Your eyes are relatively small parts of your body, but they’re immensely complex. Your eyes are full of dozens of different parts, all of which work together to produce your vision. One of the most important parts within the eye is the retina.
What Is the Retina?
The retina is the layer of cells positioned at the back of your eyeball. This layer senses the light that comes into your eyeball and sends signals to your brain.
The key retina parts include the rods and cones, which convert light into electrical signals for the brain, and the macula, which allows you to see details clearly.
What Does the Retina Do?
The job of the retina is to capture light that comes through the eye and change that light into an electrical signal that your brain interprets as an image.
Proper retina function depends on each part of the retina doing its job.
Macula. The macula is in charge of seeing the fine details of the objects directly in front of you. This may include things like facial details, text on a book or page, and differences between colors.
Photoreceptors. Photoreceptor cells are the specific cells within the retina that convert light into signals for the brain to interpret. You have two types of photoreceptor cells: rods and cones. Rods are very sensitive to light, giving you your night vision. Rods are also responsible for peripheral vision and allow you to see black and white.
Cones are responsible for giving us our color vision. They’re concentrated in the macula. Human eyes have three types of cone cells: red-sensing cone cells, green-sensing cone cells, and blue-sensing cone cells. 60% of your cones are red-sensing, 30% are green-sensing, and the remaining 10% are blue-sensing.
What Is the Retina Made Of?
The retina is made up of layers upon layers of cells.
The retina structure consists of ten separate layers. Listed from the innermost layer to the outermost layer, these layers are:
- Inner limiting membrane. The inner limiting membrane creates a boundary between the retina and the vitreous fluid inside the eye.
- Retinal nerve fiber layer. This layer contains:
- Ganglion cells, the cells that will form the optic nerve
- Astrocytes, cells that help with eye development
- Müller cells, which are responsible for homeostasis and metabolic support of neurons in the retina
- Ganglion cell layer. The ganglion cell layer consists exclusively of ganglion cells.
- Inner plexiform layer. In the inner plexiform layer, the bipolar cells (cells that take information from cones and rods to pass onto other cells) pass information to the ganglion cells.
- Inner nuclear layer. The inner nuclear layer consists of cells that moderate feedback for the cones and rods. It also contains amacrine cells, a type of neuron.
- Outer plexiform layer. In the outer plexiform layer, the photoreceptor cells pass on information to extensions of nerve cells.
- Outer nuclear layer. The outer nuclear layer contains the cell bodies of the rods and cones.
- External limiting membrane. This layer separates the cell bodies of the rods and cones from the inner and outer segments.
- Photoreceptor layer. The photoreceptor layer is home to the inner and outer segments of the rods and cones. These segments are the parts responsible for converting light into electrical signals.
- Retinal pigment epithelium. The retinal pigment epithelium is the outermost layer of the retina. It provides nutrition and removes waste.
Where Is the Retina Located?
The retina is located at the back of the eyeball.
Your eyeball has many, many parts. For simplicity, we’ll break it into three segments: the surface of the eye, the front of the eye, and the back of the eye.
The surface of the eye. The role of the surface of your eye is to protect the front of your eye and keep it healthy. The eye surface consists of:
- Conjunctiva, a clear membrane that lines the surface of your eye and inside of your eyelids
- Tear film, three layers that produce tears and keep the eyes from becoming dry
- Lacrimal glands, a gland on the outside edge of the eyebrow that makes the watery part of tears
- Meibomian glands, oil-producing glands on the edges of your eyelids
- Tear duct, the duct in the inner corner of your eye that drains excess tears
The Front of the Eye. The front of the eye lets light in and focuses that light. It includes the:
- Cornea, the dome-shaped part over the iris and pupil that focuses light
- Anterior chamber, the chamber behind the cornea, filled with aqueous humor, a fluid that keeps the eye nourished, hydrated, and round.
- Iris, the colored part of the eye behind the anterior chamber. The iris muscles can widen and narrow to mediate the amount of light going into the pupil.
- Pupil, the dark center of your eye that takes in light
- Lens, a clear part of the eye behind the pupil that focuses the light onto the retina
The back of the eye. The back of the eye is where the retina sits. Other parts of the back of the eye include the:
- Vitreous cavity, the space between the lens and the retina filled with vitreous humor, a jelly-like fluid
- Optic nerve, the nerve that sends impulses from your eye to your brain for processing
- Optic disk, the place in your retina where the optic nerves leave the eye
Retinal Conditions and Diseases
Many conditions can affect the retina, making it difficult to see properly. These include conditions such as:
- Color blindness, a condition in which cones are missing or not working properly, causing you to be unable to see certain colors or to see colors in a distorted fashion
- Diabetic retinopathy, a condition caused by diabetes in which the capillaries in the back of your eye leak fluid into and underneath the retina
- Epiretinal membrane, cases when a thin layer of scar tissue pulls on the retina and distorts vision
- Macular degeneration, as a result of which the macula degenerates and causes blurred vision or a blind spot
- Macular hole, caused by injury or friction
- Retinal detachment, a case in which fluid comes through a retinal tear and detaches the retina from the tissue behind it
- Retinitis pigmentosa, a genetic condition that causes a change in how your retina responds to light, resulting in loss of vision and difficulty seeing color
- Retinal tear, cases when the retina tears, often due to the vitreous tugging on the tissue
If you suspect you’ve sustained a retinal injury or are having an issue with your retina, see your doctor right away. Some conditions are curable if treated early.
