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Etiology of blindness in an urban community hospital setting
Etiology of Blindness in an Urban Community Hospital Setting Rajendra S. Apte, MD, PhD, Tina A. Scheufele, MD, Preston H. Blomquist, MD, FACS Objective: To determine the cause of monocular and binocular blindness in a predominately nonwhite urban community hospital setting. Design: Retrospective hospital-based cross-sectional study. Participants: All 3562 unique subjects examined in the New and General Ophthalmology clinic at Parkland Memorial Hospital, Dallas, Texas, from July 1 to September 30, 1998. Methods: The EYEstation program by Datamedic was queried to conduct a detailed review of electronic medical records of the participants listed previously. Main Outcome Measures: Blindness was defined as visual acuity ⱕ20/200 in at least one eye. Records of blind subjects were subjected to further review. Results: Of the 3562 subjects examined, 321 (9.0%) were blind in one eye and 76 (2.1%) were blind in both eyes. Retinal disease was the leading cause of blindness (90 ⫽ 22.7%), with retinal vascular occlusions and retinal detachments accounting for more than half of retinal causes. Trauma (71 ⫽ 17.9%), diabetes (68 ⫽ 17.1%), and glaucoma (62 ⫽ 15.6%) were the next most frequent causes. Trauma was the leading cause of blindness among subjects less than 40 years old and among blind new subjects. The most common cause of blindness among the 40- to 59-year-old age group was diabetes, accounting for 26.1% of cases. Age-related macular degeneration accounted for only 1.3% (n ⫽ 5) of blindness. Conclusions: Retinal diseases, especially retinal vascular occlusions and retinal detachments, are leading causes of blindness in this predominately nonwhite and uninsured subject population. Trauma is a significant cause of severe, unilateral vision loss, especially in the young and in newly presenting subjects. Diabetes was the leading cause of blindness among the 40- to 59-year-old population. Age-related macular degeneration plays a relatively minor role in the cause of blindness in the study population. Ophthalmology 2001;108:693– 696 © 2001 by the American Academy of Ophthalmology. The prevention and treatment of vision loss is a laudable goal of any public health program. The socioeconomic impact of severe visual loss, including the degradation of one’s quality of life, is devastating. Previous studies on blindness and visual impairment have primarily used social services1 or blindness registries,2– 4 low-vision clinic records,5,6 or selective population-based approaches.7–13 Most of these studies have focused on select age groups or predominately Caucasian populations. In low-vision clinic reports from developed countries, age-related macular degeneration (ARMD) is the major cause of blindness. Review of 4744 low-vision examinations in Ontario, Canada, revealed ARMD to be the primary diagnosis 75% of the time.5 Review of 218 consecutively
Originally received: May 2, 2000. Accepted: November 27, 2000. Manuscript no. 200264. Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas. Presented in part as a PAAO Select Free paper at the Joint AAO/PAAO meeting, Orlando, Florida, October 1999. Supported in part by an unrestricted research grant from Research to Prevent Blindness, Inc., New York, New York. Reprint requests to Preston H. Blomquist, MD, FACS, Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9057. © 2001 by the American Academy of Ophthalmology Published by Elsevier Science Inc.
