Blocked blood flow may bring strokes in some parts of the body, including the eye. Eye-related blockage can be caused by damage to any vital eye structures or parts such as the retina and optic nerve. Once an ocular blockage is caused, nutrients and oxygen can no longer flow through the blood, which in turn may result in eye strokes. Eye exams can search out signs of an eye occlusion. There are mainly four types of eye occlusion, depending on the location in which they are found.
Occlusion of the branch retinal artery
A painless branch retinal artery occlusion (BRAO) can cause peripheral vision and central vision loss. The main reason for BRAO is a blood clot in the carotid or from certain valve in the heart. A BRAO can lead to visual acuity loss if the arterial blood flow is disrupted or the macula is swelling. “Symptoms” of a BRAO include narrowing carotid, high blood pressure, cardiac disease or combinations of these conditions.
Ocular massage can be applied to treat acute or sudden arterial occlusion. And a glaucoma medication can be used to dislodge the embolus within 12 to 24 hours after a BRAO happens. A majority of patients with BRAO can restore visual acuity of 20/40 or better and complications such as neovascular glaucoma are rare.
Occlusion of the central retinal artery
Central retinal artery occlusion (CRAO) always affects only one eye and leads to vision loss. CRAO is usually caused by a blood clot from the neck artery or the heart, which blocks blood flow to the retina. CRAO patients usually also suffer from high blood pressure and carotid artery disease, cardiac valvular disease or diabetes. Symptoms of a CRAO can be pale retina and narrowed vessels.
Eye doctors may use a fluorescein angiogram to determine that if there is a CRAO. Within 24 hours after acute vision loss begins, it is possible for an eye doctor to take some treatments such as glaucoma medications for eye pressure decrease, ocular massage and a minor surgery named an anterior chamber paracentesis. Statistics show that most patients suffer severe visual loss.
Occlusion o the branch retinal vein
Another type of occlusion is branch retinal vein occlusion (BRVO), which may cause decreased vision, peripheral vision loss or blind spots. As its name reflects, BRVO is caused by a localized blood clot in a branch retinal vein. BRVO always occurs in people with high blood pressure accompanied by retinal bleeding. There are some risk factors for branch vein occlusion, e.g. hypertension, glaucoma, diabetes mellitus, leukemia, optic nerve drusen, anemia, vasculitis etc.
BRVO patients should receive eye exams every one to two months, in order to detect potential conditions such as macular swelling and neovascularization. Persistent macular edema requires a laser treatment named laser photocoagulation. And significant neovascularization requires a pan-retinal laser photocoagulation. Most patients can resume a 20/40 vision after taking a proper treatment.
Occlusion of the central retinal vein
A fourth type of occlusion is central retinal vein occlusion (CRVO). CRVO patients always have mild to severe hemorrhages and cotton-wool spots in the retina. The risky factors for branch retinal vein occlusion are also dangerous for central retinal vein occlusion. Moreover, if an occlusion of the central vein occurs in both eyes, there is a greater possibility of an underlying systemic cause.
There are generally two types of CRVO: ischemic and non-ischemic. Non-ischemic CRVO is more easily to treat than ischemic CRVO. Ischemic CRVO always brings dissatisfying visual acuity and other complications. If the initial vision is bad, a CRVO will result in severe visual acuity. The evaluation of signs for neovascularization or abnormal vessel growth is also important. The treatment for both two types of CRVO is usually a pan-retinal photocoagulation.