An Interval-Scaled Scoring Algorithm for Visual Function Questionnaires

Purpose. The primary purpose of the study is to present and test a simple algorithm for scoring visual function questionnaires (VFQs) that approximates person measure estimates from Rasch analysis, does not introduce nonlinearities at extreme scores, and is insensitive to missing data. A secondary purpose is to test the hypothesis that all VFQs measure the same visual ability variable and can be calibrated to a common measurement scale. Methods. Each of 407 consecutively recruited low vision patients were administered two of four visual function questionnaires: Activities of Daily Living Scale (ADVS), National Eye Institute Visual Functioning Questionnaire (NEI VFQ), 14-item Visual Functioning Index (VF-14), Visual Activities Questionnaire (VAQ). Separate Rasch analyses, using the Andrich rating scale model, were performed on responses to each of the four VFQs and again on the merged data of all instruments. An approximation of visual ability, based on average functional reserve and an inverse hyperbolic tangent transformation, is presented and tested by comparing visual ability estimates from the Rasch analyses to corresponding estimates from the approximations. Results. Relative to person measure estimates from Rasch analysis, the approximations were observed to be linear and highly reliable (intraclass correlations ranged from 0.97 to 0.997). The measurement scale of each of the four instruments was observed to be a linear transformation of the measurement scale estimated from the merged responses of all four instruments. The approximation algorithm transforms rating scale responses for each instrument to a common measurement scale. By randomly censuring item responses for each subject, it was demonstrated that the approximation algorithm is robust and insensitive to missing data. Conclusions. A simple scoring algorithm based on an inverse hyperbolic tangent transformation of average functional reserve produces highly reliable approximations of visual ability estimated from Rasch analysis for the ADVS, NEI VFQ, VAQ, and VF-14. All four instruments measure the same visual ability variable in units that can be calibrated to a common measurement scale.

[1]  G. D. Barnett,et al.  Visual disability variables. I: the importance and difficulty of activity goals for a sample of low-vision patients. , 2005, Archives of physical medicine and rehabilitation.

[2]  Barnaby C Reeves,et al.  A randomized controlled trial to determine the effectiveness of prism spectacles for patients with age-related macular degeneration. , 2005, Archives of ophthalmology.

[3]  J. Lovie-Kitchin,et al.  The development of the LV Prasad-Functional Vision Questionnaire: a measure of functional vision performance of visually impaired children. , 2003, Investigative ophthalmology & visual science.

[4]  C. Terwee,et al.  Psychometric properties of vision‐related quality of life questionnaires: a systematic review , 2004, Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians.

[5]  R. Massof,et al.  A self-assessment instrument designed for measuring independent mobility in RP patients: generalizability to glaucoma patients. , 2002, Investigative ophthalmology & visual science.

[6]  M. Espallargues,et al.  Content-based interpretation aids for health-related quality of life measures in clinical practice. An example for the visual function index (VF-14) , 2004, Quality of Life Research.

[7]  K. Pesudovs,et al.  Influence of photodynamic therapy for age related macular degeneration upon subjective vision related quality of life , 2006, Graefe's Archive for Clinical and Experimental Ophthalmology.

[8]  D. Andrich.  A rating formulation for ordered response categories , 1978 .

[9]  E. B. Andersen,et al.  A goodness of fit test for the rasch model , 1973 .

[10]  Konrad Pesudovs,et al.  The Quality of Life Impact of Refractive Correction (QIRC) Questionnaire: Development and Validation , 2004, Optometry and vision science : official publication of the American Academy of Optometry.

[11]  R. Massof.  Likert and Guttman scaling of visual function rating scale questionnaires , 2004, Ophthalmic epidemiology.

[12]  K. Pesudovs,et al.  A quality of life comparison of people wearing spectacles or contact lenses or having undergone refractive surgery. , 2006, Journal of refractive surgery.

[13]  B. Wright,et al.  An instrument to measure the activity level of the blind , 1985, International journal of rehabilitation research. Internationale Zeitschrift fur Rehabilitationsforschung. Revue internationale de recherches de readaptation.

[14]  G. D. Barnett,et al.  Visual disability variables. II: The difficulty of tasks for a sample of low-vision patients. , 2005, Archives of physical medicine and rehabilitation.

[15]  C. Velozo,et al.  A Comparison of the Separation Ratio and Coefficient &agr; in the Creation of Minimum Item Sets , 2004, Medical care.

[16]  R. Hays,et al.  Development of the 25-item National Eye Institute Visual Function Questionnaire. , 2001, Archives of ophthalmology.

[17]  David B. Elliott,et al.  The Refractive Status and Vision Profile: Evaluation of psychometric properties and comparison of Rasch and summated Likert-scaling , 2006, Vision Research.

[18]  Robert W Massof,et al.  Use of Rasch person-item map in exploratory data analysis: a clinical perspective. , 2004, Journal of rehabilitation research and development.

[19]  K. Pesudovs.  Patient-centred measurement in ophthalmology – a paradigm shift , 2006, BMC ophthalmology.