presenting subjects at the low-vision clinic at the University of Wales revealed that ARMD was by far the most common cause of low vision (48% of subjects), with myopia (9.7%) a distant second and cataract (7.4%) third.6 Studies that used blindness registries of predominately Caucasian populations have shown similar results. In reviewing the 674 blind persons newly registered with social services in the Wu¨rttemberg-Hohenzollern region in Germany (where blindness is defined as ⬍1/50, and there are monetary incentives to register), 32.3% were blind from ARMD, 16.6% from diabetic retinopathy, 13.2% from glaucoma, and 6.4% from high myopia. ARMD was the cause of more than half of legal blindness for subjects older than 75 years of age, whereas diabetic retinopathy was the most common cause in subjects 45 to 75 years of age.1 Review of 1585 new applications for the Danish Society of the Blind for 1993 revealed ARMD was the cause of the blindness 71.4% of the time. ARMD accounted for the blindness in 78% of registrants 60 years of age or older, whereas diabetic retinopathy was the predominant cause (36%) in registrants 20 to 59 years old.2 Of blind and partially sighted registration forms for the county of Avon over a 2-year period, 49% listed ARMD as the cause of vision loss, followed by glaucoma (15%) and diabetes (6%).3 A population-based study of 6775 subjects 55 years of age or older living in the city district of Ommoord in ISSN 0161-6420/00/$–see front matter PII S0161-6420(00)00653-9
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Ophthalmology Volume 108, Number 4, April 2001 Table 1. Best-corrected Visual Acuity of Subjects with Monocular or Binocular Blindness
Best-corrected Visual Acuity
20/200– 20/400 (%)
Counting Fingers (%)
Hand Motion (%)
Light Perception (%)
No Light Perception (%)
Monocular blindness (n ⫽ 321) Binocular blindness—better eye (n ⫽ 76) Binocular blindness—worse eye (n ⫽ 76)
86 (26.8) 38 (50.0) 15 (19.7)
57 (17.8) 18 (23.7) 17 (22.4)
67 (20.9) 12 (15.8) 10 (13.2)
36 (11.2) 7 (9.2) 11 (14.5)
75 (23.4) 0 (0) 24 (31.6)
Rotterdam, The Netherlands, revealed ARMD to be the major cause of blindness (58%) in that predominately white population.7 In a population-based study of 3647 persons living west of Sydney, Australia, ARMD was the cause of blindness in 21 of the 24 people found with corrected visual acuity ⱕ20/200.8 Although ARMD is a major cause of blindness in Caucasians, comparatively little information is currently available on the cause of blindness in a predominately nonwhite, uninsured urban community population in the United States. In this study, we assess the burden of blindness in an urban county hospital population and analyze the various causes of severe monocular and binocular visual loss.
glaucoma. Cataracts and aphakia accounted for lenticular causes of blindness. Corneal causes included abrasions, infections, and keratoconus. Optic nerve damage was secondary to anterior ischemic optic neuropathy, optic atrophy, or optic neuritis. Causes of uveitis when diagnosed included sarcoidosis, syphilis, and fibromyalgia. A demographic analysis of blindness was also performed to include age, gender, and laterality.
Statistical Analysis Chi-square test (SigmaStat, Jandel Corp.; San Rafael, CA) was used to assess group differences with respect to case frequencies.
Results Materials and Methods Study Site and Data Collection Parkland Memorial Hospital is the general public hospital for Dallas County, Texas, and the primary teaching hospital for the University of Texas Southwestern Medical Center at Dallas. Parkland’s New and General Outpatient Ophthalmology clinic serves Dallas county patients 13 years and older, most of whom are indigent. Ophthalmology clinic medical records are maintained on a computer database, the EYEstation program by Datamedic (Hauppauge, NY).
Subject Selection Medical records from all 3562 unique subjects seen at Parkland’s New and General eye clinic from July 1, 1998 to September 30, 1998, were reviewed to identify subjects with blind eyes. Blindness in this study was defined as best-corrected visual acuity of ⱕ20/200 in either eye.
Etiologic Analysis The records of 397 subjects met the study criteria for blindness and were reviewed in further detail. An etiologic analysis of blindness was performed and classified into eleven categories: retina, trauma, diabetes, glaucoma, lens, cornea, amblyopia, optic nerve, uveitis, tumor, and unknown/miscellaneous. Retinal causes encompassed retinal artery and vein occlusions, retinal detachments, infections (cytomegalovirus, histoplasmosis, toxoplasmosis), macular pathosis (ARMD, holes, and scars), and hereditary diseases (retinitis pigmentosa, cone/rod dystrophy, choroidal degeneration). Blindness caused by retinal complications of diabetes was considered separately. Blindness in diabetes was secondary to proliferative retinopathy, vitreous hemorrhage, or clinically significant macular edema. Glaucoma was subclassified to include primary open-angle glaucoma, secondary open-angle glaucoma, neovascular glaucoma, normal tension glaucoma, and combined mechanism
