My 83-year-old mother has both glaucoma and macular degeneration. Twenty years ago, she also suffered a detached retina from an accidental blow to her head. She has enough vision to see shapes, forms and colors, but no detail. Recently, her doctor advised her that there is a new laser treatment for her type of macular degeneration that may result in improved vision. The procedure is so new that her doctor has only performed it on 14 people so far, mostly with good results. Of course, the doctor said there are no guarantees. Our family is in a real quandary. What should we do to make an intelligent decision regarding this new laser procedure?

D.P.

Your mother's situation may not be quite as complicated as you think. To begin with, a retinal detachment that has been successfully repaired would have no impact on the development of macular degeneration, and therefore should not influence your mother's choice of treatment. Also, because glaucoma affects an entirely different part of the visual pathway than macular degeneration, it too should not have any influence on the outcome of laser therapy for macular degeneration.

Therefore, your main focus should be to determine whether your mother has the type of macular degeneration that could benefit from this laser treatment, which is called photodynamic therapy. Macular degeneration may take one of two forms -- called dry and wet. Dry macular degeneration occurs when the retinal cells gradually die, causing mild to moderate vision loss. Wet macular degeneration occurs when abnormal blood vessels grow beneath the retina, and leak fluid and blood into the central retina (called the macula). The swelling of the retina leads to loss of vision, which may occur quickly and may be severe.

There is currently no treatment to stall the advance of dry macular degeneration. However, wet macular degeneration can be treated by a traditional laser, which uses heat to close the abnormal blood vessels and potentially halt further fluid leakage. Traditional laser therapy has been shown to be very effective in slowing or halting vision loss in many cases of wet macular degeneration. However, it is uncommon for traditional laser treatment to restore vision that has already been lost. Also, traditional laser treatment can sometimes make things worse by indiscriminately wiping out a patient's healthy retina cells -- and the vision associated with those cells.

Efforts to develop a better treatment for wet macular degeneration recently reached fruition with the U.S. Food and Drug Administration's approval of photodynamic therapy. In this procedure, a photoactive dye is injected into the bloodstream. Within about 15 minutes, the dye collects in the area of abnormal vessels beneath the retina. An infrared laser is then used to activate the dye, causing it to destroy the abnormal blood vessels. In contrast to traditional laser therapy's shotgun approach that may kill healthy retina cells along with abnormal blood vessels, photodynamic therapy selectively targets only abnormal blood vessels.

However, it is important to keep in mind that photodynamic therapy is not a panacea for all forms of wet macular degeneration. In fact, the new therapy has proven to be more effective than traditional laser treatment only in certain well-defined situations, including cases in which the abnormal blood vessels are located directly beneath the central retina. Currently, it is estimated that less than 5 percent of patients with wet macular degeneration stand to benefit from treatment with photodynamic therapy. Also, since this treatment is extremely expensive, you should certainly consider taking your mother to another eye doctor to get a second opinion on whether it is likely that she could be helped by the new therapy.