NOV 22, 2013
This retrospective case series found that rapid involution and contraction of neovascular tissue adherent to the undersurface of the retinal pigment epithelium (RPE) may impart a substantial contractile force that tears this already-strained tissue layer after anti-VEGF injection.
The authors evaluated the pre- and post-tear OCT images of eight eyes that developed RPE tears following the administration of intravitreal anti-VEGF agents for wet AMD.
In all eyes, pre-tear images revealed a vascularized pigment epithelial detachment containing hyperreflective material consistent with choroidal neovascularization. This neovascularization was adherent to the undersurface of the RPE and created contractile folds in the RPE contour. In six eyes, contractile neovascular tissue spanned the pigment epithelial detachment causing outward bowing of the Bruch membrane and a peaked appearance to the overlying RPE monolayer.
The authors conclude that the key finding of this study is that prior to tearing, the choroidal neovascularization adherent to the RPE appears to contract. The tensile force derived from contracture of the adherent RPE places undue strain on the bare RPE at the attached–detached RPE junction. The increase in the magnitude of these forces after VEGF therapy contributes to the structural failure of the RPE monolayer.
They add that an important feature of every case in this series is that there remained a vulnerable segment of bare RPE not bolstered by the choroidal neovascularization or by attachments to the Bruch membrane. Their proposed mechanism for the development of RPE tears is predicated on the assumption that anti-VEGF agents will cause additional contraction of the neovascular tissue in some pigment epithelial detachment.
They say that although the retrospective nature of this study limits the scope of their conclusions, the presence of OCT findings suggestive of RPE stress, such as those described in this study, may serve as a premonitory sign of impending RPE tear. In order to limit this complication, they suggest close monitoring of eyes at risk for wet AMD and prompt therapeutic intervention prior to the development of large pigment epithelial detachments or substantial type 1choroidal neovascularization. They note that future studies may allow for the development of a numerical model that can characterize the degree of RPE strain and provide pre-injection estimates of tear risk.