Retina 

The retina (from Latin: rēte ) is the inner, light-sensitive layer of the eye tissue of most vertebrates and certain molluscs. The optics of the eye create a focused two-dimensional image of the visual world in the retina, which translates this image into electrical nerve impulses in the brain to create visual perception. The retina serves a function similar to that of the film or image sensor on a camera.

Structure

Inverted against the non-inverted retina.

The vertebrate retina inverted in the sense that light-feeling cells are at the back of the retina, so that light must pass through layers of neurons and capillaries before reaching the rods and cones. Ganglion cells, whose axons form the optic nerve, are at the front of the retina; Therefore, the optic nerve must cross through the retina en route to the brain. In this area there are no photo receptors that cause the blind spot. In contrast, in the cephalopods retina the photoreceptors are in front, with the treatment neurons and capillaries behind them.

Development

Retinal development begins with the establishment of mesh fields mediated by the SHH and SIX3 proteins, with the subsequent development of optical vesicles regulated by pax6 and LHX2 proteins. Pax6’s role in eye development was elegantly demonstrated by Walter Gehring and colleagues, who showed that the ectopic expression of Pax6 can lead to eye formation in Drosophila antennas, feathers, and feet. Optical vesicle creates three structures: the neural retina, the retina colored epithelium, and the optic strain. The neural retina contains the progeny cells of the retina (RPCs) that cause the seven types of retinal cells. Differentiation begins with retinal ganglion cells and is completed with the production of Muller glia. Although each cell type differs from RPC in sequential order, there is significant overlap in the schedule when individual cell types are differentiated. The indications that determine a daughter RPC cell fate are encoded by multiple transcription factor families, including bHLH and homeodomain agents.

Function

Adjustment (eye) and Visual acuity.

The retina translates an optical image into neural impulses starting with the patterned excitation of the colour-sensitive pigments of its rods and cones, the retina’s photoreceptor cells. The excitation is processed by the neural system and various parts of the brain working in parallel to form a representation of the external environment in the brain.

The cones respond to bright light and mediate high-resolution color vision during daylight lighting (also called photoscopy vision). The rod responses are saturated in daylight levels and do not contribute to pattern vision. However, the rods respond to dim light and mediate lower resolution, monochromatic vision under very low levels of light (called scotopic vision). The lighting in most office settings varies between these two levels and is called mesoscopic vision. At mesoscopic light levels, both rods and cones actively contribute to pattern information.

Source: Wikipedia – January 2021.

Clarification: This text is an excerpt from a published Wikipedia article.