694
Parkland outpatient clinics serve a racially diverse population. For the year 1998, a breakdown of the outpatient population by race was 37.5% black, 37.1% Hispanic, 21.2% white, and 4.2% other. An analysis of the payer status for Parkland outpatient clinic patients for the year 1998 revealed that 19.5% of patients had Medicaid coverage, 15.7% had Medicare, 5.1% had commercial insurance, and 59.7% were uninsured. The ophthalmologic medical records of the 3562 subjects seen in the Parkland New and General Outpatient Ophthalmology clinics from July 1, 1998 to September 30, 1998, were reviewed. Of the 397 (11.1%) subjects blind in at least one eye, 214 (53.9%) were women and 183 (46.1%) were men. The mean age of affected subjects was 55.2 years (range, 8 –92 years). Three hundred twenty-one subjects (9.0% of all subjects seen) were blind in one eye, and 76 subjects (2.1%) were blind in both eyes. One hundred sixty-five (51.4%) of monocularly blinded eyes were right eyes. Forty-nine (64.5%) of bilaterally blind subjects were women. Of the 397 blind subjects, 50.6% had hypertension, 43.1% had diabetes, and 30.7% had both hypertension and diabetes. Table 1
Table 2. Etiologic Analysis of Blindness in Subjects with Bestcorrected Visual Acuity ⱕ20/200 in at Least One Eye
Etiology
All Subjects (%)
New Subjects (%)
Retina Trauma Diabetes Glaucoma Lens Cornea Amblyopia Optic nerve Miscellaneous/unknown Uveitis Tumor Total
90 (22.7) 71 (17.9) 68 (17.1) 62 (15.6) 34 (8.6) 21 (5.3) 19 (4.8) 12 (3.0) 9 (2.3) 8 (2.0) 3 (0.8) 397 (100.0)
15 (17.6) 24 (28.2) 10 (11.8) 3 (3.5) 13 (15.3) 10 (11.8) 4 (4.7) 5 (5.9) 0 (0.0) 0 (0.0) 1 (1.2) 85 (100.0)
Apte et al 䡠 Blindness in an Urban Community Hospital Setting Table 3. Retinal Causes of Blindness Etiology
No. of Subjects
% Retinal Causes
Retinal vascular occlusion Retinal detachment Infections (mainly CMV) Macular hole/scar Other Degeneration/dystrophy ARMD Total
24 23 11 10 9 8 5 90
26.7 25.6 12.2 11.1 10.0 8.9 5.6 100.0
ARMD ⫽ Age-related macular degeneration; CMV ⫽ cytomegalovirus.
documents the visual status of the blind eye in monocularly blind subjects and the visual status of both eyes in binocularly blind subjects. Retinal pathosis (90 ⫽ 22.7%), trauma (71 ⫽ 17.9%), diabetes (68 ⫽ 17.1%), and glaucoma (62 ⫽ 15.6%) were the leading causes of blindness in subjects with ⱕ20/200 best-corrected visual acuity in at least one eye (n ⫽ 397) (Table 2). Of the retinal causes, retinal vascular occlusions (26.7%) and retinal detachments (25.6%), accounted for a significant percentage of the visual loss (Table 3). Cytomegalovirus retinitis was the most common infectious cause of retinal blindness. ARMD accounted for blindness in only five subjects (5.6% of retinal causes). Sequelae of proliferative diabetic retinopathy were directly responsible for blindness in 58 (85.3%) of 68 subjects blinded as a result of diabetic ocular disease. Forty-five (72.6%) of 62 subjects with blindness secondary to glaucoma had primary open-angle glaucoma. We also performed an etiologic analysis of blindness in new subjects. These were subjects who had never been examined in the Parkland ophthalmology clinics before the current presentation. Among 85 new subjects, trauma (28.2%) was the leading cause of blindness (Table 2). The difference in case frequencies of causes between all blind subjects and those newly presenting were not statistically significant except for a decreased incidence in glaucoma in new subjects (P ⫽ 0.01). Figure 1 contrasts the causes of unilateral and bilateral blindness. Although trauma was one of the leading causes of unilateral blindness (20.9%), it played a relatively minor role in bilateral blindness (5.3%) (P ⫽ 0.009). Trauma was twice as prevalent a factor in visual loss in men (24.6%) than in women (12.2%, P ⫽ 0.01) (Fig 2). Not surprisingly, the prevalence of glaucoma and retinal disorders as a cause of blindness increased with age (Fig 3). Diabetes was the most common cause of blindness among the 40- to 59-year-old age group. Trauma was significantly more common as a cause of
Figure 1. Causes of unilateral versus bilateral blindness. Glauc ⫽ glaucoma.
