What are the 10 Layers of Retina?

The retina is the innermost layer of the eye wall which is responsible for visual processing and turning the light energy in the form of photons to three dimensional images. It is located in the back of the eyeball and is the only extended part of the brain that can be viewed physically from outside.

The retina itself is composed of 10 different layers with 6 different types of cells present in the layers. Let us look into the layers and cells in detail.

Layers of Retina

The 10 differentiating layers of the retina from closest to farthest to the vitreous body are –

1. Inner Limiting Membrane

The inner limiting membrane is a boundary between the retina and vitreous body, it is lined with astrocytes and Müller cells.

2. Nerve Fibre Layer

The nerve fibre layer or the stratum opticum, is a layer that is formed by the expansion of optic nerves. The axons of the ganglion cells bodies also lie in this layer.

3. Ganglion Cell Layer

The ganglion cell layers are composed of the retinal ganglion cells and some of the displaced amacrine cells. It is made up of flask shaped cells that send its axons to the stratum opticum.

4. Inner Plexiform Layer

The inner plexiform layer, also called the inner synaptic layer, consists of axons of the bipolar cells and the dendritic processes of the ganglion and amacrine cells. Sometimes, a few spongioblasts are also found embedded in the layer.

5. Inner Nuclear Layer

The inner nuclear layer is composed of the cell bodies of horizontal cells, amacrine cells and bipolar cells.

6. Outer Plexiform Layer

The outer plexiform layer or the outer synaptic layer is a layer consisting of a dense network of neuronal synapses between the dendrites of horizontal cells and the photoreceptor cells (rods and cones) that extend from the outer nuclear layer.

7. Outer Nuclear Layer

The outer nuclear layer consists of the cells bodies of the photoreceptor cells of the retina – rods and cones.

8. External Limiting Membrane

The external limiting membrane is a distinguishing layer of the retina that separates the inner segments of the photoreceptor cells from their nuclei.

9. The Layer of Rods and Cones
10. Retinal Pigment Epithelium

It is a layer of cuboidal epithelial cells that is attached to the choroid. Its function is to provide nourishment to the retinal visual cells. This layer consists of a black pigment that prevents reflection in the eyeball.

Cells of Retina

The ten layers of the retina have six different types of cells that help in converting the incoming photons into a three dimensional visual image. Find out the details of these cells below.

1. Rods

The rod cells are one of the photoreceptor cells found in the retina of the eyes of vertebrates. The rod cells help in identifying the shape, size and brightness of images. They cannot perceive light as compared to cone cells that are less sensitive to light.

The rod cells are found concentrated in the outer edges of the retina and are much more abundant than the cone cells. They work better in dim light and are fully responsible for night vision. They play no role in colour vision.

2. Cones

The cone cells are less sensitive to light and are responsible for perceiving colour and fine details of a visual image. The cone cells respond differently to different wavelengths of light hence helping in visualising different colours.

There are usually 6-7 million cone cells concentrated in the fovea centralis of the eye which is a rods free area.

3. Retinal Ganglion Cells

The retinal ganglion cells are a type of neuron that are located in the ganglion cell layer of the retina. It receives visual information from the rod and cone cells via the bipolar and amacrine cells.

These cells have a distinguishingly long axon that extends into the brain. The retinal ganglion cells collect both visual and non visual information in the form of action potentials and transmits it to the thalamus, hypothalamus and midbrain.

4. Bipolar Cells

The bipolar cells are named so because they have a central body out of which two processes arise. They are present between the photoreceptor cells and ganglion cells and help in the transmission of signals between the two.

5. Horizontal Cells

The horizontal cells are neurons that are present in the inner nuclear layer of the retina. It helps in maintaining contrast of the visual image by adapting to both bright and dim lights. The horizontal cells give negative feedback to the photoreceptor cells by depolarising the rod and cone cells.

6. Amacrine Cells

Amacrine cells are interneuronal cells that are distinguished by their short neuritic processes. The dendrites of the amacrine cells lie in the inner plexiform layer and are synaptically associated with the retinal ganglion and bipolar cells. The amacrine cells are inhibitory neurons that contain GABA or glycine as their neurotransmitters.

This sums up the details on layers and cells of the retina. Stay tuned to BYJU’S for more information related to NEET.

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