The single most important risk factor for undetected glaucoma may be the lack of health insurance, said Dr. Varma, referring to the fact that 30 percent of all participants with eye disease lacked health care coverage.
Get out your sphygmomanometers. And it found low perfusion pressure, low diastolic blood pressure, and high systolic and mean arterial blood pressures are associated with a higher prevalence of OAG. Also, a higher prevalence of glaucoma was seen with low perfusion pressure, which is blood pressure minus IOP. The vascular theory of the pathogenesis of OAG suggests that low blood pressure, particularly in the face of elevated IOP, can reduce perfusion pressure at the optic nerve head, causing ischemic damage to the retinal ganglion cells.
Varma said the vascular hypothesis is compelling because Latinos have a high prevalence of a number of vascular problems, including retinopathy. In , M. Roy Wilson, MD, MS, challenged the medical community to explain why differences in disease burden occur among the races. For example, the OHTS found that thinner corneas are a risk factor for glaucoma. Perhaps, said Dr.
Wilson, thin corneas are more important as an isolated factor than race, per se. Girkin agreed. This observational cohort is designed to obtain data on visual function and optic nerve structure for the eyes of Americans of African ancestry and compare it with those of European descent.
No other study has followed this high-risk population with advanced imaging and functional testing, which optimizes the detection of disease and progressive glaucomatous injury. Girkin, who is professor of ophthalmology at the University of Alabama in Birmingham and director of the glaucoma service there. Anatomic variations can be important. Hispanics may be particularly susceptible to damage from poor blood flow to the optic nerve because there is a high prevalence in this population of diseases that affect the blood vessels, such as diabetes.
The National Eye Institute recommends that everyone over age 60, but especially Mexican Americans, be evaluated for glaucoma. Thus far we have been discussing the most common form of glaucoma in the U. However, for primary angle-closure glaucoma PACG there are also differences among various ethnic groups. This is not to say that primary open-angle glaucoma is not seen in Asian Americans.
This can be a particularly insidious form of glaucoma because the eye pressure is never elevated. There are also differences among various other Asian ethnicities in the risk of having narrow angles a precursor to having primary angle-closure glaucoma. For example, Vietnamese Americans, Pakistani Americans, and Chinese Americans have been found to have a greater risk of narrow angles compared to other Asian American populations.
It is difficult to know why Asian Americans have higher rates of primary open-angle glaucoma but it likely has to do with the anatomy of the eye, which may likely reflect some genetic contribution. Narrow angles are much less common in African American and Hispanic populations.
Pseudoexfoliation glaucoma is another form of open-angle glaucoma that occurs in different ethnic groups at varying rates. It is more common in patients with heritage from Scandinavian countries, although it is found in all populations to varying degrees.
A genetic association has been found with the lysyl oxidase-like 1 gene LOXL1 but the interesting thing is that even many patients without pseudoexfoliation glaucoma have changes in this gene. This suggests that genetic factors are not the only contributing factor, and that the environment could be playing a very important role. Of course, despite all of these differences in glaucoma risk and severity of disease, one has to wonder whether ethnicity is really driving these differences that we see.
It is possible that certain ethnic groups have specific anatomic changes that predispose them to glaucoma, such as the thinner corneas in African Americans and Latinos. It is very important for those who have an increased risk of developing glaucoma to have a thorough eye examination by an ophthalmologist and to follow up on any recommendations or treatments. Yvonne Ou, MD, is a board certified ophthalmologist who specializes in glaucoma, including medical, laser and surgical therapies; cataract evaluation and treatment including combined cataract and glaucoma surgery; glaucoma filtering and implant surgery; and newer procedures.
Back to Expert Advice. Expert Advice. Glaucoma is the leading cause of blindness among African-Americans. Compared to Caucasians, glaucoma is about six times more common in African-Americans, and blindness caused by glaucoma is roughly 16 times more likely in African-Americans. Siegfried, MD. The researchers measured oxygen levels in the eyes of patients who were having surgery for cataracts or glaucoma or both.
At the beginning of surgery, they inserted a probe to measure oxygen in five places in the front part of the eye. They took measurements near the center of the cornea; in the middle of the anterior chamber of the eye; and in a section of the eye called the anterior chamber angle, located where the cornea meets the iris.
They also measured oxygen in two locations near the lens of the eye in patients having cataract surgery. Oxygen was significantly higher in African-Americans at all five locations. Like cataracts, glaucoma is a disease associated with aging. Oxidative stress, an imbalance between these free radicals and antioxidants, is linked to the aging process and many other age-related conditions like cardiovascular and neurodegenerative diseases. And our discovery about cataracts led us, somewhat surprisingly, to glaucoma.
Siegfried then joined us, confirming the connection between oxygen and glaucoma, and the link between oxygen and race was yet another surprise. All of the patients in this study were having eye surgery, so the researchers did not have a comparison or control group. But the African-American patients having surgery often were younger than Caucasians.
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