DISEASES OF THE RETINA

The eye is a highly specialised complex sensory organ which contains many structures to enable vision. Light enters the eye through the pupil, is focused by the lens and lands at the back of the eye on the retina which contains millions of light-sensitive receptor cells as well as other nerve cells that receive and organise visual information. The light is converted into electrical impulses which travel via the optic nerve to the brain where they are processed and interpreted.

The two primary photoreceptor cells are the rods and cones. Rods, which are responsible for black and white vision, are generally situated around the edges of the retina. They can detect the lowest amounts of light, allowing people to see at night. Cones are present in the macula, the central part of the retina, and help people distinguish colours and see in typical light conditions. There are different types of cones, depending on the colour to which they are sensitive.

Retinal disorders are conditions that can affect any part of the retina. They vary widely, but most of them cause visual symptoms. Some may mildly affect a person’s vision, while others can cause severe vision loss or blindness. Anything that affects the retina should be taken seriously since with some conditions vision cannot be restored once it has been lost. Depending on the specific condition, treatment is available, the goal of which may be to stop or slow down its progression. The earlier the condition is detected, the better the long-term prognosis.

TYPES OF RETINAL CONDITIONS

Retinal tear. A retinal tear occurs when the clear, gel-like substance in the centre of the eye, the vitreous, shrinks and pulls on the retina, causing a tear. It can happen when the vitreous detaches as part of the aging process, or it can result from trauma.

Macular hole. Similar to retinal tears, macular holes are small breaks or holes in the macula that typically occur due to pulling between the retina and the vitreous.

Retinal detachment. When there is a build-up of fluid under the retina or the blood vessels under the retina are damaged and cause scar tissue, the retina lifts away or detaches from the underlying tissues which provide the eye with oxygen and nutrients. Retinal detachment is a medical emergency that requires immediate medical attention. Without treatment it may lead to permanent vision loss.

Diabetic retinopathy. Retinopathy is a common complication of diabetes and is a leading cause of blindness in adults. High blood sugar levels in diabetes impact blood vessels throughout the body, including the small vessels that feed the retina, causing them to deteriorate and leak fluid into and under the retina. Because symptoms often do not appear in the early stages, it is important that the eyes are checked regularly by an optometrist so that signs of diabetic retinopathy can be detected and treated early before vision has been affected.

Macular degeneration. Macular degeneration is a progressive disease characterised by a breakdown of the macula, the part of the retina responsible for central vision. The two types are wet and dry macular degeneration. Most people have the dry form, which can progress to the more severe wet form. The first noticeable symptoms often include changes in central vision which is gradually lost over time, but peripheral vision is maintained.

Epiretinal membrane. Epiretinal membrane, also known as a macular pucker, is a delicate tissue-like scar or membrane on top of the retina. There are usually no symptoms, but over time as it contracts it can pull on the retina, distorting central vision.

Retinal vein occlusion. Retinal vein occlusion is a blockage in the main retinal vein or one of its smaller branches due to a clot. The blockage cuts off circulation, which can cause nerve cells to die and blocked blood vessels to bleed and leak fluid onto the retina.

Retinitis pigmentosa. Retinitis pigmentosa is an inherited degenerative disease in which the light-detecting cells on the retina degenerate and cause a gradual loss of peripheral and later central vision. It can affect either the rods or the cones or both.

Retinoblastoma. Retinoblastoma is an extremely rare cancer that starts in immature cells in the retina. About 90% of cases develop before the age of 5 years. Vision is retained in most cases when the condition is treated early.

SYMPTOMS OF RETINAL DISEASE

While they do vary from condition to condition, many retinal diseases share certain common symptoms. These may include seeing floaters or flashes of light, blurred or distorted vision, a shadow over the field of vision, gradual loss of peripheral vision, poor night vision, muted colour vision, light sensitivity or difficulty adjusting to light changes. Certain conditions cause eye pain and sudden changes in vision, which are usually warning signs of potentially serious retinal disease and need prompt medical intervention.

Symptoms often do not appear in the early stages of the condition, but progress slowly over time. Depending on the specific condition, once vision has been lost, it cannot be restored, but early signs can be detected by an optometrist and steps can be taken to slow or even halt the progression before vision loss occurs.

RISK FACTORS FOR RETINAL DISEASE

While many different factors may contribute to the development of retinal disease and every retinal condition is unique, certain risk factors to be aware of include aging, family history, diabetes, certain autoimmune conditions, high blood pressure, obesity, smoking and eye injury or trauma.

TREATMENT OF RETINAL DISORDERS

Treatment varies depending on the type and extent of the retinal condition, but generally the goals of treatment are to restore or preserve vision and to prevent and delay the progression of the disease and damage to the retina. Treatment options may range from medications and vitamin supplements to injections, surgery, and laser treatments. The most suitable option for each specific condition should be discussed with your optometrist. Early detection is the key to a successful outcome.