Quality of vision is an integral part of quality of life. Visual impairment causes difficulties with everyday living, hampering activities previously taken for granted such as dressing, eating, writing, traveling from place to place, and simple communications or interacting with others. Low-vision services enable people who are visually impaired to use adaptive devices and techniques to independently perform daily activities. Studies measuring the direct effect of low-vision intervention frequently concentrate on measures of task performance such as visual acuity change, magnification prescribed, or reading speed obtained as part of the process of evaluating, training, and prescribing for individual patients. Recent literature reviews 1 have been critical of this approach. Although these measures are important, if used alone, they may not be a successful indicator of the overall impact of low-vision intervention. This is because demonstrated ability may not be important to the individual or address the individual’s specific needs or lifestyle. This paper provides a general overview of quality-of-life instruments and their use in vision disorders. Studies on self-reported quality of life of adults with low vision are reviewed to answer two questions. First, does low vision affect quality of life? Second, does quality of life improve after low-vision intervention? Studies reported from 1990 to 2000 are reviewed.
WHAT IS QUALITY OF LIFE?
Quality of life has had different meanings over the centuries. 2 During the Great Depression, quality of life was often measured in terms of the necessities of food, clothing, and shelter. As the economy grew strong and basic needs were met, quality of life expanded to include the “American dream,” pursuit of happiness, and a general sense of well-being. Most recently, quality of life is often used in discussions of health care and is referred to as “health-related quality of life.”3 Because many definitions exist for this widely used term, it is not surprising that researchers and practitioners have differing views of the meaning of quality of life and which aspects of daily living should be considered in measuring quality of life. There is a tendency to confuse functional status measurements with quality-of-life scales. Functional status measures include the familiar activities of daily living scales that are often brief questionnaires covering commonly required activities (e.g., climbing stairs). The current approach, reported by Aaronson, 4 is to view quality of life as multidimensional by including physical (disease symptoms and their treatment), functional (self care, mobility, activity level, and activities of daily living), social dimensions (social contact and interpersonal relationships), and psychological dimensions (cognitive function, emotional status, well-being, life satisfaction, and happiness).
Although many clinicians make medical management decisions based on patient quality of life, practitioners and patients often rate quality of life after treatment differently. 2, 5–7 Patient self-ratings 8 may stress social, emotional, and psychological aspects of health, whereas physicians may emphasize physical and functional aspects. Surveys completed by caregivers may 9 or may not correlate well with those completed by their patients. Consequently, it has been established 10–12 that obtaining the patient’s point of view is of prime importance when evaluating medical care outcomes.
MEASUREMENT OF HEALTH-RELATED QUALITY OF LIFE
The literature on quality-of-life measurement includes both general health measures and disease-specific measures. General health status measures2 such as the Sickness Impact Profile (SIP) 13 and the Medical Outcomes SF-36 14 address different populations and cover many health issues. These are generic in determining the effects of various diseases on different aspects of quality of life. Their power to measure changes in quality of life of patients with specific problems is limited. 15 Included in general instruments are health profiles, health indices, and utility measures. Health profiles incorporate a number of different dimensions and produce a measure for each dimension (e.g., social interaction, mobility, travel, or cognition). The Sickness Impact Profile is an example of a health profile. Health indices bring the various dimensions together, representing health status as a single point on an index. A utility concept is used in some health indices to measure the value of a health state. Time trade-off and the standard gamble methods are techniques that are frequently used to measure utilities. In utility analysis, health states are given a single value on an interval scale. As an example, death equals zero, and the state of complete wellness equals one. When combined with data demonstrating the years of life gained by various health interventions, the utility values enable the calculation of the number of quality-adjusted life-years gained from treatment.
