Retina: Anatomy and layers

Last update: May 25th, 2023

Retina is the inner sensory layer of the eyeball that is sensitive to light. It contains special receptor cells that are light-sensitive and which transform light signals from the outside world into nerve signals that are interpreted by the brain. The interpretation provides us with the ability to understand what we see.

Retina consists of 10 layers divided into two parts. The first nine layers belong to the neural retina, which consists of numerous photoreceptors and cells. The second part and the 10th layer of the retina is called the pigmented retina and it consists of the retinal pigmented epithelium. This layer has several functions, some of which include absorbing the light so it doesn’t reflect back onto the neural retina, as well as to protect and nourish the neural retina.

In the following text we are going to cover in more detail the layers and functions of the retina.

Retina
Definition and function	Sensory layer of the eyeball that detects the light and transmits it via the optic nerve. In the CNS, these stimuli are interpreted and experienced as vision.
Cells of the retina	Photoreceptors (cones and rods), conducting neurons, association neurons and supporting cells
Layers of the retina	Retinal pigmented epithelium (RPE) Layer of photoreceptors Outer limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Nerve fiber layer Inner limiting membrane

Structure

The retina consists of several types of cells that are distributed throughout its ten layers. These cell types are namely the photoreceptors, conducting neurons, association neurons and supporting cells.

Photoreceptor cells are called cones and rods. The rods are more sensitive to the low light grayscale spectrum, enabling the dark or light shading of the perceived image. The cones are sensitive to high intense light, enabling color vision. Photoreceptor cells are elongated and consist of three regions: outer segment, central segment that contains their nuclei, and inner segment that synapses with retinal neurons.
Conducting neurons are divided into bipolar and ganglion cells. The bipolar cells connect on one side with the photoreceptors and on the other side with the ganglion cells. They are neural cells and as such mark the first order neuron of the visual pathway. Each ganglion cell receives signals from bipolar cells and then projects an axon that actually represents a fiber of the optic nerve.
Associating neurons include a variety of cells, such as horizontal, centrifugal, interplexiform and amacrine neurons. Their main function is to interconnect the retinal cells with one another to establish modulation circuits.
Supporting cells, namely Müller’s cells, microglial cells and astrocytes support and nurture the retinal layers.

Learn the anatomy of the eyeball with interactive video tutorials and quizzes.

An image showing the parts of the retina and the visual pathway, the Rod, and Pigmented layer are labeled

An image showing the parts of the retina and the visual pathway, the Cone, Rod, and Pigmented layer are labeled

An image showing the parts of the retina and the visual pathway, the Bipolar cell, Cone, Rod, and Pigmented layer are labeled

An image showing the parts of the retina and the visual pathway, the Ganglion cell, Bipolar cell, Cone, Rod, and Pigmented layer are labeled

An image showing the parts of the retina and the visual pathway, the Horizontal cell, Ganglion cell, Bipolar cell, Cone, Rod, and Pigmented layer are labeled

An image showing the parts of the retina and the visual pathway, the Amacrine cell, Horizontal cell, Ganglion cell, Bipolar cell, Cone, Rod, and Pigmented layer are labeled

Cells of the retina

Retinal layers

In the following text we will help you understand how these cell types connect and distribute to form the ten layers of the retina. From deep to superficial, these are the retinal layers:

Retinal pigmented epithelium (RPE) consists of epithelial cells that rest on a membrane called the Bruch’s membrane. The cells of this epithelium absorb light to prevent it from reflecting back onto the inner layers of the regina.
Layer of cones and rods is the layer that consists of the outer segment of rods and cones
Outer limiting membrane consists of densely packed processes of the Müller’s cells
Outer nuclear layer contains the central segments of the cones and rods
Outer plexiform layer consists of the synaptic parts of the cones and rods and their synapses with the conducting neurons
Inner nuclear layer consists of the cell bodies and nuclei of the bipolar and supporting cells
Inner plexiform layer contains the synapses between the associating neurons and supporting cells and conducting neurons
Ganglion cell layer contains the ganglion cells nuclei
Nerve fiber layer consists of the axons of the ganglion cells that form the optic nerve
Inner limiting membrane consists of another densely packed layer of the processes from Müller’s cells on the anterior surface of the retina.