The underlying causes of glaucoma are unknown. There are genetic links to several types of glaucoma.  Contributing and risk factors include:

• Increased eye pressure. People with elevated pressure inside the eye (intraocular pressure) are more prone to, but do not always develop, glaucoma. In addition, some people with normal or low eye pressure develop the disease.
  
  
• Age and race. High-risk groups are blacks over age 40 and anyone over age 60, especially Mexican-Americans, according to the U.S. government's National Eye Institute. Asians are susceptible to angle-closure glaucoma. Japanese people are susceptible to normal-tension glaucoma.
  

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  Family medical history. A family history of glaucoma indicates increased likelihood of developing the disease.
  
  
• High blood pressure. Glaucomatous damage is exacerbated by above-normal blood pressure (hypertension).
  
  
• Diabetes. Elevated glucose (blood sugar), high blood pressure and heart disease related to diabetes all raise the odds of developing glaucoma. People with type 2 diabetes have higher rates of cataracts (clouding of the lens) and glaucoma leading to vision loss compared to the general population, in addition to their risk of diabetic retinopathy.
  
  
• Eye injuries. Severe physical trauma to the eye, burns from chemicals or penetrations can all lead to increased eye pressure, lens dislocations or blockage of drainage.
  
  
• Nearsightedness or farsightedness. Inability to see objects at far or close distances without glasses or contact lenses increases the likelihood of developing this disease.
  
  
• Prolonged use of corticosteroids.  Anti-inflammatory medication commonly used to prevent asthma, arthritis and allergy attacks. Secondary glaucoma is more likely in longtime users of corticosteroids, including cortisone. Longtime use of corticosteroids is also a risk factor for secondary diabetes, cataracts, osteoporosis and other conditions.
  
  
• Eye abnormalities. Structural eye abnormalities increase susceptibility to certain kinds of glaucoma, such as reduced thickness of the central cornea or narrow optic nerves.
  
  
• Pseudoexfoliation syndrome. A condition involving shedding of protein in the aqueous humor. Pigment and pseudoexfoliatiative material clogs the trabecular meshwork, elevating intraocular pressure. A whitish material builds up on the lens and can be seen by slit-lamp examination. This syndrome increases the risk of glaucoma (open-angle) by six times, according to the Glaucoma Foundation. Ten percent of people over age 50 have this syndrome, the organization reports.
  
  
• Other medical conditions. Migraines, poor circulation, retinal detachment, eye tumors and eye inflammations increase the risk of developing glaucoma. Some types of eye surgery may also lead to secondary glaucoma.