EVALUATING RISK FACTORS
Epidemiology
Each individual has a unique set of risk factors based on genetics, environment, and culture. An awareness of risk factors assists physicians in detecting and preventing disease, developing screening strategies, and counseling patients.
From an epidemiologic perspective, there are some marked differences in the prevalence of glaucoma among races. For example, studies have reported the prevalence of the disease among white northern Europeans aged 75 to 79 years at between 1.1% (Rotterdam)1 and 6.4% (Australian Blue Mountains).2 These figures differ vastly from those reported for predominantly African-derived populations, for whom the prevalence of glaucoma in the same age group ranges from 5.1% in Tanzania3 to 17.5% in Barbados.4 Does this difference hold up in Baltimore, however? Yes, in the Baltimore Eye Survey,5 the prevalence of glaucoma in the same age groups varied from 9% in blacks to 1.7% in whites. When defined by patients, race constituted a real difference in the prevalence of glaucoma. In essence, this study found an age-adjusted prevalence of glaucoma that was 6.5 times higher in blacks than whites. Glaucoma screenings would therefore be better targeted at primarily black versus mainly white communities.
Also noteworthy is that the prevalence of glaucoma among Hispanics in the southwestern US is similar to that of whites in Baltimore until the age of 65, at which point open-angle glaucoma is as common in Hispanics as in older black patients, if not more so.6 Likewise, the prevalence of glaucoma in Latinos aged between 70 and 79 years was 14.7%, seemingly much higher than in other racial groups.7
Anatomy
Certain anatomic markers may facilitate glaucoma diagnosis and treatment. Because two studies found that blacks have larger optic discs than whites, practitioners should realize that a large cup in a black patient may not be pathologic and in need of treatment.8,9 (This anatomic finding may or may not imply that the lamina cribosa is structurally different and more susceptible to injury at comparable IOPs.)
In their unilateral analysis of the Ocular Hypertension Treatment Study, Zangwill et al10 also found that thinner corneas and larger disk sizes—both risk factors for developing glaucoma—were more common in black than white subjects. Additionally, Herndon et al11 found that glaucoma may progress quicker in patients with thinner corneas.
Biology
The Advanced Glaucoma Intervention Study (AGIS) is an NEI-sponsored, multicenter study that has attempted to enroll a proportionate number of black compared with white recruits. Investigators identified differences in blacks' and whites' responses to therapy. On maximum medication, blacks who then underwent argon laser trabeculoplasty needed fewer second and third interventions than whites. By contrast, those blacks who received trabeculectomy required more second and third interventions than whites. Compared with whites, blacks in the argon laser trabeculoplasty-trabeculectomy-trabeculectomy group less often required cataract surgery but needed more medications to achieve an IOP of less than 18 mm Hg. Blacks in the trabeculectomy-first group had a more difficult time achieving IOP control, and had both more vision and visual field loss than whites. Travoprost, a prostaglandin analogue, lowers IOP 1.8 mm Hg more in black patients.12,13
Social Differences
The AGIS investigators have reported many racial differences, some of which are social and may have potentially clinically significant implications. A patient's family members may assist the treatment of an asymptomatic disease such as glaucoma by helping to explain the disease process or reminding the patient to take medications. AGIS investigators found that 56% of black versus 34% of white subjects had never married, were widowed, or were divorced. With less familial support, black subjects may be less likely to comply with treatment and therefore may be more at risk of progressive glaucomatous damage. The study also determined that 51% of black versus 78% of white subjects had at least a high-school education. Educational level may affect patients' understanding of their disease, its significance, and its treatment as well as their comprehension of directions for taking medications and their compliance with therapy. Physicians might therefore wish to bear these statistics in mind, include marital status and educational level in the patient history, and simplify their discussions with certain individuals.
In blacks, glaucoma is the leading cause of blindness and visual disability. Moreover, blindness from the disease is 50% more common in black versus white nursing home residents.14 Nursing home residents also have a greater burden of unoperated glaucoma.15 The disease can begin 10 years earlier9 and progresses more rapidly in black versus white patients.16,17 In addition, studies have indicated that black patients underwent trabeculoplasty and trabeculectomy at 47% below the expected age/sex-adjusted rate18 and that the undertreatment of black Medicare beneficiaries primarily involved limited access to eye care.19 Recognizing that this lack of access appears to be related to race may permit the redress of inequalities in the healthcare delivery system. Physicians should attempt to increase black individuals' access to medical care.
