The Contact Lens Impact on Quality of Life (CLIQ) Questionnaire: development and validation.

PURPOSE: To develop and validate a questionnaire for the measurement of the impact of contact lenses on quality of life (QoL): The Contact Lens Impact on Quality of Life (CLIQ) Questionnaire. METHODS: The questionnaire was developed and validated using conventional methods and Rasch analysis to assure content validity, repeatability, construct validity, and low respondent burden. Item identification and selection (647 items) were performed with an extensive literature review, professional advice, and lay focus groups. Item reduction used focus groups and data obtained from 161 subjects completing a 90-item pilot questionnaire. Validity and reliability, from data of 128 additional subjects, were assessed using Rasch analysis, intraclass correlation coefficient, and Bland-Altman limits of agreement. RESULTS: A 28-item CLIQ Questionnaire was developed and shown to have good validity and reliability by Rasch analysis statistics: real person separation, 2.02; model person separation, 2.17; reliability, 0.80; root mean square measurement error, 2.73; mean square+/-SD infit, 1.01+/-0.18; outfit, 1.01+/-0.19. The items (mean score, 49.8+/-4.9) were well targeted to the subjects (mean score, 51.2+/-6.2) with a mean difference of 1.35 (scale range, 0-100) units. Test-retest intraclass correlation coefficient (0.86) and coefficient of repeatability (+/-8.00 units) demonstrated good repeatability. CONCLUSIONS: Rasch analysis and standard psychometric analyses demonstrated that the 28-item CLIQ Questionnaire is a valid and reliable measure of QoL in contact lens wearers. A scoring algorithm is provided for CLIQ Questionnaire users to convert raw scores into the Rasch analysis-derived linear person measures.

A quality of life comparison of people wearing spectacles or contact lenses or having undergone refractive surgery.

PURPOSE: To demonstrate the use of the Quality of Life Impact of Refractive Correction (QIRC) questionnaire for comparing the quality of life of pre-presbyopic individuals with refractive correction by spectacles, contact lenses, or refractive surgery. METHODS: The 20-item QIRC questionnaire was administered to 104 spectacle wearers, 104 contact lens wearers, and 104 individuals who had undergone refractive surgery (N = 312). These groups were similar for gender, ethnicity, socioeconomic status, and refractive error. The main outcome measure was QIRC overall score (scaled from 0 to 100), a measure of refractive correction related quality of life. Groups were compared for overall QIRC score and on each question by analysis of variance, adjusted for age, with post hoc significance testing (Sheffé). RESULTS: On average, refractive surgery patients scored significantly better (mean QIRC score 50.2 +/- 6.3, F(2,309) = 15.18, P < .001) than contact lens wearers (46.7 +/- 5.5, post hoc P < .001) who were in turn significantly better than spectacle wearers (44.1 +/- 5.9, post hoc P < .01). Convenience questions chiefly drove the differences between groups, although functioning, symptoms, economic concerns, heath concerns, and well being were also important. Spectacle wearers with low strength prescriptions (46.18 +/- 5.05) scored significantly better than those with medium strength prescriptions (42.74 +/- 6.08, F(2,190) = 3.66, P < .05, post hoc P < .05). A small number (n = 7, 6.7%) of refractive surgery patients experienced postoperative complications, which impacted quality of life (37.86 +/- 2.13). CONCLUSIONS: Quality of life was lowest in spectacle wearers, particularly those with higher corrections. Contact lens wearers had significantly better QIRC score than spectacle wearers. Refractive surgery patients scored significantly better than both. However, this was accompanied by a small risk of poor quality of life due to postoperative complications. The QIRC is an effective outcome measure for quality of life impact of refractive correction.

The Refractive Status and Vision Profile: evaluation of psychometric properties and comparison of Rasch and summated Likert-scaling.

The psychometric properties of the Refractive Status and Vision Profile (RSVP) questionnaire were evaluated using Rasch analysis. Ninety-one myopic patients from a refractive surgery clinic and general optometric practice completed the RSVP. Rasch analysis of the RSVP ordinal data was performed to examine for unidimensionality and item reduction. The traditional Likert-scoring system was compared with a Rasch-scored RSVP and a reduced item Rasch-scored RSVP. Rasch analysis of the original RSVP showed poor targeting of item difficulty to patient quality of life, items with a ceiling effect and underutilized response categories. Combining the underutilized response scales and removal of redundant and misfitting items improved the internal consistency and targeting of the RSVP, and the reduced 20-item Rasch scored RSVP showed greater relative precision over standard Likert scoring in discriminating between the two subject groups. A Rasch scaled quality of life questionnaire is recommended for use in refractive outcomes research.

Changes in quality of life after laser in situ keratomileusis for myopia.

