Retina: Anatomy, Function & Common Conditions

Contributing Author: Dr. Bernard Dib, M.D.

We rely heavily on our vision since it connects us to our surroundings and allows us to stay safe, learn, and create memories. The retina is an important component of the eye because it transmits light entering the eye into the optic nerve, which in turn sends the information to the brain. Any damage to the retina can result in impaired vision. Consult with an ophthalmologist immediately if you notice any changes in your vision.

What Is the Retina?

According to the American Academy of Ophthalmology (AAO), the retina is a thin layer of tissue that lines the rear wall of your eye. This layer of tissue detects light and delivers messages to the brain, allowing you to see.

As light passes through the lens in the front of the eye and strikes the retina, photoreceptors (light-sensitive cells in the retina) convert light energy into an electrical signal which is carried by the optic nerve and transmitted to the brain. The retina’s nerve cells are therefore responsible for all forms of vision, enabling you to see in low-light conditions, perceive an entire range of colors and the sharp edges of delicate images, and have a wide field of vision.

The Anatomy of the Retina

The retina typically appears red or orange because it is surrounded by numerous blood vessels and consists of the following components:

Macula – The macula is a small but vital portion of the central retina. The macula is essential for seeing details of objects in front of you, such as faces and written text.
- Fovea – The depression in the center of the macula, also known as the fovea centralis, is the sharpest point of focus at the very center of your vision. The fovea is perhaps the most important part of the human eye.
Peripheral retina –The peripheral retina is the retinal tissue outside the macula. It provides us with peripheral (side) vision and vision in dim light settings.
Photoreceptors – Photoreceptors are found on the outermost layer of the retina. Photoreceptor cells are nerve cells that transform light into an electrochemical signal, the first and crucial step in the process of light and color perception. Photoreceptor cells are classified into two types: rods and cones.
- Rods – These photoreceptor cells are very sensitive to low light levels and contribute to our night vision. They are located in the peripheral retinal regions and are therefore also essential for peripheral vision.
- Cones – Cone cells are photoreceptors that sense and process the colors red, blue, and green to provide full color vision. Cones are in charge of bright-light detailed vision and color vision. Because they are almost exclusively located in the macula, cones are significantly less numerous (6 million) than rods (120 million).

Eye Problems That Can Affect the Retina

There are many retinal diseases that can affect your vision, some of which are outlined below.

Age-Related Macular Degeneration (AMD) – AMD is the leading cause of visual loss in adults over 50. Individuals with AMD experience central vision loss and difficulty reading or seeing things in front of them. AMD almost never causes total blindness but can significantly impact daily life.

Diabetic Retinopathy – This common eye disease occurs when high blood sugar levels damage the retinal blood vessels. When damaged, retinal blood vessels can leak, bleed, or close off, all of which can lead to vision loss. Occasionally, pain may occur if the blood supply to the eye becomes more compromised. It is critical for every patient with diabetes to be examined at least once yearly by an ophthalmologist or optometrist.

Retinal Vein or Artery Occlusion – Arteries and veins transport blood to all body parts, including the retina. Without adequate blood supply, the retina cannot function adequately and may suffer permanent damage. The retina contains one major artery for supply and one major vein for drainage. When either one becomes obstructed, blood flow to the retina is compromised, potentially leading to temporary or permanent vision loss. The vision loss is often sudden and usually painless.

Retinal Detachment – A detached retina is a serious eye disorder that impairs vision and, if untreated, frequently leads to blindness. It occurs when the retinal tissue separates from the underlying eye wall to which it normally adheres. This condition often runs in families, but it can also be precipitated by trauma (e.g., a blow to the head) or eye surgery. Retinal detachment is painless, but warning signs include new floaters, flashes of light, or loss of peripheral vision.

Macular hole – The eye is full of a gel called the vitreous humor. As we age, the vitreous shrinks and eventually separates from the retina, which is a normal aging process. Occasionally however, the gel can pull hard enough on the macula (the center of the retina) to cause a hole. A macular hole usually causes vision problems in the center of the vision and typically requires surgery to be fixed.

Macular pucker – With age, as the vitreous gel separates from the retina, it can occasionally leave some gel cells on the surface of the macula (the center of the retina). Those cells can proliferate into a scar tissue membrane (macular pucker), which can distort and wrinkle the macula, leading to blurry and distorted vision. If significant, the scar tissue membrane may require surgical removal in the operating room.

