Glaucoma is a disease characterized by elevated intraocular pressure, or IOP, which results in damage to the optic nerve. The factors that contribute to elevated IOP and optic nerve damage differ for each type of glaucoma. Awareness of the different causes and risk factors for glaucoma may help you identify the condition early on, as timely diagnosis of glaucoma is vital to preventing vision loss. The sections below contain information about the causes of various types of glaucoma.
General Risk Factors for Glaucoma
Certain people are at a heightened risk of developing glaucoma. These include:
- African-Americans over 40 years of age
- People who have a family history of glaucoma
- Steroid users
- People with prior ocular injuries
- Patients with ocular hypertension
- People over 60 years of age
There are also several medical conditions that increase a person’s risk of glaucoma, including:
- Sickle cell anemia
Learn more about the symptoms of glaucoma.
Causes of Open-Angle Glaucoma
The most common form of glaucoma, open-angle glaucoma, affects approximately three million Americans. Causes of open-angle glaucoma include:
- Aging - The aging process reduces the size of the eye’s drainage angle, resulting in increased intraocular pressure.
- Genes - Several genetic factors can contribute to glaucoma. Mutations in the GLC1A gene cause it to overproduce a substance that clogs the angle where fluid drains from the eye. In addition, the LMX1B gene is believed to cause some cases of glaucoma.
- Nitric oxide deficiencies - Low levels of nitric oxide contribute to unhealthy blood vessels, which in turn elevate intraocular pressure.
- Nutritional deficiencies - This may cause damage to optic nerve fibers.
- Brain chemical abnormalities - Large amounts of glutamate (a neurotransmitter) can contribute to the destruction of nerve fibers within the eye.
Open-angle glaucoma does not typically present symptoms in its early stages. However, eventually the patient will begin to lose his or her peripheral vision.
Causes of Closed-Angle Glaucoma
Closed-angle glaucoma, a rare form of the disease accounting for just 15 percent of all glaucoma cases in the country, is caused by a structural defect within the eye that creates a narrow angle between the iris and cornea. If the iris slips forward, it may block the fluid drainage angle. This condition can be triggered by medications that dilate the pupil, such as antihistamines and tricyclic antidepressants. It can also occur naturally, when the eye dilates in low light. People who suffer from hyperopia (farsightedness) are at a heightened risk for acute closed-angle glaucoma because their eyes have narrow drainage angles. Closed-angle glaucoma produces symptoms of severe eye pain, blurred or haloed vision, nausea, vomiting, and headache.
Causes of Normal-Tension Glaucoma
Since elevated IOP is not a factor in normal-tension glaucoma, doctors are not sure what causes optic nerve damage. Theories include:
- Reduced blood flow
- Early nerve cell death
- Nerve irritation
- Excess glutamate production
- Autoimmune disease
Normal-tension glaucoma may result in a loss of peripheral vision.
Causes of Congenital Glaucoma
Congenital glaucoma is present at or near the time of birth. Typical causes of congenital glaucoma include genetic defects in the drainage canal or other existing eye conditions. Approximately 85 percent of congenital glaucoma cases can be attributed to an inherited genetic defect. Congenital glaucoma is referred to as infantile when it is present within the first three years of life and juvenile if it occurs after three years of age. Studies have shown that congenital glaucoma affects male children more often (65 percent) than females. Congenital glaucoma occurs bilaterally (in both eyes) in 70 percent of studied cases. Congenital glaucoma can be difficult to recognize because children often have trouble discerning the symptoms.
Causes of Secondary Glaucoma
Secondary glaucoma is associated with a previous illness, injury, or disease. There are many secondary causes of glaucoma. Secondary glaucoma can be either of the open-angle or closed-angle variety, and are associated with:
- Developmental glaucoma, as in neurofibromatosis
- Ocular disease – pigment dispersion and neovascular glaucoma
- Systemic diseases and drugs – corticosteroid glaucoma
- Inflammation – uveitis
- Trauma – angle recession, RBC associated glaucoma
- Ocular surgery – aphakic glaucoma, aqueous misdirection
Find a Doctor for Diagnosis and Treatment of Glaucoma
If you would like more information about the causes of congenital glaucoma, open-angle glaucoma, or another form of glaucoma, DocShop can provide you with a list of eye care professionals in your area that would be happy to answer your questions. Find a glaucoma specialist near you.