Blindness and Visual Impairment in Urban Population The Baltimore
an
American
Eye Survey
James M. Tielsch, PhD; Alfred Sommer, MD, the Baltimore Eye Survey Research Group
\s=b\ Data on the prevalence of blindness and visual impairment in multiracial urban populations of the United States are not readily available. The Baltimore Eye Survey was designed to address this lack of information and provide estimates of prevalence in age-race subgroups that had not been well studied in the past. A population\x=req-\ based sample of 5300 blacks and whites from east Baltimore, Md, received an ophthalmologic screening examination that included detailed visual acuity measurements. Blacks had, on average, a twofold excess prevalence of blindness and visual impairment than whites, irrespective of definition. Rates rose dramatically with age for all definitions of vision loss, but there was no difference in prevalence by sex. More than 50% of subjects improved their presenting vision after refractive correction, with 7.5% improving three or more lines. Rates in Baltimore are as high or higher than those reported from previous studies. National projections indicate that greater than 3 million persons are visually impaired, 890 000 of whom are bilaterally blind by US definitions.
(Arch Ophthalmol. 1990;108:286-290)
Accepted for publication September 20, 1989. From the Dana Center for Preventive Ophthalmology, The Wilmer Eye Institute, and the School of Hygiene and Public Health (Drs Tielsch and Sommer and Mss Witt and Katz), the Department of Biostatistics, the School of Hygiene and Public Health (Dr Royall), The Johns Hopkins University, Baltimore, Md. Reprint requests to The Johns Hopkins School of Medicine, Wilmer Room 120, 600 N Wolfe St, Baltimore, MD 21205 (Dr Tielsch).
MHSc; Kathe Witt, COMT; Joanne Katz, MS; Richard M. Royall, PhD;
A ccurate and timely data on the prev-
"^
alence of blindness and visual im¬ pairment in US urban populations are not readily available. Existing data have come from blindness registration systems, large multipurpose national health surveys, and detailed surveys of small, limited populations.14 Each of these has well-recognized limitations regarding generalizability to multira¬ cial, urban populations. The Baltimore Eye Survey was spe¬ cifically designed to address this lack of information in a large, multiracial population that could serve as a repre¬ sentative model for many urban areas in the United States. This report de¬ scribes the prevalence of blindness and visual impairment in east Baltimore, Md, as well as identifying demo¬ graphic subgroups of the population at especially high risk. Such information is critical for quantifying the need for treatment and rehabilitative services, focusing blindness prevention pro¬ grams where they are most needed, identifying priority areas for research, and measuring the spread of new ther¬ apeutic modalities into the general medical care system. METHODS
The Baltimore Eye Survey is a popula¬ tion-based prevalence survey of ocular dis¬ ease among noninstitutionalized people 40 years of age and older residing in east Bal¬ timore. In general, the study area is similar to the city of Baltimore in its demographic characteristics but has a higher proportion of blacks than the United States as a whole.
Downloaded From: http://archopht.jamanetwork.com/ by a Michigan State University User on 06/14/2015
The socioeconomic status ranges from poor to middle class and has a lower owneroccupied housing rate than the rest of the city and the country. This area was chosen because of the presumed socioeconomic comparability of the black and white popu¬ lations and because the residents of this area have cooperated in previous commu¬ nity-based health surveys and programs. The primary aim of this study was to compare the prevalence of ocular disease in black and white populations. To optimize this comparison, the sampling plan was de¬ signed to select approximately equal num¬ bers of black and white subjects, with a to¬ tal sample size target of 5000 people. A stratified cluster sampling strategy was chosen with the probability of selection proportionate to size. This approach was used to minimize the distance between sub¬ jects' homes and our neighborhood screen¬ ing centers and to enable the use of com¬ munity leaders and the media to encourage participation. To balance the sample on race, clusters were stratified by the racial characteristics of the census tracts. Within each race stratum, census tracts were ordered geographically from east to west to avoid clustering of the sample pop¬ ulation near any particular medical care provider, and a systematic sample of clus¬ ters was chosen from each race stratum. Originally, a total of 10 clusters were se¬ lected but it became apparent early on that the 1980 census data overestimated the number of eligible subjects in these clusters and that additional clusters would be needed to obtain the necessary sample size. The end result was a total of 16 clusters, 6 from black census tracts, 8 from white cen¬ sus tracts, and 2 from mixed-race census tracts. Within the geographic boundaries of each cluster, all residential dwelling units were identified and screened to identify el-
Fig 1.—Prevalence of visual impairment (
an
American
Eye Survey
James M. Tielsch, PhD; Alfred Sommer, MD, the Baltimore Eye Survey Research Group
\s=b\ Data on the prevalence of blindness and visual impairment in multiracial urban populations of the United States are not readily available. The Baltimore Eye Survey was designed to address this lack of information and provide estimates of prevalence in age-race subgroups that had not been well studied in the past. A population\x=req-\ based sample of 5300 blacks and whites from east Baltimore, Md, received an ophthalmologic screening examination that included detailed visual acuity measurements. Blacks had, on average, a twofold excess prevalence of blindness and visual impairment than whites, irrespective of definition. Rates rose dramatically with age for all definitions of vision loss, but there was no difference in prevalence by sex. More than 50% of subjects improved their presenting vision after refractive correction, with 7.5% improving three or more lines. Rates in Baltimore are as high or higher than those reported from previous studies. National projections indicate that greater than 3 million persons are visually impaired, 890 000 of whom are bilaterally blind by US definitions.
