4. The Division Between Nonexudative and Exudative AMD May Not Be Absolute
Optical coherence tomography angiography (OCT-A) is a rapid, noninvasive imaging technique that allows for three-dimensional visualization of retinal and choroidal microvasculature. OCT-A is a sensitive and valuable tool for the identification of CNV in AMD and provides several advantages over traditional fluorescein angiography, particularly in regard to speed and patient tolerability.
It has previously been recognized that a subset of patients with "dry" AMD have CNV that is subclinical (ie, nonexudative). Historically, indocyanine green angiography (ICGA) has been used to characterize these lesions, but because it is often not a routine part of AMD evaluation, the applicability of these findings in the clinic has been limited. However, the introduction of OCT-A has now given clinicians a rapid and reliable way to detect nonexudative CNV in patients with dry AMD.
These eyes have a higher risk of developing exudative disease than eyes without CNV detectable by OCT-A. In one series, nonexudative CNV was identified in 14% of fellow eyes (intermediate AMD or geographic atrophy) of patients with unilateral exudative AMD, and these eyes were 15 times more likely to develop exudation within 1 year.
In general, these lesions should simply be monitored closely; anti-VEGF therapy is not currently indicated in the absence of fluid leakage or clinical symptoms. It remains possible, however, that anti-VEGF treatment could prevent lesion growth or subsequent exudation. Ongoing research is exploring the role of anti-VEGF therapy in eyes at high risk for progression to exudative disease.
5. Not All Choroidal Neovascularization Is Wet AMD
Although CNV is the defining characteristic of wet AMD, it is not a pathognomonic finding. CNV may also be associated with high myopia, uveitis, central serous chorioretinopathy, and other pathologies. These forms of CNV often occur in patients who are younger than their counterparts with AMD. As in AMD, CNV due to other etiologies may cause significant irreversible vision loss in the absence of any interventions.
CNV secondary to pathologic myopia has received the most attention among non-AMD etiologies of CNV. Severe myopia may lead to degenerative changes in the sclera, choroid, and retina, with CNV being a relatively common complication in these eyes. Clinical studies have shown that anti-VEGF therapy is effective for CNV secondary to pathologic myopia.[34,35] Notably, good anatomic and visual outcomes may be achieved with fewer injections than are typically needed in wet AMD. For example, in the phase 3 RADIANCE trial, patients received a median of just two to four injections through 12 months, depending on treatment group.
Subsequent research has explored the efficacy of anti-VEGF therapy for CNV due to causes other than AMD and myopia. The phase 3 MINERVA trial demonstrated the efficacy of ranibizumab (+9.5 letters over 12 months) in a population with diverse underlying causes of CNV, including idiopathic chorioretinopathy, angioid streaks, postinflammatory retinochoroidopathy, and central serous chorioretinopathy. These data have led to the approval of ranibizumab in Europe for CNV due to any cause.
More Work to Be Done
Overall, although great strides have been made in the understanding and management of wet AMD and related diseases, there is still much work to be done. Ongoing basic, clinical, and translational research will be critical to making further advances and improving patient outcomes.
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Medscape Ophthalmology © 2018 WebMD, LLC
Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Age-Related Macular Degeneration: 5 Things to Know - Medscape - Dec 14, 2018.