We have already covered how some diseases, such as high blood pressure and diabetes, can cause retinopathy, and may be a threat to vision. Beyond the threat of hypertensive or diabetic retinopathy, people with poorly controlled high blood pressure and diabetes may carry a higher risk for an artery or vein occlusion inside the eye, also referred to as an “eye stroke.” Strokes in the eye can occur when blood flow is blocked through the arteries or veins in the retina, and significant damage to retinal tissue may occur. Artery or vein occlusions inside the eye may be significant threats to vision and should be immediately evaluated by your eye doctor.
Strokes in the Eye: Retinal Vein Occlusions
Retinal veins are the small vessels in the back of the eye that help drain blood from the eye. When a retinal vein occlusion occurs, these vessels are blocked, leading to leakage of blood out of the vessels and into the retinal tissue. Vein occlusions are painless, but have the potential to cause significant vision loss. The leakage of blood and loss of blood flow can lead to areas of retinal swelling and ischemia, which can compromise the visual outcome. In a central retinal vein occlusion, or a CRVO, the main vein responsible for draining blood from the entirety of the retina is affected. A branch retinal vein occlusion, or BRVO, occurs when one of the secondary branches of the central vein is blocked, and affects a smaller portion of the retina. CRVO’s tend to be more problematic and carry worse consequences than BRVO’s, and can lead to vision loss that is moderate to severe. Risk factors for a CRVO include significant vascular disease such as high blood pressure or diabetes, blood clotting disorders, glaucoma, and history of a previous stroke. A BRVO most commonly occurs in those with diabetes or hypertension.
Vein occlusions need to be immediately evaluated so the appropriate treatment course can be identified. Both CRVO and BRVO may require treatments that include laser photocoagulation to prevent the growth of new blood vessels, or injections to help reduce retinal swelling. While these treatment courses may not completely restore vision, they have proven to give more positive visual outcome.
Strokes in the Eye: Retinal Artery Occlusions
An artery occlusion occurs when the vessel carrying blood to the retina is blocked or clogged. When this happens, the eye stops receiving the blood flow it needs, and the retinal tissue can be severely damaged. Like in vein occlusions, retinal artery occlusions are painless and can occur in the central retinal artery (CRAO) or a branch retinal artery (BRAO). A CRAO is most typically caused by a significant blood clot in the carotid artery, and can be indicative of dangerous artery disease. A central retinal artery occlusion typically has a much worse visual outcome than a vein occlusion. While a BRAO can lead to moderate vision loss or blind spots, those who have had a CRAO could be left with very little usable vision in the affected eye. Unfortunately, there is currently no effective treatment for a CRAO or BRAO, and management includes taking measures to preserve vision in the other unaffected eye.