A laser is a powerful beam of light that, combined with ophthalmic equipment and lenses, can be focused on the retina. All lasers cause a certain amount of controlled damage in order to elicit the desired effect. Small bursts of the laser can be used to seal leaky blood vessels, destroy abnormal blood vessels, seal retinal tears, and destroy abnormal tissue in the back of the eye.
Laser photocoagulation is a type of laser treatment performed in the office that usually requires no anesthesia other than an eye drop. The procedure may take a few minutes, or can last up to half an hour, depending on the type of treatment needed. Most patients do not require a patch or medications following retinal laser, and can resume normal activities immediately.
Different laser procedures are used in the treatment of specific retinal diseases:
- Focal macular laser for macular edema
- Panretinal photocoagulation for proliferative diabetic retinopathy and retinal vein occlusion
- Laser treatment of choroidal neovascularization
Focal macular laser for macular edema
After laser is applied, the blood vessels tend to stabilize or regress. Since this treatment affects the function of the retinal periphery, some patients will experience decreased peripheral and night vision. The size of the pupil and the central vision may also be affected in some patients.
Laser treatment of choroidal neovascularization
- Conventional (“hot”) laser treatment coagulates blood vessel membranes. The procedure is painless and does not take long to perform. The vision in the area of treatment is permanently affected, and recurrences are common, but this is the procedure of choice in many circumstances.
- Photodynamic therapy (PDT, or “cold” laser) involves the intravenous injection of a light-sensitive drug, Visudyne®, which then accumulates in the blood vessel membranes. The drug is injected over a 10-minute period. A low-intensity laser is then applied to the retina for 83 seconds, activating the drug and closing the blood vessel membrane. Patients must avoid sunlight or other bright light for at least 2 days following the procedure; severe sunburn can occur if the drug is still in the system. There is no significant damage to normal tissue, but the blood vessels tend to re-open, and repeated treatments are often necessary, usually every 3 months or so, for several sessions. This is a useful treatment in patients with certain types of blood vessel growth beneath the central macula. The dye will make you sensitive to sunlight and halogen light. It is essential to avoid any bright source of light for 5 days following the treatment.
- Transpupillary thermotherapy (TTT, or “warm” laser) may also be useful in certain patients with blood vessel growth beneath the central macula. TTT involves a laser that warms the abnormal blood vessel membrane by several degrees, but not enough to cause a burn. This may cause the membrane to regress. A repeat treatment is necessary in some patients. Although this treatment shows some promise, it has not yet been proven to be effective in a clinical trial. Ongoing research will better define the role of this laser in the treatment of choroidal neovascularization.