Netthinnen

Netthinnen, or retina, is a light-sensitive multilayer tissue that lines the inner surface of the eye. It converts light into neural signals that are transmitted to the brain via the optic nerve, enabling vision. The retina contains photoreceptors, supporting neurons, blood vessels, and a network that performs initial image processing.

Anatomy and subdivisions: The retina consists of multiple layers, including photoreceptor cells (rods for low light and cones for color and acuity), the outer nuclear layer, bipolar and horizontal cells, the inner nuclear layer, ganglion cells, and the nerve fiber layer that forms the optic nerve. The retinal pigment epithelium lies behind the photoreceptors and supplies nutrients and recycles visual pigments. The macula holds the fovea, a small pit with densely packed cones responsible for sharp central vision; the surrounding peripheral retina governs peripheral vision.

Circulation: The inner retina receives nutrients from the central retinal artery, while the outer retina depends on the choroidal circulation and the retinal pigment epithelium. The fovea has a relatively avascular zone to minimize light scattering, aiding acuity.

Function and processing: Photoreceptors convert light into electrical signals that pass through bipolar and ganglion cells before reaching the brain as the optic nerve. The retina contains horizontal and amacrine cells that modulate signals. There is a natural blind spot at the optic disc where no photoreceptors are present.

Clinical relevance: Retinal disorders include detachment, diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, and retinal vein occlusion. Diagnosis uses ophthalmoscopy, optical coherence tomography (OCT), and electroretinography (ERG). Treatments include laser therapy, anti-VEGF injections for AMD and diabetic retinopathy, and surgical procedures for detachments and tears.