Figure 2. Causes of blindness by gender. Glauc ⫽ glaucoma.
blindness in the subject population less than 40 years of age compared with older age groups (P ⫽ 0.004).
Discussion Preservation and maintenance of vision is a principal focus of ophthalmic practice. It has been estimated that the total cost of global blindness is about one fourth to one sixth of the United Kingdom’s gross national product.9 A number of studies have studied the cause of blindness by use of lowvision clinic records, blindness registries, or selective population-based approaches. Previous reports of the incidence and prevalence of blindness have predominantly been restricted to either racially homogeneous or older populations. The population studied and the approach to data collection taken have a significant impact on the results obtained. As such, ARMD has been the leading cause of severe visual impairment in most of these study settings.1– 8 In contrast, in this study ARMD was the cause of ⬍1.5% of the severe vision loss found. The Parkland Health and Hospital System population is racially diverse. Only 21.2% of outpatients in 1998 were white compared with 37.5% black and 37.1% Hispanic. Blacks have been shown to have a higher prevalence of blindness than whites.10 –12 In addition, blacks are more likely to have blindness from glaucoma compared with whites, who are more likely to have blindness from ARMD.11–13 The Baltimore Eye Survey and the Baltimore Nursing Home Eye Survey found that unoperated cataract was the leading cause of blindness in their respective study populations, suggesting underuse of health
Figure 3. Causes of blindness by age.
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Ophthalmology Volume 108, Number 4, April 2001 services, especially in the black and elderly population.12,13 Lenticular causes accounted for only 8.6% of cases of blindness in at least one eye in this study, although it accounted for 15.3% of blind new subjects initially seen in the outpatient clinic. Instead, retinal causes were the most common cause of blindness, whether unilateral or bilateral, in this study. Retinal vascular occlusions and retinal detachment accounted for more than half of retinal blindness. Trauma was the second most common cause of blindness and may reflect Parkland Memorial Hospital’s status as a Level I Trauma Center for the Dallas area. Trauma was the most common cause of blindness in subjects initially seen in the clinic and was almost as common as retinal causes for unilaterally blind subjects. Not surprisingly, traumatic blindness was more common in men and was the most common cause of blindness in young adults. Diabetic retinopathy was the third most common cause of blindness overall and the second most common cause of bilateral blindness. This may reflect the large proportion of Hispanics in the Parkland outpatient population. Similar to previous studies,1,2 we found diabetic retinopathy to be the leading cause of blindness in the 40- to 59-year-age group. Glaucoma was the fourth leading cause of blindness overall and the third major cause of bilateral blindness. This likely reflects the large proportion of blacks in the Parkland population. Clearly, the Parkland population differs from previously studied populations. Aside from differences in racial makeup, the subjects included in this study sought out ophthalmologic care at an urban outpatient clinic that primarily cares for the indigent. Only a 3-month period was studied, leading to a potential bias toward excluding subjects with blinding diseases requiring less frequent followup. It is unknown whether compliance with follow-up differs between subjects with different causes of blindness. Also, are subjects undergoing medical treatment with drops more likely to keep follow-up appointments than subjects under observation only? We speculated that looking at newly presenting subjects to the clinic (i.e., excluding established subjects) would give a more accurate impression of blindness burden from various causes. However, except for a decrease in glaucoma as a cause for blindness in new subjects, group differences between all blind subjects and new blind subjects were not statistically significant. This study has implications for spending Dallas county tax revenue to decrease severe visual loss in the Parkland population. Early detection and treatment of diabetes and systemic hypertension may lower the incidence of blindness caused by retinopathy and retinal vascular occlusive disease. Screening for glaucoma in middle-aged and older adults would appear to be beneficial, especially in view of the proportion of blacks in the Parkland population. Trauma
696
is a major cause of vision loss, especially in young adults and men. Traumatic visual loss is commonly unilateral and may (e.g., work-related) or may not (e.g., assault) be easily preventable. We found that retinal pathosis, trauma, diabetes, and glaucoma were the major causes of visual loss in the predominately nonwhite Parkland outpatient ophthalmology clinic population. The prevalence of retinal disorders and glaucoma as the cause of blindness increased with age of the subject. Similar to previous studies, we found diabetes to be the most common cause of blindness among 40- to 59-yearold subjects, whereas trauma was more common in subjects less than 40 years and in men. Unlike previous studies, ARMD accounted for ⬍1.5% of severe vision loss, likely because of the racial heterogeneity of our urban population.
