Glaucoma in African Americans

Glaucoma is a disease that affects the optic nerve, and can eventually cause the loss of sight. Glaucoma damages the optic nerve by an increase of intraocular pressure or IOP. The optic nerve is a serious of many neurons that relay information brought in through the eyes and then integrated and organized by the visual cortex. Damage to this nerve, as a result, is often the cause for blindness. It is long been known that African Americans are at higher risk than Caucasians; new research is now explaining some of those reasons for increased susceptibility of the disease. African Americans are about six times more likely to contract Glaucoma and sixteen times more likely to experience blindness from the disease than Caucasians’ (Siegfried, 2011). Scientists are now discovering that these staggering statistics are a result of increased oxygen levels within the ocular cavity of African Americans (Siegfried, 2011). Experiments at the University of Washington set out to explain this phenomenon. Researchers placed instruments that detect PO2 levels in five significant locations within the eye; such as the anterior chamber angle which is important for intraocular fluid drainage. If fluid cannot drain properly from the eye, pressure will then build up as a result (Siegfried, 2011). Many researchers view this difference in oxygen levels as a physiological problem. Increased metabolic activity in the ocular tissue is one theory that may explain these oxygen differences (Anderson, 2011). Experiments conducted by Clara Siegfried M.D., showed that in the anterior chamber angle had a mean pressure of roughly 4.9 mm Hg difference between the Caucasian 11.7 mm Hg and the African American 16.6 mm Hg. This high pressure difference was observed in all African Americans that underwent the experiment (Anderson, 2011). "Glaucoma often affects African-Americans at a younger age," Siegfried says. "And when we used statistical methods to adjust for differences in age, the difference in oxygen levels between African-Americans and Caucasians became more significant. Then, when we controlled for racial differences, we found that increased age became an important indicator of elevated oxygen levels in certain locations in the front part of the eye (Siegfried, 2011).” This difference in oxygen concentration by age groups of African Americans are leading scientists to postulated that older African Americans may not consume oxygen in the ocular cavity at as high of rates as younger patients (Siegfried, 2011). With this said it is safe to assume that overproduction of oxygen may not be the underlying problem as other theories have proposed thus far. Dr. Siegfried still believes that there are many tests and research needed to completely unlock the physiological and genetic mechanisms that cause this race associated difference in Glaucoma patients, but will no doubt become evident in the near future. If scientists can understand why oxygen is more prevalent in African Americans, they can no doubt find a way to decrease the rate of sight loss significantly among the African American population. Though there is not yet a cure for Glaucoma, perhaps completely understanding the difference between African Americans and Caucasians with the disease can uncover new information that may one day lead to a cure.

REFERENCES

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Siegfried, C.J. (2011). More oxygen in eyes of African-americans may help explain glaucoma risk. Manuscript, Department of Integrative Physiology, University of Colorado, Boulder, Retrieved from http://www.colorado.edu/intphys/

Carla J. Siegfried, MD; Ying-Bo Shui, MD; Nancy M. Holekamp, MD; Fang Bai, MD; David C. Beebe, PhD Arch Ophthalmol. 2011;129(7):849-85doi:10.1001/archophthalmol.2011.169

Anderson, P. (2011, July 13). Oxidative metabolism in the eye differs according to race. Medscape Medical News, Retrieved from http://www.medscape.com/viewarticle/746271