INFLAMMATORY CAUSES

MCP is characterized by chorioretinal atrophic spots, peripapillary scarring, CNV, and linear streaks in the periphery, accompanied by intraocular inflammation. During the active phase, patients may have visual field defects, including enlarged blind spots and isolated scotomas, which resolve with resolution of the acute inflammation. Acute spots are a creamy yellow color, and with time the spots become more atrophic. The spots in MCP are usually smaller and more numerous and variable in size than those seen in POHS.2

TREATMENT

Despite its importance as a cause of visual impairment, no effective treatment has been established for CNV secondary to non-AMD-related causes. The design of therapeutic modalities for CNV is limited by the gaps in our understanding of the pathogenesis of CNV. Treatment for non-AMD-related CNV has been based on therapies developed for AMD, a much more common entity with more significant public health implications.9

CONVENTIONAL LASER

PHOTOCOAGULATION

For many years, thermal laser photocoagulation was the only proven treatment for CNV. Controlled trials showed a benefit from laser photocoagulation in well-demarcated CNV lesions associated with AMD. Laser photocoagulation has therefore been applied to the treatment of CNV due to myopia, POHS, and other non-AMD-related causes with variable results.

Several retrospective studies have demonstrated laser photocoagulation to be of limited benefit in improvement or stabilization of vision in myopic CNV.22,23 These studies showed that while laser photocoagulation might cause occlusion of the myopic CNV and temporary vision improvement, prominent enlargement of the atrophic photocoagulation scar eventually results in a worse long-term visual prognosis.

In contrast to the results of laser treatment for myopic CNV, the Macular Photocoagulation Study (MPS) demonstrated that argon and krypton laser photocoagulation is effective in treating well-defined extrafoveal and juxtafoveal CNV associated with POHS. Eyes with extrafoveal CNV were randomized to argon laser treatment or to no treatment.24 Untreated eyes demonstrated 3.6 times the risk of treated eyes of losing 6 lines or more of visual acuity (VA). After 5 years, treated eyes lost a mean of 0.9 lines of VA, compared to a loss of 4.4 lines in observed eyes. Eyes with juxtafoveal CNV secondary to POHS were randomized to krypton laser treatment or no treatment.25 Approximately 11% of treated eyes lost 6 lines or more of VA compared with 30% of untreated eyes. As laser photocoagulation causes irreversible destruction of the retina and RPE, with resulting scotoma and immediate visual loss, the MPS did not evaluate the efficacy of laser photocoagulation in treating subfoveal CNV from histoplasmosis.

The MPS also demonstrated the benefits of laser photocoagulation in patients with extrafoveal and juxtafoveal idiopathic CNV.26 Patients with idiopathic CNV were randomly assigned to krypton laser photocoagulation or to observation. After 3 years of follow-up, 10% of treated eyes compared with 37% of untreated eyes lost 6 lines or more of VA.

Retrospective studies of laser photocoagulation of CNV in patients with angioid streaks demonstrated that laser photocoagulation can result in closure of the CNV and either stabilization of VA or slowing of visual loss. A high rate of recurrence was reported, however, with CNV recurring in 77% of eyes.27,28

PHOTODYNAMIC THERAPY

Photodynamic therapy (PDT) with verteporfin (Visudyne; Novartis, Basel, Switzerland) consists of an intravenous infusion of verteporfin, a photosensitive drug which is activated by a laser light at 689 nm delivered at an intensity of 600 mW/cm2 over 83 seconds. PDT causes incomplete occlusion of the treated vessels. The advantage of PDT lies in its ability to target CNV selectively without destroying the overlying retina.29

PDT for CNV secondary to pathologic myopia was evaluated in the Verteporfin in Photodynamic therapy (VIP) trial. Patients with subfoveal myopic CNV were randomly assigned to verteporfin or placebo. At 12 months, 72% of verteporfin-treated patients compared with 44% of placebo-treated patients lost fewer than 8 letters, and 32% versus 15% improved at least 5 letters. Moderate vision loss (>15 letter loss) occurred in 14% of PDT-treated eyes compared with 33% of placebo eyes.30 While the 24-month data showed no statistically significant difference in the percentage of eyes losing at least 8 or 15 letters, the distribution of change in VA was in favor of a benefit for the patients assigned to verteporfin. Improvement by at least 5 letters was observed in 40% of verteporfin cases versus 13% of placebo cases, and improvement by at least 15 letters was seen in 12% of verteporfin cases versus 0 placebo cases. Based on both the 1- and 2-year results, the VIP study group recommended a consideration for verteporfin therapy for subfoveal CNV resulting from pathologic myopia.31

The Verteporfin in Ocular Histoplasmosis (VOH) study demonstrated the safety and efficacy of PDT with verteporfin for the treatment of subfoveal CNV in patients with POHS.32 At 24 months, 22 patients treated with PDT had a median VA improvement of 6 letters. Ten patients (45%) gained 7 or more letters, whereas 4 patients (18%) lost 8 or more letters. There was absence of leakage on FA from classic CNV in 85% of the patients, and no leakage from occult CNV was observed.

PDT with verteporfin for the treatment of CNV secondary to angioid streaks has been evaluated in several retrospective case series, showing that PDT does not significantly prevent the progression of the disease and associated visual loss.33,34 A small prospective study demonstrated an initial benefit of PDT after 1 year, but there was a progressive decline in vision after 2 years, as well as a failure to prevent subfoveal progression in the majority of cases.35

The treatment of CNV associated with idiopathic or inflammatory causes using PDT with verteporfin has been evaluated in several case series. Although the studies have been limited by a small number of patients and a short follow-up, these case series demonstrated that PDT