[20]  Robert W. Massof,et al.  Evaluation of the NEI visual functioning questionnaire as an interval measure of visual ability in low vision , 2001, Vision Research.

[21]  C. Dickinson,et al.  Spatial localization in visual impairment. , 2006, Investigative ophthalmology & visual science.

[22]  K. Pesudovs,et al.  Comparison of autologous serum eye drops with conventional therapy in a randomised controlled crossover trial for ocular surface disease , 2004, British Journal of Ophthalmology.

[23]  R. Massof.  Application of Stochastic Measurement Models to Visual Function Rating Scale Questionnaires , 2005, Ophthalmic epidemiology.

[24]  Konrad Pesudovs,et al.  The development of a symptom questionnaire for assessing virtual reality viewing using a head-mounted display. , 2005, Optometry and vision science : official publication of the American Academy of Optometry.

[25]  G. Spaeth,et al.  Assessment of Function Related to Vision (AFREV) , 2006, Ophthalmic epidemiology.

[26]  K. Pesudovs,et al.  Changes in quality of life after laser in situ keratomileusis for myopia , 2005, Journal of cataract and refractive surgery.

[27]  I. Hsueh,et al.  A Rasch Analysis of a Self-perceived Change in Quality of Life Scale in Patients with Mild Stroke , 2005, Quality of Life Research.

[28]  A W Johnston,et al.  The development of the Melbourne low-vision ADL index: a measure of vision disability. , 2001, Investigative ophthalmology & visual science.

[29]  Robert W Massof,et al.  Measuring outcomes of vision rehabilitation with the Veterans Affairs Low Vision Visual Functioning Questionnaire. , 2006, Investigative ophthalmology & visual science.

[30]  Robert W Massof,et al.  Measuring low-vision rehabilitation outcomes with the NEI VFQ-25. , 2002, Investigative ophthalmology & visual science.

[31]  Stuart Peacock,et al.  Vision and quality of life: the development of a utility measure. , 2005, Investigative ophthalmology & visual science.

[32]  M. R. Espejo.  Applying the Rasch Model: Fundamental Measurement in the Human Sciences , 2004 .

[33]  Shortening the VF-14 visual disability questionnaire. , 2006, Journal of cataract and refractive surgery.

[34]  G. Rao,et al.  Perceived visual ability for functional vision performance among persons with low vision in the Indian state of Andhra Pradesh. , 2004, Investigative ophthalmology & visual science.

[35]  E. B. Wilson,et al.  The Distribution of Chi-Square. , 1931, Proceedings of the National Academy of Sciences of the United States of America.

[36]  P. Nirmalan,et al.  The impact of visual impairment on functional vision of children in rural South India: the Kariapatti Pediatric Eye Evaluation Project. , 2004, Investigative ophthalmology & visual science.

[37]  B. Wright,et al.  An Assessment of the Needs of Rehabilitated Veterans , 1985 .

[38]  R. Massof,et al.  Performance of the Veterans Affairs Low Vision Visual Functioning Questionnaire , 2004 .

[39]  A. Damiano,et al.  The VF-14. An index of functional impairment in patients with cataract. , 1994, Archives of ophthalmology.

[40]  T. Mallinson,et al.  Maintaining instrument quality while reducing items: application of Rasch analysis to a self-report of visual function. , 2000, Journal of outcome measurement.

[41]  Patrick E. McKnight,et al.  Evaluating psychometric properties of a clinical and a self-report blind rehabilitation outcome measure. , 2005, Journal of rehabilitation research and development.

[42]  Robert W Massof,et al.  The Measurement of Vision Disability , 2002, Optometry and vision science : official publication of the American Academy of Optometry.

[43]  R. Massof,et al.  Perceived visual ability for independent mobility in persons with retinitis pigmentosa. , 1999, Investigative ophthalmology & visual science.

[44]  Julie F Pallant,et al.  The Impact of Vision Impairment Questionnaire: an evaluation of its measurement properties using Rasch analysis. , 2006, Investigative ophthalmology & visual science.

[45]  R W Massof,et al.  A Systems Model for Low Vision Rehabilitation. II. Measurement of Vision Disabilities , 1998, Optometry and vision science : official publication of the American Academy of Optometry.

[46]  E F Cook,et al.  Development of the Activities of Daily Vision Scale: A Measure of Visual Functional Status , 1992, Medical care.

[47]  Erling B. Andersen,et al.  Sufficient statistics and latent trait models , 1977 .

[48]  K. Pesudovs,et al.  The Contact Lens Impact on Quality of Life (CLIQ) Questionnaire: development and validation. , 2006, Investigative ophthalmology & visual science.

[49]  Konrad Pesudovs,et al.  The Activities of Daily Vision Scale for cataract surgery outcomes: re-evaluating validity with Rasch analysis. , 2003, Investigative ophthalmology & visual science.

[50]  Robert W Massof,et al.  Psychometric properties of the Veterans Affairs Low-Vision Visual Functioning Questionnaire. , 2004, Investigative ophthalmology & visual science.