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Quality of life of low-vision patients and the impact of low-vision services
Quality of Life of Low-Vision Patients and the Impact of Low-Vision Services INGRID U. SCOTT, MD, MPH, WILLIAM E. SMIDDY, MD, JOYCE SCHIFFMAN, MS, WILLIAM J. FEUER, MS, AND CHARLES J. PAPPAS, OD
● PURPOSE:
To investigate the functional status and quality of life of patients at a low-vision clinic and to evaluate the impact of low-vision services. ● METHODS: Interviews, including the Medical Outcomes Study 36-Item Short Form (SF-36), the Visual Function-14 (VF-14), and the 51-item Field Test Version of the National Eye Institute Visual Functioning Questionnaire (NEI-VFQ), were administered to 156 consecutive patients 1 week before and 3 months after their low-vision clinic visit. ● RESULTS: Low-vision patients scored lower (P < .001) in physical functioning and role limitations caused by physical and emotional health problems than published SF-36 scores of the age-appropriate United States normal population, patients with congestive heart failure, and clinically depressed patients. Low-vision services were associated with improvement in the subjective functional status of 150 patients (98.7%) and were rated “very useful” by 82 (53.9%) patients. The SF-36 scores did not change significantly after low-vision services. The VF-14 mean score improved from 35.8 to 41.2 (P < .001). Four NEI-VFQ subscale scores improved significantly (P < .001): general vision, near activities, distance activities, and peripheral vision. ● CONCLUSIONS: The SF-36, VF-14, and NEI-VFQ demonstrate that low-vision clinic patients perceive marked impairment of functional status and quality of life. Low-vision services are associated with high patient satisfaction. Vision-targeted questionnaires are more sensitive than general health-related quality of life questionnaires to changes in functional status and quality of life after low-vision services, and they may help elucidate the outcomes of low-vision services. (Am J Ophthalmol 1999;128:54 – 62. © 1999 by Elsevier Science Inc. All rights reserved.)
Accepted for publication Feb 19, 1999. From the Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida. Reprint requests to William E. Smiddy, MD, Bascom Palmer Eye Institute, 900 NW 17th St, Miami, FL 33136; fax: (305) 326-6417.
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L
OW VISION HAS BEEN DEFINED AS A PERMANENT VI-
sual impairment that is not correctable with spectacles, contact lenses, or surgical intervention and that interferes with normal everyday functioning.1 It is estimated that approximately 1% of the population of Western countries suffers from low vision2,3 and that visual impairment affects nearly 5 million Americans to the extent that they are unable to read newsprint, even with the aid of full refractive correction.4 Because individuals older than 65 years have more vision loss than any other age group5,6 and because it is projected that the number of Americans over the age of 65 will more than double between 1995 and 2030,7 the burden of low vision is expected to increase markedly. Vision loss has been ranked third, behind arthritis and heart disease, among conditions that cause persons older than 70 years to need assistance in activities of daily living.8 Despite their increasing public health significance, the functional status and quality of life of patients with low vision have been incompletely studied. In addition, lowvision services typically are not included in health insurance plans, managed care plans, and Medicare benefits, presumably in part because of insufficient data concerning the outcomes of such services.9 As the population of low-vision patients continues to grow, attention must be focused on evaluating the effectiveness of low-vision services, especially because it is reported that 90% of individuals affected by low vision maintain sufficient vision to benefit from training in the use of optical and nonoptical devices and adaptive skills.10 –12 Studies have demonstrated the effect of low-vision interventions on objective task-specific measures of functional abilities, such as reading speed, reading duration, and ability to read a certain print size.13–16 Patient satisfaction with low-vision services15,17–20 and the frequency and type of low-vision aids used13,14,21–28 have also been investigated. However, we are unaware of studies that focus on the impact of low-vision services on healthrelated quality of life, and we could find no such reference in a computerized search on Medline. We were also unable to find a reference to any studies that investigated the
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usefulness of previously developed and widely used functional status/quality of life questionnaires in evaluating patients with low vision and the impact of low-vision services.29 The current study was designed to investigate the functional status and quality of life of patients at a low-vision clinic, as well as the potential impact of low-vision services on these health status measures. Established outcomes instruments were used to quantitate these measures and included a general health status questionnaire (the Medical Outcomes Study 36-Item Short Form [SF-36]) and two vision-targeted questionnaires (the Visual Function-14 [VF-14] and the 51-item Field Test Version of the National Eye Institute Visual Functioning Questionnaire [NEI-VFQ]).
METHODS THE STUDY POPULATION CONSISTED OF 156 CONSECUTIVE
patients evaluated for the first time at the Bascom Palmer Eye Institute Low-Vision Clinic between December 1995 and December 1996. Patients either were referred to the Low-Vision Clinic by an ophthalmologist or were selfreferred. To study a representative sample of low-vision clinic patients, consecutive patients evaluated in the Low-Vision Clinic during the 1-year study period were included; a specific visual acuity level was not used as an inclusion criterion. The questionnaires used in this study were chosen because of specific features. The SF-36 is a general healthrelated quality of life measure30 –32 and consists of eight subscales: physical functioning, role limitations caused by physical health problems, bodily pain, general health, vitality (energy/fatigue), social functioning, role limitations caused by emotional problems, and mental health (psychological distress and psychological well-being). Each of the subscales is scored from 0 to 100 (100 indicates the best possible score and 0 indicates the worst possible score). Our reported scores are based on a published algorithm for the SF-36.33 This questionnaire was chosen to assess participants’ quality of life because its validity and reliability have been demonstrated repeatedly.34 – 49 Furthermore, comparative normative data are available for the general populations in the United States and Great Britain26,31,50 –52 and for patients with a variety of medical conditions, including hypertension, congestive heart failure, type II diabetes mellitus, acute myocardial infarction, and clinical depression.53 The SF-36 was used to assess the effect of cataract extraction and intraocular lens implantation on quality of life54 and is currently being used in the Ocular Hypertension Treatment Study and the Collaborative Ocular Melanoma Study. The VF-14 was developed to identify a broad spectrum of vision-dependent activities performed in everyday life that can be affected by cataract.55 This questionnaire VOL. 128, NO. 1
measures difficulty with 14 vision-targeted activities ranging from reading print of various sizes to driving. Each item has five response options, ranging from “no difficulty” to “unable to do this activity.” Items are scored from 0 (unable to do activity) to 5 (no difficulty), and an average score is generated from the answered items. This score is then transformed to a 0 to 100 point scale, with 0 indicating an inability to do any of the activities and 100 indicating no difficulty in any activities. The VF-14 was selected as one measure of vision-specific functioning because it has been shown to be a reliable and valid measure of functional impairment caused by cataract and provides information not conveyed by visual acuity testing or the Sickness Impact Profile, a measure of general health status.55,56 The American Academy of Ophthalmology has recently included the VF-14 as part of its National Outcomes Database for cataract patients. The potential usefulness of the VF-14 among patients with glaucoma was recently investigated.57–59 The 51-item field test version of the NEI-VFQ60 was designed to evaluate the impact of visual disability on health-related quality of life. The content of the NEI-VFQ field test version was derived from condition-specific focus groups including patients with age-related cataract, agerelated macular degeneration, glaucoma, diabetic retinopathy, and cytomegalovirus retinitis. Unlike the VF-14, the NEI-VFQ was designed for ophthalmic patients in general rather than for patients with cataract. The NEI-VFQ consists of the following subscales: general health, general vision, visual pain, near activities, distance activities, vision-specific social functioning, vision-specific mental health, vision-specific expectations, vision-specific role difficulties, vision-specific dependency, driving, color vision, and peripheral vision. Subscales are scored on a 0 to 100 point scale in which 100 indicates the best possible score and 0 indicates the worst. The potential usefulness of the NEI-VFQ among patients with glaucoma was recently investigated.57–59 It should be noted that a 25-item version of the NEI-VFQ, developed at RAND under the sponsorship of the National Eye Institute, became available in July 1996. The study protocol was approved by the University of Miami School of Medicine Institutional Review Board. Because a considerable proportion of patients seen at the Bascom Palmer Eye Institute speak only Spanish, the Spanish versions of the VF-14, NEI-VFQ, and SF-36 were administered to these patients.57,59 All patients scheduled for an initial evaluation at the Bascom Palmer Eye Institute Low-Vision Clinic between December 1995 and December 1996 were called 1 week before their Low-Vision Clinic appointment, and after informed consent was obtained one bilingual interviewer administered a telephone interview, including the SF-36, VF-14, and NEI-VFQ. To assess nonophthalmic comorbidities, the NEI-VFQ health status survey was administered.60 Subjects were
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TABLE 1. Patient Characteristics No. of patients Age (yrs) Mean (SD) Median (range) Male (no. [%]) Ethnicity (no. [%]) White, non-Hispanic Hispanic Black, non-Hispanic Comorbidity score, preappointment Mean (SD) Median (range) No. (%) of patients who completed interview in English Primary ocular diagnosis (no. [%]) Age-related macular degeneration Diabetic retinopathy Macular hole Histoplasmosis Myopia Idiopathic central serous retinopathy Other macular disease Glaucoma Optic neuropathy Cataract Other Distance visual acuity* in best eye, preintervention Median Range Distance visual acuity in best eye, preintervention (no. [%]) 20/25–20/30 20/40–20/60 ⬍20/60–20/160 20/200 ⬍20/200–20/400 ⬍20/400 Weighted logMAR,† preintervention Mean (SD) Median (range) Near visual acuity‡ in best eye, preintervention Median Range Near visual acuity in best eye, preintervention (no. [%]) J1⫹-J2 J3-J5 J7-J10 J16 ⬍J16
156 72.5 (17.1) 77.5 (15–93) 71 (45.5) 98 (63.2) 52 (33.5) 5 (3.2) 2.7 (2.0) 2.0 (0–8) 111 (71.2) RE 84 (53.8) 17 (10.9) 3 (1.9) 2 (1.3) 2 (1.3) 2 (1.3) 6 (3.8) 13 (8.3) 5 (3.2) 2 (1.3) 20 (12.8)
LE 86 (55.1) 18 (11.5) 4 (2.6) 2 (1.3) 2 (1.3) 2 (1.3) 6 (3.8) 13 (8.3) 5 (3.2) 2 (1.3) 16 (10.3) 20/200 20/25–CF 4 (2.6) 33 (21.2) 41 (26.3) 41 (26.3) 29 (18.6) 8 (5.1) 1.0 (0.4) 1.0 (0.12–2.4) J5 (J1⫹–⬍J16) 49 (31.4) 30 (19.2) 33 (21.2) 29 (18.6) 15 (9.6)
CF ⫽ counting fingers. *Visual acuity measurements refer to the visual acuity attained with habitual correction. † Weighted logMAR ⫽ (0.75 ⫻ logMAR acuity in best eye) ⫹ (0.25 ⫻ logMAR acuity in worst eye), where MAR ⫽ numerator of visual acuity divided by denominator of visual acuity. ‡ Near visual acuity (classified according to the Jaeger scale of a standard Rosenbaum chart) was measured at a distance selected by the patients rather than at a “standard” distance.
