Intracocular pressure (IOP) is kept in balance by the production and drainage of aqueous fluid in the eye; the normal IOP is between 10 to 20mm of mercury. Elevated IOP can lead to glaucoma, according to the Mayo Clinic. Glaucoma is high IOP that damages the optic nerve by compressing the nerve fibers that surround it. Many factors affect IOP; elevated IOP should be treated to avoid the development of glaucoma.
Age
Elevated IOP is more common as people age. The incidence of glaucoma is higher in people of every race who are over age 60, according to the "Aging Eye Digest" published by the University of Illinois Eye and Ear Infirmary.
Race
African Americans are more likely to have elevated IOP. This may be because of several factors: African Americans are also more likely to have high blood pressure and diabetes, which carry additional risk of elevated IOP. People with dark-colored eyes are also more likely in general to have elevated IOP. African Americans have thinner corneas than Caucasians, according to the "Aging Eye Digest," which found that corneal thickness of less than 555 microns increased the chance of developing glaucoma by 300 percent. Mexican Americans and Japanese Americans also have an increased risk, according to the Mayo Clinic.
Family History
People with a family history are at least three times more likely to be at risk for developing glaucoma, according to "The Eye Digest." This may be related to a specific gene, or to the fact that a tendency toward diabetes or high blood pressure, as well as race and eye color, can increase the chance of developing elevated IOP. Only 3 percent of cases of glaucoma are associated with a specific gene, according to "The Eye Digest."
Myopia
People who have high myopia, or nearsightedness, are two to three times more likely to develop glaucoma, according to "The Eye Digest." This is true only of people who are extremely nearsighted; people with low myopia are not at risk.
Diabetes
There is some additional risk of developing glaucoma if you have diabetes, although the association isn't clear, according to the "Eye Digest." Use of steroid injection in the eye to reduce swelling caused by diabetes can also increase the risk, according to an article published in 2003 in the "British Journal of Ophthalmology" by J. Jonas.
Hypertension
High blood pressure may cause a very slight elevation in glaucoma rates, according to the "Eye Digest." However, a lower diastolic blood pressure number coupled with a higher IOP can increase the chance of glaucoma. Therefore, someone with well-controlled blood pressure but higher IOP may be more at risk for developing glaucoma.
Lifestyle Issues
Intraocular pressure is more likely to be elevated in people who are overweight, and often drops when people exercise, according to Optometry.com. IOP is also likely to be higher in the morning and in the winter.
