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When it comes to understanding eye diseases and provision of eye care, should race and ethnicity matter? Yes … and no, say clinicians and epidemiologists, first acknowledging that even the terms “race” and “ethnicity” are difficult to define and encompass a range of genetic, geographic, and socioeconomic factors. Moreover, any given race has a highly diverse genetic profile.
“Although a few ophthalmic diseases are clearly at increased risk within certain racial groups, common eye diseases are genetically complex,” said Alfred Sommer, MD, MHS. Dr. Sommer is professor of ophthalmology at the Johns Hopkins University School of Medicine as well as dean emeritus and professor of epidemiology and international health at the Johns Hopkins Bloomberg School of Public Health.
“Very few diseases are unique to any one race,” said Dr. Sommer, who in 1985 launched the Baltimore Eye Study, which was the first community-based ophthalmic survey of its kind and uncovered high rates of glaucoma and untreated cataract among the urban poor, especially African-Americans. “What this means is the ophthalmologist has to consider all possibilities—remembering that every patient is at risk for everything.”
Insights About Diseases
Keeping Dr. Sommer’s advice in mind, clinicians should be aware of some key demographic differences for specific diseases.
Open-angle glaucoma. There is now robust evidence that African-Americans and Hispanics have a much higher prevalence and incidence of primary open-angle glaucoma (POAG) than non-Hispanic whites, said Rohit Varma, MD, MPH, principal investigator of the Los Angeles Latino Eye Study (LALES) and director of the Ocular Epidemiology Center at the Doheny Eye Institute, University of Southern California. “African-Americans develop a more severe form—and earlier.”
One possible explanation for this difference was highlighted by the Ocular Hypertension Treatment Study, which found that the mean corneal thickness in African-Americans was 23 µm thinner than in whites.1
This led to concerns that thinner corneas may also delay diagnosis by artifactually lowering the IOP reading on an applanation tonometer, said Leon W. Herndon, MD, associate professor of ophthalmology at Duke Eye Center in Durham, N.C. He cautioned that “if you just look at pressures, you might send a patient away, saying, ‘Come back in a year, Mrs. Jones, you’re fine.’” He added that thinner corneas could also play a role in therapy: Easier corneal penetration might be one reason that certain medications have tended to do better in this racial group.
Findings from the Advanced Glaucoma Intervention Study spotlighted another racial difference: African-Americans had much worse outcomes with trabeculectomy than with laser trabeculoplasty,2 which supports the value of a tailored approach to treatment, said Dr. Herndon.
Angle-closure glaucoma. The prevalence of angle-closure glaucoma (ACG) varies greatly according to the definitions used in different studies, but it is known to be substantially higher in East Asians than in Caucasians or African-Americans. Structurally smaller, more-crowded angles as well as physiological differences likely make the Asian eye more susceptible to this type of glaucoma, said Tien Yin Wong, MD, PhD, chairman of the department of ophthalmology at the National University of Singapore and director of the Singapore Eye Research Institute. ACG may occur in an acute form that causes pain, very high pressures, and a rapid visual loss. “Trials are under way to determine when and how preventive laser peripheral iridotomy is appropriate in this population,” he said.
Age-related macular degeneration. The rates of age-related macular degeneration (AMD) are highest among non-Hispanic whites and low in Hispanics and African-Americans, said Dr. Varma. “We’re still struggling to determine the reasons, although genetic predisposition to the advanced, vision-threatening form is likely.” There is also some “armchair speculation,” he said, about differences in fundus pigmentation.
Although AMD was previously thought to be uncommon in Asians, there is increasing evidence that the prevalence of and risk factors for AMD in Asians are comparable to those in Caucasians, said Dr. Wong. But these two groups may differ in presentation as well as the efficacy of therapy.3
“In Asian populations with AMD, up to 50 percent of patients don’t respond to anti-VEGF therapies,” he said, partly due to the occurrence of a variant of AMD called polypoidal choroidal vasculopathy (PCV), which is more common in this group.4 It leads to a more aggressive presentation with more hemorrhage and exudation. “Although Lucentis and Avastin are almost revolutionary therapies in most Western populations,” he said, “in Asians, photodynamic therapy remains an important treatment of choice for PCV.”
Diabetic retinopathy. A quarter of Hispanics age 40 years and older have diabetes, among the highest rates in the United States, said Dr. Varma. Rates are also high in African-Americans, he said, and are growing among Asians. Dr. Wong added that exposure to Western lifestyles has dramatically accelerated the increase of diabetes in Asian populations, for example, doubling its prevalence in Singapore during each of the three preceding decades.
Clinicians need to be aware of an increasingly common phenomenon, called metabolic obesity, among Asians. Patients with this condition may have metabolic syndrome—and thus an increased risk of diabetes—even at a normal body mass index.
In the United States, diabetic retinopathy is a leading cause of blindness that disproportionately affects racial and ethnic minorities;5 however, rates are high across the board, said Dr. Varma. “Somewhere between 30 and 50 percent of those with diabetes develop diabetic retinopathy.”
“In fact, drivers of diabetic retinopathy are very similar between races,” said Dr. Wong. “Variations between races appear to be related to health education, risk factor control, and access to care instead of inherent differences between races.”