References 1. Krumpaszky HG, Lu¨dtke R, Mickler A, et al. Blindness incidence in Germany. A population-based study from Wu¨rttemberg-Hohenzollern. Ophthalmologica 1999;213:176 – 82. 2. Rosenberg T, Klie F. Current trends in newly registered blindness in Denmark. Acta Ophthalmol Scand 1996;74:395– 8. 3. Grey RHB, Burns-Cox CJ, Hughes A. Blind and partial sight registration in Avon. Br J Ophthalmol 1989;73:88 –94. 4. Munier A, Gunning T, Kenny D, O’Keefe M. Causes of blindness in the adult population of the Republic of Ireland. Br J Ophthalmol 1998;82:630 –3. 5. Elliott DB, Trukolo-Ilic M, Strong JG, et al. Demographic characteristics of the vision-disabled elderly. Invest Ophthalmol Vis Sci 1997;38:2566 –75. 6. Leat SJ, Rumney NJ. The experience of a university-based low vision clinic. Ophthalmic Physiol Opt 1990;10:8 –15. 7. Klaver CCW, Wolfs RCW, Vingerling JR, et al. Age-specific prevalence and causes of blindness and visual impairment in an older population: the Rotterdam Study. Arch Ophthalmol 1998;116:653– 8. 8. Attebo K, Mitchell P, Smith W. Visual acuity and causes of visual loss in Australia. The Blue Mountains Eye Study. Ophthalmology 1996;103:357– 64. 9. Smith AF, Smith JG. The economic burden of global blindness: a price too high! Br J Ophthalmol 1996;80:276 –7. 10. Tielsch JM, Sommer A, Witt K, et al. Blindness and visual impairment in an American urban population. The Baltimore Eye Survey. Arch Ophthalmol 1990;108:286 –90. 11. Bath PE. Rationale for a program in community ophthalmology. J Natl Med Assoc 1979;71:145– 8. 12. 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;332:1205–9. 13. Sommer A, Tielsch JM, Katz J, et al. Racial differences in the cause-specific prevalence of blindness in east Baltimore. N Engl J Med 1991;325:1412–7.
Originally received: May 2, 2000. Accepted: November 27, 2000. Manuscript no. 200264. Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas. Presented in part as a PAAO Select Free paper at the Joint AAO/PAAO meeting, Orlando, Florida, October 1999. Supported in part by an unrestricted research grant from Research to Prevent Blindness, Inc., New York, New York. Reprint requests to Preston H. Blomquist, MD, FACS, Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9057. © 2001 by the American Academy of Ophthalmology Published by Elsevier Science Inc.
presenting subjects at the low-vision clinic at the University of Wales revealed that ARMD was by far the most common cause of low vision (48% of subjects), with myopia (9.7%) a distant second and cataract (7.4%) third.6 Studies that used blindness registries of predominately Caucasian populations have shown similar results. In reviewing the 674 blind persons newly registered with social services in the Wu¨rttemberg-Hohenzollern region in Germany (where blindness is defined as ⬍1/50, and there are monetary incentives to register), 32.3% were blind from ARMD, 16.6% from diabetic retinopathy, 13.2% from glaucoma, and 6.4% from high myopia. ARMD was the cause of more than half of legal blindness for subjects older than 75 years of age, whereas diabetic retinopathy was the most common cause in subjects 45 to 75 years of age.1 Review of 1585 new applications for the Danish Society of the Blind for 1993 revealed ARMD was the cause of the blindness 71.4% of the time. ARMD accounted for the blindness in 78% of registrants 60 years of age or older, whereas diabetic retinopathy was the predominant cause (36%) in registrants 20 to 59 years old.2 Of blind and partially sighted registration forms for the county of Avon over a 2-year period, 49% listed ARMD as the cause of vision loss, followed by glaucoma (15%) and diabetes (6%).3 A population-based study of 6775 subjects 55 years of age or older living in the city district of Ommoord in ISSN 0161-6420/00/$–see front matter PII S0161-6420(00)00653-9
693
