Visual Disability Variables. I: The Importance and Difficulty of Activity Goals for a Sample of Low-Vision Patients


      Massof RW, Hsu CT, Baker FH, Barnett GD, Park WL, Deremeik JT, Rainey C, Epstein C. Visual disability variables. I: The importance and difficulty of activity goals for a sample of low-vision patients.


      To test the validity and reliability of latent trait measures estimated from ratings by low-vision patients of the importance and difficulty of selected activity goals.


      Validation of a telephone-administered functional assessment instrument using Rasch analysis of self-assessment ratings.


      Telephone interviews of respondents in their homes.


      Consecutive series of 600 outpatients with low vision.


      Not applicable.

      Main outcome measures

      Ratings of the importance and difficulty of achieving 41 activity goals. Person and item traits were measured with the Andrich rating scale model. Measurement validity and reliability were tested statistically by comparing response patterns and distributions with measurement model expectations.


      Patients could distinguish only 3 categories of importance and 4 categories of difficulty. The distributions of person and item measure fit statistics were consistent with 2 unidimensional constructs: value of independence estimated from importance ratings and visual ability estimated from difficulty ratings. However, 8 of 41 activity goals were poor estimators of value of independence and 7 of 41 activity goals were poor estimators of visual ability. Person measure distributions could be divided into 3 statistically distinct strata for estimates from both importance ratings and difficulty ratings. Item measure distributions could be divided into 21 strata for estimates from importance ratings and 7 strata for estimates from difficulty ratings.


      The 2 variables that define visual disability—value of independence and visual ability—are valid constructs that can be estimated accurately and reliably from patient ratings of the importance and difficulty of activity goals.