Myopia. Among Asians, the prevalence of myopia is as much as three times higher than in other populations. Often attributed to a longer axial length, myopia can affect other ocular disease processes as well, said Dr. Wong. “For example, myopic macular degeneration is more common in people with myopia of 6 D or higher,” he said. High myopia is also linked to retinal detachment, cataract, and glaucoma. However, a large, recent meta-analysis offers the clinician this caveat: The link between myopia and glaucoma is not limited to high myopia.6
When Access to Care Is an Issue
Although certain racial minorities are affected disproportionately, insufficient health care utilization in the United States is an issue that transcends racial boundaries, said Dr. Varma. “At least 50 percent of eye disease in all ethnic groups remains undetected.”
Whether referring patients or becoming involved as a volunteer, ophthalmologists can address this need, in part, by tapping into EyeCare America, a public service program of the Foundation of the American Academy of Ophthalmology. Its mission is to preserve sight by raising awareness about eye disease and providing access to free medical eye care for those who qualify.
To learn more about volunteering, go to www.eyecareamerica.org/eyecare/help/Volunteer.cfm.
Lessons for the Clinic
How can the findings from population studies on race and eye disease be applied to clinical practice? Here is some guidance from epidemiologists.
Clinical population may not reflect disease prevalence. “From the Baltimore Eye Study, we learned that you couldn’t base your rationale or understanding of a disease simply on the people who show up at an eye doctor’s office,” said Dr. Sommer. This can give you highly skewed samples from which the wrong conclusions are drawn.
For example, pain from angle-closure glaucoma prompts the patient to see the doctor, whereas the silent nature of open-angle glaucoma does not. “This is why, until 20 years ago, the Chinese and Japanese erroneously thought that angle-closure glaucoma was 90 percent of their problem,” said Dr. Sommer. In fact, OAG is more common than ACG among Asians.7
Another factor is that certain ethnic groups—whether because of cultural or socioeconomic factors—tend to not use doctors except in emergencies, said Dr. Sommer. “So you don’t get an idea of the frequency of disease in those populations; you won’t see them in a review of clinic charts.”
Screening guidelines should reflect risk. Knowledge of the relative risk for ophthalmic disorders in certain racial groups is particularly important in screening for otherwise silent diseases, said Dr. Sommer. In other words, a higher level of suspicion demands greater vigilance. For example, the Academy’s Preferred Practice Patterns guidelines recommend that people at higher risk for glaucoma, including African-Americans and Hispanics, have comprehensive eye exams on the following schedule:
- Every 1 to 3 years between ages 40 and 54
- Every 1 to 2 years between ages 55 and 64
- Every 6 to 12 months after age 64.
This recommended schedule incorporates earlier and more frequent exams than for lower-risk groups.
Utilization of care is lower in certain groups. Unfortunately, many within these high-risk populations are less likely to come in for routine exams than are patients from other groups, said Dr. Sommer. A LALES study of Latinos 40 and older living in Southern California illustrates this point: Only 36 percent reported having an eye care visit of any kind in the past year, 19 percent reported having a comprehensive (dilated) eye exam in the past year, and 57 percent reported ever having a dilated eye exam in their lifetime.8
Another LALES study showed that, among the 53 percent of Latino participants who were found to have eye disease or refractive error, the prevalence of previously undetected eye disease (UED) was over 60 percent. Notably, the UED prevalence was over 80 percent for AMD, DR, and glaucoma.9 “This study was done in a large metropolitan area with one of the largest public hospitals in the country within five miles,” said Dr. Varma. “But people who were visually impaired, had treatable disease, or had advanced disease were not receiving treatment.”
Compliance involves many factors. Although connections between race, eye care, and compliance do exist, said Dr. Sommer, the clinician should consider whether these disparities are related to bias, socioeconomic status, cultural differences, or other factors. Are patients choosing between using medication and feeding their kids?
For example, several studies have shown lower rates of compliance with glaucoma medications among African-Americans, said Dr. Herndon. And cataract surgery rates are also lower in African-Americans and Hispanics than in non-Hispanic whites, added Dr. Varma. Is this an access-to-care issue, language barrier, or something else? Among Hispanics, in particular, there may be a propensity to view a problem like cataracts as an inevitable part of the aging process, he said. “There is also a sense among many of these seniors that they should take care of the children and grandchildren, rather than focusing on their own problems.”10
Follow-through is key. “If you see someone who is at high risk, particularly from a lower socioeconomic status, you really have to do a thorough examination for any and all kinds of eye disease,” said Dr. Sommer. “If you find an eye disease or a disease such as diabetes that can lead to ocular complications, you have to go out of your way to encourage the patient to come back for regular exams, to comply with a better diet or a diabetes regimen.” And it is critical to communicate with his or her primary doctor to ensure regular eye exams, he said. “You might even want to create an outreach program, to set up an automatic referral from the primary care office.”
Dr. Herndon is a member of Alcon’s glaucoma advisory board. Drs. Sommer and Varma report no related financial interests. Dr. Wong is a consultant to Abbott, Allergan, Bayer, Novartis, and Pfizer. LALES was funded by NEI Grant EY11753.
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8 Morales LS et al. Ophthalmology. 2010;117(2):207-215.e1.
9 Varma R et al. Med Care. 2008;46(5):497-506.
10 Unzueta M et al; Los Angeles Latino Eye Study Group. Ethn Dis. 2004;14(2):285-291.