Due to block in a branch of retinal vein, lead to increase in blood back pressure leading to leakage of fluid and blood from vessels, which collects within the retina leading to reduced vision. Treatment options for this condition will the intravitreal injections of anti VEGF or Steroid, Sectoral laser.
If sectoral Laser is not done, there may be chances of Vitreous hemorrhage which may need surgery. Read more in section Floaters due to vitreous hemorrhage after BRVO.