Non-Exudative Macular Neovascularization – A systematic review of prevalence, natural history, and recent insights from OCT angiography

ABSTRACT Topic To review the available literature on the prevalence, incidence, natural history, and exudative conversion rates of subclinical (treatment naive) non-exudative macular neovascularization (MNV) in patients with age-related macular degeneration (AMD). Clinical Relevance Non-exudative MNV is now known to be more prevalent in patients with AMD than initially thought and is bringing new insights into both the natural history and management of this very prevalent disease. Methods We conducted a literature search on PubMed, Scopus and Web of Science, along with a manual search, from January 2014 to June 2019. We included studies that used optical coherence tomography angiography (OCTA) as a primary diagnostic tool to evaluate subclinical (treatment naive), non-exudative, neovascular AMD. Results Of the 258 screened articles, 12 were included. The prevalence of subclinical non-exudative neovascular AMD in the fellow eyes of patients with unilateral exudative AMD ranged from 6.25% to 27%. Although these lesions were not associated with a significant decrease in visual acuity, the presence of non-exudative MNV seems to be an important predictor of exudative disease. Incidence of exudation in the reviewed studies ranged from 20-80% (follow-up 6 months to 2 years). There is some evidence that non-exudative MNV may slow down the growth of adjacent geographic atrophy (GA). As long as exudation does not occur, it appears that subclinical non-exudative MNV is not responsible for the deterioration of visual function. Conclusions Non-exudative MNV is an asymptomatic condition. While non-exudative MNV appears to be a precursor andfor the formation of exudative neovascular AMD, there is evidence suggesting a protective effect in slowing the progression of GA. Early detection of non-exudative MNV before exudation develops should result in better monitoring of patients who are at high risk of conversion to exudative AMD.While no controlled clinical trial has been performed to provide definitive recommendations, the authors of the studies included in this review agree that non-exudative lesions should not be treated until symptomatic exudation develops. Moreover, the existence of a non-exudative form of neovascular AMD would suggest that the term neovascular AMD should be preceded by either exudative or non-exudative when describing this neovascular stage of AMD.