Laser Surgery : Retinal Photocoagulation

Laser Photocoagulation

A laser is a powerful beam of light which, 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 treatment is performed in the office, and usually requires no anesthesia other than an eyedrop. 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.

Several different laser procedures are used in the treatment of the following retinal diseases:

Focal Macular Laser for Macular Edema

Patients with disorders affecting the blood vessels of the macula, in particular diabetic retinopathy and retinal vein occlusion, often require this procedure. The laser decreases the leakage from damaged blood vessels, helping to preserve normal retinal thickness and function. The procedure is painless and does not take long to perform.

Panretinal Photocoagulation

When abnormal retinal blood vessel growth (neovascularization) occurs in diseases such as proliferative diabetic retinopathy or retinal vein occlusion, laser must be applied in a "scatter" pattern to large areas of the peripheral retina. These areas of the retina have poor blood flow (ischemia), and are responsible for releasing growth factors that cause the neovascularization. Untreated, retinal neovascularization often leads to bleeding in the eye (vitreous hemorrhage), traction retinal detachment, and/or neovascular glaucoma. 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 recognize decreased peripheral and night vision. The size of the pupil and the central vision may also be affected in some patients.

Laser Teatment of Choroidal Neovascularization

Abnormal blood vessel membranes can grow beneath the retina in age-related macular degeneration and other similar conditions. There are three main types of laser treatment which are used to eliminate these membranes:

• 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 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.
• 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 which 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 chroidal neovascularization.

Laser Retinopexy (treatment of retinal tears)

When a retinal tear or a small retinal detachment occurs, laser treatment may be applied to prevent further accumulation of fluid beneath the retina and minimize the risk of a vision-threatening retinal detachment. The laser is applied around the retinal defect. Over the course of a few weeks, the treated area develops a scar, which forms a tight seal between the retina and the underlying tissue. This procedure is sometimes performed around weak areas in the retina, such as lattice degeneration, in patients who may be at higher risk for retinal detachment. Laser retinopexy is often performed in conjunction with surgical treatments for retinal detachment, such as vitrectomy or pneumatic retinopexy.