitioning of photoreceptor cells.
 FOLDER 24.2 Clinical Correlation: Retinal Detachment fovea area ofretinalarea of detachmentretinal detachment optic disc FIGURE F24.2.1 • Retinal detachment. This image shows a view of the fundus of the right eye in a patient with retinal detachment. The central retinal vessels emerging from the optic disc are in focus, but in the area of the retinal detachment they appear to be out of focus. This is due to the fact that the area of retinal detachment is elevated (note multiple ridges and shadows) and is located anterior to the plane of focus of the ophtalmoscope. (Courtesy of Dr. Renzo A. Zaldivar.) 3.
Outer limiting membrane—the apical boundary of Mler’s cells 4.
Outer nuclear layer—contains the cell bodies (nuclei) of retinal rods and cones 5.
Outer plexiform layer—contains the processes of retinal rods and cones and processes of the horizontal, amacrine, and bipolar cells that connect to them 6.
Inner nuclear layer—contains the cell bodies (nuclei) of horizontal, amacrine, bipolar, and Mler’s cells 7.
Inner plexiform layer—contains the processes of horizontal, amacrine, bipolar, and ganglion cells that connect to each other 8.
Ganglion cell layer—contains the cell bodies (nuclei) of ganglion cells 9.
Layer of optic nerve fbers—contains processes of ganglion cells that lead from the retina to the brain 10.
Inner limiting membrane—composed of the basal lamina of Mler’s cells
Each of the layers is more fully described in the following sections (see corresponding numbers).
The cells of the RPE (layer 1) have extensions that surround the processes of the rods and cones.
The RPE is a single layer of cuboidal cells about 14 m wide and 10 to 14 m tall. The cells rest on Bruch’s membrane of the choroid layer. The pigment cells are tallest in the fovea and adjacent regions, which accounts for the darker color of this region.
Adjacent RPE cells are connected by a junctional complex consisting of gap junctions and elaborate zonulae occludentes and adherentes. This junctional complex is the site of the blood–retina barrier.