PURPOSE: To measure quality of life (QoL) outcome in prepresbyopic myopic patients having laser in situ keratomileusis (LASIK) refractive surgery using the Quality of Life Impact of Refractive Correction (QIRC) questionnaire and to compare the QoL of preoperative patients with a sample of spectacle and contact lens wearers not considering refractive surgery. SETTING: Department of Optometry, University of Bradford, Bradford, and Ultralase, Leeds, West Yorkshire, United Kingdom. METHODS: The validated QIRC questionnaire was prospectively completed by 66 patients before and 3 months after LASIK. Patients had myopia greater than 0.50 diopters (D) (range --0.75 to --10.50 D) and were aged 16 to 39 years. Patients were also directly asked to evaluate their QoL after surgery. RESULTS: Overall QIRC scores improved after LASIK from a mean of 40.07+/- 4.30 (SD) to 53.09+/- 5.25 (F(1,130)=172.65, P<.001). Greater improvements occurred in women (53.83+/- 5.46) than in men (49.39+/- 5.94; F(1,64)=9.37, P<.005). Overall, 15 of the 20 questions (especially convenience, health concerns, and well-being questions) showed significantly improved scores (P<.05). Patients who "strongly agreed" (53.96+/- 4.91, n=33) or "agreed" (51.78+/- 6.19, n=23) had improved QoL and had significantly higher QIRC scores than those who "neither agreed nor disagreed" (44.36+/- 4.97, n=5) or "strongly disagreed" (42.82, n=1) (F(1,60)=11.24, P<.001). The matched group not contemplating LASIK scored 42.41 +/- 3.89 on QIRC overall. CONCLUSIONS: Large improvements in QIRC QoL scores were found after LASIK for myopia in the majority of patients, with greater improvements in women. A small number of patients (4.5%) had decreased QIRC QoL scores, and these were associated with complications. People presenting for LASIK scored measurably poorer than matched patients not contemplating refractive surgery.

The Quality of Life Impact of Refractive Correction (QIRC) Questionnaire: development and validation.

BACKGROUND: The purpose of the study was to develop a questionnaire that could quantify the quality of life (QOL) of people with refractive correction by spectacles, contact lenses, and refractive surgery in the prepresbyopic age group. METHODS: The questionnaire was developed and validated using traditional methods and Rasch analysis. A 90-item pilot questionnaire was developed through extensive literature search and use of professional and lay focus groups. Pilot study data were obtained from 306 subjects for item reduction to produce the 20-item Quality of Life Impact of Refractive Correction (QIRC) questionnaire. Validity and reliability studies (test-retest reliability with intraclass correlation coefficient and Bland-Altman limits of agreement, and internal consistency with Rasch fit statistics, factor analysis, and Cronbach's alpha) were performed from data of an additional 312 subjects. RESULTS: Rasch analysis demonstrated QIRC has good precision, reliability, and internal consistency (person separation, 2.03; reliability, 0.80; root-mean-square measurement error, 3.25; mean square +/- SD infit, 0.99 +/- 0.38; outfit, 1.00 +/- 0.39; item infit range, 0.70 to 1.24; and item outfit range, 0.78 to 1.32). The items (mean score, 50.3 +/- 7.3) were well targeted to the subjects (mean score, 47.8 +/- 5.5) with a mean difference of 2.45 (scale range, 0 to 100) units. Test-retest reliability (intraclass correlation coefficient, 0.88; coefficient of repeatability, +/-6.85 units), factor loading range (0.40 to 0.76), and Cronbach's alpha (0.78) also indicated the reliability and validity of QIRC. CONCLUSIONS: The 20-item QIRC questionnaire, which quantifies the QOL of people with refractive correction by spectacles, contact lenses, and refractive surgery in the prepresbyopic age group, was developed using Rasch analysis and shown to be valid and reliable. The use of Rasch scaling allows scores to be treated as a valid continuous variable. QIRC has broad applicability for cross-sectional and outcomes research.

The Activities of Daily Vision Scale for cataract surgery outcomes: re-evaluating validity with Rasch analysis.

PURPOSE: The Activities of Daily Vision Scale (ADVS) has been extensively validated by traditional methodology. In the current study, Rasch analysis was used to explore further the validity of the ADVS and to determine whether improvements could be made. METHODS: Forty-three patients with cataract underwent visual acuity (VA) and contrast sensitivity (CS) testing and completed the ADVS. The data were Rasch analyzed and the value of response scale and item reduction explored. A shortened version and the original ADVS were tested for criterion validity by determining correlations with VA and CS. RESULTS: The ADVS data contained abnormally distributed items and items with ceiling effects and empty response categories. Therefore, items benefited from shortening the response scale, the optimum length being three responses. There was poor targeting of item difficulty to patient ability, because many patients with cataract were sufficiently able that they had no difficulty with many activities. Items were eliminated if the task was too easy or did not fit with the overall concept of visual disability determined by the Rasch model. A reduced ADVS version was established that had adequate precision, equivalent criterion validity, and improved targeting of item difficulty to patient ability, but this version was still not ideal. CONCLUSIONS: Despite careful traditional validation, the ADVS data contained inadequacies exposed by Rasch analysis. Through Rasch scaling, particularly with response scale reduction, the ADVS can be improved, but additional questions seem to be needed to suit the more able, including patients undergoing second eye cataract surgery. There remains a need to develop Rasch-scaled measures of visual disability for use in ophthalmic outcomes research.