Glaucoma is a group of diseases that can damage the eye's optic nerve and result in vision loss and blindness. Early treatment is important to prevent serious vision loss.here are 5 types of glaucoma:

1. Open-angle glaucoma. This is the most common type. It is characterized by slowly increasing eye pressure and the gradual loss of side vision. In medical term, eye pressure is called intraocular pressure (IOP). It is the fluid pressure inside the eye.
2. Low-tension or normal-tension glaucoma. The optic nerve is damaged but the eye pressure is normal.
3. Closed-angle glaucoma. This type produces a sudden increase in eye pressure. Symptoms include severe pain and nausea, as well as redness of the eye and blurred vision. This is a medical emergency and requires immediate treatment. Without treatment, blindness may occur in 1 or 2 days.
4. Congenital glaucoma. This type affects children who are born with eye defects that slows the normal drainage of fluid. These children usually have obvious symptoms, such as cloudy eyes, sensitivity to light, and excessive tearing.
5. Secondary glaucoma. This type develops as a complication of other medical conditions. It may be associated with eye surgery or advanced cataracts, eye injuries, certain eye tumors, or uveitis (eye inflammation). Pigmentary glaucoma occurs when pigment from the iris flakes off and blocks the meshwork, slowing fluid drainage. A severe form, called neovascular glaucoma, is linked to diabetes. Corticosteroid drugs used to treat eye inflammations and other diseases can trigger glaucoma in some people.