      Key words

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        • Black N.M.
        • Snell A.C.
        • Patton J.
        • Gradle H.S.
        Report of Committee on Compensation for Eye Injuries.
        JAMA. 1925; 85: 113-115
      1. GUIDES to the evaluation of permanent impairment; the visual system.
        J Am Med Assoc. 1958; 168: 475-488
        • American Medical Association
        Committee on Rating of Mental and Physical Impairment. Guides to the evaluation of permanent impairment. AMA Pr, Chicago1971
      2. Houston T.P. Doege T.C. Guides to the evaluation of permanent impairment. 4th ed. AMA Pr, Chicago1993
        • World Health Organization
        International classification of impairments, disabilities, and handicaps. WHO, Geneva1980
        • World Health Organization
        International classification of functioning, disability, and health. WHO, Geneva2001
        • Colenbrander A.
        The visual system.
        in: Cocchiarella L. Andersson B.J. Guides to the evaluation of permanent impairment. 5th ed. AMA Pr, Chicago2000: 277-304
        • Massof R.W.
        • Dagnelie G.
        • Deremeik J.
        • DeRose J.L.
        • Alibhai S.S.
        • Glasner N.M.
        Low vision rehabilitation in the U.S. health care system.
        J Vis Rehabil. 1995; 9: 3-31
        • Colenbrander A.
        Dimensions of visual performance.
        Trans Am Acad Ophthalmol Otolaryngol. 1977; 83: 332-337
        • Kiresuk T.
        • Sherman R.
        Goal attainment scaling.
        Community Ment Health J. 1968; 4: 443-453
        • Ottenbacher K.J.
        • Cusick A.
        Goal attainment scaling as a method of clinical service evaluation.
        Am J Occup Ther. 1990; 44: 519-525
        • Stanley B.
        Evaluation of treatment goals.
        J Adv Nurs. 1984; 9: 351-356
        • Massof R.W.
        • Rubin G.S.
        Visual function assessment questionnaires.
        Surv Ophthalmol. 2001; 45: 531-548
        • Steinberg E.P.
        • Tielsch J.M.
        • Schein O.D.
        • et al.
        The VF-14. An index of functional impairment in patients with cataract.
        Arch Ophthalmol. 1994; 112: 630-638
        • Mangione C.M.
        • Phillips R.S.
        • Seddon J.M.
        • et al.
        Development of the “Activities of Daily Vision Scale”.
        Med Care. 1992; 30: 1111-1126
        • Mangione C.M.
        • Lee P.P.
        • Pitts J.
        • Gutierrez P.
        • Berry S.
        • Hays R.D.
        Psychometric properties of the National Eye Institute Visual Function Questionnaire (NEI-VFQ).
        Arch Ophthalmol. 1998; 116: 1496-1504
        • Massof R.W.
        A systems model for low vision rehabilitation. II. Measurement of vision disabilities.
        Optom Vis Sci. 1998; 75: 349-373
        • Leat S.J.
        • Legge G.E.
        • Bullimore M.A.
        What is low vision? A re-evaluation of definitions.
        Optom Vis Sci. 1999; 76: 198-211
        • Massof R.W.
        A systems model for low vision rehabilitation. I. Basic concepts.
        Optom Vis Sci. 1995; 72: 725-736
        • Committee on Disability Determination for Individuals with Visual Impairments
        Lennie P. Van Hemel S.B. Visual impairments determining eligibility for Social Security benefits. Natl Acad Pr, Washington (DC)2002 (National Research Council)
        • Fisher Jr, W.P.
        • Harvey R.F.
        • Taylor P.
        • Kilgore K.M.
        • Kelly C.K.
        Arch Phys Med Rehabil. 1995; 76: 113-122
        • Massof R.W.
        The measurement of vision disability.
        Optom Vis Sci. 2002; 79: 516-552
        • Massof R.W.
        A model of the prevalence and incidence of low vision and blindness among adults in the U.S.
        Optom Vis Sci. 2002; 79: 31-38
        • Andrich D.
        A rating formulation for ordered response categories.
        Psychometrika. 1978; 43: 561-573
        • Bond T.G.
        • Fox C.M.
        Applying the Rasch model. Erlbaum, London2001
        • Kirby R.L.
        The nature of disability and handicap.
        in: Basmajian J.V. Kirby R.L. Medical rehabilitation. Williams & Wilkins, Baltimore1984: 14-18
        • Linacre J.M.
        • Wright B.
        A user’s guide to Winsteps Rasch model computer program. Mesa Pr, Chicago2001
        • Wright B.
        • Masters G.N.
        Rating scale analysis. Mesa Pr, Chicago1982
        • Smith R.M.
        The distributional properties of Rasch item fit statistics.
        Educ Psychol Meas. 1991; 51: 541-565
        • Linacre J.M.
        Detecting multidimensionality.
        J Outcome Meas. 1998; 2: 266-283
        • Massof R.W.
        • Hsu C.T.
        • Baker F.H.
        • et al.
        Visual disability variables. II: The difficulty of tasks for a sample of low-vision patients.
        Arch Phys Med Rehabil. 2005; 86: 954-967
        • Stensen H.
        • Wilkinson L.
        Factor analysis. SYSTAT 10: statistics I. SPSS, Chicago2000: 327-364
        • Seaberg J.R.
        • Gillespie D.F.
        Goal attainment scaling.
        Soc Work Res Abstr. 1977; 13: 4-9
        • Cytrynbaum S.
        • Ginath Y.
        • Birdwell J.
        • Brandt L.
        Goal attainment scaling.
        Eval Q. 1979; 3: 5-40
        • Sloane M.E.
        • Ball K.
        • Owsley C.
        • Bruni J.R.
        • Roenker D.L.
        The visual activities questionnaire: developing an instrument for assessing problems in everyday visual tasks. Technical digest, noninvasive assessment of the visual system. Optical Society of America, Washington (DC)1992: 26-29
        • Weih L.M.
        • Hassel J.B.
        • Keeffe J.
        Assessment of the impact of vision impairment.
        Invest Ophthalmol Vis Sci. 2002; 43: 927-935