Ophthalmology Volume 108, Number 4, April 2001 Table 1. Best-corrected Visual Acuity of Subjects with Monocular or Binocular Blindness
Best-corrected Visual Acuity
20/200– 20/400 (%)
Counting Fingers (%)
Hand Motion (%)
Light Perception (%)
No Light Perception (%)
Monocular blindness (n ⫽ 321) Binocular blindness—better eye (n ⫽ 76) Binocular blindness—worse eye (n ⫽ 76)
86 (26.8) 38 (50.0) 15 (19.7)
57 (17.8) 18 (23.7) 17 (22.4)
67 (20.9) 12 (15.8) 10 (13.2)
36 (11.2) 7 (9.2) 11 (14.5)
75 (23.4) 0 (0) 24 (31.6)
Rotterdam, The Netherlands, revealed ARMD to be the major cause of blindness (58%) in that predominately white population.7 In a population-based study of 3647 persons living west of Sydney, Australia, ARMD was the cause of blindness in 21 of the 24 people found with corrected visual acuity ⱕ20/200.8 Although ARMD is a major cause of blindness in Caucasians, comparatively little information is currently available on the cause of blindness in a predominately nonwhite, uninsured urban community population in the United States. In this study, we assess the burden of blindness in an urban county hospital population and analyze the various causes of severe monocular and binocular visual loss.
glaucoma. Cataracts and aphakia accounted for lenticular causes of blindness. Corneal causes included abrasions, infections, and keratoconus. Optic nerve damage was secondary to anterior ischemic optic neuropathy, optic atrophy, or optic neuritis. Causes of uveitis when diagnosed included sarcoidosis, syphilis, and fibromyalgia. A demographic analysis of blindness was also performed to include age, gender, and laterality.
Statistical Analysis Chi-square test (SigmaStat, Jandel Corp.; San Rafael, CA) was used to assess group differences with respect to case frequencies.
Results Materials and Methods Study Site and Data Collection Parkland Memorial Hospital is the general public hospital for Dallas County, Texas, and the primary teaching hospital for the University of Texas Southwestern Medical Center at Dallas. Parkland’s New and General Outpatient Ophthalmology clinic serves Dallas county patients 13 years and older, most of whom are indigent. Ophthalmology clinic medical records are maintained on a computer database, the EYEstation program by Datamedic (Hauppauge, NY).
Subject Selection Medical records from all 3562 unique subjects seen at Parkland’s New and General eye clinic from July 1, 1998 to September 30, 1998, were reviewed to identify subjects with blind eyes. Blindness in this study was defined as best-corrected visual acuity of ⱕ20/200 in either eye.
Etiologic Analysis The records of 397 subjects met the study criteria for blindness and were reviewed in further detail. An etiologic analysis of blindness was performed and classified into eleven categories: retina, trauma, diabetes, glaucoma, lens, cornea, amblyopia, optic nerve, uveitis, tumor, and unknown/miscellaneous. Retinal causes encompassed retinal artery and vein occlusions, retinal detachments, infections (cytomegalovirus, histoplasmosis, toxoplasmosis), macular pathosis (ARMD, holes, and scars), and hereditary diseases (retinitis pigmentosa, cone/rod dystrophy, choroidal degeneration). Blindness caused by retinal complications of diabetes was considered separately. Blindness in diabetes was secondary to proliferative retinopathy, vitreous hemorrhage, or clinically significant macular edema. Glaucoma was subclassified to include primary open-angle glaucoma, secondary open-angle glaucoma, neovascular glaucoma, normal tension glaucoma, and combined mechanism
694