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TABLE 2. Low-Vision Services Provided
TABLE 3. Patients’ Assessments of Usefulness of LowVision Services
Service
No. (%) of Patients
Spectacle prescription Spectacle magnifier Hand-held magnifier Stand magnifier Hand-held illuminated magnifier Stand illuminated magnifier Neck/chest–borne magnifier Spectacle-mounted microscope Telemicroscope Spectacle-mounted telescope Hand-held telescope Electronic devices Nonoptical devices Catalogue of devices/appliances Information, directory of services Referral to Lighthouse for the Blind None
73 (47.1) 63 (40.4) 21 (13.5) 11 (7.1) 52 (33.3) 40 (25.6) 3 (1.9) 26 (16.7) 9 (5.8) 66 (42.3) 13 (8.3) 6 (3.8) 4 (2.6) 1 (0.6) 63 (40.4) 9 (5.8) 4 (2.6)
No. (%) of Patients
asked if they suffered from any of 16 health conditions. In order to better assess the severity of comorbidities, a scale was added to the NEI-VFQ comorbidity assessment; for each comorbidity reported, subjects were asked to specify how much that condition interfered with their activities (for example, general functioning). A comorbidity score was then assigned to each of these responses (1, not at all; 2, a little; and 3, a great deal). An overall comorbidity score for each patient was computed by summing the scores. A similar comorbidity scale has been published.57,59,61 The Low-Vision Clinic examination included a review of the patient’s ocular history and visual functional complaints, establishment of goals of the Low-Vision Clinic evaluation, measurement of distance and near visual acuity with habitual correction, measurement of prescription of current glasses, retinoscopy and refraction at distance and near, assessment of binocularity, and, when indicated, visual field assessment. Because this study was designed to evaluate everyday functional status and quality of life, near visual acuity (classified according to the Jaeger scale of a standard Rosenbaum chart) was measured at a distance selected by the patients rather than at a “standard” distance. Magnification necessary for performing specific activities (for example, reading newsprint, watching television, writing) was determined, and training in the use of low-vision aids was provided. For patients unable to utilize their eccentric fixation effectively, eccentric viewing training and, if indicated, prism relocation were incorporated into the Low-Vision Clinic evaluation. The duration of each patient’s Low-Vision Clinic visit was 60 to 90 minutes. The same interviewer conducted a second telephone interview, including the same questionnaires, 3 months VOL. 128, NO. 1
Do low-vision services enable you to do more of the things you need or want to do? Yes No Missing data On a scale of 1 to 5 how useful are the lowvision services in helping you do more of the things you need or want to do? 1 (not useful at all) 2 3 4 5 (very useful) Missing data In terms of helping you do more of the things you need or want to do, do low-vision services help you less, as much, or more than you expected they would? Less As much More Missing data
150 (98.7) 2 (1.3) 4
1 (0.7) 1 (0.7) 13 (8.6) 55 (36.2) 82 (53.9) 4
3 (2.0) 82 (53.9) 67 (44.1) 4
after each patient’s Low-Vision Clinic visit. Patients were asked to rate, on a scale of 1 to 5, how useful low-vision services were in helping them to do more of the things they needed or wanted to do. Demographic and clinical data, including the types of low-vision services provided, were abstracted from patients’ medical records. For analytic purposes, patients’ visual acuities were classified into groups similar to those used in the Baltimore Eye Survey62 and the Blue Mountain Eye Study.63 The logMAR visual acuity of the one patient whose visual acuity (counting fingers) was not measured by Snellen visual acuity was calculated according to a published conversion scale.57,59,61 Descriptive summary statistics were calculated for clinical and demographic variables and for questionnaire scores. T tests were used to compare the SF-36 scores of this study’s low-vision patients with published SF-36 scores (means and standard errors) of other study populations.53 Paired t tests were used to assess differences between questionnaire scores before and after patients’ Low-Vision Clinic visits.
RESULTS CHARACTERISTICS OF THE STUDY POPULATION ARE DIS-
played in Table 1, and the low-vision services provided are listed in Table 2. The mean number of low-vision devices or services provided was 3.4 (SD, 2.3; median, 3; range, 0
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FIGURE. Mean SF-36 subscale scores of patients with low vision compared with published48,53 mean scores of the United States normal population 75 years of age and older, patients with congestive heart failure, and patients with clinical depression. Although patients with low vision scored significantly (P < .001) better than the three populations in bodily pain (BP), vitality (V), and social functioning (SF), they scored significantly (P < .001) worse than the three populations in physical functioning (PF), role limitations caused by physical health problems (RP), and role limitations caused by emotional problems (RE). GH ⴝ general health; MH ⴝ mental health.
activities (38.3 to 41.1, P ⫽ .001), and peripheral vision (37.9 to 42.6, P ⬍ .001).
to 9). Twenty-one patients (13.5%) received only a change in spectacle prescription. There was no change in the mean comorbidity score after the Low-Vision Clinic visit (P ⫽ .895). The subjective responses concerning the value of lowvision services provided are shown in Table 3. Low-vision services improved the subjective functional status of 150 patients (98.7%). The services were rated “very useful” by 82 patients (53.9%) and more helpful than expected by 67 patients (44.1%). The Figure displays mean SF-36 subscale scores of low-vision patients compared with published48,53 mean scores of the United States normal population aged 75 years or more, patients with congestive heart failure, and patients with clinical depression. Summary statistics for the questionnaires administered are listed in Table 4. None of the subscales of the SF-36 changed significantly after low-vision services were provided. The VF-14 score improved from 35.8 to 41.2 (P ⬍ .001). The NEI-VFQ subscale scores associated with statistically significant improvement after the provision of low-vision services were general vision (42.8 to 46.1, P ⬍ .001), near activities (38.0 to 46.3, P ⬍ .001), distance 58
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DISCUSSION THE SCORES ON THE SF-36, VF-14, AND NEI-VFQ DEMON-
strate that Low-Vision Clinic patients perceived that their functional status and quality of life were markedly impaired. The Figure demonstrates that although low-vision patients scored significantly (P ⬍ .001) better than the three comparison populations in bodily pain, vitality, and social functioning, they scored significantly (P ⬍ .001) worse than the three comparison populations in physical functioning, role limitations caused by physical health problems, and role limitations caused by emotional problems. The marked impairment in perceived functional status and quality of life among Low-Vision Clinic patients is consistent with a recent study that reported that having blurred vision more than once or twice a month has a significant impact on functional status and well-being (as measured by SF-36 scores), especially in role limitations OF
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TABLE 4. Summary Statistics for SF-36, VF-14, and NEI-VFQ Questionnaires
Questionnaire Scale
N
Mean (SD) Score Before LVC
Mean (SD) Score After LVC
Difference (SD)
P Value
SF-36 PF SF-36 RP SF-36 BP SF-36 GH SF-36 V SF-36 SF SF-36 RE SF-36 MH VF-14 NEI-VFQ GH NEI-VFQ GV NEI-VFQ VP NEI-VFQ NA NEI-VFQ DA NEI-VFQ VSSF NEI-VFQ VSMH NEI-VFQ VSE NEI-VFQ VSRD NEI-VFQ VSD NEI-VFQ D NEI-VFQ CV NEI-VFQ PV
156 156 156 156 156 156 156 156 156 156 156 156 151 153 129 156 153 156 156 13 152 153
35.0 (31.5) 5.0 (20.2) 84.6 (15.3) 52.0 (9.1) 64.7 (8.1) 86.9 (15.6) 5.6 (22.0) 76.9 (6.1) 35.8 (13.1) 53.2 (10.3) 42.8 (10.7) 97.3 (8.3) 38.0 (14.5) 38.3 (13.6) 62.9 (23.8) 65.9 (10.0) 42.7 (6.0) 47.9 (16.2) 54.0 (17.0) 34.1 (19.1) 60.2 (24.0) 37.9 (14.9)
36.4 (30.7) 4.2 (18.6) 86.2 (14.8) 51.3 (7.8) 64.4 (7.6) 87.3 (14.7) 4.7 (19.5) 77.5 (6.0) 41.2 (12.6) 52.6 (8.9) 46.1 (9.5) 97.0 (7.9) 46.3 (13.8) 41.1 (12.6) 61.7 (22.1) 66.4 (7.5) 42.5 (5.9) 48.4 (13.8) 54.7 (18.5) 37.9 (16.3) 59.9 (21.0) 42.6 (13.7)
1.4 (21.3) ⫺0.8 (18.3) 1.5 (12.2) ⫺0.7 (8.0) ⫺0.4 (7.7) 0.4 (12.5) ⫺0.9 (20.7) 0.6 (6.5) 5.4 (11.1) ⫺0.6 (7.1) 3.4 (9.0) ⫺0.2 (4.8) 8.3 (11.8) 2.8 (10.5) ⫺1.2 (19.7) 0.5 (9.4) ⫺0.2 (7.0) 0.5 (14.9) 0.7 (16.5) 3.8 (12.1) ⫺0.3 (18.9) 4.7 (15.1)
.400 .585 .118 .271 .569 .689 .607 .263 ⬍.001 .287 ⬍.001 .533 ⬍.001 .001 .480 .492 .667 .683 .577 .275 .830 ⬍.001
LVC ⫽ Low-Vision Clinic visit; NEI-VFQ ⫽ Field Test Version of the National Eye Institute Visual Functioning Questionnaire; SF-36 ⫽ Medical Outcomes Study 36-Item Short Form; VF-14 ⫽ Visual Function 14. For SF-36: BP ⫽ bodily pain; GH ⫽ general health; MH ⫽ mental health; PF ⫽ physical functioning; RE ⫽ role emotional; RP ⫽ role physical; SF ⫽ social functioning; V ⫽ vitality. For NEI-VFQ: CV ⫽ color vision; D ⫽ driving; DA ⫽ distance activities; GH ⫽ general health; GV ⫽ general vision; NA ⫽ near activities; PV ⫽ peripheral vision; VP ⫽ visual pain; VSD ⫽ vision-specific dependency; VSE ⫽ vision-specific expectations; VSMH ⫽ vision-specific mental health; VSRD ⫽ vision-specific role difficulties; VSSF ⫽ vision-specific social functioning.
