Study: glaucoma rates in Hispanics are between those of whites and blacks

Also, the prevalence of open-angle glaucoma in Hispanics increased more quickly with increasing age than in other ethnic groups.

Issue: March 15, 2002

BALTIMORE — With much of the attention of recent glaucoma drug studies focusing on response rates for white and black participants, a new study suggests that the rate of open-angle glaucoma in Hispanic participants may need to be studied further. The study found that the prevalence of OAG in Hispanic people was in the middle of reported values for whites and blacks.

Perhaps more surprising was that OAG was found to increase more quickly as Hispanics aged than in other ethnic groups.

The study was part of the Johns Hopkins School of Medicine Proyecto VER (Vision Evaluation Research).

Rarely studied Hispanic population

Harry A. Quigley, MD, and Sheila West, MD, with a team of investigators from both Johns Hopkins and the Universtiy of Arizona, used 1990 census data from Arizona to select participants. The survey was designed to estimate the prevalence of blindness and visual impairment from the major ocular diseases, including glaucoma, among a representative sample of Hispanic persons in the southwestern United States.

Groups of people living in sections of Tucson and Nogales were randomly selected with a probability proportional to the Hispanic population older than age 40. The investigators attempted to recruit all eligible adults in homes with one self-described Hispanic adult.

Detailed ocular examinations at a local clinic included visual acuity testing, applanation tonometry, gonio scopy, an optic disc evaluation and a threshold visual field test.

In all, researchers found 4,255 homes in the Tucson and Nogales area, in which they found 6,658 eligible adult residents. Participants were narrowed down to the 4,774 persons who underwent the home interview and the examination.

The proportion of men and women affected did not differ significantly. Among those affected by OAG, 61 of 94 (65%) were women. From the 94 subjects with OAG in the study, 58 were unaware of their diagnosis before the survey.

The mean IOP for eyes with glaucoma was 18.5 Hg. The subjects with OAG had a vertical cup-to-disc ratio of 0.71.

Five people (0.1%) were found to have angle-closure glaucoma (ACG).

Risk factors other than age — diabetes, hypertension, body mass index and cigarette smoking — did not confer statistically significant risk.

In a univariate analysis some risk factors were associated with OAG, including lower level of schooling attained, father identified as Mexican and residency in Nogales. However, when these factors were adjusted for age, none had a significant relationship to OAG.

In the paper, Dr. Quigley said that while those of European and African decent had been well studied, current data on glaucoma did not include large well-designed studies of the many ethnic groups in the world.

“In particular, to our knowledge, there are no population-based studies of glaucoma in Hispanic persons,” said Dr. Quigley, a professor at Johns Hopkins Wilmer Eye Institute.

Considering that Latin America has a population of 500 million, and assuming the prevalence of glaucoma is similar to rates among European-derived people, Dr. Quigley believes nearly 2 million Hispanic people would be affected by OAG or ACG throughout North and South America.

Age, race key factors

In the survey, Dr. Quigley commented that the age-specific prevalence of OAG among Hispanic people is intermediate between reported rates for white and black people in past surveys, with a steeper slope against age than that of either blacks or whites.

“In fact, the prevalence among Hispanic persons overlapped that of white persons in the younger age groups and increased to overlap that of black persons in the older age groups,” he said. “Because the age-specific prevalence of OAG increases more rapidly in Hispanic persons than in either the white or black population, according to our data, it is probable that the incidence of OAG in Hispanic persons has a steeper increase than that modeled from published data.”

He said he believed these findings suggest that the shift to a higher proportion of older people in the Mexican population will be associated with an even greater increase in OAG prevalence than the same shifts in population age will cause in European and African groups.

The study cited that in the Baltimore Eye Survey, blindness from glaucoma was inversely related to socioeconomic status and educational level. Hispanic Americans are more likely to have a lower economic status and are less likely to have health insurance. Dr. Quigley said the cost of care and the distrust of the majority culture are potential barriers for this group to access preventive health services. This is probably a contributing factor in the 62% undiagnosed rate for OAG among the Hispanic persons in this study, which is even higher than the 50% undiagnosed rate for white and black people in the United States and other developed countries.

The IOP of Hispanic people in this study is similar to that reported in white and black populations in previous surveys. Dr. Quigley said the use of IOP as a method of screening for glaucoma would clearly fail, as has been repeatedly recognized. The low rate of already diagnosed glaucoma in this population may, in part, be a reflection of continued physician reliance on the IOP measurement instead of on optic disc and visual field examinations.

While the number of Hispanics and other groups of people who are blind from glaucoma is large, the proportion of people with OAG who become legally blind is relatively modest, 3.2% of the subjects in this study.

While this survey can not attest if this Hispanic group will be representative of other Hispanic groups from different regions of Latin America, “glaucoma is already the most frequent cause of bilateral legal blindness in the Hispanic group that we studied, it merits serious attention in public health planning for early detection and treatment,” Dr. Quigley said.

For Your Information:

Harry A. Quigley, MD, can be reached at Johns Hopkins Wilmer Eye Institute, 600 N. Wolfe Maumenee B-110, Baltimore, MD 21287; (410) 955-2777; fax: (410) 955-2542.

Reference:

Quigley HA, West SK, et al. The prevalence of glaucoma in a population-based study of Hispanic subjects. Arch Ophthalmol. 2001;119:1819-1826.