Although hypertension and diabetes increase the chance of developing a CRVO, most eyes that sustain a CRVO are healthy. Although the exact mechanism is not clear, the main retinal vein gets choked as it enters the eye via the optic nerve. Most patients experience sudden, painless loss of vision. Others may experience loss of vision over a period of weeks. Unfortunately, the loss of vision is permanent. Regular visits with your eye doctor are encouraged to prevent neovascular glaucoma from developing. This rare, painful type of glaucoma can be seen in several settings, but commonly is associated with central retinal vein occlusions. It can be prevented if diagnosed early.