caused by physical health problems.64 Given the growing number of sight-impaired individuals, low vision is a major public health issue. The use of and access to low-vision services appears to be limited. A recent national survey conducted by The Lighthouse determined that more than half of all middle-aged and elderly Americans have been affected by either their own visual impairment or that of a close relative, friend, or neighbor, yet 43% were unaware of low-vision services in their community.65 In a Canadian survey of visually impaired noninstitutionalized persons older than 65 years, 55% had not received aid from any low-vision service.66 In Great Britain, only 50% of elderly patients with low vision who had attended a general ophthalmology clinic had received formal low-vision assessments, and only 3% had used a large-print book.24 In the current study, low-vision services are associated with statistically significant improvements in the scores of the VF-14 and of four subscales of the NEI-VFQ. Thus, it appears that vision-targeted health status questionnaires are more sensitive than general health-related quality of life questionnaires to differences in functional status and VOL. 128, NO. 1
quality of life before and after the provision of low-vision services. This finding is consistent with previous studies demonstrating that the VF-14 is more responsive than general health status measures to change in functional impairment related to vision among cataract patients55,67,68 and with studies reporting that scores of the VF-14 and NEI-VFQ correlated more strongly with visual field impairment than did SF-36 scores.57–59 Despite the high rate of patient satisfaction and the highly statistically significant questionnaire score improvements (P ⬍ .001), the absolute increases in questionnaire scores may be considered modest, with improvements ranging from 2.8 units on the NEI-VFQ distance activities subscale to 8.3 units on the NEI-VFQ near activities subscale. These questionnaires, however, were not designed specifically for a low-vision population. The VF-14, for instance, was designed for patients with cataract, and several of the 14 activities included in this questionnaire, such as doing fine handiwork, daytime driving, and nighttime driving, may not be expected to improve as a result of low-vision services. In addition, it is important to empha-
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2. Dowie AT. Management and practice of low visual acuity. London: The Eastern Press, 1988. 3. Strong JG, Pace RJ, Plotkin AD. Low vision services: a model for sequential intervention and rehabilitation. Can J Public Health 1988;79:50 –54. 4. Nelson K, Dimitrova G. Statistical brief #36: “severe visual impairment” in the U.S. and the states. J Vis Impair Blindness 1993;87:80 – 85. 5. Kirchner C. Data on blindness and visual impairment in the US: a resource manual on characteristics, education, employment, and service delivery. New York: American Foundation for the Blind, 1985. 6. 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. 7. National Advisory Eye Council. Vision research: a national plan 1994 –1998. Bethesda: National Eye Institute, National Institutes of Health, 1993:305–321. 8. LaPlante MP. Prevalence of conditions causing need for assistance in activities of daily living. In: Data on disability from the National Health Interview Survey, 1983–1985: info use report. Washington, DC: National Institute on Disability and Rehabilitation Research, 1988. 9. Massof RW, Dagnelie G, Deremeik JT, DeRose JL, Alibhai SS, Glasner NM. Low vision rehabilitation in the U.S. health care system. J Vision Rehabil 1995;9:3–31. 10. Faye EE, editor. Clinical low vision, 2nd ed. Boston: Little, Brown & Company, 1984:171–212. 11. National Society to Prevent Blindness. Data analysis, vision problems in the United States. New York: National Society to Prevent Blindness, 1980:5, 19. 12. Faye EE. A functional classification of eye diseases. In: Faye EE, editor. Clinical low vision. Boston: Little, Brown & Company, 1976:203–231. 13. Nilsson U. Visual rehabilitation of patients with and without educational training in the use of optical aids and residual vision: a prospective study of patients with advanced agerelated macular degeneration. Clin Vis Sci 1990;6:3–10. 14. Nilsson UL, Nilsson SEG. Rehabilitation of the visually handicapped with advanced macular degeneration. Doc Ophthalmol 1986;62:345–367. 15. Sloan LL. Reading aids for the partially-sighted: factors which determine success or failure. Arch Ophthalmol 1968; 80:35–38. 16. Rosenberg R, Faye E, Fischer M, Budicks D. Role of prism relocation in improving visual performance of patients with macular dysfunction. Optom Vis Sci 1989;66:747–750. 17. McIlwaine GG, Bell JA, Dutton GN. Low vision aids: is our service cost effective? Eye 1991;5:607– 611. 18. Robbins HG, McMurray NE. Psychological and visual factors in low vision rehabilitation of patients with age related maculopathy. J Vis Rehabil 1988;2:11–21. 19. Hall A, Sacks SZ, Dornbusch H, et al. A preliminary study to evaluate patient services in a low vision clinic. J Vis Rehabil 1987;1:7–25. 20. Humphrey RC, Thompson GM. Low vision aids: evaluation in a general eye department. Trans Ophthalmol Soc U K 1986;105:296 –303. 21. Davis C, Lovie-Kitchin J, Thompson B. Psychosocial adjustment to age-related macular degeneration. J Vis Impair Blindness 1995;89:16 –27. 22. Leat SJ, Fryer A, Rumney NJ. Outcome of low vision aid provision: the effectiveness of a low vision clinic. Optom Vis Sci 1994;71:199 –206. 23. Watson GR, Beck S, De l’Aune W, et al. A national survey of the impact of low vision prosthetic device use among veterans [abstract]. Optom Vis Sci 1994;71(suppl):20.
size that a limitation of the current study is that the impact of only a single low-vision clinic visit was evaluated; studies have suggested the importance of follow-up lowvision services and training.69 –71 Furthermore, because vision is critical to so many aspects of daily function, even a modest increase in visual performance may translate into large increases in patient satisfaction. The significant improvement in the NEI-VFQ peripheral vision subscale may, at first glance, be counterintuitive because the magnifiers, microscopes, and telescopes frequently provided through low-vision services may be associated with a decreased field of view. Although the significance of the NEI-VFQ peripheral vision subscale could represent a spurious finding, the perceived improvement in peripheral vision may be caused by improved overall vision (for example, resulting from a change in spectacle prescription, which was performed in 47.1% of patients) or the eccentric viewing training often provided during the Low-Vision Clinic visit. That we did not document which patients received eccentric viewing training is a limitation of the current study and could be a useful variable to consider in future studies. Twenty-one patients (13.5%) in the study were treated with only a change in spectacle prescription. Although we can only speculate as to why the prescription was not changed by the patients’ primary eye care providers— objective visual acuity measurements with refraction may not have significantly improved; Low-Vision Clinic personnel may have been more experienced in performing refraction in low-vision patients; Low-Vision Clinic personnel may have had more time to perform refraction; primary care providers’ offices may not have had equipment such as a Feinbloom chart or 1-diopter Jackson cross cylinder—it appears that refraction is an important component of the Low-Vision Clinic evaluation and that patients frequently benefited from a change in spectacle prescription. The findings of the current study indicate that lowvision patients perceive that their functional status and quality of life are markedly impaired. Vision-targeted health status questionnaires may be useful in tandem with the clinical examination to fully understand the outcomes of low-vision services. Questionnaires that provide evidence that low-vision services are associated with increased functional status and quality of life may increase public awareness of the potential benefits of low-vision services and may encourage Medicare and managed care plans to pay for such services. We hope that confirmation of the measured improvements in visual function will lead to greater access to low-vision services.