Parkland outpatient clinics serve a racially diverse population. For the year 1998, a breakdown of the outpatient population by race was 37.5% black, 37.1% Hispanic, 21.2% white, and 4.2% other. An analysis of the payer status for Parkland outpatient clinic patients for the year 1998 revealed that 19.5% of patients had Medicaid coverage, 15.7% had Medicare, 5.1% had commercial insurance, and 59.7% were uninsured. The ophthalmologic medical records of the 3562 subjects seen in the Parkland New and General Outpatient Ophthalmology clinics from July 1, 1998 to September 30, 1998, were reviewed. Of the 397 (11.1%) subjects blind in at least one eye, 214 (53.9%) were women and 183 (46.1%) were men. The mean age of affected subjects was 55.2 years (range, 8 –92 years). Three hundred twenty-one subjects (9.0% of all subjects seen) were blind in one eye, and 76 subjects (2.1%) were blind in both eyes. One hundred sixty-five (51.4%) of monocularly blinded eyes were right eyes. Forty-nine (64.5%) of bilaterally blind subjects were women. Of the 397 blind subjects, 50.6% had hypertension, 43.1% had diabetes, and 30.7% had both hypertension and diabetes. Table 1
Table 2. Etiologic Analysis of Blindness in Subjects with Bestcorrected Visual Acuity ⱕ20/200 in at Least One Eye
Etiology
All Subjects (%)
New Subjects (%)
Retina Trauma Diabetes Glaucoma Lens Cornea Amblyopia Optic nerve Miscellaneous/unknown Uveitis Tumor Total
90 (22.7) 71 (17.9) 68 (17.1) 62 (15.6) 34 (8.6) 21 (5.3) 19 (4.8) 12 (3.0) 9 (2.3) 8 (2.0) 3 (0.8) 397 (100.0)
15 (17.6) 24 (28.2) 10 (11.8) 3 (3.5) 13 (15.3) 10 (11.8) 4 (4.7) 5 (5.9) 0 (0.0) 0 (0.0) 1 (1.2) 85 (100.0)
Apte et al 䡠 Blindness in an Urban Community Hospital Setting Table 3. Retinal Causes of Blindness Etiology
No. of Subjects
% Retinal Causes
Retinal vascular occlusion Retinal detachment Infections (mainly CMV) Macular hole/scar Other Degeneration/dystrophy ARMD Total
24 23 11 10 9 8 5 90
26.7 25.6 12.2 11.1 10.0 8.9 5.6 100.0
ARMD ⫽ Age-related macular degeneration; CMV ⫽ cytomegalovirus.
documents the visual status of the blind eye in monocularly blind subjects and the visual status of both eyes in binocularly blind subjects. Retinal pathosis (90 ⫽ 22.7%), trauma (71 ⫽ 17.9%), diabetes (68 ⫽ 17.1%), and glaucoma (62 ⫽ 15.6%) were the leading causes of blindness in subjects with ⱕ20/200 best-corrected visual acuity in at least one eye (n ⫽ 397) (Table 2). Of the retinal causes, retinal vascular occlusions (26.7%) and retinal detachments (25.6%), accounted for a significant percentage of the visual loss (Table 3). Cytomegalovirus retinitis was the most common infectious cause of retinal blindness. ARMD accounted for blindness in only five subjects (5.6% of retinal causes). Sequelae of proliferative diabetic retinopathy were directly responsible for blindness in 58 (85.3%) of 68 subjects blinded as a result of diabetic ocular disease. Forty-five (72.6%) of 62 subjects with blindness secondary to glaucoma had primary open-angle glaucoma. We also performed an etiologic analysis of blindness in new subjects. These were subjects who had never been examined in the Parkland ophthalmology clinics before the current presentation. Among 85 new subjects, trauma (28.2%) was the leading cause of blindness (Table 2). The difference in case frequencies of causes between all blind subjects and those newly presenting were not statistically significant except for a decreased incidence in glaucoma in new subjects (P ⫽ 0.01). Figure 1 contrasts the causes of unilateral and bilateral blindness. Although trauma was one of the leading causes of unilateral blindness (20.9%), it played a relatively minor role in bilateral blindness (5.3%) (P ⫽ 0.009). Trauma was twice as prevalent a factor in visual loss in men (24.6%) than in women (12.2%, P ⫽ 0.01) (Fig 2). Not surprisingly, the prevalence of glaucoma and retinal disorders as a cause of blindness increased with age (Fig 3). Diabetes was the most common cause of blindness among the 40- to 59-year-old age group. Trauma was significantly more common as a cause of
Figure 1. Causes of unilateral versus bilateral blindness. Glauc ⫽ glaucoma.
Figure 2. Causes of blindness by gender. Glauc ⫽ glaucoma.
blindness in the subject population less than 40 years of age compared with older age groups (P ⫽ 0.004).