Disease-specific instruments2 measure quality of life relative to specific diseases and their treatment. Patrick and Deyo 15 report on scales that have been developed for arthritis, back pain, cancer, chronic lung disease, diabetes, digestive diseases, heart, neurological-head injury, and multiple sclerosis. These scales have been reported to be useful measures in relation to each condition alone, but are incapable of comparing the effects of different diseases. 15 Scale batteries2 are a series of separate scales each focusing on a different parameter that collectively result in a useful measure. Scale batteries are used to measure quality of life components such as cognitive functioning, depression, activities of daily living, or social functioning. Their value lies in the ability to assess selected parameters in depth. However, results may not be comparable across studies. 16
Both generic and disease-specific measures are often included in the same investigation. Patrick and Deyo 15 noted that a disease-specific measure should be responsive to changes in vision and that a more generic measure should be used for comparison with other conditions and populations. As an example, the author suggests that the National Eye Institute Visual Function Questionnaire (NEI-VFQ)-25, a vision questionnaire with scale battery, could be combined with SF-36, a general health status questionnaire. This combination of instruments facilitates comparison of the impact of vision disorders to systemic disorders. A standardized generic measure2, such as the SF-36, facilitates cross-study comparisons. Some subscales also may be substituted for full-length questionnaires because selected subscales have been shown to demonstrate association between vision and functional status and quality of life. 17
DEVELOPMENT OF INSTRUMENTS TO MEASURE VISION-SPECIFIC QUALITY OF LIFE
In 1988, the National Eye Institute sponsored a workshop 18 on “Measuring the Quality of Life of People with Visual Impairment.” The workshop was based on recognition from the scientific and medical community that the most meaningful outcome of a clinical trial may be the patient’s own perception of changes in his or her well-being. These changes may be just as important as traditional outcome measures such as changes in clinical manifestations and increased longevity. Quality-of-life measures can be used to compare treatments within a trial or to relate to data on other healthcare interventions where common measurement and comparability are the main requirements. Additional information is also provided for clinical diagnosis and to assist in individual patient assessment and management.
The need to develop instruments to measure both general and specific visual disorders is recognized by the scientific community. Although scores of general health-related quality-of-life questionnaires and their subscales independently predict visual acuity, 17 they are not sensitive to severity of impairment in ocular diseases such as age-related macular degeneration (AMD) 19 and glaucoma 20 or changes in functional status after low-vision services. 21 Vision-specific measures including the VF-14 22 and NEI-VFQ 20,21,23 are more sensitive to decreased functional status secondary to vision loss than the general health-related quality-of-life measures such as the SF-36 and SIP.
One practical approach to outcomes measurement is to modify existing instruments. 18 By changing directions, expanding content, or eliminating questions that are irrelevant to the populations being studied, sensitivity of questionnaires can be improved. Gresset et al. 24 use this approach to modify the VF-14 by eliminating the questions on driving and adding additional questions on the use of prosthetic low-vision devices. This approach is also used by the Blind Rehabilitation Service, Department of Veterans Affairs. 25,26 De l’Aune et al. 25,26 build on studies previously done in the 1980s to assess changes in performance of 57 functional items on a two-dimensional scale including ratings of independence and difficulty 27 as well as studies to modify the Functional Independence Measure (FIM) 28 used to assess persons with physical impairments for use with individuals with visual impairment. 29,30 The resulting instrument, Functional Independence Measure for Blind Adults (FIMBA), 31 went through additional modifications by teams of investigators. In 1996, a Veterans Affairs (VA) Blind Rehabilitation Task Group on Outcomes developed the Blind Rehabilitation Service Function Outcomes Survey (BRSFOutSur) to be used with a Blind Rehabilitation Service Satisfaction Survey (BRSSatSur) and a Blind Rehabilitation Service Database (BRDDBase). The BRSFOutSur, assesses self report of behavior and tasks linked to blind rehabilitation skill courses taught to veterans regaining their independence. Items targeted are from classes in Visual Skills, Orientation and Mobility, Manual Skills, and Living Skills. The research plan is to assess >3600 visually impaired veterans from VA Blind Rehabilitation programs and as may as 3000 nonveterans from non-VA blind rehabilitation programs taking part in the study.
Vision-specific quality-of-life measures may also be developed through well-established methods. 13–15,32 The Vision Quality of Life Instrument 32 is a good example of a questionnaire that was developed according to this format. The first step is to identify relevant quality-of-life issues. This is usually done through in-depth interviews with patients with vision loss or focus groups to assess their functional problems. Expert service providers are also interviewed, and literature searches are performed. Issues are then converted to individual questions, called items. Questions may have yes or no responses, a level of agreement (e.g., strongly agree, agree, and don’t agree), a numerical rating on a scale (e.g., rate 1 to 10), or include a rating of difficulty (e.g., very difficult, difficult, and not difficult). 33 Short versions of the questionnaire with different layouts and phasing are tested. Pretesting the questionnaire on individuals with varying levels of vision loss, different social and educational backgrounds, a specific vision disorder, or a group of pathologies is then followed by large-scale field testing. Some items from the pool are eliminated for various reasons such as being irrelevant to a significant percentage of patients, repetitive, annoying, or confusing. The items retained should be useful for discriminating among patients with mild to severe impairment. These items are usually grouped into subscales based on face validity to maintain internal consistency. A numerical rating is given based on the rank of the response. Summary scores referred to as “raw scores” are developed for each subscale by summing or averaging item scores. 14 Then, they are used in statistical analysis to determine the validity and reliability of the instrument. 13 The scales vary quite a bit from instrument to instrument, although similar items are found.
