Neovascularization of the Retina and Iris

Neovascularization of the iris (NVI) is a true eye emergency. If this condition is left untreated, a patient can quickly lose all vision in the affected eye. Anytime vision is lost in one or both eyes, seek treatment as soon as possible. It is very unlikely for vision to return to normal without treatment and the sooner treatment is initiated the greater the chance of recovering some vision.  The most common causes of NVI are proliferative diabetic retinopathy and ischemic central retinal vein occlusion. NVI can result from any condition that results in severe damage to the retina and its vascular system without completely killing the retinal tissue. The severely damaged retinal tissue desires fresh nutrients and metabolites from the vascular system to allow the tissue to repair itself and continue functioning. However, the damage to the vascular system of the retina prevents sufficient blood flow to these damaged areas of the retina.  In desperation, the damaged retinal tissue releases vascular endothelial growth factors (VEGFs) to recruit new blood vessels into the damaged area. This sounds beneficial, but unfortunately it is not. The new blood vessels that develop also create large areas of scar tissue, that destroy any residual retinal function and can cause tractional detachments of the retina that destroy the function of any unaffected areas of the retina.  The process is very destructive and significantly impairs visual function.  The VEGFs released by these damaged areas of the retina can also affect the iris (colored portion of the eye). VEGFs are carried from the posterior portion of the eye through the vitreous humor into the anterior portion of the eye into the aqueous humor. Once in the aqueous humor these VEGFs collect in the drainage structures of the eye (iris, ciliary body, schlemm's canal, trabecular meshwork, Schwalbe's line). The iris is close in proximity to the trabecular meshwork (structure that determines eye pressure/IOP).  These VEGFs cause irregular blood vessels and scar tissue to close off the drainage structures of the eye, similar to zipping up a zipper. The result is an instant glaucoma. Depending on the extent of closure  the eye pressure spikes. Due to a pressure gradient if the eye pressure is high enough, the central retinal artery won't be able to pump blood into the retina, resulting in the death of all retinal cells (except possibly a few in the macular region due to a supplemental blood supply). This can result in total darkness or the visual system being unable to perceive even the presence of light.  Neovascularization of the retina and the iris are eye emergencies brought on by damaged areas of retina. Maintaining a healthy cardiovascular system significantly decreases the risk of developing these conditions. If these conditions are identified early enough laser treatment of the retina, anti-VEGF injections and iridotomy can be utilized to spare function to the unaffected areas of the retina.