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Correctable visual impairment in an older population: the blue mountains eye study
Correctable Visual Impairment in an Older Population: The Blue Mountains Eye Study SURIYA FORAN, MBBS, MPH, KATHRYN ROSE, PHD, JIE JIN WANG, MMED, PHD, AND PAUL MITCHELL, MD, PHD
● PURPOSE:
To describe temporal changes in the characteristics of older persons with visual impairment in their better eye correctable by refraction. ● DESIGN: Study of two cross sections of a community 6 years apart. ● METHODS: The Blue Mountains Eye Study examined 3654 persons aged 49 to 97 during 1992 to 1994 (cross-section 1) and 3509 persons (2335 cohort survivors plus 1174 persons who moved to the area and age group) during 1997 to 2000 (cross-section 2). Logarithm of minimal angle of resolution visual acuity was measured before and after refraction. Correctable visual impairment was defined as visual impairment < 20/40 in the better eye before refraction that improved after refraction to no impairment (> 20/40). Factors associated with correctable visual impairment and persistent correctable impairment were determined. ● RESULTS: Cross-sections 1 and 2 had similar agegender distributions. In cross-section 1, 7.5% of participants had correctable visual impairment, 3.6% had noncorrectable visual impairment, and 88.9% had no impairment. Corresponding rates in cross-section 2 were 5.6%, 2.7%, and 91.7%. In both cross sections, similar proportions (around 68%) of those visually impaired had correctable visual impairment and similar sociodemographic measures predicted correctable visual impairment. Cross-section 1 participants who were married, owned their home, had high job prestige, gained qualifications after high school, or were current drivers were less likely to have correctable visual impairment after controlling for age and gender. Adjusted odds for correctable visual impairment increased in those living alone, Accepted for publication June 11, 2002. From the Department of Ophthalmology, University of Sydney (Center for Vision Research, Westmead Hospital) and the Westmead Millennium and Save Sight Institutes, Sydney, Australia (S.F., J.J.W., P.M.); School of Applied Vision Sciences, Faculty of Health Sciences, University of Sydney, Sydney, Australia (K.R.). This work was supported by the Australian National Health & Medical Research Council, Canberra, Australia (grants 974159, 991407). Inquiries to Paul Mitchell, MD, PhD, University of Sydney Department of Ophthalmology (Centre for Vision Research), Westmead Hospital, Hawkesbury Road, Westmead, NSW, Australia, 2145; fax: (⫹ 61) 2- 9845- 6117; e-mail [email protected]
712
©
2002 BY
using community support services, dependent on others, with myopia, wearing distance glasses, or with low perceived health and heart disease. Histories of stroke, cancer, and diabetes were similar between groups with correctable and no visual impairment. ● CONCLUSION: Socioeconomic parameters, myopia, wearing distance glasses, reported health problems, and poor perceived health were associated with correctable visual impairment in this older population. (Am J Ophthalmol 2002;134:712–719. © 2002 by Elsevier Science Inc. All rights reserved.)
V
ISUAL IMPAIRMENT HAS BEEN SHOWN TO HAVE
numerous impacts in older persons and has been associated with use of community support services,1,2 nursing home placement,3 falls,4 – 6 mortality,7–9 and low self-rated health.8 While most population studies have assessed the impacts of noncorrectable visual impairment, a number10 –14 have documented a high frequency of older persons with correctable visual impairment, that is, presenting with vision that could be improved by providing or changing distance glasses. Recent reports show that visual impairment associated with uncorrected refraction was also associated with substantial impacts, though at a lower magnitude.1,9 Few studies have assessed factors associated with correctable visual impairment, and none has examined temporal changes in correctable impairment and its associated factors in an older population. This report aims, firstly, to describe the frequency of correctable visual impairment; secondly, to compare socioeconomic factors and other considerations associated with correctable visual impairment and with no visual impairment; and thirdly, to examine whether there has been a change in the frequency of correctable visual impairment and socioeconomic factors over time.
DESIGN THIS STUDY ANALYZED TWO CROSS SECTIONS OF A COM-
munity 6 years apart.
ELSEVIER SCIENCE INC. ALL
RIGHTS RESERVED.
0002-9394/02/$22.00 PII S0002-9394(02)01673-2
METHODS ● STUDY POPULATION: The Blue Mountains Eye Study (BMES) is a population-based survey of vision and common eye diseases in an urban population aged 49 years or older resident in two postal codes of the Blue Mountains region, west of Sydney, Australia. A number of reports have described the methods used.1,12,13 The present report uses findings from two cross sections from this population. Blue Mountain Eye Study I identified 4433 eligible noninstitutionalized permanent residents in a door-to-door census conducted during 1991, of whom 3654 (82.4%) participated in the examinations from 1992 to 1994. Of the 779 (17.6%) persons who did not participate, 353 (8.0%) permitted only an interview, 148 (3.3%) refused, 210 (4.7%) had moved out of the area, and 68 (1.5%) had died. A previous report compared participants and nonparticipants at baseline.12 After 5 years, all BMES I participants were invited to attend repeat examinations during 1997 to 1999 (BMES IIA). By the time these examinations commenced, 383 persons (10.5%) had moved, 394 (10.8%) refused to participate, 543 (14.9%) had died, and 2335 (75.1%) were reexamined. A repeat door-to-door census conducted in 1999 of the same area identified 1378 additional eligible permanent residents who had moved into the area or were now aged 50 or older. We examined 1174 (85.2%) of this group during 1999 to 2000 (BMES IIB). Thus, crosssection 2 comprises 3509 participants from BMES IIA and IIB. ● OBSERVATION PROCEDURES: Previous BMES reports12,15,16 describe the survey methods and procedures, which were similar for the two examinations. Participants gave written informed consent on both occasions. The Western Sydney Human Ethics Committee provided ethical approval. Details of the sociodemographic parameters explored have been previously reported.2 In brief, parameters described in this report include marital and cohabitation status, dwelling ownership, principal occupation during working life, and qualifications gained after high school. We did not directly ask questions regarding income. Use of community support services was defined as regular use of “Meals on Wheels,” home care, or regular visits by a community nurse. Dependency was defined as the inability to go shopping, visit friends, or go to town alone. Whether participants were current drivers and the mode of transport used to attend the study center were determined. Participants were asked if they had ever been advised by a doctor that they had angina, myocardial infarct (“heart attack”), stroke, cancer, or diabetes. Heart disease was defined as a positive response to the questions about angina or myocardial infarct. Participants were also asked to rate their overall health as excellent, good, fair, or poor. Visual acuity was measured by a logarithm of the
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minimum angle of resolution (logMAR) chart, retroilluminated with automatic calibration to 85 cd/m2 (Vectorvision CSV-100TM, Vectorvision, Inc., Dayton, Ohio, USA), and read at 8 ft (244 cm).12 Distance visual acuity in each eye was initially measured with current distance glasses if worn. An autorefractor (Allergan Humphrey, Model 530, San Leandro, California, USA) provided objective refraction. Subjective refraction was performed according to the Beaver Dam Eye Study modification of the Early Treatment Diabetic Retinopathy Study protocol.11 For each eye, visual acuity was recorded as the number of letters read correctly from 0 to 70. Spherical equivalent (0.5 cylinder ⫹ sphere) was calculated from the best refractive correction. A spherical equivalent between ⫺1.0 and ⫹ 1.0 defined emmetropia, less than ⫺1.0 defined myopia, and greater than ⫹ 1.0 defined hyperopia. We defined visual impairment as acuity worse than 20/40, based on the minimum legal visual acuity requirement for obtaining a driver’s license in many states in the United States and Australia. In this report, visual impairment was defined as fewer than 39 letters read on the logMAR chart (allowing one incorrect letter on the 20/40 line). The World Health Organization International Classification for Disease-10 (WHO ICD-10) category 1 or higher defines visual impairment as worse than 20/70 in the better eye, which was taken as fewer than 29 letters read. The WHO ICD-10 category 2 or higher defines visual impairment as worse than 20/200 (blindness in Australia), taken as fewer than four letters read.17 Correctable visual impairment was defined as visual impairment ⬍ 20/40 before refraction (with distance glasses if worn) that improved after refraction to no impairment (ⱖ 20/40). In this report, the better eye has been chosen as reference. Statistical Analysis System (SAS Institute Inc., Cary, North Carolina, USA) was used for analyses, including 2 and logistic regression. All odds ratios are given with 95% confidence intervals and are adjusted for age and gender.