Reliability refers to the instrument’s capacity to provide reproducible measurements. Internal consistency indicates how strongly the items are related to each other or whether the items measure a single characteristic. The test most frequently used is Cronbach’s alpha. The ability to provide the same measurement on different occasions is called test–retest reliability. Because it is difficult to administer the same instrument multiple times to the same person, internal consistency is sometimes used as an estimate of test–retest reliability
Validity tells us how well the instrument measures what it is intended to measure. Content validity 34 is the degree to which items are representative of the information being tested. Criterion validity 34 determines how well the measurement predicts the characteristics associated with the measure. Validity is often established by comparison to a gold standard. Construct validity 34 indirectly demonstrates that the measure is related to similar measures of the same characteristic and is not related to other characteristics. Using several instruments in the same group and investigating patterns of relationships among measures usually establishes this.
A gold standard does not exist for comparison of the vision-specific quality-of-life measures. Thus, comparison to visual impairment measures such as visual acuity or other general, well-established health-related quality-of-life measures such as the SIP and SF-36 is often made. Content validity is most often established through use of expert panels of service providers as well as a literature search.
In a critical review of the validity and reliability of vision function questionnaires, Massof and Rubin 33 report that the statistical procedures used and the amount of validation varies among the vision-specific quality-of-life instruments. Most validation studies report high response consistency across items and significant correlations of instrument score with visual impairment measures, whereas test–retest reliability is infrequently reported. According to Massof and Rubin, measurement properties of instruments must be considered. Most of the assessment instruments for visual function yield ordinal ratings of difficulty of task performance. Although we do not know the actual value of each category, rating categories are often given numerical ratings that are averaged. Some investigators convert scores to interval scales through statistical procedures such as Rasch analysis. In the opinion of these investigators, this conversion produces more accurate interpretation of rating categories and facilitates calibration of different instruments to a common scale.
Early disease-specific quality-of-life measures for assessment of visual function that include the Visual Function Index, 35 the VF-14, 22 and Activities of Daily Vision Scale (ADVIS) 36 were developed as indices of functional impairment in patients with cataracts. ADVIS is divided into subscales including night driving, day driving, far vision, near vision, and glare disability; whereas the VF-14 is a list of fourteen activities. The activities included on the VF-14 are as follows 33 :
- 1. Read small print, such as labels on medicine bottles, a telephone book, or food labels.
- 2. Reading a newspaper or book.
- 3. Reading a large-print book or newspaper or the numbers on a telephone.
- 4. Recognizing people when they are close to you.
- 5. Seeing steps, stairs, or curbs.
- 6. Reading traffic, street, or store signs.
- 7. Doing fine handwork such as sewing, knitting, crocheting, or carpentry.
- 8. Writing checks or filling out forms.
- 9. Playing games such as bingo, dominos, card games, or mahjong.
- 10. Taking part in sports such as bowling, handball, tennis, or golf.
- 11. Cooking.
- 12. Watching television.
- 13. Daytime driving.
- 14. Nighttime driving.
SIP-v, a vision-related version of the general health status measure SIP, has also been used as an index of visual function in patients with cataract 37,38 and other eye diseases. 17 Questionnaires measuring vision-specific quality of life including the VCM1 32 and NEI-VFQ 39,40 are intended to be used with patients representing a broad range of diagnoses. Frost et al. 32 developed a large pool of 232 items for a final parent questionnaire of 139 items for the Vision Quality of Life instrument. From this parent questionnaire, ten broadly applicable items referring to physical, social, and psychological issues were selected for a core questionnaire, the VCM1. According to Frost et al., 32 the items measure the degree of dissatisfaction or concern relating to the impairment, but not the cause of the concern.
The 51-Item Field Test Version of the NEI-VFQ 39,40 was developed by Rand Corporation for use in clinical trials to assess patient perception of visual function and the influence of visual disability on health-related quality of life. Mangione et al. 39,40 demonstrated that the instrument detected disability across conditions including cataract, diabetes, glaucoma, macular degeneration, and low vision from any cause. Before test development, 246 patients participated in condition-specific focus groups to determine item content. Although patients mentioned problems unique to their disease, across conditions, the problems reported are similar. 39 Included are reading, driving, general problems with seeing clearly, and mental health complaints caused by poor vision. The three most common components of each problem were difficulty or ease of performance (13%), psychological distress associated with performance of the activity (11%), and complete inability to participate in a visual activity (11%). Subscales for the NEI-VFQ-25, a shortened version of the 51-Item Field Test Version, include the following:
- 1. General health status.
