​Retinopathy of Prematurity (ROP) is a disorder of the eye that occurs in premature babies.  It is caused by the abnormal development of blood vessels in the retina (the tissue that lines the back of the eye) of an immature eye.  When severe, these abnormal blood vessels can leak and pull on the retina (the thin photosensitive layer at the back of the eye), resulting in a retinal detachment and visual loss.