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:
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.
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 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
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.