- 2. Difficulty with general vision activities.
- 3. Difficulty with activities at distance.
- 4. Difficulty with activities at near.
- 5. Role difficulty.
- 6. Social functioning.
- 7. Dependency on others.
- 8. Mental health symptoms.
- 9. Driving difficulties.
- 10. Limitations in peripheral vision.
- 11. Color vision and ocular pain.
The NEI-VFQ is of considerable significance bacause the National Eye Institute now requires measures of quality of life as outcome variables in clinical studies that they support. 41
QUALITY OF LIFE OF PERSONS WITH LOW VISION
The author searched Medline and PsychINFO from 1990 to 2000 with the key words of vision or vision disorders, quality of life, and low-vision rehabilitation. Reports of instrument development, clinical trials, or treatments that restore vision, such as cataract surgery, and community-based studies of sensory impairment are excluded. Included are studies on quality of life of adults with low vision and studies on quality of life as an outcome measure in low-vision rehabilitation. Eighteen reports that were identified in the literature review are summarized in Table 1.
Studies of quality of life of persons with low vision report that visual impairment is significantly associated with decreased functional status, decreased self-reported quality of life, 17,19–21,23,42–49,52 and increased emotional distress. 21,42 Low-vision patients scored lower than the age-appropriate United States normal population with congestive heart failure and clinical depression. The scores were lower for physical functioning and role limitations caused by physical as well as emotional health problems. Decreased visual acuity and 17,19,43,44,46,47 visual field loss 23,43,44 are associated with decreased quality of life. When visual acuity loss is permanent, the level of visual acuity rather than the specific disease process was related to mean utility values. 46 The average person with 20/40 vision in the better-seeing eye was willing to trade 2 of every 10 years of life in return for perfect vision, whereas the average person with count fingers vision in the better eye was willing to trade 5 of every remaining 20 years.
Studies report decreased quality of life of persons with glaucoma, 20,23,43–45 age-related macular degeneration, 19,39,40,47,48 and diabetes. 49,50 Studies indicate the functional status of patients with open-angle glaucoma to be reduced;20,23,43–45 but reduction does not occur at the time of initial diagnosis or as long as vision is intact. 43,51 Decreased visual acuity, visual field loss, and complexity of therapy were correlated to lower health-related quality-of-life scores in glaucoma patients. 44
Patients with AMD were more likely than a national sample of elders to need help with daily activities. 42 Severity of AMD was associated with poorer scores for near-vision activities 47 and driving. 19 Ratings for quality of life and emotional distress were comparable to those reported by people with chronic illnesses. 42 AMD patients, however, show substantial decrease in utility values 48 that are highly dependent on the degree of visual loss in the better-seeing eye. Patients with near normal vision in the better-seeing eye were willing to trade 11% of their remaining lifetime for perfect vision in each eye, whereas those with count fingers to light perception were willing to trade a mean of 60%.
Studies of patients with diabetic retinopathy also indicate utility values to be directly dependent on the visual acuity loss associated with the disease. 50 The length of time the patient has been visually impaired and the number of years of formal education do not affect the utility value. The mean percent remaining years of life patients were willing to trade for perfect vision varied from 15% for those with near normal vision in the better seeing eye to 41% for those with count fingers to hand motion in the better-seeing eye.
Low-vision services are associated with increased self-reported functional status and quality of life. 21,52 Scott et al. 21 demonstrated that low-vision services were associated with improvement in subjective functional status with both the NEI-VFQ 51-Item Test Version and the VF-14. Stelmack et al. 52 evaluated the potential use of the NEI-VFQ-25 to assess the impact of low-vision care on quality of life in a VA blind center. Conclusions were that the NEI-VFQ-25 needs to be modified based on focus groups for more applicable use with an elderly population that is more chronically ill and with permanent vision loss as severe as legal blindness. Problems noted included difficulty with administration because test directions do not include consideration of prosthetic device use, confusion with different interpretations of language, and the activities covered are insufficient to include those important to persons with vision loss that are addressed in rehabilitation programs. With NEI-VFQ-25 directions modified to include use of prosthetic low-vision devices in addition to glasses and contact lenses, Stelmack et al. 53 demonstrated that the NEI-VFQ-25 can be used to compare outcomes of low-vision programs. Targeted activities such as reading ordinary print, small print, and street signs are easier to perform after rehabilitation for graduates of both the VA Blind Rehabilitation Center and VICTORS Low-Vision Rehabilitation Program.
