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Early detection and treatment of incident choroidal neovascularization in eyes with age-related macular degeneration may offer patients the best opportunity to retain vision. Clinical trials have provided guidance on defining patient risk and the frequency of follow-up. An ongoing study is examining the role of noninvasive technologies as monitoring tools.
Baltimore-Monitoring for choroidal neovascularization (CNV) in patients with age-related macular degeneration (AMD) is extremely important because early treatment of small neovascular lesions might offer the best visual prognosis, said Diana V. Do, MD, at Current Concepts in Ophthalmology.
"Especially now, when we have effective therapies for neovascular AMD, clinicians need to identify eyes at high risk for conversion to exudative disease and provide careful, frequent follow-up for early detection," said Dr. Do, assistant professor of ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore.
The need to monitor for incident CNV is underscored by statistics that estimate 8 million adults in the United States have intermediate-stage AMD, of whom 1.3 million will advance to the severe stage within 5 years. There are three factors to consider in monitoring patients with AMD:
2. Determining how often they should be evaluated.
3. Identifying the best method for early detection of CNV.
Investigators in the Age-Related Eye Disease Study (AREDS) developed a simplified severity scale for clinicians to use in determining a patient's 5-year risk for developing advanced AMD. The method is based on two readily identifiable features seen in fundus examination:
1. The presence of at least one large druse (diameter at least 125 μm) located within 2 disc diameters of the foveal center.
2. The presence of any pigmentary changes within 1,500 μm of the foveal center.
To use the scale, each eye is graded independently and assigned 1 point for each feature present so that the possible total score for a patient ranges from 0 to 4. A patient with a score of 0 has a negligible risk for developing advanced AMD over the next 5 years while a score of 1 confers a 3% risk. Patients with a score of 3 or 4 are considered at highest risk with 5-year risk rates of 25% and 50%, respectively.
Guidelines on monitoring for the development of AMD-related CNV are available in the American Academy of Ophthalmology's Preferred Practice Pattern. That document states that patients with intermediate or advanced AMD in one eye should return for an exam at an interval between 6 and 24 months if they are asymptomatic but promptly if symptoms develop.
"Those guidelines are quite vague, but a recent report from the Submacular Surgery Trials (SST) Research Group provides evidence that these patients should be followed more closely," said Dr. Do.
The SST publication reported on the development of incident CNV in fellow eyes of 364 patients with unilateral subfoveal CNV. All patients were followed at 3, 6, 12, and 24 months and annually thereafter with BCVA, fundus examination, stereoscopic fundus photography, and fluorescein angiography.
The cumulative rates of incident CNV were 14% at 1 year, 22% at 2 years, and 37% at 4 years. The vast majority of incident lesions (90%) were predominantly CNV at presentation. Two-thirds of the CNV lesions were occult without classic features. Importantly, 30% were extrafoveal, 9% were juxtafoveal, and 61% were relatively small (3 disc areas or less).
"These data on lesion characteristics support the conclusion that frequent angiographic follow-up may help to detect incident CNV that has a more favorable prognosis if treated promptly," noted Dr. Do.
"Based on the findings, the SST Research Group recommended careful and frequent follow-up with fluorescein angiography of at-risk fellow eyes, at least every 3 to 6 months within the first year after onset of CNV in the first eye."