100-day glaucoma, also known as neovascular glaucoma, can be associated with various ocular conditions. Specifically, it is commonly seen after central retinal vein occlusion (CRVO). When a CRVO occurs, the blood flow through the central retinal vein is obstructed, leading to ischemia (lack of oxygen) in the retina. This ischemia stimulates the production of factors that promote neovascularization, or the abnormal growth of new blood vessels. These vessels can grow over the iris and into the drainage angle of the eye, obstructing fluid outflow. This process leads to an increase in intraocular pressure, resulting in neovascular glaucoma. The term "100-day glaucoma" is used because this type of glaucoma can develop around 100 days (about 3 months) following an ischemic CRVO.
Hence, the correct answer is:
Central retinal vein occlusion (CRVO)