Nervous layer

The nervous layer (Latin: tunica interna bulbi) or the retina is the deepest layer. The retina can be further divided into two layers: pigmented or outer layer and neurosensory or inner layer. The retina is the light-sensitive structure of the eye, where the neural visual pathway begins. The neural retina contains three layers of neural cells: light-sensitive photoreceptor cells, bipolar cells, and ganglion cells of the retina. The retina is continuous with the optic nerve.

The space between two layers is known as the subretinal space. The retina has ten layers. From the deep to the superficial layer, they are:

  • The inner limiting membrane
  • Nerve fiber layer
  • Ganglion cell layer
  • Inner plexiform layer
  • Inner nuclear layer
  • Outer plexiform layer
  • Outer nuclear layer
  • External limiting membrane
  • Rod and cone layer
  • Retinal pigment epithelium

The neural retina has six types of cells in it:

  • photoreceptors - rods and cones. The rodes produce the images in grayscale, while the cones enable colour vision;
  • bipolar cells - they are the first neurons in the visual pathway;
  • ganglion cells - their axons include the optic nerve;
  • horizontal cells - located around the apices of the rods and cones;
  • amacrine cells - work as an indirect connection between bipolar and ganglion cells;
  • supporting cells - called the Muller cells. The cells are scattered all over the neural retina.

The retinal pigment epithelium lies on the Bruch's membrane of the choroid. The retinal pigment epithelium houses a large amount of dark pigment.

The retina is the place where the visual pathway starts. The retina receives light from the lens, converts it into neural signals, and sends the information to the brain.