CONCLUSION
Although so-called race is in no way a perfect means of distinguishing two different populations, it has some profound implications for general practice. For instance, it seems that screening efforts should be targeted at black communities, the members of which appear to be underserved. Moreover, race has helped to highlight an apparent disparity in the health care system that must be resolved. More succinctly, race can help practitioners to deliver better, more effective care to all.
Alan L. Robin, MD, is Clinical Professor of Ophthalmology at the University of Maryland in Baltimore. Dr. Robin may be reached at (410) 377-2422; glaucomaexpert@cs.com.
1. Dielemans I, Vingerling JR, Wolfs RC, et al. The prevalence of primary open-angle glaucoma in a population based study in the Netherlands. The Rotterdam Study. Ophthalmology. 1994;101:1851-1855.
2. Mitchell P, Smith W, Attebo K, Healey PR. Prevalence of open-angle glaucoma in Australia. The Blue Mountains Eye Study. Ophthalmology. 1996;103:1661-1669.
3. Buhrmann RR, Quigley HA, Barron Y, et al. Prevalence of glaucoma in a rural East African population. Invest Ophthalmol Vis Sci. 2000;41:40-48.
4. Leske MC, Connell AM, Schachat AP, Hyman L. The Barbados Eye Study. Prevalence of open angle glaucoma. Arch Ophthalmol. 1994;112:821-829.
5. Rahmani B, Tielsch JM, Katz J, et al. The cause-specific prevalence of visual impairment in an urban population. The Baltimore eye Survey. Ophthalmology. 1996;103:1721-1726.
6. Quigley HA, West SK, Rodriguez J, et al. The prevalence of glaucoma in a population-based study of Hispanic subjects: Proyecto VER. Arch Ophthalmol. 2001;119:1819-1826.
7. Varma R, Ying-Lai M, Francis BA, et al; the Los Angeles Latino Eye Study Group. Prevalence of open-angle glaucoma and ocular hypertension in Latinos: the Los Angeles Latino Eye Study. Ophthalmology. 2004;111:1439-1448.
8. Varma R, Tielsch JM, Quigley HA, et al. Race-, age-, gender-, and refractive error-related differences in the normal optic disc. Arch Ophthalmol. 1994;112:1068-1076.
9. Martin MJ, Sommer A, Gold EB, Diamond EL. Race and primary open-angle glaucoma. Am J Ophthalmol. 1985;99:383-387.
10. Zangwill LM, Weinreb RN, Berry CC, et al; Confocal Scanning Laser Ophthalmoscopy Ancillary Study to the Ocular Hypertension Treatment Study. Racial differences in optic disc topography: baseline results form the confocal scanning laser ophthalmoscopy ancillary study to the Ocular Hypertension Treatment Study. Arch Ophthalmol. 2004;122:22-28.
11. Herndon LW, Weizer JS, Stinnett SS. Central corneal thickness as a risk factor for advanced glaucoma damage. Arch Ophthalmol. 2004;122:17-21.
12. Netland PA, Robertson SM, Sullivan EK, et al; Travoprost Study Groups. Response to travoprost in black and nonblack patients with open-angle glaucoma or ocular hypertension. Adv Ther. 2003;20:3:149-163.
13. Travatan [package insert]. Fort Worth, TX: Alcon Laboratories, Inc.
14. Tielsch JM, Javitt JC, Coleman A, et al. The prevalence of blindness and visual impairment among nursing home residents in Baltimore. N Engl J Med. 1995;332:1205-1209.
15. Friedman DS, West SK, Munoz B, et al. Racial variation in causes of vision loss in nursing homes: The Salisbury Eye Evaluation in Nursing Home Groups (SEEING) Study. Arch Ophthalmol. 2004;122:1019-1024.
16. Lichter PR, Musch DC, Gillespie BW, et al. Interim clinical outcomes in the Collaborative Initial Glaucoma Treatment Study comparing initial treatment randomized to medications or surgery. Ophthalmology. 2001;108:1943-1953.
17. Smith SD, Katz J, Quigley HA. Analysis of progressive change in automated visual fields in glaucoma. Invest Ophthalmol Vis Sci. 1996;37:1419-1428.
18. Devgan U, Yu F, Kim E, Coleman AL. Surgical undertreatment of glaucoma in black beneficiaries of Medicare. Arch Ophthalmol. 2000;118:253-256.
19. Wang F, Javitt JC, Tielsch JM. Racial variations in treatment for glaucoma and cataract among Medicare recipients. Ophthalmic Epidemiol. 1997;4:89-100.