RESULTS TABLE 1 SHOWS CHARACTERISTICS OF PARTICIPANTS IN
cross-sections 1 and 2. Age and gender distribution, the duration since the last eye examination, and the proportions married, living alone, owning their home, selfreporting heart disease and stroke, or currently having distance glasses were similar. However, in cross-section 2, a significantly higher proportion had high occupational prestige or self-reported cancer and diabetes, were current drivers, or were dependent on others. Although the mean numbers of letters read correctly by the two groups were very similar, persons in cross-section 2 read a significantly greater number of letters. Cross-section 2 had a significantly lower proportion who gained further qualifications after high school, used community support services, or who rated their health as only fair or poor. In cross-section 2,
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TABLE 1. Participant Characteristics in Cross-section 1 (n ⫽ 3,654) and Cross-section 2 (n ⫽ 3,508) Cross-section 1
Age (mean) 49–59 60–69 70–79 80⫹ Female Married Lives alone Owns home High job prestige Gained qualifications after high school Drives car Uses community support services Dependent Self reported history Heart disease Stroke Cancer Diabetes Fair–poor self rated health Emmetropia§ Myopia§ Hyperopia§ Distance glasses worn during eye examination (Mean duration [years] since eye care service) (Mean number of letters read correctly)‡
Cross-section 2
n*
%
n*
(66.2) 1019 1309 960 366 2072 2288 991 3152 2213 1732 2452 180 111
27.9 35.8 26.3 10.0 56.7 62.8 27.4 88.7 62.2 47.4 69.0 5.2 3.3
(66.7) 930 1238 978 359 1997 2156 936 3140 2319 1574 2504 121 194
26.5 35.3 27.9 10.2 57.0 61.7 26.8 89.7 69.0† 44.9‡ 85.5† 3.5† 5.6†
586 194 310 218 907 1558 442 1633 2473
16.1 5.3 8.5 6.0 25.3 42.9 12.2 45.0 67.7
593 186 443 255 709 1478 495 1532 2372
17.1 5.3 12.7† 7.3† 20.3† 42.2 14.1‡ 43.7 69.3
(2.5) (49.8)
%
(2.5) (50.6)
*n ⫽ number of persons. P ⬍ 0.01. ‡ P ⬍ 0.05. § Best spherical equivalent refractive correction. †
the proportion of persons with myopia significantly increased by 1.9%. Table 2 shows the visual impairment status of participants in cross-sections 1 and 2. Eight subjects were excluded from cross-section 2, as they reported having distance glasses, but did not bring them to the examination. In cross-section 1, 7.5% of participants had correctable visual impairment, 3.6% had noncorrectable impairment, and 88.9% had no impairment. The corresponding rates in cross-section 2 were 5.6%, 2.7% and 91.7%. A significantly lower proportion of the population had correctable visual impairment and a higher proportion had no visual impairment in cross-section 2 than in cross-section 1. However, the proportion of correctable visual impairment among the total number of people who were visually impaired remained similar at the two times (68.2% in cross-section 1 vs 67.5% in cross-section 2). 714
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TABLE 2. Visual Impairment (VI) Status of Participants Cross-section 1 n*
No VI Correctable to no VI Noncorrectable VI Improvement but still VI No improvement Total (excluding missing)‡
%
Cross-section 2 n*
%
91.7† 5.6†
3245 274
88.9 7.5
3203 195
23 107 3649
0.6 2.9 100.0
17 78 3493
0.5 2.2 100.0
*n ⫽ number of persons. † P ⬍ .01. ‡ Excludes eyes where either presenting (for example, did not bring current distance glasses) or best-corrected visual acuity was missing (n ⫽ 8).
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FIGURE 1. Age-specific rates of correctable visual impairment and no visual impairment in cross-sections 1 and 2.
Figure 1 shows the age-specific rates of correctable visual impairment and no visual impairment in cross-sections 1 and 2. Of the 274 persons with correctable impairment in cross-section 1, 237 (86.5%) improved from ⬍ 20/40 –20/ 70, 36 (13.1%) from ⬍ 20/70 –20/200, and 1 (0.4%) from ⬍ 20/200 to no visual impairment. Of the 195 persons with correctable impairment in cross-section 2, 170 (87.2%) improved from ⬍ 20/40 –20/70, 24 (12.3%) from ⬍ 20/70 –20/200, and one (0.5%) from ⬍ 20/200 to no visual impairment. Characteristics of persons with no visual impairment and with correctable visual impairment in cross-sections 1 and 2 are shown in Tables 3 and 4, respectively. In both cross sections, the mean age of persons with correctable visual impairment was higher by around 8 years than those with no visual impairment. With each decade of increasing age, the likelihood of correctable visual impairment increased (odds ratio [OR], 2.3–2.6). After controlling for age, gender was not significantly associated with correctable visual impairment. Odds ratios for the associations explored generally had the same direction and magnitude in the two cross sections. In both, persons who had correctable visual impairment read a mean of 33 letters correctly compared with persons with no visual impairment, who read a mean of 52 letters. Participants with myopia were more likely to have correctable visual impairment. In cross-section 1, persons who were married, owned their home, had high job prestige, gained qualifications after high school, or were current drivers were less likely (OR, 0.5– 0.8) to have correctable visual impairment after controlling for age and gender. The odds for correctable visual impairment were increased in those living alone (OR, 1.6), using community support services (OR, 1.8), dependent on others (OR, 3.0), wearing distance glasses (OR, 4.2), and who self-reported heart disease (OR, 1.3). Histories of stroke, cancer, and diabetes were not signifiVOL. 134, NO. 5
cantly different between the group with correctable visual impairment and with no visual impairment after adjusting for age and gender. Those who rated their health as only fair or poor were significantly more likely to have correctable visual impairment (OR, 1.4). Similar sociodemographic measures predicted correctable visual impairment in cross-sections 1 and 2. Although the duration since the last eye examination was slightly longer for persons with correctable impairment than in unimpaired subjects, this difference was statistically significant only for cross-section 1. Table 5 shows the characteristics of persons with correctable and no visual impairment at both BMES I and II. Of those attending both examinations, 34 (1.5%) had correctable impairment, 293 (12.6%) had noncorrectable impairment, and 2000 (85.9%) had no impairment. Of the 34 persons with persisting correctable impairment, 32 (94.1%) improved from ⬍ 20/40 –20/70 and 2 (5.9%) from ⬍ 20/70 –20/200 to no visual impairment. Correctable visual impairment was associated with increasing age, but not with gender. Compared with those without visual impairment, a higher proportion of those with correctable visual impairment were women, but after controlling for age this was not statistically significant. After adjusting for age and gender, persons with correctable visual impairment were more likely to live alone and to give a history of heart disease. They were less likely to be currently married, own their homes, received higher education, have higher occupational prestige, be current drivers, or to wear distance glasses. Type of refractive correction was not associated with persistent correctable visual impairment. Many of the associations found were strongest for those with persistent correctable visual impairment.
