Choroidal neovascular membranes (CNVMs) are associated with many diseases. The most common causes are age-related macular degeneration (AMD),
presumed ocular histoplasmosis syndrome (POHS),
myopic macular degeneration,
trauma, and angioid streaks; however, many cases are idiopathic.
The natural history of patients with AMD should not be overlooked when pilot studies of new therapies are reported. In a randomized trial (of 481 patients) of interferon alpha-2, 62% of the placebo group stabilized at 1 year, losing less than 3 lines of vision. Randomized clinical trials are necessary in assessing treatment efficacy in cases of CNVM secondary to AMD as well as other causes. Submacular surgery, photodynamic therapy, translocation, and transpupillary thermotherapy (TTT) were once advocated as a means of stabilizing vision, where stable is defined a modest reduction in the rate of vision loss. True stabilization should be defined as no visual loss. A therapy that purports to stabilize vision requires large numbers of patients in a randomized trial with long-term follow-up to prove stabilization.
Clinical trials of ranibizumab not only showed true stabilization in approximately 75% of cases (ie, avoidance of 3 lines [15 ETDRS letters] of visual loss [defined as moderate visual loss]) but also 30-40% of patients had visual improvement.
Subfoveal CNVMs do not result in a loss of ambulatory vision if untreated. The natural history of subfoveal CNVMs never results in total blindness, while this outcome is all too frequent with macular translocation and occasionally with submacular surgery.