There are many different causes of glaucoma. In general, it is caused by an inability to maintain the proper balance of fluid within the eyes. Different types of glaucoma develop based on the cause of the fluid imbalance. Types of glaucoma include open-angle glaucoma, closed-angle glaucoma, and normal-tension glaucoma. Other types are congenital glaucoma and secondary glaucoma.
The fluid inside the eye, which is responsible for eye pressure, is produced by the cillary body, located just behind the iris. This fluid, which is called aqueous humor, is supposed to drain, relieving pressure through a structure in the eye. This structure is called the drainage angle. The fluid is released into the system of veins outside the eye. When the aqueous humor does not drain properly, intraocular pressure builds within the eye.
The eye is dependent on stable fluid pressure in order to maintain its shape and see properly. The eye has no way to relieve built-up pressure. A tire will pop when there is too much air in it. The eyes cannot pop or spring a leak. Instead, the pressure pushes against the optic nerve until the nerve is damaged enough to cause irreversible blindness.
Open-angle glaucoma occurs when the drainage angle is too open and the fluid cannot properly drain from the eye. This is the most common causes of glaucoma. Aging, genes, and brain chemical abnormalities can cause this type of glaucoma. Nutritional deficiencies and nitric oxide deficiencies can also cause open-angle glaucoma.
One of the rarest causes of glaucoma is a structural defect within the eye, making the drainage angle too narrow. This type of glaucoma can develop if the iris slips forward and blocks the drainage angle. It may be triggered by medications that dilate the pupil or if the eye dilates in low light.
The causes of glaucoma are not limited to abnormal levels of eye pressure. An example of this is normal-tension glaucoma. Sometimes a person's optic nerves are overly sensitive to pressure. In this case, what is considered to be a normal level of eye pressure can cause permanent eye damage. The cause of normal-tension glaucoma is not known, but some researchers think poor blood flow to the optic nerve may be a contributing factor.
Another one of the causes of glaucoma is genetics. This is called congenital glaucoma. It shows up at birth or in early childhood. Congenital glaucoma is usually caused by an existing eye condition or genetic defects in the eye.
Secondary glaucoma is when the condition develops from a previous injury or disease. It can be either open-angle or closed-angle glaucoma. There are many secondary causes of glaucoma, including ocular disease, trauma, and inflammation.
There are several factors that can contribute to the chances of developing glaucoma. Those with a family history of glaucoma, people who use steroids, and people more than 60 years of age are at increased risk. People with previous ocular injuries or ocular hypertension are at risk for developing glaucoma. Diabetes, leukemia, and hypothyroidism also increase the risk of developing glaucoma.