DISCUSSION RECENT REPORTS FROM THE VISUAL IMPAIRMENT PROJECT
(VIP) and the Blue Mountains Eye Study (BMES) from Australia have highlighted the high frequency of undercorrected or uncorrected refractive error as a cause of visual impairment in older persons.12,18,19 The VIP assessed the causes of visual impairment (⬍20/40) and blindness (either ⬍ 20/200 or ⬍ 20/400) for both presenting and best-corrected acuity. Under-corrected refraction was responsible for 58% of visual impairment. In the BMES, under-corrected refraction was also frequently present in those who developed bilateral visual impairment (around 75%), but was not present in those who developed blindness. Many people with under-corrected refraction do not feel that they need, or they dislike wearing, distance glasses. Many stated that they had distance glasses, but did not always wear them. Thus, while simple optical measures may correct a large proportion of visual impairment, many people may not feel the need for correction (particularly
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TABLE 3. Characteristics of Persons With no Visual Impairment (VI) and Correctable Visual Impairment in the Better Eye in Cross-section 1 No VI n
Total number (Mean age in years) Female Married Lives alone Owns home High job prestige Gained qualifications after high school Drives car Uses community support services Dependent History of heart disease Fair to poor self-rated health Emmetropia‡ Myopia‡ Hyperopia‡ Distance glasses worn during eye examination (Mean duration [years] since eye care service)§ (Mean number of letters read correctly)§
3245 (65.0) 1824 2117 813 2823 2004 1586 2296 109 54 488 771 1449 364 1423 2250 (2.5) (52.3)
Correctable VI %
n
%
Odds Ratio*
56.2 65.2 25.3 89.3 61.8 48.9 72.3 3.6 1.8 15.1 24.1 44.8 11.2 44.0 69.3
274 (72.8) 153 128 116 223 149 104 132 33 21 66 86 74 47 151 125 (3.3) (33.3)
55.8 46.7 43.1 83.8 54.4 38.0 49.6 12.7 8.2 24.1 32.0 27.2 17.3 55.5 45.6
2.3† (2.0–2.6) 1.0 (0.8–1.3) 0.6 (0.5–0.8) 1.6 (1.2–2.2) 0.7 (0.5–0.9) 0.8 (0.6–1.0) 0.7 (0.6–0.9) 0.5 (0.4–0.7) 1.8 (1.1–2.8) 3.0 (1.7–5.3) 1.3 (1.0–1.8) 1.4 (1.0–1.8) 1.0 reference 1.9 (1.3–2.7) 1.2 (0.9–1.6) 4.2 (3.2–5.5)
*Odds ratios, presented with 95% confidence intervals, adjusted for age and gender. Odds ratio for each decade of increasing age. ‡ Best spherical equivalent refractive correction. § P ⬍ .05. †
when only one eye is impaired) until other eye problems develop. Accumulating evidence, however, suggests that under-corrected refraction may have an impact on independent living in older people, indicating the potential public health importance of refractive correction. Cross-section 1 examined 82.4% and cross-section 2 examined 85.2% of those eligible. BMES IIA examined 75.1% of survivors from the initial study after 5 years. A potential limitation of our study is that we may have underestimated the number with correctable visual impairment. Persons with correctable visual impairment were older than those with no impairment or with noncorrectable impairment, so more had died before the 5-year follow-up examinations (32.5% vs 13.4%). Consequently, fewer persons with correctable impairment returned to BMES IIA (46.4% vs. 65.3%). We did not directly ask about personal income; this issue is sensitive, and such questions could affect participation. However, there is no reason to consider that this omission would have introduced any bias between the two cross sections. The BMES I study population was found to be representative of the Australian population measured in the Australian Bureau of Statistics Census in 1991.20 The next Australian census in 1996 indicated minimal population demographic changes in the upper Blue Mountains region between these years. Our two population cross sections had 716
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a very similar age and gender distribution, suggesting that these two groups were representative of the region’s population at these two times. However, differences in some socioeconomic variables reflected educational changes (qualifications, job prestige) and differences in access to community support services over this period. The differences in self-reported disease may reflect better health education and earlier presentation. Our study suggests some temporal changes in the proportion of the population with visual impairment, both correctable and noncorrectable. A lower prevalence of overall visual impairment was documented in the second cross section. This could reflect improvements in public education about the benefits of regular eye examinations, recent trends in some countries for earlier cataract surgery, and an increased availability of local ophthalmologic and optometric services. Conduct of the eye study in the region itself could also have had an impact on community awareness. However, the proportion of total visual impairment correctable by refraction was very similar on both occasions. Over two thirds of the cases of visual impairment in both cross sections in this study represented uncorrected refractive error. Independent factors associated with correctable visual impairment included whether participants had distance glasses, were older, self-reported poorer OF
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TABLE 4. Characteristics of Persons With No Visual Impairment (VI) and Correctable Visual Impairment in the Better Eye in Cross-section 2 No VI
Correctable VI
n
Total number (Mean age in years) Female Married Lives alone Owns home High job prestige Gained qualifications after high school Drives car Uses community support services Dependent History of heart disease Fair to poor self-rated health Emmetropia‡ Myopia‡ Hyperopia‡ Distance glasses worn during eye examination (Mean duration [years] since eye care service) (Mean number of letters read correctly)§
3203 (65.8) 1806 2016 801 2893 2160 1469 2386 82 124 502 624 1368 437 1398 2218
%
n
%
Odds Ratio*
56.4 63.2 25.2 90.4 70.5 45.9 87.5 2.6 3.9 15.8 19.6 42.7 13.6 43.7 70.7
195 (74.1) 118 96 79 165 108 64 100 15 28 52 54 62 33 100 88
60.5 49.5 40.9 84.6 56.5 32.8 71.9 7.8 14.6 26.9 27.8 16.9 31.8 51.3 46.1
2.6† (2.2–3.1) 0.8 (0.7–1.2) 0.8 (0.5–1.0) 1.4 (1.1–2.0) 0.6 (0.4–0.9) 0.7 (0.5–0.9) 0.6 (0.4–0.8) 0.6 (0.4–1.0) 1.1 (0.6–2.1) 1.5 (0.9–2.5) 1.3 (0.9–1.8) 1.4 (1.0–1.9) 1.0 reference 1.6 (1.1–2.5) 1.2 (0.9–1.6) 4.7 (3.4–6.5)
(2.5) (52.5)
(2.7) (33.2)
*Odds ratios, presented with 95% confidence intervals, adjusted for age and gender. Odds ratio for each decade of increasing age. ‡ Best spherical equivalent refractive correction. § P ⬍ .05. †