Preliminary analyses of data from the VA National Outcomes Study 26 indicate that the average changes associated with blind rehabilitation programs in both the VA and private sector are positive. The self-perceived level of independence and satisfaction with task performance often showed larger changes than the frequency of accomplishing a specific task. Findings are that 93.7% of veterans and 99% of nonveterans were satisfied or completely satisfied with their blind rehabilitation program.
Recommendations from the NEI Workshop 18 on quality of life were that self-reports of difficulties with everyday life should supplement but not replace objective measures of performance. Functional limitation in the ability to carry out daily activities as a result of visual impairment is one of the most important measures of outcomes because it represents the impact of visual impairment on individuals in their daily lives. Functional limitation can be measured objectively through tests of performance conducted during clinical programs or subjectively through self-reports of community function. When measurements of device use or rehabilitation training are taken under controlled clinical conditions, efficacy is measured. When self-reports are used, effectiveness is measured. Both measures of efficacy and effectiveness are needed to assess outcomes of low-vision service delivery. In addition, patients should be questioned as to how they perform activities. It is important to recognize improvement in quality of life without improvement in performance with low-vision devices and improvement in performance of device use without improvement in quality of life. Reading the newspaper is a good example. Patients may adapt to vision loss through utilization of nonvisual methods to read such as listening to the news on the television or radio. The patient who performs well with low-vision devices for reading may consider the slower reading speed and amount of effort needed to visually read as a minimal improvement in function or quality of life.
The National Eye Institute research priority 54 for visual impairment and its rehabilitation is to determine which low-vision interventions are most effective and to develop research tools so that these interventions can be scientifically evaluated to improve clinical care of the visually impaired population. The difficulty encountered is that few instruments are currently available to measure quality of life as an outcome of low-vision service delivery. Studies previously reported have used the SF-36, NEI-VFQ 51-Item Test Version, the NEI-VFQ-25, and the VF-14 to measure outcomes. The SF-36 scores 21 did not change after low-vision intervention. The NEI-VFQ instrument is not well suited to evaluation of low-vision outcomes as previously described. 52 The VF-14 does not cover the full range of skills taught in vision rehabilitation programs, which limits its usefulness as an outcome measure for low-vision rehabilitation.
Additional instruments are needed. They should be sensitive to changes both short term and long term after low-vision rehabilitation for patients with a continuum of vision loss including both the legally blind and visually impaired. Questionnaires with short administration times and the potential for administration by volunteers or assisted by family members before a low-vision clinic appointment are important in managed care environments. Instruments must be clear and have concise language because previous studies 52 indicate that elderly patients are confused by frequent changes in format and ambiguity in questions. Instruments should be sensitive to skills taught in rehabilitation and contain enough items to assess individual patient needs and progress, techniques, devices, programs, and their relative costs and benefits. Attention must be paid to measurement properties, validity, and reliability.
Caution should be used both in instrument development and selection to preserve the dignity of persons with visual impairment. Patients entering the rehabilitation process need support and encouragement to adjust to vision loss. They often perceive loss of vision secondary only to cancer as the most dreaded consequence of aging. 55 Use of utility assessments questioning how many years of life one would trade for perfect vision may reinforce these fears and negatively impact rehabilitation by implying that life without vision is not worth living. When utility assessments are used, comparison of values for patients with adventitious loss to values for patients with congenital or early onset visual loss would be useful. Persons who are congenitally blind who have learned to successfully function nonvisually may be unwilling to trade any years of life for perfect vision and even find these questions ridiculous or insulting.
The impact of the quality-of-life research reported on low-vision clinical practice should be considered. Self-report questionnaires may be used along with clinical testing in the rehabilitation of individual patients. Information from questionnaires administered before rehabilitation could be used to assess or document patient needs and formulate individualized rehabilitation plans. Questionnaires administered after rehabilitation could provide information to evaluate or document functional improvement and provide the justification for insurance coverage of services. Although some local Medicare carrier policies include use of the NEI-VFQ-25, reports on the usefulness of ADVIS, VF-14, NEI-VFQ-25, SIPV, or BRSFOS questionnaires in the rehabilitation of individual patients or methods of administration in a private practice setting were not found in this literature review. These are topics for further research.
