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Understanding Who is at High Risk of Having Glaucoma
Nearly half of those with glaucoma do not know they have the disease. This has been shown repeatedly in studies conducted in developed countries. Even more concerning, though, are two recent publications on Hispanics in the United States documenting that 65 to 75% of those with glaucoma are undiagnosed. This is a great failing of the healthcare system, but determining the best approaches to screening for glaucoma remains a challenge. Glaucoma is a slowly progressive, silent disease, and those who present with symptoms often have severe vision loss. Identifying people with glaucoma remains a challenge, however, because screening tests are not perfect.
Some groups are at very high risk of having glaucoma. Based in well-designed research, we know that siblings of persons diagnosed with glaucoma have nearly a 10-fold increased risk of having glaucoma when compared to siblings of persons without glaucoma. This means that a 65 year old sibling of a European-derived person has about a 10% chance of having glaucoma, while a 65 year old sibling of an African-American has nearly a 20% chance of having glaucoma. Clearly brothers and sisters of patients with glaucoma can benefit from regular eye examinations with special attention to careful screening for glaucoma.
Other populations are at high risk. Recent studies in Hispanics document that in older age groups, the risk of glaucoma is nearly as high as that for African-Americans (who are known to have nearly four times the risk of European-derived persons). Some research indicates that for African-Americans and Hispanic Americans the risk of having glaucoma can approach 20% in persons over 75 years of age. Clearly these individuals should have regular evaluations for glaucoma. Medicare currently provides a screening benefit for older African-Americans for this reason.
What factors put different groups at higher risk? Why do Hispanics and African-Americans appear to have higher rates of glaucoma than European-derived populations? These remain important questions, and we hope that one way to find the answers is to study genetic differences in these populations. Most genetics research in glaucoma has been carried out on European-derived populations, but we are working (through a grant from the Glaucoma Research Foundation) to enroll African-American families in a study of glaucoma genetics at Johns Hopkins. Given the rapid decline in the cost of studying DNA, we believe that the major limiting factor in carrying out successful genetics research will be the lack of well characterized families and individuals with glaucoma for genetic analysis. We have therefore been working to identify families with glaucoma and have been storing blood and examination data for future genetics research.
There is much more to glaucoma care than just identifying patients who do not know they have glaucoma. But, given the large number out there who remain undiagnosed, this is an essential first step if we are going to do a better job of preventing unnecessary vision loss from this disease.
Remember:
• Early diagnosis and treatment is key in preventing vision loss from glaucoma. GRF recommends that African-Americans get a thorough check for glaucoma every one to two years after age 35.
• Talk to family members about glaucoma. If family members have glaucoma, then your glaucoma risk is increased.
• If you have diabetes or high blood pressure, your risk of developing glaucoma increases.
• Hispanic Americans in older age groups are also at greater risk for glaucoma.
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Article by David S. Friedman, MD, MPH, Department of Ophthalmology and International Health, Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD.
Dr. Friedman is conducting a GRF-funded study of African-American families with glaucoma. By studying medical records of African-Americans who have two or more siblings with glaucoma, and using specific diagnostic approaches, the resulting information will allow scientists who want to look at the genes responsible for glaucoma in these families to do so with confidence.
This article appeared in the January 2006 issue of Gleams. Subscribe