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The Role of Verteporfin Photodynamic Therapy in Current Therapy for Exudative Age-related Macular Degeneration

US Sensory Disorders Review, 2006:5-6 DOI:
Received: January 10, 2011 Accepted: January 10, 2011

Exudative age-related macular degeneration (AMD) develops in approximately 10 of out 1000 people per three-year period in the US, which projects an estimated 125,000 new cases per year. Exudative AMD is the commonest cause of legal blindness in developed countries. Given the increasing size of the aging population, this condition presents a substantial threat to quality of life in this group. Fortunately, enormous advances in treatment have occurred in the last few years, and at an accelerating pace.This has resulted in a sea change in both patients’ and physicians’ expectations from treatment, changing from the beneficial but unsatisfying outcome in 2003 of delayed vision loss, to the current status of the typical patient regaining previously lost vision. This review will detail the advances in pharmacologic therapy of AMD responsible for these improvements in quality of life for patients with this disease.

Thermal laser was the only treatment available for choroidal neovascularization (CNV) until the introduction of verteporfin photodynamic therapy (PDT) in 2000. Several National Institutes of Health (NIH)-funded studies detailed the application of thermal laser for CNV in AMD, ocular histoplasmosis and idiopathic CNV. Unfortunately, only a minority of patients were eligible for treatment with this modality, and those who were treated had a high failure rate.The majority of patients with AMD had occult or poorly defined CNV and were not suitable candidates for a thermal laser approach since the borders of treatment could not be delineated. In addition, patients with subfoveal CNV who were treated with laser lost vision immediately as a consequence of treatment, though there was a benefit of treatment in that they tended to lose less vision over time than their untreated cohorts. It was difficult to convince patients of this benefit.

The first major pharmacological agent for exudative AMD treatment was verteporfin (Visudyne.) This is a benzoporphyrin derivative formulated in a lipid-based solution for intravenous injection. Verteporfin PDT is a two-part treatment. The drug is infused intravenously and accumulates selectively in the endothelial cells of CNV. A low-powered, non-thermal, 689-nanometer laser is then used to activate verteporfin causing release of singlet oxygen. This reactive molecule damages vascular endothelium, which results in vasoconstriction and thrombus formation. This selectively occludes CNV while sparing the overlying retinal circulation.

Verteporfin PDT was evaluated in multiple clinical studies including AMD with classic subfoveal CNV— treatment of AMD with PDT (TAP) study—myopic CNV—verteporfin in photodynamic therapy (VIP) study—and occult or minimally classic CNV— Visudyne in minimally classic (VIM) study).Verteporfin PDT treatment was shown to result in slowing of vision loss in treated patients compared with controls. This treatment was approved by the US Food and Drug Administration (FDA) for use in April 2000 and entered clinical practice. This treatment held the promise of a greater number of treatable lesions, and possible visual improvement, but in fact a minority of patients achieved visual improvement and/or reading vision. Both patients and physicians were frustrated by the typical outcome of slow visual decline as a result of an expensive treatment.