Most visually impaired patients are Medicare beneficiaries. 56 With increased longevity, societal cost is a dominant issue in health care, particularly in view of mounting bills for health care of the elderly and the emergence of managed care. Medicare is under pressure to contain costs, eliminate fraud and abuse, and minimize regional inconsistencies in coverage policies. 56 Evidence for medical effectiveness, medical necessity, and documentation of need and rendering of services is mandated. 56
In November 1999, Congress passed a technical amendment to Section 1833(g) of the Social Security Act (42 U.S.C. 1391(g). Sec. 221 Revision of Provisions relative to therapy services HR3075 57 that has had a major impact on low-vision care. Since this technical amendment, optometrists meet physician supervision requirements for outpatient therapy services. Previously, optometrists were excluded from the list of providers approved to prescribe these services. Persons with low vision (defined as vision impairment not correctable with conventional eyewear) may be covered when in the care of or a treatment plan ordered by a medical doctor, osteopath, or optometrist. The Medicare carriers and the Health Care Financing Administration are designated the responsibility to make coverage decisions. Based on recommendations of professional organizations representing optometry and ophthalmology, it is expected that the codes used for coverage would be limited to 97530, 97535, and 97537.
Coverage for low-vision service is determined locally through the responsibilities and authority of the individual carriers. Thus, medical care coverage policies differ among the carriers. Policy for Medicare Part B for Kansas, Nebraska, and Western Missouri Low-Vision Services 58 uses scores ≤70 on the NEI-VFQ-25 as a criterion of functional visual impairment to qualify patients for low-vision services when the patient has moderate visual impairment (vision <20/60) or if visual efficiency (product of central visual acuity and visual field efficiency in the better eye) is >20%. Other carriers have also proposed this criterion in draft policy. With managed care forcing the collection of outcome data and the significance of quality-of-life issues in low-vision rehabilitation, it is expected that instruments to measure self-reported quality of life will become integrated into clinical practice.
Presented at a meeting of the American Academy of Optometry, Seattle, Washington, December 13, 1999.
Received September 15, 2000; revision received January 5, 2001.
1. Raasch TW, Leat SJ, Kleinstein RN, Bullimore MA, Cutter GR. Evaluating the value of low-vision services. J Am Optom Assoc 1997; 68:287–95.
2. Hoffman LG, Rouse MW, Brin BN. Quality of life
: a review. J Am Optom Assoc 1995; 66:281–9.
3. Padilla GV. Validity of health-related quality of life
subscales. Prog Cardiovasc Nurs 1992; 7:13–20.
4. Aaronson NK. Quality of life
: what is it? How should it be measured? Oncology (Huntingt) 1988; 2:69–76.
5. Orth-Gomer K, Britton M, Rehnqvist N. Quality of care in an outpatient department: patient’s views. Soc Sci Med 1979; 13A:347–50.
6. Thomas MR, Lyttle D. Patient expectations about success of treatment and reported relief from low back pain. J Psychosom Res 1980; 24:297–301.
7. Jachuck SJ, Brierley H, Jachuck S, Willcox PM. The effect of hypotensive drugs on the quality of life
. J R Coll Gen Pract 1982; 32:103–5.
8. Hall JA, Epstein AM, McNeil BJ. Multidimensionality of health status in an elderly population: construct validity of a measurement battery. Med Care 1989; 27:S168–77.
9. Sprangers MA, Aaronson NK. The role of health care providers and significant others in evaluating the quality of life
of patients with chronic disease: a review. J Clin Epidemiol 1992; 45:743–60.
10. Guyatt G, Feeny D, Patrick D. Issues in quality-of-life measurement in clinical trials. Control Clin Trials 1991; 12:81S–90S.
11. Lomas J, Pickard L, Mohide A. Patient versus clinician item generation for quality-of-life measures: the case of language-disabled adults. Med Care 1987; 25:764–9.
12. Elam JT, Graney MJ, Beaver T, el Derwi D, Applegate WB, Miller ST. Comparison of subjective ratings of function with observed functional ability of frail older persons. Am J Public Health 1991; 81:1127–30.
13. Bergner M, Bobbitt RA, Carter WB, Gilson BS. The Sickness Impact Profile: development and final revision of a health status measure. Med Care 1981; 19:787–805.
14. Ware JE, Snow KK, Kosinski M, Gandek B, New England Medical Center. Health Institute SF-36 Health Survey: Manual and Interpretation Guide. Boston: The Health Institute New England Medical Center, 1993.
15. Patrick DL, Deyo RA. Generic and disease-specific measures in assessing health status and quality of life
. Med Care 1989; 27:S217–32.
16. de Haan R, Aaronson N, Limburg M, Hewer RL, van Crevel H. Measuring quality of life
in stroke. Stroke 1993; 24:320–7.
