A stroke is the blockage of blood flow to the brain or bleeding into the tissue of the brain. One-in-four people globally can be expected to have a stroke during their lifetime. While this knowledge may not be uncommon, “strokes” can also occur within the retina of the eye causing a sudden, painless loss of vision. These retinal vein occlusions occur when there is a blockage of veins carrying blood with oxygen and nutrients to the nerve cells in the retina. A blockage in the retina’s main vein is known as a central retinal vein occlusion (CRVO), while a blockage in a smaller vein is called a branch retinal vein occlusion (BRVO).
The majority of BRVOs will occur at an arteriovenous crossing, an intersection between a retinal artery and vein. These vessels share connective tissue, therefore when the artery loses elasticity, the vein becomes compressed. By narrowing the vein, blood flow becomes turbulent promoting clotting, thus leading to a blockage or occlusion of the vein. Due to this blockage, blood drainage at the arteriovenous crossing may lead to fluid leakage in the center of vision and ischemia, poor blood flow in the blood vessels supplying the macula.
The common risk factors for BRVO are uncontrolled hypertension, obesity, heart disease, glaucoma, and blood clotting tendencies. Treatment begins with identifying these underlying risk factors and treating them. We can assess these risk factors using several methods such as blood pressure monitoring, measuring blood cholesterol or lipid levels, blood tests to determine if there is an abnormal tendency to form blood clots, etc.
Eye treatment is aimed at treating retinal complications rather than trying to remove the blockage itself. For example, macular edemas, the main component of visual loss from BRVOs, is often treated with intraocular injections of anti-VEGF drugs which are designed to stop the growth of abnormal blood vessel formation and decrease leakage. These injections will be given after proper numbing of the eye to minimize discomfort and are usually done on an injection schedule determined on a case-by-case basis. In hard-to-treat cases, laser treatment may also be performed alongside anti-VEGF injections where light laser pulses are applied to the macula in a grid pattern.
Sources:
Risk of stroke is up worldwide. what can be done about it?. UCLA Health. (2023, May 3). https://www.uclahealth.org/news/article/risk-stroke-up-worldwide-what-can-be-done-about-it#:~:text=All%20told%2C%20the%20data%20suggest,behind%20the%20increase%20in%20strokes%3F
The The American Society of Retina Specialists. (n.d.). Branch retinal vein occlusion. Branch Retinal Vein Occlusion - Patients - The American Society of Retina Specialists. https://www.asrs.org/patients/retinal-diseases/24/branch-retinal-vein-occlusion Assessed and Endorsed by the MedReport Medical Review Board