Age-related macular degeneration (AMD) is one of the most common causes of poor vision after age 60. AMD is a deterioration or breakdown of the macula. The macula is a small area at the center of the retina in the back of the eye that allows us to see fine details clearly and perform activities such as reading and driving.

The visual symptoms of AMD involve loss of central vision. While peripheral (side) vision is unaffected, with AMD, one loses the sharp, straight-ahead vision necessary for driving, reading, recognizing faces, and looking at detail. Early AMD changes can be detected at home with the use of an Amsler grid (on the right of this paragraph). Patients should test one eye at a time, covering the other eye and looking at the grid. If the lines of the grid appear wavy, distorted or missing, the test is abnormal and the finding should be investigated by an optometrist or ophthalmologist.

Although the specific cause is unknown, AMD seems to be part of aging. While age is the most significant risk factor for developing AMD, heredity, blue eyes, high blood pressure, cardiovascular disease, and smoking have also been identified as risk factors. AMD accounts for 90% of new cases of legal blindness in Canada.

“Dry” AMD

Nine out of 10 people who have AMD have atrophic or “ dry” AMD, which results in thinning of the macula. Dry AMD takes many years to develop. A specific vitamin regimen based on the AREDS (Age Related Eye Disease Study) has been shown to slow progression of dry AMD.

“Wet” AMD

Exudative or “ wet” AMD is less common (occurring in one out of 10 people with AMD) but is more serious. In the wet form of AMD, abnormal blood vessels may grow in a layer beneath the retina, leaking fluid and blood and creating distortion or a large blind spot in the center of your vision. If the blood vessels are not growing directly beneath the macula, laser surgery is usually the treatment of choice. The procedure usually does not improve vision but tries to prevent further loss of vision. For those patients with wet AMD whose blood vessels are growing directly under the center of the macula, intravitreal injections with an anti-vascular endothelial growth factor agent called Lucentis (ranibizumab) has been shown to preserve vision in 95% of patients and restore or partially restore it in 40% of patients. a procedure called photodynamic therapy (PDT), is also sometimes used. Intravitreal injections of other medications can also be used in some cases.

Promising AMD research is being done on many fronts. In the meantime, high-intensity reading lamps, magnifiers, and other low vision aids help people with AMD to maximize their visual abilities.

AMD TREATMENTS

AMD is a disease of the macula, the most sensitive part of the retina, which is the light-sensitive film in the eye that allows us to see light. AMD affects the central vision, and interferes with reading, driving, and other activities that require good vision. There are two main types of AMD: the “dry” type, which usually progresses slowly, and the “wet” type, which can lead to rapid vision loss. Treating wet AMD is time sensitive, as delays can result in poorer visual outcomes in a matter of a week or less. There are currently two main treatments available for wet AMD:

ANTI-VEGF injections

The best treatment for wet-AMD is an injection with a type of drug called an anti-vascular endothelial growth factor (anti-VEGF). The anti-VEGF drug designed specifically for the eye is called Lucentis (ranibizumab). Lucentis works by inhibiting the growth of new blood vessels such as those found in “wet” AMD, and by shrinking existing leaky vessels. Research has also shown the drug to be beneficial for restoring/preserving the vision of patients with other eye problems with macular thickening. Treatment with Lucentis involves injecting the drug into the eye. About 40% of AMD patients experience visual improvements with these injections, with some patients gaining significant amounts of vision. Complications with this procedure are rare, but include retinal tear (1%) and infection (0.1%). Lucentis is the preferred anti-VEGF drug in the treatment of “wet” AMD, as it has been developed and tested and proven safe and effective for use in the eye specifically. Lucentis is covered by OHIP for patients who have developed wet AMD within the past three months and who have not had photodynamic therapy. Some patients with other retinal diseases or those under the age of 65 may benefit from Lucentis but do not qualify for OHIP coverage. For these patients, your ophthalmologist may recommend using another anti-VEGF drug named Avastin (bevacizumab) that is similar to Lucentis in its effect but much less expensive. Avastin injections cost around $320 each versus $1800 each for Lucentis. With either drug patients require an average of six treatments per year, at four to six week intervals.

Photodynamic therapy

The second treatment is called photodynamic therapy (PDT). PDT involves injecting a drug (visudyne) into the bloodstream and then activating the drug in the macula using a laser.

The drug works to seal up the leaking blood vessels in the macula. Visudyne makes patients light sensitive for 48 hours, so special precautions must be taken to stay out of bright light following treatment with PDT. PDT prevents further loss of vision from AMD in 2/3 of patients, but only 17% of patients see visual improvement with PDT. About 4% of patients have a decrease in vision after PDT; for most this loss is temporary.

OHIP would like Ontario ophthalmologists to choose either Lucentis or PDT as a treatment for AMD patients, but not both for any one patient. As Lucentis is so much more effective than PDT, I almost always choose Lucentis as a treatment and only choose to use PDT in patients who 1) are not covered for Lucentis injections and cannot afford Avastin, or 2) cannot tolerate the idea of an injection in the eye, or 3) who have not had success with Lucentis treatments.