health, and had measures of lower socioeconomic status or increasing dependency. The pattern of associations did not differ markedly between the two cross sections. However, among those persons who had correctable visual impairment at both visits 5 years apart, many associations were of a higher magnitude than in either cross section alone, albeit with wider confidence intervals reflecting the smaller numbers. Few other studies have reported the prevalence of and associations with, correctable visual impairment. The Visual Impairment Project (VIP) conducted in Victoria, Australia, found uncorrected refractive error (defined as improvement by one or more lines on a logMAR chart) in 10% of 4735 persons aged 40 years and older.14 Significantly higher rates of under-corrected refractive error were independently associated with older age, lower education, longer duration from last examination, lack of distance correction, myopic refractive error, and presence of cataract. While our study examined improvement from measured visual impairment (⬍20/40 in the better eye) to no impairment after refraction, it finds many similar associations to those reported by the VIP. These include the effects of age, education, duraVOL. 134, NO. 5
tion from the last eye examination, lack of distance correction, and myopia. The Baltimore Eye Survey, using the same level of visual impairment (⬍20/40), reported a very similar proportion (74.3%) of white subjects whose impairment was correctable with refraction (7.8% of subjects aged 40 years and older).10 In a recent report from a southern Indian population covering all ages, over 60% of visual impairment ⬍ 20/40 was due to uncorrected refractive error.21 We are not able to determine from our study whether the associations we found with poorer self-reported health, lower socioeconomic status, and higher dependency were a result of correctable visual impairment or whether these associations impacted attendance to eye care practitioners. Both effects may be operating. Encouraging older people to undergo regular eye examinations may help to address this problem. However, our data indicate that the mean duration from the last reported eye examination was only slightly longer in those with correctable impairment (3.3 years) than among unimpaired subjects (2.5 years), and this difference was much smaller for the second cross section of participants (2.7 vs 2.5 years). From this, it appears that many people do not wish to
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TABLE 5. Characteristics of Persons With Persistent Correctable Visual Impairment (VI) and No Visual Impairment in the Better Eye at Both Examinations No VI n
Total number (Mean age in years) Female Married Lives alone Owns home High job prestige Gained qualifications after high school Drives car Uses community support services Dependent History of heart disease Fair to poor self-rated health Emmetropia‡ Myopia‡ Hyperopia‡ Distance glasses worn during eye examination (Mean duration [years] since eye care service)§ (Mean number of letters read correctly)§
2000 (63.4) 1130 1358 468 1812 1277 170 1042 38 14 268 400 894 229 876 1402 (2.4) (53.4)
Correctable VI %
n
%
Odds Ratio*
56.5 68.0 23.6 92.6 63.9 8.7 52.1 2 0.7 13.5 20.2 44.7 11.5 43.8 70.1
34 (72.3) 24 14 17 30 15 9 10 5 2 13 9 10 4 20 8 (3.0) (33.4)
70.6 41.2 53.1 90.9 44.1 28.1 29.4 15.2 6.5 38.2 26.5 29.4 11.8 58.8 23.5
2.7† (1.8–4.0) 0.6 (0.3–1.2) 0.5 (0.2–1.0) 2.3 (1.1–4.9) 0.9 (0.3–2.9) 0.5 (0.3–1.1) 2.5 (1.1–5.8) 0.5 (0.2–1.0) 3.8 (1.3–11.5) 5.4 (1.1–27.3) 3.6 (1.8–7.5) 1.5 (0.7–3.3) 1.0 reference 1.4 (0.5–4.2) 1.1 (0.5–2.2) 14.8 (6.3–34.6)
*Odds ratios, presented with 95% confidence intervals, adjusted for age and gender. Odds ratio for each decade of increasing age. ‡ Best spherical equivalent refractive correction. § P ⬍ .05. †
wear distance glasses, even after the potential improvement in vision is demonstrated. For those not driving, sharp distance acuity may not be perceived as necessary, and regular vision testing for license renewal may not occur. Our data confirmed a higher rate of correctable impairment among people who did not drive. Many people, however, such as those who are relatively dependent or in poor health, could benefit from distance glasses, but this may not be a high priority. New approaches that could reduce the burden of correctable visual impairment are needed and may include better public and primary care practitioner education about the benefits from refractive correction. Practitioners conducting aged care services should also screen visual acuity in their clients and actively refer those found impaired so that remedial measures such as glasses or cataract surgery may be undertaken. Our survey includes only noninstitutionalized residents. The rate of correctable visual impairment among nursing home residents is likely to be much higher.3 In summary, correctable visual impairment accounted for two thirds of all cases of visual impairment in two temporal cross sections of an older community. This remedial cause of visual impairment has not been the subject of detailed assessments in the past. Given the substantial impacts demonstrated from visual impairment, 718
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including that associated with uncorrected refractive error, further study is overdue.
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8. Wang JJ, Mitchell P, Smith W. Vision and low self-rated health: the Blue Mountains Eye Study. Invest Ophthalmol Vis Sci 2000;41:49 –54. 9. Wang JJ, Mitchell P, Simpson JM, et al. Visual impairment, age-related cataract, and mortality. Arch Ophthalmol 2001; 119:1186 –1190. 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 –290. 11. Klein R, Klein BE, Linton KL, et al. The Beaver Dam Eye Study: visual acuity. Ophthalmology 1991;98:1310 –1315. 12. Attebo K, Mitchell P, Smith W. Visual acuity and the causes of visual loss in Australia. The Blue Mountains Eye Study. Ophthalmology 1996;103:357–364. 13. Attebo K, Ivers RQ, Mitchell P. Refractive errors in an older population: the Blue Mountains Eye Study. Ophthalmology 1999;106:1066 –1072. 14. Liou HL, McCarty CA, Jin CL, et al. Prevalence and predictors of undercorrected refractive errors in the Victorian population. Am J Ophthalmol 1999;127:590 –596.
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15. Mitchell P, Smith W, Attebo K, et al. Prevalence of age-related maculopathy in Australia. The Blue Mountains Eye Study. Ophthalmology 1995;102:1450 –1460. 16. Mitchell P, Smith W, Attebo K, et al. Prevalence of open-angle glaucoma in Australia. The Blue Mountains Eye Study. Ophthalmology 1996;103:1661–1669. 17. World Health Organization website: www.who.int/pbd/pbl/ img/icd10.gif 18. Weih LM, VanNewkirk MR, McCarty CA, et al. Agespecific causes of bilateral visual impairment. Arch Ophthalmol 2000;118:264 –269. 19. VanNewkirk MR, Weih L, McCarty CA, et al. Causespecific prevalence of bilateral visual impairment in Victoria, Australia: the Visual Impairment Project. Ophthalmology 2001;108:960 –967. 20. Australian Bureau of Statistics. CData91: Australian Population Census 1991. Cat. No. 2721.0 – 8. 1994. Canberra. 21. Dandona L, Dandona R, Naduvilath TJ, et al. Burden of moderate visual impairment in an urban population in southern India. Ophthalmology 1999;106:497–504.
