What is the retina?

The retina is an extremely thin tissue that lines the inside of the back of the eye. When we look around, light from the objects we are trying to see enters the eye. The light image is focused onto the retina by both the cornea and the lens. This light striking the retina causes a complex biochemical change within layers of the retina and this, in turn, stimulates an electrical response within other layers of the retina. Nerve endings within the retina transmit these electrical signals to the brain through the optic nerve. Within specific areas of the brain, this electrical energy is received and processed to allow us both to see and to understand what we are seeing. The retina has been compared to the film of a camera. However, once used, film has a permanent image on it. The retina, in contrast, continually renews itself chemically and electrically, allowing us to see millions of different images every day without them being superimposed.

The retina is about the size of a postage stamp. It consists of a central area called the macula and a much larger peripheral area of the retina. The light receptor cells within the retina are of two types, called the rods and the cones. Rods allow us to see in conditions of reduced illumination. Cones provide us with the sharpness of central vision and colour vision. The peripheral retina allows us to see objects on either side (peripheral vision) and, therefore, provides the vision needed for a person to move about safely. Since this part of the retina contains a lesser concentration of cones, it does not allow for appreciation of visual detail. Its larger concentration of rods provides better vision during conditions of darkness.

In contrast, the macula is a smaller, central area of the retina that contains a high concentration of cones. Accordingly, it enables clear central vision to see fine details for such activities as seeing small objects at a distance, reading or threading a needle. The macula is particularly sensitive to circulatory changes, especially those that occur with aging, such as decreased blood flow. The retina contains a network of branching arteries, which supplies blood that carries the needed oxygen and nutrients to the retina, and a network of accompanying veins, which then carry the blood away together with the waste products of retinal metabolism.

Retina Problems

There is a wide variety of retina problems, conditions and diseases. Here is a short list of the more common retina problems:

Macular degeneration. Age-related macular degeneration (AMD) is the most common serious, age-related eye disease, affecting 9.1 million Americans. And the prevalence of AMD — which affects one in 14 Americans over age 40 and more than 30 percent of seniors over age 75 — is increasing as the U.S. population continues to age.

Diabetic retinopathy. One of the devastating consequences of diabetes is damage to the blood vessels that supply and nourish the retina, leading to significant vision loss.

Macular oedema. This is an accumulation of fluid and swelling of the macula, causing distortion and blurred central vision. Macular oedema has several causes, including diabetes. In some cases, swelling of the macula can occur after cataract surgery.

Central serous retinopathy. This is when fluid builds up under the central retina, causing distorted vision. Though the cause of central serous retinopathy (CSR) often is unknown, it tends to affect men in their 30s to 50s more frequently than women, and stress appears to be a major risk factor.

Hypertensive retinopathy. Chronic high blood pressure can damage the tiny blood vessels that nourish the retina, leading to significant vision problems. Risk factors for hypertensive retinopathy are the same as those for high blood pressure, including obesity, lack of physical activity, eating too much salt, a family history of hypertension and a stressful lifestyle.

Solar retinopathy. This is damage to the macula from staring at the sun, which can cause a permanent blind spot (scotoma) in your visual field. The risk of solar retinopathy (also called solar maculopathy) is greatest when viewing a solar eclipse without adequate eye protection.

Detached retina. A retinal detachment — a pulling away of the retina from the underlying choroid layer of the eye that provides its nourishment — is a medical emergency. If the retina is not surgically reattached as soon as possible, permanent and worsening vision loss can occur.

Importance Of Routine Eye Exams

It’s essential to keep your retina functioning properly to enjoy a lifetime of good eyesight. Many retina problems can be detected by your eye doctor before you notice any significant symptoms.

Routine eye exams enable your eye doctor to examine your eyes for signs of macular degeneration and other serious retina problems so treatment can begin as soon as possible.

If your eye doctor discovers a retinal detachment or other serious retina problem, he or she may refer you to an ophthalmologist who is a retina specialist for surgical or medical care.