Retina and its structure

Retina

• Retina is innermost, most sensitive, and pigmented layer of eye.
• Its inner surface faces vitreous chamber which maintains retina and lens and outer surface faces aqueous chamber which provide nutrition to cornea and lens.
• Area on retina present just opposite to lens is yellow spot which contains only cones
• Area on retina from where optic nerves leaves eyeball is blind spot which do not contain rods or cones cells.
• It is formed of four layers of cells:

1. Pigment epithelium
2. Photoreceptor cells
3. Bipolar cells
4. Ganglion cells

Photoreceptors cells are Rod and Cone cells.

Structure

1. Pigment epithelium layer

• Outermost retinal layer.
• Single layer of hexagonal cells.
• Functions:

Renew and provide mechanical support to photoreceptors.

2. Photoreceptors layer

• These are layers of rods and cone cells.
• Rods contain pigment called rhodopsin sensitive to dim light and responsible for black and white vision and more numerous than cones.
• Cones contain pigment called idospin sensitive to bright light and responsible for colour vision.

3. External limiting membrane

• Situated at base of rods and cones.
• Junction between photoreceptors and muller cells.
• Maintain structure of retina.

4. Outer nuclear layer

• These are formed by nuclei of rods and cones.
• Lie in single layer.

5. Outer plexiform layer

• Layer of synapses between photoreceptor cells with dendrites of bipolar cells.

6. Inner nuclear layer

• Layer of inner granules.
• Consists of cell bodies of bipolar cells, horizontal and amacrine cells.

7. Inner plexiform layer

• Synapses between bipolar cells and dendrites of ganglion cells.

8. Ganglion cell layer

• Formed of cell body and nuclei of ganglion cell.
• Convey information from retinal neuron to brain.

9. Nerve fibre layer

• Formed of ganglion cell axons.

10. Internal limiting membrane

• True basement membrane.
• Junction between vitreous body and nerve fibre layer.