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OLDER POPULATION
719
● PURPOSE:
To describe temporal changes in the characteristics of older persons with visual impairment in their better eye correctable by refraction. ● DESIGN: Study of two cross sections of a community 6 years apart. ● METHODS: The Blue Mountains Eye Study examined 3654 persons aged 49 to 97 during 1992 to 1994 (cross-section 1) and 3509 persons (2335 cohort survivors plus 1174 persons who moved to the area and age group) during 1997 to 2000 (cross-section 2). Logarithm of minimal angle of resolution visual acuity was measured before and after refraction. Correctable visual impairment was defined as visual impairment < 20/40 in the better eye before refraction that improved after refraction to no impairment (> 20/40). Factors associated with correctable visual impairment and persistent correctable impairment were determined. ● RESULTS: Cross-sections 1 and 2 had similar agegender distributions. In cross-section 1, 7.5% of participants had correctable visual impairment, 3.6% had noncorrectable visual impairment, and 88.9% had no impairment. Corresponding rates in cross-section 2 were 5.6%, 2.7%, and 91.7%. In both cross sections, similar proportions (around 68%) of those visually impaired had correctable visual impairment and similar sociodemographic measures predicted correctable visual impairment. Cross-section 1 participants who were married, owned their home, had high job prestige, gained qualifications after high school, or were current drivers were less likely to have correctable visual impairment after controlling for age and gender. Adjusted odds for correctable visual impairment increased in those living alone, Accepted for publication June 11, 2002. From the Department of Ophthalmology, University of Sydney (Center for Vision Research, Westmead Hospital) and the Westmead Millennium and Save Sight Institutes, Sydney, Australia (S.F., J.J.W., P.M.); School of Applied Vision Sciences, Faculty of Health Sciences, University of Sydney, Sydney, Australia (K.R.). This work was supported by the Australian National Health & Medical Research Council, Canberra, Australia (grants 974159, 991407). Inquiries to Paul Mitchell, MD, PhD, University of Sydney Department of Ophthalmology (Centre for Vision Research), Westmead Hospital, Hawkesbury Road, Westmead, NSW, Australia, 2145; fax: (⫹ 61) 2- 9845- 6117; e-mail [email protected]
712
©
2002 BY
using community support services, dependent on others, with myopia, wearing distance glasses, or with low perceived health and heart disease. Histories of stroke, cancer, and diabetes were similar between groups with correctable and no visual impairment. ● CONCLUSION: Socioeconomic parameters, myopia, wearing distance glasses, reported health problems, and poor perceived health were associated with correctable visual impairment in this older population. (Am J Ophthalmol 2002;134:712–719. © 2002 by Elsevier Science Inc. All rights reserved.)
V
ISUAL IMPAIRMENT HAS BEEN SHOWN TO HAVE
numerous impacts in older persons and has been associated with use of community support services,1,2 nursing home placement,3 falls,4 – 6 mortality,7–9 and low self-rated health.8 While most population studies have assessed the impacts of noncorrectable visual impairment, a number10 –14 have documented a high frequency of older persons with correctable visual impairment, that is, presenting with vision that could be improved by providing or changing distance glasses. Recent reports show that visual impairment associated with uncorrected refraction was also associated with substantial impacts, though at a lower magnitude.1,9 Few studies have assessed factors associated with correctable visual impairment, and none has examined temporal changes in correctable impairment and its associated factors in an older population. This report aims, firstly, to describe the frequency of correctable visual impairment; secondly, to compare socioeconomic factors and other considerations associated with correctable visual impairment and with no visual impairment; and thirdly, to examine whether there has been a change in the frequency of correctable visual impairment and socioeconomic factors over time.
DESIGN THIS STUDY ANALYZED TWO CROSS SECTIONS OF A COM-
munity 6 years apart.
ELSEVIER SCIENCE INC. ALL
RIGHTS RESERVED.
0002-9394/02/$22.00 PII S0002-9394(02)01673-2
METHODS ● STUDY POPULATION: The Blue Mountains Eye Study (BMES) is a population-based survey of vision and common eye diseases in an urban population aged 49 years or older resident in two postal codes of the Blue Mountains region, west of Sydney, Australia. A number of reports have described the methods used.1,12,13 The present report uses findings from two cross sections from this population. Blue Mountain Eye Study I identified 4433 eligible noninstitutionalized permanent residents in a door-to-door census conducted during 1991, of whom 3654 (82.4%) participated in the examinations from 1992 to 1994. Of the 779 (17.6%) persons who did not participate, 353 (8.0%) permitted only an interview, 148 (3.3%) refused, 210 (4.7%) had moved out of the area, and 68 (1.5%) had died. A previous report compared participants and nonparticipants at baseline.12 After 5 years, all BMES I participants were invited to attend repeat examinations during 1997 to 1999 (BMES IIA). By the time these examinations commenced, 383 persons (10.5%) had moved, 394 (10.8%) refused to participate, 543 (14.9%) had died, and 2335 (75.1%) were reexamined. A repeat door-to-door census conducted in 1999 of the same area identified 1378 additional eligible permanent residents who had moved into the area or were now aged 50 or older. We examined 1174 (85.2%) of this group during 1999 to 2000 (BMES IIB). Thus, crosssection 2 comprises 3509 participants from BMES IIA and IIB. ● OBSERVATION PROCEDURES: Previous BMES reports12,15,16 describe the survey methods and procedures, which were similar for the two examinations. Participants gave written informed consent on both occasions. The Western Sydney Human Ethics Committee provided ethical approval. Details of the sociodemographic parameters explored have been previously reported.2 In brief, parameters described in this report include marital and cohabitation status, dwelling ownership, principal occupation during working life, and qualifications gained after high school. We did not directly ask questions regarding income. Use of community support services was defined as regular use of “Meals on Wheels,” home care, or regular visits by a community nurse. Dependency was defined as the inability to go shopping, visit friends, or go to town alone. Whether participants were current drivers and the mode of transport used to attend the study center were determined. Participants were asked if they had ever been advised by a doctor that they had angina, myocardial infarct (“heart attack”), stroke, cancer, or diabetes. Heart disease was defined as a positive response to the questions about angina or myocardial infarct. Participants were also asked to rate their overall health as excellent, good, fair, or poor. Visual acuity was measured by a logarithm of the
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minimum angle of resolution (logMAR) chart, retroilluminated with automatic calibration to 85 cd/m2 (Vectorvision CSV-100TM, Vectorvision, Inc., Dayton, Ohio, USA), and read at 8 ft (244 cm).12 Distance visual acuity in each eye was initially measured with current distance glasses if worn. An autorefractor (Allergan Humphrey, Model 530, San Leandro, California, USA) provided objective refraction. Subjective refraction was performed according to the Beaver Dam Eye Study modification of the Early Treatment Diabetic Retinopathy Study protocol.11 For each eye, visual acuity was recorded as the number of letters read correctly from 0 to 70. Spherical equivalent (0.5 cylinder ⫹ sphere) was calculated from the best refractive correction. A spherical equivalent between ⫺1.0 and ⫹ 1.0 defined emmetropia, less than ⫺1.0 defined myopia, and greater than ⫹ 1.0 defined hyperopia. We defined visual impairment as acuity worse than 20/40, based on the minimum legal visual acuity requirement for obtaining a driver’s license in many states in the United States and Australia. In this report, visual impairment was defined as fewer than 39 letters read on the logMAR chart (allowing one incorrect letter on the 20/40 line). The World Health Organization International Classification for Disease-10 (WHO ICD-10) category 1 or higher defines visual impairment as worse than 20/70 in the better eye, which was taken as fewer than 29 letters read. The WHO ICD-10 category 2 or higher defines visual impairment as worse than 20/200 (blindness in Australia), taken as fewer than four letters read.17 Correctable visual impairment was defined as visual impairment ⬍ 20/40 before refraction (with distance glasses if worn) that improved after refraction to no impairment (ⱖ 20/40). In this report, the better eye has been chosen as reference. Statistical Analysis System (SAS Institute Inc., Cary, North Carolina, USA) was used for analyses, including 2 and logistic regression. All odds ratios are given with 95% confidence intervals and are adjusted for age and gender.