REFERENCES 1. Mehr EB. Low vision care. Chicago: Professional Press, 1975:254.
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24. Elliott AJ. Poor vision and the elderly: a domiciliary study. Eye 1989;3:365–369. 25. Temel A. Low vision aids (evaluation of 195 patients). Ophthalmic Physiol Opt 1989;9:327–331. 26. Nilsson UL. Visual rehabilitation of patients with advanced diabetic retinopathy: a follow-up study at the Low Vision Clinic, Department of Ophthalmology, University of Linkoping. Doc Ophthalmol 1986;62:369 –382. 27. Watson GR, De l’Aune W, Stelmack J, Maino J, Long S. National survey of the impact of low vision device use among veterans. Optom Vis Sci 1998;74:249 –259. 28. Watson GR, De l’Aune W, Long S, Maino J, Stelmack J. Veterans’ use of low vision devices for reading. Optom Vis Sci 1997;74:260 –265. 29. Raasch TW, Leat SJ, Kleinstein RN, Bullimore MA, Cutter GR. Evaluating the value of low-vision services. J Am Optom Assoc 1997;68:287–295. 30. Ware JE, Sherbourne CD. The MOS 36-Item Short-Form Health Survey (SF-36), I: conceptual framework and item selection. Med Care 1992;30:473-483. 31. McHorney CA, Ware JE, Raczek AE. The MOS 36-Item Short Form Health Survey (SF-36), II: psychometric and clinical tests of validity in measuring physical and mental health constructs. Med Care 1993;31:247–263. 32. Hays RD, Sherbourne CD, Mazel RM. The RAND 36-Item Health Survey 1.0. Health Econ 1993;2:217–227. 33. Ware JE Jr, Snow KK, Kosiniski M, et al. SF-36 health survey manual and interpretation guide. Boston: The Health Institute, New England Medical Center, 1993. 34. Ware JE Jr, Snow KK, Kosinski M, et al. SF-36 health survey manual and interpretation guide. Chapters 7 and 9. Boston: The Health Institute, New England Medical Center, 1993. 35. McHorney CA, Ware JE Jr. Construction and validation of an alternate form general mental health scale for the MOS SF-36 Health Survey. Med Care 1995;33:15–28. 36. McHorney CA, Kosinski M, Ware JE Jr. Comparisons of the costs and quality of norms collected by mail versus telephone interview: results from a national survey. Med Care 1994;32: 551–567. 37. McHorney CA, Ware JE Jr, Lu JFR, Sherbourne CD. The MOS 36-Item Short-Form Health Survey (SF-36), III: tests of data quality, scaling assumptions, and reliability across diverse patient groups. Med Care 1994;32:40 – 66. 38. Garratt AM, Ruta DA, Abdalla MI, et al. The SF-36 health profile: an outcome measure suitable for routine use within the NHS? Br Med J 1993;306:1440 –1444. 39. Jenkinson C, Coulter A, Wright L. The Short Form 36 (SF-36) Health Survey Questionnaire: normative data for adults of working age. Br Med J 1993;306:1437–1440. 40. Brazier JE, Harper R, Jones NMB, et al. Validating the SF-36 Health Survey Questionnaire: new outcome measure for primary care. Br Med J 1992;305:160 –164. 41. Kantz ME, Harris WJ, Levitsky K, et al. Methods for assessing condition-specific and generic functional status outcomes after total knee replacement. Med Care 1992;30(suppl): MS240 –MS252. 42. Kurtin PS, Davies AR, Meyer KB, et al. Patient-based health status measures in outpatient dialysis: early experiences in developing an outcomes assessment program. Med Care 1992;30(suppl):MS136 –MS149. 43. Nerenz DR, Repasky DP, Whitehouse FW, Kahkonen DM. Ongoing assessment of health status in patients with diabetes mellitus. Med Care 1992;30(suppl):MS112–MS124. 44. Wachtel T, Piette J, Mor V, et al. Quality of life in persons with human immunodeficiency virus infection: measurement by the Medical Outcomes Study instrument. Ann Intern Med 1992;116:129 –137.
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45. Cleary PD, Epstein AM, Oster G, et al. Health-related quality of life among patients undergoing percutaneous transluminal coronary angioplasty. Med Care 1991;29:939 – 950. 46. Wu AW, Rubin HR, Mathews WC, et al. A health status questionnaire using 30 items from the Medical Outcomes Study: preliminary validation in persons with HIV infection. Med Care 1991;29:786 –798. 47. Gelberg L, Linn LS. Psychological distress among homeless adults. J Nerv Ment Dis 1989;177:291–295. 48. Stewart AL, Greenfield S, Hays RD, et al. Functional status and well-being of patients with chronic conditions: results from the Medical Outcomes Study. JAMA 1989;262:907– 913. 49. Stewart AL, Hays RD, Ware JE Jr. The MOS Short-Form General Health Survey: reliability and validity in a patient population. Med Care 1988;26:724 –735. 50. Ware JE Jr, Snow KK, Kosinski M, et al. SF-36 health survey manual and interpretation guide. Boston: The Health Institute, New England Medical Center, 1993:1–7, 14 –21. 51. Wetzler HP, Radosevich DM. Health status questionnaire (SF-36) technical report. InterStudy 1992. 52. Thalji L, Haggerty CC, Rubin R, et al. 1990 national survey of functional health status: final report. Chicago: National Opinion Research Center, 1991. 53. Ware JE Jr, Snow KK, Kosiniski M, et al. SF-36 health survey manual and interpretation guide. Boston: The Health Institute, New England Medical Center, 1993:1–38. 54. Mangione CM, Phillips RS, Lawrence MG, Seddon JM, Orav EJ, Goldman L. Improved visual function and attenuation of declines in health-related quality of life after cataract extraction. Arch Ophthalmol 1994;112:1419 –1425. 55. Steinberg EP, Tielsch JM, Schein OD, et al. The VF-14: an index of functional impairment in patients with cataract. Arch Ophthalmol 1994;112:195–203. 56. Bergner M, Bobbitt RA, Kressel S, et al. The Sickness Impact Profile: conceptual and methodology for the development of a health status measure. Int J Health Serv 1976;6:393– 415. 57. Parrish RK II, Gedde SJ, Scott IU, et al. Visual function and quality of life among patients with glaucoma. Arch Ophthalmol 1997;115:1447–1455. 58. Gutierrez P, Wilson MR, Johnson C, et al. Influence of glaucomatous visual field loss on health-related quality of life. Arch Ophthalmol 1997;115:777–784. 59. Parrish RK II. Visual impairment, visual functioning, and quality of life assessments in patients with glaucoma. Trans Am Ophthalmol Soc 1996;94:919 –1028. 60. Mangione CM, Berry S, Spritzer K, et al. Identifying the content area for the 51-item National Eye Institute Visual Function Questionnaire: results from focus groups with visually impaired persons. Arch Ophthalmol 1998;116: 227–233. 61. Scott IU, Schein OD, Bandeen-Roche K, et al. Functional status and quality of life measurement among ophthalmic patients. Arch Ophthalmol 1994;112:329 –335. 62. Tielsch JM, Sommer A, Witte K, Katz J, Royall RM, the Baltimore Eye Survey Research Group. Blindness and visual impairment in an American urban population: the Baltimore Eye Survey. Arch Ophthalmol 1990;108:286 –290. 63. Attebo K, Mitchell P, Smith W. Visual acuity and the causes of visual loss in Australia. Ophthalmology 1996;103:357– 364. 64. Lee PP, Spritzer K, Hays RD. The impact of blurred vision on functioning and well-being. Ophthalmology 1997;104:390 – 396. 65. The Lighthouse. The Lighthouse national survey on vision loss: the experience, attitudes and knowledge of middle-aged
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of generic versus disease-specific measures of functional impairment in patients with cataract. Med Care 1995;33(4, suppl):AS120 –AS130. 69. Jackson AJ, Silver JS, Archer DB. An evaluation of follow-up systems in two low vision clinics in the UK. In: Woo GC, editor. Low vision: principles and applications. Berlin, Springer-Verlag, 1986:396 – 417. 70. Giltrow-Tyler JF. The Bristol low vision project: a multidisciplinary approach. Optom Today 1988;28:352–354. 71. Stoll S, Sarma S, Hoeft WW. Low vision aids training in the home. J Am Optom Assoc 1995;66:32–38.
and older Americans. New York: The Lighthouse, Inc, Louis Harris and Associates, Inc, 1994:17. 66. Gresset J, Baumgarten M. A survey of the utilisation of rehabilitation services by the visually impaired elderly population. In: Kooijman AC, editor. Low vision, research and new developments in rehabilitation. Amsterdam: IOS Press, 1994:481– 484. 67. Desai P, Reidy A, Minassian DC, Vafidis G, Bolger J. Gains from cataract surgery: visual function and quality of life. Br J Ophthalmol 1996;80:868 – 873. 68. Damiano AM, Steinberg EP, Cassard SD, et al. Comparison
Authors Interactive威 We encourage questions and comments regarding this article via the Internet on Authors Interactive威 at http://www.ajo.com/ Questions, comments, and author responses are posted.