17. Scott IU, Schein OD, West S, Bandeen-Roche K, Enger C, Folstein MF. Functional status and quality of life
measurement among ophthalmic patients. Arch Ophthalmol 1994; 112:329–35.
18. Drummond M. Measuring the Quality of Life
of People with Visual Impairment. Proceedings of a Workshop, October 1–5, 1990. NIH publication No. 90-3078. Bethesda, MD: US Department of Health and Human Services, Public Health Service, National Institute of Health, National Eye Institute, 1990.
19. Mangione CM, Gutierrez PR, Lowe G, Orav EJ, Seddon JM. Influence of age-related maculopathy on visual functioning and health-related quality of life
. Am J Ophthalmol 1999; 128:45–53.
20. Parrish RK, Gedde SJ, Scott IU, Feuer WJ, Schiffman JC, Mangione CM, Montenegro-Piniella A. Visual function and quality of life
among patients with glaucoma. Arch Ophthalmol 1997; 115:1447–55.
21. Scott IU, Smiddy WE, Schiffman J, Feuer WJ, Pappas CJ. Quality of life
of low-vision patients and the impact of low-vision services. Am J Ophthalmol 1999; 128:54–62.
22. Steinberg EP, Tielsch JM, Schein OD, Javitt JC, Sharkey P, Cassard SD, Legro MW, Diener-West M, Bass EB, Damiano AM, Steinwachs DM, Sommer A. The VF-14: an index of functional impairment in patients with cataract. Arch Ophthalmol 1994; 112:630–8.
23. Gutierrez P, Wilson MR, Johnson C, Gordon M, Cioffi GA, Ritch R, Sherwood M, Meng K, Mangione CM. Influence of glaucomatous visual field loss on health-related quality of life
. Arch Ophthalmol 1997; 115:777–84.
24. Gresset J, Durand MJ, Bolduc M. Responsiveness of a modified version of the visual functioning index (VF-12) for visual rehabilitation (VF-12R): preliminary results. In: Stuen C, Arditi A, Horowitz A, et al., eds. Vision Rehabilitation: Assessment, Intervention and Outcomes. Lisse, The Netherlands: Swets & Zeitlinger, 2000: 152–5.
25. De l’Aune WR, Williams MD, Welsh RL. Outcome assessment of the rehabilitation of the visually impaired. J Rehabil Res Dev 1999; 36:273–93.
26. De l’Aune W, Welsh R, Williams M. A national outcomes assessment of the rehabilitation of adults with visual impairments. J Vis Impair Blind 2000; 94:281–91.
27. Granger CJ. A conceptual model for functional assessment. In: Granger CV, Gresham GE, eds. Functional Assessment in Rehabilitation Medicine. Baltimore: Williams & Wilkins, 1984: 20.
28. Crews JE. Strategic planning and independent living for elders who are blind. J Vis Impair Blind 1991; 85:52–7.
29. Long RG, Crews JE. Final report: functional independence measure for blind adults (Project C699-RA). Research and Development Center, VA Medical Center–Atlanta, 1995.
30. Nieuwenhuijsen ER, Frey WD, Crews JE. Measuring small gains using the ICIDH severity of disability scale: assessment practice among older people who are blind. Int Disabil Stud 1991; 13:29–33.
31. Long RG, Crews JE, Mancil R. Creating measures of rehabilitation outcomes for people who are visually impaired: the FIMBA project. J Vis Impair Blind 2000; 94:292–306.
32. Frost NA, Sparrow JM, Durant JS, Donovan JL, Peters TJ, Brookes ST. Development of a questionnaire for measurement of vision-related quality of life
. Ophthalmic Epidemiol 1998; 5:185–210.
33. Massof RW, Rubin GS. Visual function assessment questionnaires. Surv Ophthalmol 2001; 45:531–48.
34. Dawson-Saunders B, Trapp RG. Basic and Clinical Biostatistics, 2nd ed. Norwalk, CT: Appleton & Lange, 1994: 58–9.
35. Bernth-Petersen P. Visual functioning in cataract patients: methods of measuring and results. Acta Ophthalmol (Copenh) 1981; 59:198–205.
36. Mangione CM, Phillips RS, Seddon JM, Lawrence MG, Cook EF, Dailey R, Goldman L. Development of the ‘Activities of Daily Vision Scale’: a measure of visual functional status. Med Care 1992; 30:1111–26.
37. Alonso J, Espallargues M, Andersen TF, Cassard SD, Dunn E, Bernth-Petersen P, Norregaard JC, Black C, Steinberg EP, Anderson GF. International applicability of the VF-14: an index of visual function in patients with cataracts. Ophthalmology 1997; 104:799–807.