Retinitis Pigmentosa (RP) – is a hereditary disorder that alters the retina’s sensitivity to light, making it difficult to see. Depending on a person’s condition, the type and rate of vision loss associated with RP varies from person to person.

Retinoblastoma – Cancerous retinal tumors occur when nerve cells in the retina transform, multiply and form a tumor. Typically, the cells disseminate throughout and around the eye, and they can spread to other regions of the body, including the brain and spine. Retinoblastoma often affects young children; however, it can occasionally afflict adults.

According to the Centers for Disease Control and Prevention (CDC), age-related eye diseases such as age-related macular degeneration (AMD), diabetic retinopathy, cataract, and glaucoma are the major causes of blindness and impaired vision in the United States.

Signs and Symptoms of Retinal Disease

Retinal diseases can share a variety of symptoms, such as:

Blurry vision
Distorted vision
Need for brighter lighting when performing day-to-day tasks
Sudden onset of floaters
Flashes of light
Reduced central or peripheral vision
Impaired color vision
Shadows in your visual field
Poor depth perception
Sensitivity to bright light
Eye pain
Partial or full loss of vision

Many of these symptoms can appear unexpectedly and without warning. Your eye doctor will perform a thorough exam to determine the cause of your symptoms and recommend treatment options.

How Are Retinal Disorders Diagnosed?

Typically, in order to assess and diagnose retinal disorders, ophthalmologists first inquire about the patient’s medical history. This allows them to explore underlying issues that may be affecting a patient’s eyesight. Then, they perform a comprehensive front-to-back eye exam to determine the cause of the symptoms. This may require dilating drops to dilate the pupil and allow a more comprehensive retinal examination. Specialized imaging such as optical coherence tomography (scans of the retina), fluorescein angiography (dye test), and ocular ultrasound may be obtained as needed to aid in diagnosis and management.

Treatment Options for Retinal Disease

The primary objective of treatment is to stop or delay the advancement of the disease and to preserve, improve, or restore eyesight. Damage that has already happened is sometimes irreversible, making early detection crucial. Your doctor will work with you to determine the best course of action. The treatment of retinal disease can be complicated and, at times, urgent. Treatment options may include:

Laser surgery – A retinal tear can be repaired using laser surgery. Your surgeon will heat small pinpoints on the retina, which helps bind the retina to the underlying tissue. Immediate laser treatment of a new retinal tear can reduce the likelihood of it progressing into a retinal detachment. Laser surgery can also be helpful in shrinking abnormal retinal blood vessels that are bleeding or about the bleed, a technique called panretinal photocoagulation. Diabetic retinopathy patients may benefit from this treatment.

Injecting medicine into the eye – Your doctor may suggest injecting medications into your eye. This technique may be useful in treating patients with wet macular degeneration, diabetic retinopathy, and retinal vein occlusion.

Retinal detachment surgery – Retinal detachment usually requires surgical repair. This can be achieved with a technique called vitrectomy, where the surgeon removes the gel that fills your eye and replaces it with oil or gas to push the retina back onto the eye wall. Another technique, scleral buckling, involves pushing the eye wall inward with a silicone band to encourage retinal reattachment.

Macular hole/pucker repair – In macular hole or pucker repair, the surface layers of the retina are peeled and removed with very fine instruments. In macular hole cases, the eye is then filled with a gas bubble to push on the hole and force it to close.

How Often Should You Get Your Eyes Checked?

Most children and adults should have a comprehensive eye exam every one to two years. Individuals at higher risk of developing an eye disease may need to have their eyes checked more frequently. You may require more frequent eye examinations if you:

Are over age 60
Have a family history of eye disease
Wear thick glasses
Have a health condition that can cause eye problems, such as diabetes
Had eye surgery or eye damage from a stroke

During a comprehensive eye exam, your ophthalmologist will examine your eyes and perform several tests. Some of these tests help assess your vision and determine whether you require glasses or contacts. Other tests evaluate your eye health and look for signs of eye diseases.

When to Seek Treatment?

Consult with a healthcare provider as soon as you notice changes in your vision. Whether it’s as simple as needing new glasses or as complicated as partial vision loss, don’t wait for symptoms to worsen before getting your eyes checked. Although many vision problems can be corrected, some must be diagnosed and treated early to prevent permanent damage. Maintaining frequent eye checkups is therefore important to keep your eyes healthy. Your doctor will advise you on how often you need to be seen based on the health of your eyes.

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