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● PURPOSE:
To investigate the functional status and quality of life of patients at a low-vision clinic and to evaluate the impact of low-vision services. ● METHODS: Interviews, including the Medical Outcomes Study 36-Item Short Form (SF-36), the Visual Function-14 (VF-14), and the 51-item Field Test Version of the National Eye Institute Visual Functioning Questionnaire (NEI-VFQ), were administered to 156 consecutive patients 1 week before and 3 months after their low-vision clinic visit. ● RESULTS: Low-vision patients scored lower (P < .001) in physical functioning and role limitations caused by physical and emotional health problems than published SF-36 scores of the age-appropriate United States normal population, patients with congestive heart failure, and clinically depressed patients. Low-vision services were associated with improvement in the subjective functional status of 150 patients (98.7%) and were rated “very useful” by 82 (53.9%) patients. The SF-36 scores did not change significantly after low-vision services. The VF-14 mean score improved from 35.8 to 41.2 (P < .001). Four NEI-VFQ subscale scores improved significantly (P < .001): general vision, near activities, distance activities, and peripheral vision. ● CONCLUSIONS: The SF-36, VF-14, and NEI-VFQ demonstrate that low-vision clinic patients perceive marked impairment of functional status and quality of life. Low-vision services are associated with high patient satisfaction. Vision-targeted questionnaires are more sensitive than general health-related quality of life questionnaires to changes in functional status and quality of life after low-vision services, and they may help elucidate the outcomes of low-vision services. (Am J Ophthalmol 1999;128:54 – 62. © 1999 by Elsevier Science Inc. All rights reserved.)
Accepted for publication Feb 19, 1999. From the Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida. Reprint requests to William E. Smiddy, MD, Bascom Palmer Eye Institute, 900 NW 17th St, Miami, FL 33136; fax: (305) 326-6417.
54
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1999 BY
L
OW VISION HAS BEEN DEFINED AS A PERMANENT VI-
sual impairment that is not correctable with spectacles, contact lenses, or surgical intervention and that interferes with normal everyday functioning.1 It is estimated that approximately 1% of the population of Western countries suffers from low vision2,3 and that visual impairment affects nearly 5 million Americans to the extent that they are unable to read newsprint, even with the aid of full refractive correction.4 Because individuals older than 65 years have more vision loss than any other age group5,6 and because it is projected that the number of Americans over the age of 65 will more than double between 1995 and 2030,7 the burden of low vision is expected to increase markedly. Vision loss has been ranked third, behind arthritis and heart disease, among conditions that cause persons older than 70 years to need assistance in activities of daily living.8 Despite their increasing public health significance, the functional status and quality of life of patients with low vision have been incompletely studied. In addition, lowvision services typically are not included in health insurance plans, managed care plans, and Medicare benefits, presumably in part because of insufficient data concerning the outcomes of such services.9 As the population of low-vision patients continues to grow, attention must be focused on evaluating the effectiveness of low-vision services, especially because it is reported that 90% of individuals affected by low vision maintain sufficient vision to benefit from training in the use of optical and nonoptical devices and adaptive skills.10 –12 Studies have demonstrated the effect of low-vision interventions on objective task-specific measures of functional abilities, such as reading speed, reading duration, and ability to read a certain print size.13–16 Patient satisfaction with low-vision services15,17–20 and the frequency and type of low-vision aids used13,14,21–28 have also been investigated. However, we are unaware of studies that focus on the impact of low-vision services on healthrelated quality of life, and we could find no such reference in a computerized search on Medline. We were also unable to find a reference to any studies that investigated the
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usefulness of previously developed and widely used functional status/quality of life questionnaires in evaluating patients with low vision and the impact of low-vision services.29 The current study was designed to investigate the functional status and quality of life of patients at a low-vision clinic, as well as the potential impact of low-vision services on these health status measures. Established outcomes instruments were used to quantitate these measures and included a general health status questionnaire (the Medical Outcomes Study 36-Item Short Form [SF-36]) and two vision-targeted questionnaires (the Visual Function-14 [VF-14] and the 51-item Field Test Version of the National Eye Institute Visual Functioning Questionnaire [NEI-VFQ]).
METHODS THE STUDY POPULATION CONSISTED OF 156 CONSECUTIVE
patients evaluated for the first time at the Bascom Palmer Eye Institute Low-Vision Clinic between December 1995 and December 1996. Patients either were referred to the Low-Vision Clinic by an ophthalmologist or were selfreferred. To study a representative sample of low-vision clinic patients, consecutive patients evaluated in the Low-Vision Clinic during the 1-year study period were included; a specific visual acuity level was not used as an inclusion criterion. The questionnaires used in this study were chosen because of specific features. The SF-36 is a general healthrelated quality of life measure30 –32 and consists of eight subscales: physical functioning, role limitations caused by physical health problems, bodily pain, general health, vitality (energy/fatigue), social functioning, role limitations caused by emotional problems, and mental health (psychological distress and psychological well-being). Each of the subscales is scored from 0 to 100 (100 indicates the best possible score and 0 indicates the worst possible score). Our reported scores are based on a published algorithm for the SF-36.33 This questionnaire was chosen to assess participants’ quality of life because its validity and reliability have been demonstrated repeatedly.34 – 49 Furthermore, comparative normative data are available for the general populations in the United States and Great Britain26,31,50 –52 and for patients with a variety of medical conditions, including hypertension, congestive heart failure, type II diabetes mellitus, acute myocardial infarction, and clinical depression.53 The SF-36 was used to assess the effect of cataract extraction and intraocular lens implantation on quality of life54 and is currently being used in the Ocular Hypertension Treatment Study and the Collaborative Ocular Melanoma Study. The VF-14 was developed to identify a broad spectrum of vision-dependent activities performed in everyday life that can be affected by cataract.55 This questionnaire VOL. 128, NO. 1
measures difficulty with 14 vision-targeted activities ranging from reading print of various sizes to driving. Each item has five response options, ranging from “no difficulty” to “unable to do this activity.” Items are scored from 0 (unable to do activity) to 5 (no difficulty), and an average score is generated from the answered items. This score is then transformed to a 0 to 100 point scale, with 0 indicating an inability to do any of the activities and 100 indicating no difficulty in any activities. The VF-14 was selected as one measure of vision-specific functioning because it has been shown to be a reliable and valid measure of functional impairment caused by cataract and provides information not conveyed by visual acuity testing or the Sickness Impact Profile, a measure of general health status.55,56 The American Academy of Ophthalmology has recently included the VF-14 as part of its National Outcomes Database for cataract patients. The potential usefulness of the VF-14 among patients with glaucoma was recently investigated.57–59 The 51-item field test version of the NEI-VFQ60 was designed to evaluate the impact of visual disability on health-related quality of life. The content of the NEI-VFQ field test version was derived from condition-specific focus groups including patients with age-related cataract, agerelated macular degeneration, glaucoma, diabetic retinopathy, and cytomegalovirus retinitis. Unlike the VF-14, the NEI-VFQ was designed for ophthalmic patients in general rather than for patients with cataract. The NEI-VFQ consists of the following subscales: general health, general vision, visual pain, near activities, distance activities, vision-specific social functioning, vision-specific mental health, vision-specific expectations, vision-specific role difficulties, vision-specific dependency, driving, color vision, and peripheral vision. Subscales are scored on a 0 to 100 point scale in which 100 indicates the best possible score and 0 indicates the worst. The potential usefulness of the NEI-VFQ among patients with glaucoma was recently investigated.57–59 It should be noted that a 25-item version of the NEI-VFQ, developed at RAND under the sponsorship of the National Eye Institute, became available in July 1996. The study protocol was approved by the University of Miami School of Medicine Institutional Review Board. Because a considerable proportion of patients seen at the Bascom Palmer Eye Institute speak only Spanish, the Spanish versions of the VF-14, NEI-VFQ, and SF-36 were administered to these patients.57,59 All patients scheduled for an initial evaluation at the Bascom Palmer Eye Institute Low-Vision Clinic between December 1995 and December 1996 were called 1 week before their Low-Vision Clinic appointment, and after informed consent was obtained one bilingual interviewer administered a telephone interview, including the SF-36, VF-14, and NEI-VFQ. To assess nonophthalmic comorbidities, the NEI-VFQ health status survey was administered.60 Subjects were
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TABLE 1. Patient Characteristics No. of patients Age (yrs) Mean (SD) Median (range) Male (no. [%]) Ethnicity (no. [%]) White, non-Hispanic Hispanic Black, non-Hispanic Comorbidity score, preappointment Mean (SD) Median (range) No. (%) of patients who completed interview in English Primary ocular diagnosis (no. [%]) Age-related macular degeneration Diabetic retinopathy Macular hole Histoplasmosis Myopia Idiopathic central serous retinopathy Other macular disease Glaucoma Optic neuropathy Cataract Other Distance visual acuity* in best eye, preintervention Median Range Distance visual acuity in best eye, preintervention (no. [%]) 20/25–20/30 20/40–20/60 ⬍20/60–20/160 20/200 ⬍20/200–20/400 ⬍20/400 Weighted logMAR,† preintervention Mean (SD) Median (range) Near visual acuity‡ in best eye, preintervention Median Range Near visual acuity in best eye, preintervention (no. [%]) J1⫹-J2 J3-J5 J7-J10 J16 ⬍J16
156 72.5 (17.1) 77.5 (15–93) 71 (45.5) 98 (63.2) 52 (33.5) 5 (3.2) 2.7 (2.0) 2.0 (0–8) 111 (71.2) RE 84 (53.8) 17 (10.9) 3 (1.9) 2 (1.3) 2 (1.3) 2 (1.3) 6 (3.8) 13 (8.3) 5 (3.2) 2 (1.3) 20 (12.8)
LE 86 (55.1) 18 (11.5) 4 (2.6) 2 (1.3) 2 (1.3) 2 (1.3) 6 (3.8) 13 (8.3) 5 (3.2) 2 (1.3) 16 (10.3) 20/200 20/25–CF 4 (2.6) 33 (21.2) 41 (26.3) 41 (26.3) 29 (18.6) 8 (5.1) 1.0 (0.4) 1.0 (0.12–2.4) J5 (J1⫹–⬍J16) 49 (31.4) 30 (19.2) 33 (21.2) 29 (18.6) 15 (9.6)
CF ⫽ counting fingers. *Visual acuity measurements refer to the visual acuity attained with habitual correction. † Weighted logMAR ⫽ (0.75 ⫻ logMAR acuity in best eye) ⫹ (0.25 ⫻ logMAR acuity in worst eye), where MAR ⫽ numerator of visual acuity divided by denominator of visual acuity. ‡ Near visual acuity (classified according to the Jaeger scale of a standard Rosenbaum chart) was measured at a distance selected by the patients rather than at a “standard” distance.
