Using knockout mouse models, we also provide evidence that Rap1B plays a role in containing and/or preventing choroidal endothelial cell invasion across the RPE and into the sensory retina, a step that is relevant in a number of eye diseases, including choroidal neovascularization associated with degenerative myopia, central serous retinopathy and age-related macular degeneration. Here, RAP1B is linked to pathological myopia.