Northeast Wisconsin Retina Associates

Surgical Procedures

PHOTODYNAMIC THERAPY (PDT)

PDT is an alternate form of laser treatment. The mechanism of action of PDT is much different than the thermal effect created by laser photocoagulation and its applicability is considerably more limited. PDT is used mainly in the management of wet age-related macular degeneration or other disorders where abnormal blood vessel growth occurs beneath the surface of the macula (choroidal neovascularization, CNV). CNV results in fluid leakage, bleeding and scarring leading to serious loss of central vision. Over recent years, since the advent of anti-VEGF medications administered by injection into the eye (see Intraocular Injections), the use of PDT has diminished dramatically. Nevertheless, in a select number of cases, this technique remains an important weapon in the retinal specialist’s arsenal.

PDT consists of a two-step process beginning with the administration of a drug (called a photosensitizer) by intravenous injection. Visudyne® (verteporfin) is the drug currently used for this procedure. The photosensitizer accumulates in the target blood vessels beneath the macula. The drug is then activated with low-energy laser light initiating a series of chemical reactions that causes the abnormal blood vessels to close. PDT is highly selective and attempts to minimize damage to the normal surrounding macular tissue. The goal of such selective treatment is to preserve better vision in comparison to intense laser treatment (thermal laser photocoagulation).

After treatment, it is important to avoid exposure to direct sunlight or other bright sources of light such as halogen lamps. This is critical during the first 48 hours following therapy. There are no other significant limitations or restrictions following treatment. No specific precautions are necessary with normal ambient indoor lighting. Other sources of bright illumination such as surgery in an operating room or dental procedures should also be avoided during the first 48 hours following treatment.

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