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TABLE 2. Low-Vision Services Provided
TABLE 3. Patients’ Assessments of Usefulness of LowVision Services
Service
No. (%) of Patients
Spectacle prescription Spectacle magnifier Hand-held magnifier Stand magnifier Hand-held illuminated magnifier Stand illuminated magnifier Neck/chest–borne magnifier Spectacle-mounted microscope Telemicroscope Spectacle-mounted telescope Hand-held telescope Electronic devices Nonoptical devices Catalogue of devices/appliances Information, directory of services Referral to Lighthouse for the Blind None
73 (47.1) 63 (40.4) 21 (13.5) 11 (7.1) 52 (33.3) 40 (25.6) 3 (1.9) 26 (16.7) 9 (5.8) 66 (42.3) 13 (8.3) 6 (3.8) 4 (2.6) 1 (0.6) 63 (40.4) 9 (5.8) 4 (2.6)
No. (%) of Patients
asked if they suffered from any of 16 health conditions. In order to better assess the severity of comorbidities, a scale was added to the NEI-VFQ comorbidity assessment; for each comorbidity reported, subjects were asked to specify how much that condition interfered with their activities (for example, general functioning). A comorbidity score was then assigned to each of these responses (1, not at all; 2, a little; and 3, a great deal). An overall comorbidity score for each patient was computed by summing the scores. A similar comorbidity scale has been published.57,59,61 The Low-Vision Clinic examination included a review of the patient’s ocular history and visual functional complaints, establishment of goals of the Low-Vision Clinic evaluation, measurement of distance and near visual acuity with habitual correction, measurement of prescription of current glasses, retinoscopy and refraction at distance and near, assessment of binocularity, and, when indicated, visual field assessment. Because this study was designed to evaluate everyday functional status and quality of life, near visual acuity (classified according to the Jaeger scale of a standard Rosenbaum chart) was measured at a distance selected by the patients rather than at a “standard” distance. Magnification necessary for performing specific activities (for example, reading newsprint, watching television, writing) was determined, and training in the use of low-vision aids was provided. For patients unable to utilize their eccentric fixation effectively, eccentric viewing training and, if indicated, prism relocation were incorporated into the Low-Vision Clinic evaluation. The duration of each patient’s Low-Vision Clinic visit was 60 to 90 minutes. The same interviewer conducted a second telephone interview, including the same questionnaires, 3 months VOL. 128, NO. 1
Do low-vision services enable you to do more of the things you need or want to do? Yes No Missing data On a scale of 1 to 5 how useful are the lowvision services in helping you do more of the things you need or want to do? 1 (not useful at all) 2 3 4 5 (very useful) Missing data In terms of helping you do more of the things you need or want to do, do low-vision services help you less, as much, or more than you expected they would? Less As much More Missing data
150 (98.7) 2 (1.3) 4
1 (0.7) 1 (0.7) 13 (8.6) 55 (36.2) 82 (53.9) 4
3 (2.0) 82 (53.9) 67 (44.1) 4
after each patient’s Low-Vision Clinic visit. Patients were asked to rate, on a scale of 1 to 5, how useful low-vision services were in helping them to do more of the things they needed or wanted to do. Demographic and clinical data, including the types of low-vision services provided, were abstracted from patients’ medical records. For analytic purposes, patients’ visual acuities were classified into groups similar to those used in the Baltimore Eye Survey62 and the Blue Mountain Eye Study.63 The logMAR visual acuity of the one patient whose visual acuity (counting fingers) was not measured by Snellen visual acuity was calculated according to a published conversion scale.57,59,61 Descriptive summary statistics were calculated for clinical and demographic variables and for questionnaire scores. T tests were used to compare the SF-36 scores of this study’s low-vision patients with published SF-36 scores (means and standard errors) of other study populations.53 Paired t tests were used to assess differences between questionnaire scores before and after patients’ Low-Vision Clinic visits.
RESULTS CHARACTERISTICS OF THE STUDY POPULATION ARE DIS-
played in Table 1, and the low-vision services provided are listed in Table 2. The mean number of low-vision devices or services provided was 3.4 (SD, 2.3; median, 3; range, 0
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FIGURE. Mean SF-36 subscale scores of patients with low vision compared with published48,53 mean scores of the United States normal population 75 years of age and older, patients with congestive heart failure, and patients with clinical depression. Although patients with low vision scored significantly (P < .001) better than the three populations in bodily pain (BP), vitality (V), and social functioning (SF), they scored significantly (P < .001) worse than the three populations in physical functioning (PF), role limitations caused by physical health problems (RP), and role limitations caused by emotional problems (RE). GH ⴝ general health; MH ⴝ mental health.
activities (38.3 to 41.1, P ⫽ .001), and peripheral vision (37.9 to 42.6, P ⬍ .001).
to 9). Twenty-one patients (13.5%) received only a change in spectacle prescription. There was no change in the mean comorbidity score after the Low-Vision Clinic visit (P ⫽ .895). The subjective responses concerning the value of lowvision services provided are shown in Table 3. Low-vision services improved the subjective functional status of 150 patients (98.7%). The services were rated “very useful” by 82 patients (53.9%) and more helpful than expected by 67 patients (44.1%). The Figure displays mean SF-36 subscale scores of low-vision patients compared with published48,53 mean scores of the United States normal population aged 75 years or more, patients with congestive heart failure, and patients with clinical depression. Summary statistics for the questionnaires administered are listed in Table 4. None of the subscales of the SF-36 changed significantly after low-vision services were provided. The VF-14 score improved from 35.8 to 41.2 (P ⬍ .001). The NEI-VFQ subscale scores associated with statistically significant improvement after the provision of low-vision services were general vision (42.8 to 46.1, P ⬍ .001), near activities (38.0 to 46.3, P ⬍ .001), distance 58
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DISCUSSION THE SCORES ON THE SF-36, VF-14, AND NEI-VFQ DEMON-
strate that Low-Vision Clinic patients perceived that their functional status and quality of life were markedly impaired. The Figure demonstrates that although low-vision patients scored significantly (P ⬍ .001) better than the three comparison populations in bodily pain, vitality, and social functioning, they scored significantly (P ⬍ .001) worse than the three comparison populations in physical functioning, role limitations caused by physical health problems, and role limitations caused by emotional problems. The marked impairment in perceived functional status and quality of life among Low-Vision Clinic patients is consistent with a recent study that reported that having blurred vision more than once or twice a month has a significant impact on functional status and well-being (as measured by SF-36 scores), especially in role limitations OF
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TABLE 4. Summary Statistics for SF-36, VF-14, and NEI-VFQ Questionnaires
Questionnaire Scale
N
Mean (SD) Score Before LVC
Mean (SD) Score After LVC
Difference (SD)
P Value
SF-36 PF SF-36 RP SF-36 BP SF-36 GH SF-36 V SF-36 SF SF-36 RE SF-36 MH VF-14 NEI-VFQ GH NEI-VFQ GV NEI-VFQ VP NEI-VFQ NA NEI-VFQ DA NEI-VFQ VSSF NEI-VFQ VSMH NEI-VFQ VSE NEI-VFQ VSRD NEI-VFQ VSD NEI-VFQ D NEI-VFQ CV NEI-VFQ PV
156 156 156 156 156 156 156 156 156 156 156 156 151 153 129 156 153 156 156 13 152 153
35.0 (31.5) 5.0 (20.2) 84.6 (15.3) 52.0 (9.1) 64.7 (8.1) 86.9 (15.6) 5.6 (22.0) 76.9 (6.1) 35.8 (13.1) 53.2 (10.3) 42.8 (10.7) 97.3 (8.3) 38.0 (14.5) 38.3 (13.6) 62.9 (23.8) 65.9 (10.0) 42.7 (6.0) 47.9 (16.2) 54.0 (17.0) 34.1 (19.1) 60.2 (24.0) 37.9 (14.9)
36.4 (30.7) 4.2 (18.6) 86.2 (14.8) 51.3 (7.8) 64.4 (7.6) 87.3 (14.7) 4.7 (19.5) 77.5 (6.0) 41.2 (12.6) 52.6 (8.9) 46.1 (9.5) 97.0 (7.9) 46.3 (13.8) 41.1 (12.6) 61.7 (22.1) 66.4 (7.5) 42.5 (5.9) 48.4 (13.8) 54.7 (18.5) 37.9 (16.3) 59.9 (21.0) 42.6 (13.7)
1.4 (21.3) ⫺0.8 (18.3) 1.5 (12.2) ⫺0.7 (8.0) ⫺0.4 (7.7) 0.4 (12.5) ⫺0.9 (20.7) 0.6 (6.5) 5.4 (11.1) ⫺0.6 (7.1) 3.4 (9.0) ⫺0.2 (4.8) 8.3 (11.8) 2.8 (10.5) ⫺1.2 (19.7) 0.5 (9.4) ⫺0.2 (7.0) 0.5 (14.9) 0.7 (16.5) 3.8 (12.1) ⫺0.3 (18.9) 4.7 (15.1)
.400 .585 .118 .271 .569 .689 .607 .263 ⬍.001 .287 ⬍.001 .533 ⬍.001 .001 .480 .492 .667 .683 .577 .275 .830 ⬍.001
LVC ⫽ Low-Vision Clinic visit; NEI-VFQ ⫽ Field Test Version of the National Eye Institute Visual Functioning Questionnaire; SF-36 ⫽ Medical Outcomes Study 36-Item Short Form; VF-14 ⫽ Visual Function 14. For SF-36: BP ⫽ bodily pain; GH ⫽ general health; MH ⫽ mental health; PF ⫽ physical functioning; RE ⫽ role emotional; RP ⫽ role physical; SF ⫽ social functioning; V ⫽ vitality. For NEI-VFQ: CV ⫽ color vision; D ⫽ driving; DA ⫽ distance activities; GH ⫽ general health; GV ⫽ general vision; NA ⫽ near activities; PV ⫽ peripheral vision; VP ⫽ visual pain; VSD ⫽ vision-specific dependency; VSE ⫽ vision-specific expectations; VSMH ⫽ vision-specific mental health; VSRD ⫽ vision-specific role difficulties; VSSF ⫽ vision-specific social functioning.