(Arch Ophthalmol. 1990;108:286-290)
Accepted for publication September 20, 1989. From the Dana Center for Preventive Ophthalmology, The Wilmer Eye Institute, and the School of Hygiene and Public Health (Drs Tielsch and Sommer and Mss Witt and Katz), the Department of Biostatistics, the School of Hygiene and Public Health (Dr Royall), The Johns Hopkins University, Baltimore, Md. Reprint requests to The Johns Hopkins School of Medicine, Wilmer Room 120, 600 N Wolfe St, Baltimore, MD 21205 (Dr Tielsch).
MHSc; Kathe Witt, COMT; Joanne Katz, MS; Richard M. Royall, PhD;
A ccurate and timely data on the prev-
"^
alence of blindness and visual im¬ pairment in US urban populations are not readily available. Existing data have come from blindness registration systems, large multipurpose national health surveys, and detailed surveys of small, limited populations.14 Each of these has well-recognized limitations regarding generalizability to multira¬ cial, urban populations. The Baltimore Eye Survey was spe¬ cifically designed to address this lack of information in a large, multiracial population that could serve as a repre¬ sentative model for many urban areas in the United States. This report de¬ scribes the prevalence of blindness and visual impairment in east Baltimore, Md, as well as identifying demo¬ graphic subgroups of the population at especially high risk. Such information is critical for quantifying the need for treatment and rehabilitative services, focusing blindness prevention pro¬ grams where they are most needed, identifying priority areas for research, and measuring the spread of new ther¬ apeutic modalities into the general medical care system. METHODS
The Baltimore Eye Survey is a popula¬ tion-based prevalence survey of ocular dis¬ ease among noninstitutionalized people 40 years of age and older residing in east Bal¬ timore. In general, the study area is similar to the city of Baltimore in its demographic characteristics but has a higher proportion of blacks than the United States as a whole.
Downloaded From: http://archopht.jamanetwork.com/ by a Michigan State University User on 06/14/2015
The socioeconomic status ranges from poor to middle class and has a lower owneroccupied housing rate than the rest of the city and the country. This area was chosen because of the presumed socioeconomic comparability of the black and white popu¬ lations and because the residents of this area have cooperated in previous commu¬ nity-based health surveys and programs. The primary aim of this study was to compare the prevalence of ocular disease in black and white populations. To optimize this comparison, the sampling plan was de¬ signed to select approximately equal num¬ bers of black and white subjects, with a to¬ tal sample size target of 5000 people. A stratified cluster sampling strategy was chosen with the probability of selection proportionate to size. This approach was used to minimize the distance between sub¬ jects' homes and our neighborhood screen¬ ing centers and to enable the use of com¬ munity leaders and the media to encourage participation. To balance the sample on race, clusters were stratified by the racial characteristics of the census tracts. Within each race stratum, census tracts were ordered geographically from east to west to avoid clustering of the sample pop¬ ulation near any particular medical care provider, and a systematic sample of clus¬ ters was chosen from each race stratum. Originally, a total of 10 clusters were se¬ lected but it became apparent early on that the 1980 census data overestimated the number of eligible subjects in these clusters and that additional clusters would be needed to obtain the necessary sample size. The end result was a total of 16 clusters, 6 from black census tracts, 8 from white cen¬ sus tracts, and 2 from mixed-race census tracts. Within the geographic boundaries of each cluster, all residential dwelling units were identified and screened to identify el-
Fig 1.—Prevalence of visual impairment (