38. Desai P, Reidy A, Minassian DC, Vafidis G, Bolger J. Gains from cataract surgery: visual function and quality of life
. Br J Ophthalmol 1996; 80:868–73.
39. Mangione CM, Berry S, Spritzer K, Janz NK, Klein R, Owsley C, Lee PP. 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; 116:227–33.
40. Mangione CM, Lee PP, Pitts J, Gutierrez P, Berry S, Hays RD. Psychometric properties of the National Eye Institute Visual Function Questionnaire (NEI-VFQ). NEI-VFQ Field Test Investigators. Arch Ophthalmol 1998; 116:1496–504.
41. Kupfer C. Outcomes research—translating efficacy into effectiveness. Optom Vis Sci 1998; 75:235–6.
42. Williams RA, Brody BL, Thomas RG, Kaplan RM, Brown SI. The psychosocial impact of macular degeneration. Arch Ophthalmol 1998; 116:514–20.
43. Wandell PE, Lundstrom M, Brorsson B, Aberg H. Quality of life
among patients with glaucoma in Sweden. Acta Ophthalmol Scand 1997; 75:584–8.
44. Sherwood MB, Garcia-Siekavizza A, Meltzer MI, Hebert A, Burns AF, McGorray S. Glaucoma’s impact on quality of life
and its relation to clinical indicators: a pilot study. Ophthalmology 1998; 105:561–6.
45. Wilson MR, Coleman AL, Yu F, Bing EG, Sasaki IF, Berlin K, Winters J, Lai A. Functional status and well-being in patients with glaucoma as measured by the Medical Outcomes Study Short Form-36 questionnaire. Ophthalmology 1998; 105:2112–6.
46. Brown GC. Vision and quality-of-life. Trans Am Ophthalmol Soc 1999; 97:473–511.
47. Hazel CA, Petre KL, Armstrong RA, Benson MT, Frost NA. Visual function and subjective quality of life
compared in subjects with acquired macular disease. Invest Ophthalmol Vis Sci 2000; 41:1309–15.
48. Brown GC, Sharma S, Brown MM, Kistler J. Utility values and age-related macular degeneration. Arch Ophthalmol 2000; 118:47–51.
49. Hanninen J, Takala J, Keinanen-Kiukaanniemi S. Quality of life
in NIDDM patients assessed with the SF-20 questionnaire. Diabetes Res Clin Pract 1998; 42:17–27.
50. Brown MM, Brown GC, Sharma S, Shah G. Utility values and diabetic retinopathy. Am J Ophthalmol 1999; 128:324–30.
51. Mills RP. Correlation of quality of life
with clinical symptoms and signs at the time of glaucoma diagnosis. Trans Am Ophthalmol Soc 1998; 96:753–812.
52. Stelmack J, Szlyk J, Joslin C, Swetland B, Myers L. Pilot study: use of the NEI VFQ-25 to measure outcomes of low vision
rehabilitation services in the Department of Veterans Affairs. In: Stuen C, Arditi A, Horowitz A, et al., eds. Vision Rehabilitation: Assessment, Intervention and Outcomes. Lisse, The Netherlands: Swets & Zeitlinger, 2000: 774–6.
53. Stelmack JA, Massof R, Szlyk J, Wright B, Stelmack TR. A comparison of outcomes in VA blind rehabilitation and VICTORS using the NEI VFQ-25. Optom Vis Sci, 2000; 77(Suppl):241.
54. US Department of Health and Human Services. Vision Research. A National Plan: 1999–2003. NIH Publication No. 98-4120. Bethesda, MD: National Eye Institute, 1998:122.
55. Cogan DG. Summary and conclusions. In: Han SS, Coons DH, eds. Special Senses in Aging: A Current Biological Assessment. Proceedings of the Symposium on Biology of Special Sensed in Aging, at the University of Michigan, Ann Arbor, October 10–11, 1977. Ann Arbor: Institute of Gerontology at the University of Michigan, 1979.
56. Riisager PM. Medicare: Organization and policy making. In: Massof RW, Lidoff L, eds. Issues in Low Vision
Rehabilitation: Service Delivery, Policy, and Funding. New York: AFB Press, 2001: 83–96.
57. American Optometric Association Federal Relations Committee. Low Vision
Rehabilitation Services Under Medicare, Vol 58. Bulletin No. 26. Alexandria, VA: American Optometric Association, 1999.
58. Medicare. Medicare Part B—Kansas/Nebraska/Western Missouri Low Vision
Services. Medical Policy Manual Low Vision