caused by physical health problems.64 Given the growing number of sight-impaired individuals, low vision is a major public health issue. The use of and access to low-vision services appears to be limited. A recent national survey conducted by The Lighthouse determined that more than half of all middle-aged and elderly Americans have been affected by either their own visual impairment or that of a close relative, friend, or neighbor, yet 43% were unaware of low-vision services in their community.65 In a Canadian survey of visually impaired noninstitutionalized persons older than 65 years, 55% had not received aid from any low-vision service.66 In Great Britain, only 50% of elderly patients with low vision who had attended a general ophthalmology clinic had received formal low-vision assessments, and only 3% had used a large-print book.24 In the current study, low-vision services are associated with statistically significant improvements in the scores of the VF-14 and of four subscales of the NEI-VFQ. Thus, it appears that vision-targeted health status questionnaires are more sensitive than general health-related quality of life questionnaires to differences in functional status and VOL. 128, NO. 1
quality of life before and after the provision of low-vision services. This finding is consistent with previous studies demonstrating that the VF-14 is more responsive than general health status measures to change in functional impairment related to vision among cataract patients55,67,68 and with studies reporting that scores of the VF-14 and NEI-VFQ correlated more strongly with visual field impairment than did SF-36 scores.57–59 Despite the high rate of patient satisfaction and the highly statistically significant questionnaire score improvements (P ⬍ .001), the absolute increases in questionnaire scores may be considered modest, with improvements ranging from 2.8 units on the NEI-VFQ distance activities subscale to 8.3 units on the NEI-VFQ near activities subscale. These questionnaires, however, were not designed specifically for a low-vision population. The VF-14, for instance, was designed for patients with cataract, and several of the 14 activities included in this questionnaire, such as doing fine handiwork, daytime driving, and nighttime driving, may not be expected to improve as a result of low-vision services. In addition, it is important to empha-
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2. Dowie AT. Management and practice of low visual acuity. London: The Eastern Press, 1988. 3. Strong JG, Pace RJ, Plotkin AD. Low vision services: a model for sequential intervention and rehabilitation. Can J Public Health 1988;79:50 –54. 4. Nelson K, Dimitrova G. Statistical brief #36: “severe visual impairment” in the U.S. and the states. J Vis Impair Blindness 1993;87:80 – 85. 5. Kirchner C. Data on blindness and visual impairment in the US: a resource manual on characteristics, education, employment, and service delivery. New York: American Foundation for the Blind, 1985. 6. 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. 7. National Advisory Eye Council. Vision research: a national plan 1994 –1998. Bethesda: National Eye Institute, National Institutes of Health, 1993:305–321. 8. LaPlante MP. Prevalence of conditions causing need for assistance in activities of daily living. In: Data on disability from the National Health Interview Survey, 1983–1985: info use report. Washington, DC: National Institute on Disability and Rehabilitation Research, 1988. 9. Massof RW, Dagnelie G, Deremeik JT, DeRose JL, Alibhai SS, Glasner NM. Low vision rehabilitation in the U.S. health care system. J Vision Rehabil 1995;9:3–31. 10. Faye EE, editor. Clinical low vision, 2nd ed. Boston: Little, Brown & Company, 1984:171–212. 11. National Society to Prevent Blindness. Data analysis, vision problems in the United States. New York: National Society to Prevent Blindness, 1980:5, 19. 12. Faye EE. A functional classification of eye diseases. In: Faye EE, editor. Clinical low vision. Boston: Little, Brown & Company, 1976:203–231. 13. Nilsson U. Visual rehabilitation of patients with and without educational training in the use of optical aids and residual vision: a prospective study of patients with advanced agerelated macular degeneration. Clin Vis Sci 1990;6:3–10. 14. Nilsson UL, Nilsson SEG. Rehabilitation of the visually handicapped with advanced macular degeneration. Doc Ophthalmol 1986;62:345–367. 15. Sloan LL. Reading aids for the partially-sighted: factors which determine success or failure. Arch Ophthalmol 1968; 80:35–38. 16. Rosenberg R, Faye E, Fischer M, Budicks D. Role of prism relocation in improving visual performance of patients with macular dysfunction. Optom Vis Sci 1989;66:747–750. 17. McIlwaine GG, Bell JA, Dutton GN. Low vision aids: is our service cost effective? Eye 1991;5:607– 611. 18. Robbins HG, McMurray NE. Psychological and visual factors in low vision rehabilitation of patients with age related maculopathy. J Vis Rehabil 1988;2:11–21. 19. Hall A, Sacks SZ, Dornbusch H, et al. A preliminary study to evaluate patient services in a low vision clinic. J Vis Rehabil 1987;1:7–25. 20. Humphrey RC, Thompson GM. Low vision aids: evaluation in a general eye department. Trans Ophthalmol Soc U K 1986;105:296 –303. 21. Davis C, Lovie-Kitchin J, Thompson B. Psychosocial adjustment to age-related macular degeneration. J Vis Impair Blindness 1995;89:16 –27. 22. Leat SJ, Fryer A, Rumney NJ. Outcome of low vision aid provision: the effectiveness of a low vision clinic. Optom Vis Sci 1994;71:199 –206. 23. Watson GR, Beck S, De l’Aune W, et al. A national survey of the impact of low vision prosthetic device use among veterans [abstract]. Optom Vis Sci 1994;71(suppl):20.
size that a limitation of the current study is that the impact of only a single low-vision clinic visit was evaluated; studies have suggested the importance of follow-up lowvision services and training.69 –71 Furthermore, because vision is critical to so many aspects of daily function, even a modest increase in visual performance may translate into large increases in patient satisfaction. The significant improvement in the NEI-VFQ peripheral vision subscale may, at first glance, be counterintuitive because the magnifiers, microscopes, and telescopes frequently provided through low-vision services may be associated with a decreased field of view. Although the significance of the NEI-VFQ peripheral vision subscale could represent a spurious finding, the perceived improvement in peripheral vision may be caused by improved overall vision (for example, resulting from a change in spectacle prescription, which was performed in 47.1% of patients) or the eccentric viewing training often provided during the Low-Vision Clinic visit. That we did not document which patients received eccentric viewing training is a limitation of the current study and could be a useful variable to consider in future studies. Twenty-one patients (13.5%) in the study were treated with only a change in spectacle prescription. Although we can only speculate as to why the prescription was not changed by the patients’ primary eye care providers— objective visual acuity measurements with refraction may not have significantly improved; Low-Vision Clinic personnel may have been more experienced in performing refraction in low-vision patients; Low-Vision Clinic personnel may have had more time to perform refraction; primary care providers’ offices may not have had equipment such as a Feinbloom chart or 1-diopter Jackson cross cylinder—it appears that refraction is an important component of the Low-Vision Clinic evaluation and that patients frequently benefited from a change in spectacle prescription. The findings of the current study indicate that lowvision patients perceive that their functional status and quality of life are markedly impaired. Vision-targeted health status questionnaires may be useful in tandem with the clinical examination to fully understand the outcomes of low-vision services. Questionnaires that provide evidence that low-vision services are associated with increased functional status and quality of life may increase public awareness of the potential benefits of low-vision services and may encourage Medicare and managed care plans to pay for such services. We hope that confirmation of the measured improvements in visual function will lead to greater access to low-vision services.