Following patients being treated for AMD and other retinal conditions requires special testing to monitor the effects of treatment. The two types of special testing are fluorescein angiography and optical conherence tomography.

Fluorescein Angiography

Fluorescein angiography is one testing option.  Fluorescein angiography evaluates the blood vessels in eyes with macular or retinal disease. This test requires dilation of the pupils and a small injection of vegetable dye through an intravenous needle into a vein in your arm. A series of pictures of your macula and retina are then taken over approximately 15-20 minutes. Most patients tolerate this test very well without any side effects. Some patients feel nauseated for a few minutes.

Optical Coherence Tomography (OCT)

Optical coherence tomography (OCT) testing is a retinal scan used to study the anatomy of the retina in fine detail. OCT testing requires dilation of the pupils but does not require a needle in the arm and does not involve touching the eye. A healthy retina is only ¼ of a millimeter thick, but it contains multiple layers of specialized cells. One layer converts light into nerve signals, another processes the nerve impulses, while another transmits these processed impulses to the brain where they are intrepreted. OCT testing is like having an optical biopsy of the retina; it provides excellent visualization of these layers of the retina, and aids greatly in the diagnosis and treatment of retinal disorders.

Fluorescein angiography is covered by OHIP. In Ontario OCT testing is considered non-essential and is not covered by OHIP. Because OCT testing is the superior test for following macular disease, patients are encouraged to consider taking advantage of this testing option.

DIABETIC RETINOPATHY

If you have diabetes mellitus, your body does not use and store glucose properly. Over time, diabetes can damage blood vessels in the retina, the nerve layer at the back of the eye that senses light and helps to send images to the brain. The damage to retinal vessels is referred to as diabetic retinopathy.

Non-proliferative Diabetic Retinopathy

Many people with diabetes have mild NPDR, which usually does not affect their vision. When vision is affected, it is the result of macular edema or macular ischemia, or both.

Macular Edema

Macular edema is swelling or thickening of the macula, a small area in the center of the retina that allows us to see fine details clearly. The swelling is caused by fluid leaking from retinal blood vessels. It is the most common cause of visual loss in diabetes. Vision loss may be mild to severe, but even in the worst cases, peripheral (side) vision continues to function. Laser treatment can be used to help control vision loss from macular edema. Newer treatments are being investigated.

Macular ischemia occurs when small blood vessels (capillaries) close. Vision blurs because the macula no longer receives sufficient blood supply to work properly. Unfortunately, there are no effective treatments for macular ischemia.

Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is a complication of diabetes caused by changes in the blood vessels of the eye. If you have diabetes, your body does not use and store sugar properly. High blood sugar levels create changes in the veins, arteries, and capillaries that carry blood throughout the body. This includes the tiny blood vessels in the retina, the light-sensitive nerve layer in the back of the eye.

In PDR, the retinal blood vessels are so damaged they close off. In response, the retina grows new, fragile blood vessels. Unfortunately, these new blood vessels are abnormal and grow on the surface of the retina, so they do not resupply the retina with blood.

Occasionally, these new blood vessels bleed and cause a vitreous hemorrhage. Blood in the vitreous, the clear gel-like substance that fills the inside of the eye, blocks light rays from reaching the retina. A small amount of blood will cause dark floaters, while a large hemorrhage might block all vision, leaving only light and dark perception.

The new blood vessels can also cause scar tissue to grow. The scar tissue shrinks, wrinkling and pulling on the retina and distorting vision. If the pulling is severe, the macula may detach from its normal position and cause vision loss.

Laser surgery may be used to shrink the abnormal blood vessels and reduce the risk of bleeding. The body will usually absorb blood from a vitreous hemorrhage, but that can take days, months, or even years. If the vitreous hemorrhage does not clear within a reasonable time, or if a retinal detachment is detected, an operation called a vitrectomy can be performed. During a vitrectomy, the eye surgeon removes the hemorrhage and any scar tissue that has developed, and performs laser treatment to prevent new abnormal vessel growth.

People with PDR sometimes have no symptoms until it is too late to treat them. The retina may be badly injured before there is any change in vision. There is considerable evidence to suggest that rigorous control of blood sugar decreases the chance of developing serious proliferative diabetic retinopathy.

A medical eye examination is the only way to discover any changes inside your eye. If your ophthalmologist or optometrist finds diabetic retinopathy, you may require a special test called fluorescein angiography or optical coherence tomography (OCT) to find out if you need treatment.

If you have diabetes, early detection of diabetic retinopathy is the best protection against loss of vision. You can significantly lower your risk of vision loss by maintaining strict control of your blood glucose and visiting your ophthalmologist regularly. People with diabetes should schedule examinations at least once a year. Pregnant women with diabetes should schedule an appointment in their first trimester, because retinopathy can progress quickly during pregnancy. More frequent medical eye examinations may be necessary after a diagnosis of diabetic retinopathy.