RESULTS TABLE 1 SHOWS CHARACTERISTICS OF PARTICIPANTS IN
cross-sections 1 and 2. Age and gender distribution, the duration since the last eye examination, and the proportions married, living alone, owning their home, selfreporting heart disease and stroke, or currently having distance glasses were similar. However, in cross-section 2, a significantly higher proportion had high occupational prestige or self-reported cancer and diabetes, were current drivers, or were dependent on others. Although the mean numbers of letters read correctly by the two groups were very similar, persons in cross-section 2 read a significantly greater number of letters. Cross-section 2 had a significantly lower proportion who gained further qualifications after high school, used community support services, or who rated their health as only fair or poor. In cross-section 2,
CORRECTABLE VISUAL IMPAIRMENT
IN AN
OLDER POPULATION
713
TABLE 1. Participant Characteristics in Cross-section 1 (n ⫽ 3,654) and Cross-section 2 (n ⫽ 3,508) Cross-section 1
Age (mean) 49–59 60–69 70–79 80⫹ Female Married Lives alone Owns home High job prestige Gained qualifications after high school Drives car Uses community support services Dependent Self reported history Heart disease Stroke Cancer Diabetes Fair–poor self rated health Emmetropia§ Myopia§ Hyperopia§ Distance glasses worn during eye examination (Mean duration [years] since eye care service) (Mean number of letters read correctly)‡
Cross-section 2
n*
%
n*
(66.2) 1019 1309 960 366 2072 2288 991 3152 2213 1732 2452 180 111
27.9 35.8 26.3 10.0 56.7 62.8 27.4 88.7 62.2 47.4 69.0 5.2 3.3
(66.7) 930 1238 978 359 1997 2156 936 3140 2319 1574 2504 121 194
26.5 35.3 27.9 10.2 57.0 61.7 26.8 89.7 69.0† 44.9‡ 85.5† 3.5† 5.6†
586 194 310 218 907 1558 442 1633 2473
16.1 5.3 8.5 6.0 25.3 42.9 12.2 45.0 67.7
593 186 443 255 709 1478 495 1532 2372
17.1 5.3 12.7† 7.3† 20.3† 42.2 14.1‡ 43.7 69.3
(2.5) (49.8)
%
(2.5) (50.6)
*n ⫽ number of persons. P ⬍ 0.01. ‡ P ⬍ 0.05. § Best spherical equivalent refractive correction. †
the proportion of persons with myopia significantly increased by 1.9%. Table 2 shows the visual impairment status of participants in cross-sections 1 and 2. Eight subjects were excluded from cross-section 2, as they reported having distance glasses, but did not bring them to the examination. In cross-section 1, 7.5% of participants had correctable visual impairment, 3.6% had noncorrectable impairment, and 88.9% had no impairment. The corresponding rates in cross-section 2 were 5.6%, 2.7% and 91.7%. A significantly lower proportion of the population had correctable visual impairment and a higher proportion had no visual impairment in cross-section 2 than in cross-section 1. However, the proportion of correctable visual impairment among the total number of people who were visually impaired remained similar at the two times (68.2% in cross-section 1 vs 67.5% in cross-section 2). 714
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TABLE 2. Visual Impairment (VI) Status of Participants Cross-section 1 n*
No VI Correctable to no VI Noncorrectable VI Improvement but still VI No improvement Total (excluding missing)‡
%
Cross-section 2 n*
%
91.7† 5.6†
3245 274
88.9 7.5
3203 195
23 107 3649
0.6 2.9 100.0
17 78 3493
0.5 2.2 100.0
*n ⫽ number of persons. † P ⬍ .01. ‡ Excludes eyes where either presenting (for example, did not bring current distance glasses) or best-corrected visual acuity was missing (n ⫽ 8).
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FIGURE 1. Age-specific rates of correctable visual impairment and no visual impairment in cross-sections 1 and 2.
Figure 1 shows the age-specific rates of correctable visual impairment and no visual impairment in cross-sections 1 and 2. Of the 274 persons with correctable impairment in cross-section 1, 237 (86.5%) improved from ⬍ 20/40 –20/ 70, 36 (13.1%) from ⬍ 20/70 –20/200, and 1 (0.4%) from ⬍ 20/200 to no visual impairment. Of the 195 persons with correctable impairment in cross-section 2, 170 (87.2%) improved from ⬍ 20/40 –20/70, 24 (12.3%) from ⬍ 20/70 –20/200, and one (0.5%) from ⬍ 20/200 to no visual impairment. Characteristics of persons with no visual impairment and with correctable visual impairment in cross-sections 1 and 2 are shown in Tables 3 and 4, respectively. In both cross sections, the mean age of persons with correctable visual impairment was higher by around 8 years than those with no visual impairment. With each decade of increasing age, the likelihood of correctable visual impairment increased (odds ratio [OR], 2.3–2.6). After controlling for age, gender was not significantly associated with correctable visual impairment. Odds ratios for the associations explored generally had the same direction and magnitude in the two cross sections. In both, persons who had correctable visual impairment read a mean of 33 letters correctly compared with persons with no visual impairment, who read a mean of 52 letters. Participants with myopia were more likely to have correctable visual impairment. In cross-section 1, persons who were married, owned their home, had high job prestige, gained qualifications after high school, or were current drivers were less likely (OR, 0.5– 0.8) to have correctable visual impairment after controlling for age and gender. The odds for correctable visual impairment were increased in those living alone (OR, 1.6), using community support services (OR, 1.8), dependent on others (OR, 3.0), wearing distance glasses (OR, 4.2), and who self-reported heart disease (OR, 1.3). Histories of stroke, cancer, and diabetes were not signifiVOL. 134, NO. 5
cantly different between the group with correctable visual impairment and with no visual impairment after adjusting for age and gender. Those who rated their health as only fair or poor were significantly more likely to have correctable visual impairment (OR, 1.4). Similar sociodemographic measures predicted correctable visual impairment in cross-sections 1 and 2. Although the duration since the last eye examination was slightly longer for persons with correctable impairment than in unimpaired subjects, this difference was statistically significant only for cross-section 1. Table 5 shows the characteristics of persons with correctable and no visual impairment at both BMES I and II. Of those attending both examinations, 34 (1.5%) had correctable impairment, 293 (12.6%) had noncorrectable impairment, and 2000 (85.9%) had no impairment. Of the 34 persons with persisting correctable impairment, 32 (94.1%) improved from ⬍ 20/40 –20/70 and 2 (5.9%) from ⬍ 20/70 –20/200 to no visual impairment. Correctable visual impairment was associated with increasing age, but not with gender. Compared with those without visual impairment, a higher proportion of those with correctable visual impairment were women, but after controlling for age this was not statistically significant. After adjusting for age and gender, persons with correctable visual impairment were more likely to live alone and to give a history of heart disease. They were less likely to be currently married, own their homes, received higher education, have higher occupational prestige, be current drivers, or to wear distance glasses. Type of refractive correction was not associated with persistent correctable visual impairment. Many of the associations found were strongest for those with persistent correctable visual impairment.