REFERENCES 1. Mehr EB. Low vision care. Chicago: Professional Press, 1975:254.
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24. Elliott AJ. Poor vision and the elderly: a domiciliary study. Eye 1989;3:365–369. 25. Temel A. Low vision aids (evaluation of 195 patients). Ophthalmic Physiol Opt 1989;9:327–331. 26. Nilsson UL. Visual rehabilitation of patients with advanced diabetic retinopathy: a follow-up study at the Low Vision Clinic, Department of Ophthalmology, University of Linkoping. Doc Ophthalmol 1986;62:369 –382. 27. Watson GR, De l’Aune W, Stelmack J, Maino J, Long S. National survey of the impact of low vision device use among veterans. Optom Vis Sci 1998;74:249 –259. 28. Watson GR, De l’Aune W, Long S, Maino J, Stelmack J. Veterans’ use of low vision devices for reading. Optom Vis Sci 1997;74:260 –265. 29. Raasch TW, Leat SJ, Kleinstein RN, Bullimore MA, Cutter GR. Evaluating the value of low-vision services. J Am Optom Assoc 1997;68:287–295. 30. Ware JE, Sherbourne CD. The MOS 36-Item Short-Form Health Survey (SF-36), I: conceptual framework and item selection. Med Care 1992;30:473-483. 31. McHorney CA, Ware JE, Raczek AE. The MOS 36-Item Short Form Health Survey (SF-36), II: psychometric and clinical tests of validity in measuring physical and mental health constructs. Med Care 1993;31:247–263. 32. Hays RD, Sherbourne CD, Mazel RM. The RAND 36-Item Health Survey 1.0. Health Econ 1993;2:217–227. 33. Ware JE Jr, Snow KK, Kosiniski M, et al. SF-36 health survey manual and interpretation guide. Boston: The Health Institute, New England Medical Center, 1993. 34. Ware JE Jr, Snow KK, Kosinski M, et al. SF-36 health survey manual and interpretation guide. Chapters 7 and 9. Boston: The Health Institute, New England Medical Center, 1993. 35. McHorney CA, Ware JE Jr. Construction and validation of an alternate form general mental health scale for the MOS SF-36 Health Survey. Med Care 1995;33:15–28. 36. McHorney CA, Kosinski M, Ware JE Jr. Comparisons of the costs and quality of norms collected by mail versus telephone interview: results from a national survey. Med Care 1994;32: 551–567. 37. McHorney CA, Ware JE Jr, Lu JFR, Sherbourne CD. The MOS 36-Item Short-Form Health Survey (SF-36), III: tests of data quality, scaling assumptions, and reliability across diverse patient groups. Med Care 1994;32:40 – 66. 38. Garratt AM, Ruta DA, Abdalla MI, et al. The SF-36 health profile: an outcome measure suitable for routine use within the NHS? Br Med J 1993;306:1440 –1444. 39. Jenkinson C, Coulter A, Wright L. The Short Form 36 (SF-36) Health Survey Questionnaire: normative data for adults of working age. Br Med J 1993;306:1437–1440. 40. Brazier JE, Harper R, Jones NMB, et al. Validating the SF-36 Health Survey Questionnaire: new outcome measure for primary care. Br Med J 1992;305:160 –164. 41. Kantz ME, Harris WJ, Levitsky K, et al. Methods for assessing condition-specific and generic functional status outcomes after total knee replacement. Med Care 1992;30(suppl): MS240 –MS252. 42. Kurtin PS, Davies AR, Meyer KB, et al. Patient-based health status measures in outpatient dialysis: early experiences in developing an outcomes assessment program. Med Care 1992;30(suppl):MS136 –MS149. 43. Nerenz DR, Repasky DP, Whitehouse FW, Kahkonen DM. Ongoing assessment of health status in patients with diabetes mellitus. Med Care 1992;30(suppl):MS112–MS124. 44. Wachtel T, Piette J, Mor V, et al. Quality of life in persons with human immunodeficiency virus infection: measurement by the Medical Outcomes Study instrument. Ann Intern Med 1992;116:129 –137.
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45. Cleary PD, Epstein AM, Oster G, et al. Health-related quality of life among patients undergoing percutaneous transluminal coronary angioplasty. Med Care 1991;29:939 – 950. 46. Wu AW, Rubin HR, Mathews WC, et al. A health status questionnaire using 30 items from the Medical Outcomes Study: preliminary validation in persons with HIV infection. Med Care 1991;29:786 –798. 47. Gelberg L, Linn LS. Psychological distress among homeless adults. J Nerv Ment Dis 1989;177:291–295. 48. Stewart AL, Greenfield S, Hays RD, et al. Functional status and well-being of patients with chronic conditions: results from the Medical Outcomes Study. JAMA 1989;262:907– 913. 49. Stewart AL, Hays RD, Ware JE Jr. The MOS Short-Form General Health Survey: reliability and validity in a patient population. Med Care 1988;26:724 –735. 50. Ware JE Jr, Snow KK, Kosinski M, et al. SF-36 health survey manual and interpretation guide. Boston: The Health Institute, New England Medical Center, 1993:1–7, 14 –21. 51. Wetzler HP, Radosevich DM. Health status questionnaire (SF-36) technical report. InterStudy 1992. 52. Thalji L, Haggerty CC, Rubin R, et al. 1990 national survey of functional health status: final report. Chicago: National Opinion Research Center, 1991. 53. Ware JE Jr, Snow KK, Kosiniski M, et al. SF-36 health survey manual and interpretation guide. Boston: The Health Institute, New England Medical Center, 1993:1–38. 54. Mangione CM, Phillips RS, Lawrence MG, Seddon JM, Orav EJ, Goldman L. Improved visual function and attenuation of declines in health-related quality of life after cataract extraction. Arch Ophthalmol 1994;112:1419 –1425. 55. Steinberg EP, Tielsch JM, Schein OD, et al. The VF-14: an index of functional impairment in patients with cataract. Arch Ophthalmol 1994;112:195–203. 56. Bergner M, Bobbitt RA, Kressel S, et al. The Sickness Impact Profile: conceptual and methodology for the development of a health status measure. Int J Health Serv 1976;6:393– 415. 57. Parrish RK II, Gedde SJ, Scott IU, et al. Visual function and quality of life among patients with glaucoma. Arch Ophthalmol 1997;115:1447–1455. 58. Gutierrez P, Wilson MR, Johnson C, et al. Influence of glaucomatous visual field loss on health-related quality of life. Arch Ophthalmol 1997;115:777–784. 59. Parrish RK II. Visual impairment, visual functioning, and quality of life assessments in patients with glaucoma. Trans Am Ophthalmol Soc 1996;94:919 –1028. 60. Mangione CM, Berry S, Spritzer K, et al. Identifying the content area for the 51-item National Eye Institute Visual Function Questionnaire: results from focus groups with visually impaired persons. Arch Ophthalmol 1998;116: 227–233. 61. Scott IU, Schein OD, Bandeen-Roche K, et al. Functional status and quality of life measurement among ophthalmic patients. Arch Ophthalmol 1994;112:329 –335. 62. Tielsch JM, Sommer A, Witte K, Katz J, Royall RM, the Baltimore Eye Survey Research Group. Blindness and visual impairment in an American urban population: the Baltimore Eye Survey. Arch Ophthalmol 1990;108:286 –290. 63. Attebo K, Mitchell P, Smith W. Visual acuity and the causes of visual loss in Australia. Ophthalmology 1996;103:357– 364. 64. Lee PP, Spritzer K, Hays RD. The impact of blurred vision on functioning and well-being. Ophthalmology 1997;104:390 – 396. 65. The Lighthouse. The Lighthouse national survey on vision loss: the experience, attitudes and knowledge of middle-aged
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61
of generic versus disease-specific measures of functional impairment in patients with cataract. Med Care 1995;33(4, suppl):AS120 –AS130. 69. Jackson AJ, Silver JS, Archer DB. An evaluation of follow-up systems in two low vision clinics in the UK. In: Woo GC, editor. Low vision: principles and applications. Berlin, Springer-Verlag, 1986:396 – 417. 70. Giltrow-Tyler JF. The Bristol low vision project: a multidisciplinary approach. Optom Today 1988;28:352–354. 71. Stoll S, Sarma S, Hoeft WW. Low vision aids training in the home. J Am Optom Assoc 1995;66:32–38.
and older Americans. New York: The Lighthouse, Inc, Louis Harris and Associates, Inc, 1994:17. 66. Gresset J, Baumgarten M. A survey of the utilisation of rehabilitation services by the visually impaired elderly population. In: Kooijman AC, editor. Low vision, research and new developments in rehabilitation. Amsterdam: IOS Press, 1994:481– 484. 67. Desai P, Reidy A, Minassian DC, Vafidis G, Bolger J. Gains from cataract surgery: visual function and quality of life. Br J Ophthalmol 1996;80:868 – 873. 68. Damiano AM, Steinberg EP, Cassard SD, et al. Comparison
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