Discussion Preservation and maintenance of vision is a principal focus of ophthalmic practice. It has been estimated that the total cost of global blindness is about one fourth to one sixth of the United Kingdom’s gross national product.9 A number of studies have studied the cause of blindness by use of lowvision clinic records, blindness registries, or selective population-based approaches. Previous reports of the incidence and prevalence of blindness have predominantly been restricted to either racially homogeneous or older populations. The population studied and the approach to data collection taken have a significant impact on the results obtained. As such, ARMD has been the leading cause of severe visual impairment in most of these study settings.1– 8 In contrast, in this study ARMD was the cause of ⬍1.5% of the severe vision loss found. The Parkland Health and Hospital System population is racially diverse. Only 21.2% of outpatients in 1998 were white compared with 37.5% black and 37.1% Hispanic. Blacks have been shown to have a higher prevalence of blindness than whites.10 –12 In addition, blacks are more likely to have blindness from glaucoma compared with whites, who are more likely to have blindness from ARMD.11–13 The Baltimore Eye Survey and the Baltimore Nursing Home Eye Survey found that unoperated cataract was the leading cause of blindness in their respective study populations, suggesting underuse of health
Figure 3. Causes of blindness by age.
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Ophthalmology Volume 108, Number 4, April 2001 services, especially in the black and elderly population.12,13 Lenticular causes accounted for only 8.6% of cases of blindness in at least one eye in this study, although it accounted for 15.3% of blind new subjects initially seen in the outpatient clinic. Instead, retinal causes were the most common cause of blindness, whether unilateral or bilateral, in this study. Retinal vascular occlusions and retinal detachment accounted for more than half of retinal blindness. Trauma was the second most common cause of blindness and may reflect Parkland Memorial Hospital’s status as a Level I Trauma Center for the Dallas area. Trauma was the most common cause of blindness in subjects initially seen in the clinic and was almost as common as retinal causes for unilaterally blind subjects. Not surprisingly, traumatic blindness was more common in men and was the most common cause of blindness in young adults. Diabetic retinopathy was the third most common cause of blindness overall and the second most common cause of bilateral blindness. This may reflect the large proportion of Hispanics in the Parkland outpatient population. Similar to previous studies,1,2 we found diabetic retinopathy to be the leading cause of blindness in the 40- to 59-year-age group. Glaucoma was the fourth leading cause of blindness overall and the third major cause of bilateral blindness. This likely reflects the large proportion of blacks in the Parkland population. Clearly, the Parkland population differs from previously studied populations. Aside from differences in racial makeup, the subjects included in this study sought out ophthalmologic care at an urban outpatient clinic that primarily cares for the indigent. Only a 3-month period was studied, leading to a potential bias toward excluding subjects with blinding diseases requiring less frequent followup. It is unknown whether compliance with follow-up differs between subjects with different causes of blindness. Also, are subjects undergoing medical treatment with drops more likely to keep follow-up appointments than subjects under observation only? We speculated that looking at newly presenting subjects to the clinic (i.e., excluding established subjects) would give a more accurate impression of blindness burden from various causes. However, except for a decrease in glaucoma as a cause for blindness in new subjects, group differences between all blind subjects and new blind subjects were not statistically significant. This study has implications for spending Dallas county tax revenue to decrease severe visual loss in the Parkland population. Early detection and treatment of diabetes and systemic hypertension may lower the incidence of blindness caused by retinopathy and retinal vascular occlusive disease. Screening for glaucoma in middle-aged and older adults would appear to be beneficial, especially in view of the proportion of blacks in the Parkland population. Trauma
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is a major cause of vision loss, especially in young adults and men. Traumatic visual loss is commonly unilateral and may (e.g., work-related) or may not (e.g., assault) be easily preventable. We found that retinal pathosis, trauma, diabetes, and glaucoma were the major causes of visual loss in the predominately nonwhite Parkland outpatient ophthalmology clinic population. The prevalence of retinal disorders and glaucoma as the cause of blindness increased with age of the subject. Similar to previous studies, we found diabetes to be the most common cause of blindness among 40- to 59-yearold subjects, whereas trauma was more common in subjects less than 40 years and in men. Unlike previous studies, ARMD accounted for ⬍1.5% of severe vision loss, likely because of the racial heterogeneity of our urban population.
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