DISCUSSION RECENT REPORTS FROM THE VISUAL IMPAIRMENT PROJECT
(VIP) and the Blue Mountains Eye Study (BMES) from Australia have highlighted the high frequency of undercorrected or uncorrected refractive error as a cause of visual impairment in older persons.12,18,19 The VIP assessed the causes of visual impairment (⬍20/40) and blindness (either ⬍ 20/200 or ⬍ 20/400) for both presenting and best-corrected acuity. Under-corrected refraction was responsible for 58% of visual impairment. In the BMES, under-corrected refraction was also frequently present in those who developed bilateral visual impairment (around 75%), but was not present in those who developed blindness. Many people with under-corrected refraction do not feel that they need, or they dislike wearing, distance glasses. Many stated that they had distance glasses, but did not always wear them. Thus, while simple optical measures may correct a large proportion of visual impairment, many people may not feel the need for correction (particularly
CORRECTABLE VISUAL IMPAIRMENT
IN AN
OLDER POPULATION
715
TABLE 3. Characteristics of Persons With no Visual Impairment (VI) and Correctable Visual Impairment in the Better Eye in Cross-section 1 No VI n
Total number (Mean age in years) Female Married Lives alone Owns home High job prestige Gained qualifications after high school Drives car Uses community support services Dependent History of heart disease Fair to poor self-rated health Emmetropia‡ Myopia‡ Hyperopia‡ Distance glasses worn during eye examination (Mean duration [years] since eye care service)§ (Mean number of letters read correctly)§
3245 (65.0) 1824 2117 813 2823 2004 1586 2296 109 54 488 771 1449 364 1423 2250 (2.5) (52.3)
Correctable VI %
n
%
Odds Ratio*
56.2 65.2 25.3 89.3 61.8 48.9 72.3 3.6 1.8 15.1 24.1 44.8 11.2 44.0 69.3
274 (72.8) 153 128 116 223 149 104 132 33 21 66 86 74 47 151 125 (3.3) (33.3)
55.8 46.7 43.1 83.8 54.4 38.0 49.6 12.7 8.2 24.1 32.0 27.2 17.3 55.5 45.6
2.3† (2.0–2.6) 1.0 (0.8–1.3) 0.6 (0.5–0.8) 1.6 (1.2–2.2) 0.7 (0.5–0.9) 0.8 (0.6–1.0) 0.7 (0.6–0.9) 0.5 (0.4–0.7) 1.8 (1.1–2.8) 3.0 (1.7–5.3) 1.3 (1.0–1.8) 1.4 (1.0–1.8) 1.0 reference 1.9 (1.3–2.7) 1.2 (0.9–1.6) 4.2 (3.2–5.5)
*Odds ratios, presented with 95% confidence intervals, adjusted for age and gender. Odds ratio for each decade of increasing age. ‡ Best spherical equivalent refractive correction. § P ⬍ .05. †
when only one eye is impaired) until other eye problems develop. Accumulating evidence, however, suggests that under-corrected refraction may have an impact on independent living in older people, indicating the potential public health importance of refractive correction. Cross-section 1 examined 82.4% and cross-section 2 examined 85.2% of those eligible. BMES IIA examined 75.1% of survivors from the initial study after 5 years. A potential limitation of our study is that we may have underestimated the number with correctable visual impairment. Persons with correctable visual impairment were older than those with no impairment or with noncorrectable impairment, so more had died before the 5-year follow-up examinations (32.5% vs 13.4%). Consequently, fewer persons with correctable impairment returned to BMES IIA (46.4% vs. 65.3%). We did not directly ask about personal income; this issue is sensitive, and such questions could affect participation. However, there is no reason to consider that this omission would have introduced any bias between the two cross sections. The BMES I study population was found to be representative of the Australian population measured in the Australian Bureau of Statistics Census in 1991.20 The next Australian census in 1996 indicated minimal population demographic changes in the upper Blue Mountains region between these years. Our two population cross sections had 716
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a very similar age and gender distribution, suggesting that these two groups were representative of the region’s population at these two times. However, differences in some socioeconomic variables reflected educational changes (qualifications, job prestige) and differences in access to community support services over this period. The differences in self-reported disease may reflect better health education and earlier presentation. Our study suggests some temporal changes in the proportion of the population with visual impairment, both correctable and noncorrectable. A lower prevalence of overall visual impairment was documented in the second cross section. This could reflect improvements in public education about the benefits of regular eye examinations, recent trends in some countries for earlier cataract surgery, and an increased availability of local ophthalmologic and optometric services. Conduct of the eye study in the region itself could also have had an impact on community awareness. However, the proportion of total visual impairment correctable by refraction was very similar on both occasions. Over two thirds of the cases of visual impairment in both cross sections in this study represented uncorrected refractive error. Independent factors associated with correctable visual impairment included whether participants had distance glasses, were older, self-reported poorer OF
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TABLE 4. Characteristics of Persons With No Visual Impairment (VI) and Correctable Visual Impairment in the Better Eye in Cross-section 2 No VI
Correctable VI
n
Total number (Mean age in years) Female Married Lives alone Owns home High job prestige Gained qualifications after high school Drives car Uses community support services Dependent History of heart disease Fair to poor self-rated health Emmetropia‡ Myopia‡ Hyperopia‡ Distance glasses worn during eye examination (Mean duration [years] since eye care service) (Mean number of letters read correctly)§
3203 (65.8) 1806 2016 801 2893 2160 1469 2386 82 124 502 624 1368 437 1398 2218
%
n
%
Odds Ratio*
56.4 63.2 25.2 90.4 70.5 45.9 87.5 2.6 3.9 15.8 19.6 42.7 13.6 43.7 70.7
195 (74.1) 118 96 79 165 108 64 100 15 28 52 54 62 33 100 88
60.5 49.5 40.9 84.6 56.5 32.8 71.9 7.8 14.6 26.9 27.8 16.9 31.8 51.3 46.1
2.6† (2.2–3.1) 0.8 (0.7–1.2) 0.8 (0.5–1.0) 1.4 (1.1–2.0) 0.6 (0.4–0.9) 0.7 (0.5–0.9) 0.6 (0.4–0.8) 0.6 (0.4–1.0) 1.1 (0.6–2.1) 1.5 (0.9–2.5) 1.3 (0.9–1.8) 1.4 (1.0–1.9) 1.0 reference 1.6 (1.1–2.5) 1.2 (0.9–1.6) 4.7 (3.4–6.5)
(2.5) (52.5)
(2.7) (33.2)
*Odds ratios, presented with 95% confidence intervals, adjusted for age and gender. Odds ratio for each decade of increasing age. ‡ Best spherical equivalent refractive correction. § P ⬍ .05. †
health, and had measures of lower socioeconomic status or increasing dependency. The pattern of associations did not differ markedly between the two cross sections. However, among those persons who had correctable visual impairment at both visits 5 years apart, many associations were of a higher magnitude than in either cross section alone, albeit with wider confidence intervals reflecting the smaller numbers. Few other studies have reported the prevalence of and associations with, correctable visual impairment. The Visual Impairment Project (VIP) conducted in Victoria, Australia, found uncorrected refractive error (defined as improvement by one or more lines on a logMAR chart) in 10% of 4735 persons aged 40 years and older.14 Significantly higher rates of under-corrected refractive error were independently associated with older age, lower education, longer duration from last examination, lack of distance correction, myopic refractive error, and presence of cataract. While our study examined improvement from measured visual impairment (⬍20/40 in the better eye) to no impairment after refraction, it finds many similar associations to those reported by the VIP. These include the effects of age, education, duraVOL. 134, NO. 5
tion from the last eye examination, lack of distance correction, and myopia. The Baltimore Eye Survey, using the same level of visual impairment (⬍20/40), reported a very similar proportion (74.3%) of white subjects whose impairment was correctable with refraction (7.8% of subjects aged 40 years and older).10 In a recent report from a southern Indian population covering all ages, over 60% of visual impairment ⬍ 20/40 was due to uncorrected refractive error.21 We are not able to determine from our study whether the associations we found with poorer self-reported health, lower socioeconomic status, and higher dependency were a result of correctable visual impairment or whether these associations impacted attendance to eye care practitioners. Both effects may be operating. Encouraging older people to undergo regular eye examinations may help to address this problem. However, our data indicate that the mean duration from the last reported eye examination was only slightly longer in those with correctable impairment (3.3 years) than among unimpaired subjects (2.5 years), and this difference was much smaller for the second cross section of participants (2.7 vs 2.5 years). From this, it appears that many people do not wish to
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TABLE 5. Characteristics of Persons With Persistent Correctable Visual Impairment (VI) and No Visual Impairment in the Better Eye at Both Examinations No VI n
Total number (Mean age in years) Female Married Lives alone Owns home High job prestige Gained qualifications after high school Drives car Uses community support services Dependent History of heart disease Fair to poor self-rated health Emmetropia‡ Myopia‡ Hyperopia‡ Distance glasses worn during eye examination (Mean duration [years] since eye care service)§ (Mean number of letters read correctly)§
2000 (63.4) 1130 1358 468 1812 1277 170 1042 38 14 268 400 894 229 876 1402 (2.4) (53.4)
Correctable VI %
n
%
Odds Ratio*
56.5 68.0 23.6 92.6 63.9 8.7 52.1 2 0.7 13.5 20.2 44.7 11.5 43.8 70.1
34 (72.3) 24 14 17 30 15 9 10 5 2 13 9 10 4 20 8 (3.0) (33.4)
70.6 41.2 53.1 90.9 44.1 28.1 29.4 15.2 6.5 38.2 26.5 29.4 11.8 58.8 23.5
2.7† (1.8–4.0) 0.6 (0.3–1.2) 0.5 (0.2–1.0) 2.3 (1.1–4.9) 0.9 (0.3–2.9) 0.5 (0.3–1.1) 2.5 (1.1–5.8) 0.5 (0.2–1.0) 3.8 (1.3–11.5) 5.4 (1.1–27.3) 3.6 (1.8–7.5) 1.5 (0.7–3.3) 1.0 reference 1.4 (0.5–4.2) 1.1 (0.5–2.2) 14.8 (6.3–34.6)
*Odds ratios, presented with 95% confidence intervals, adjusted for age and gender. Odds ratio for each decade of increasing age. ‡ Best spherical equivalent refractive correction. § P ⬍ .05. †
wear distance glasses, even after the potential improvement in vision is demonstrated. For those not driving, sharp distance acuity may not be perceived as necessary, and regular vision testing for license renewal may not occur. Our data confirmed a higher rate of correctable impairment among people who did not drive. Many people, however, such as those who are relatively dependent or in poor health, could benefit from distance glasses, but this may not be a high priority. New approaches that could reduce the burden of correctable visual impairment are needed and may include better public and primary care practitioner education about the benefits from refractive correction. Practitioners conducting aged care services should also screen visual acuity in their clients and actively refer those found impaired so that remedial measures such as glasses or cataract surgery may be undertaken. Our survey includes only noninstitutionalized residents. The rate of correctable visual impairment among nursing home residents is likely to be much higher.3 In summary, correctable visual impairment accounted for two thirds of all cases of visual impairment in two temporal cross sections of an older community. This remedial cause of visual impairment has not been the subject of detailed assessments in the past. Given the substantial impacts demonstrated from visual impairment, 718
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including that associated with uncorrected refractive error, further study is overdue.
REFERENCES 1. Wang JJ, Mitchell P, Smith W, et al. Impact of visual impairment on use of community support services by elderly persons: the Blue Mountains Eye Study. Invest Ophthalmol Vis Sci 1999;40:12–19. 2. Wang JJ, Mitchell P, Smith W, et al. Factors associated with use of community support services in an older Australian population. Aust N Z J Public Health 1999;23:147–153. 3. Mitchell P, Hayes P, Wang JJ. Visual impairment in nursing home residents: the Blue Mountains Eye Study. Med J Aust 1997;166:73–76. 4. Ivers RQ, Cumming RG, Mitchell P, et al. Visual impairment and falls in older adults: the Blue Mountains Eye Study. J Am Geriatr Soc 1998;46:58 – 64. 5. Campbell AJ, Reinken J, Allan BC, et al. Falls in old age: a study of frequency and related clinical factors. Age Ageing 1981;10:264 –270. 6. Jack CI, Smith T, Neoh C, et al. Prevalence of low vision in elderly patients admitted to an acute geriatric unit in Liverpool: elderly people who fall are more likely to have low vision. Gerontology 1995;41:280 –285. 7. McCarty CA, Nanjan MB, Taylor HR. Vision impairment predicts 5 year mortality. Br J Ophthalmol 2001;85:322–326. OF
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8. Wang JJ, Mitchell P, Smith W. Vision and low self-rated health: the Blue Mountains Eye Study. Invest Ophthalmol Vis Sci 2000;41:49 –54. 9. Wang JJ, Mitchell P, Simpson JM, et al. Visual impairment, age-related cataract, and mortality. Arch Ophthalmol 2001; 119:1186 –1190. 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 –290. 11. Klein R, Klein BE, Linton KL, et al. The Beaver Dam Eye Study: visual acuity. Ophthalmology 1991;98:1310 –1315. 12. Attebo K, Mitchell P, Smith W. Visual acuity and the causes of visual loss in Australia. The Blue Mountains Eye Study. Ophthalmology 1996;103:357–364. 13. Attebo K, Ivers RQ, Mitchell P. Refractive errors in an older population: the Blue Mountains Eye Study. Ophthalmology 1999;106:1066 –1072. 14. Liou HL, McCarty CA, Jin CL, et al. Prevalence and predictors of undercorrected refractive errors in the Victorian population. Am J Ophthalmol 1999;127:590 –596.
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15. Mitchell P, Smith W, Attebo K, et al. Prevalence of age-related maculopathy in Australia. The Blue Mountains Eye Study. Ophthalmology 1995;102:1450 –1460. 16. Mitchell P, Smith W, Attebo K, et al. Prevalence of open-angle glaucoma in Australia. The Blue Mountains Eye Study. Ophthalmology 1996;103:1661–1669. 17. World Health Organization website: www.who.int/pbd/pbl/ img/icd10.gif 18. Weih LM, VanNewkirk MR, McCarty CA, et al. Agespecific causes of bilateral visual impairment. Arch Ophthalmol 2000;118:264 –269. 19. VanNewkirk MR, Weih L, McCarty CA, et al. Causespecific prevalence of bilateral visual impairment in Victoria, Australia: the Visual Impairment Project. Ophthalmology 2001;108:960 –967. 20. Australian Bureau of Statistics. CData91: Australian Population Census 1991. Cat. No. 2721.0 – 8. 1994. Canberra. 21. Dandona L, Dandona R, Naduvilath TJ, et al. Burden of moderate visual impairment in an urban population in southern India. Ophthalmology 1999;106:497–504.
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