Functional outcome and satisfaction after photorefractive keratectomy - Part 1: Development and validation of a survey questionnaire

Objective: The aim of this study was to develop a valid, reliable, and easy -to-administer instrument to assess patient satisfaction and perceived outc ome after bilateral excimer laser photorefractive keratectomy. Design: Development and validation of a psychometric questionnaire. Participants: Consecutive patients who underwent bilateral excimer laser ph otorefractive keratectomy from May 1994 through May 1997 by 12 surgeons fro m four collaborating centers. To be eligible, a minimum of 4 months since t he last surgery and a maximum of 30 months since the first surgery was requ ired. Methods: The new instrument was derived in part from the Prospective Evalua tion of Radial Keratotomy (PERK) study 10-year psychometric questionnaire a nd the Visual Functional Index (VF-14), an index of functional impairment i n patients with cataract. Questions were grouped in seven scales, each cove ring a specific aspect of quality of vision. These included global satisfac tion, quality of uncorrected vision, quality of corrected vision, quality o f night vision, glare, daytime driving, and night driving. Main Outcome Measures: Acceptability, reliability, validity, and interpreta bility of the instrument, as well as its ease of administration. Results: The instrument scale structure was examined and scale scores were created. Item-discriminant validity ensured that questions belonged to thei r hypothesized scale, based on multitrait correlation analysis. The instrum ent was shown to be reliable by a high level of internal consistency, and a ll Cronbach's alpha coefficients were superior or equal to 0.83. Construct- related validity and interpretability were assessed based on correlations b etween scale scores and clinically recognized success criteria such as visu al acuity and refraction. Respondent burden was shown to be minimal. Accept ability of the instrument was shown to be very good, with a participation r ate of 74.3% (690 of 929 patients). The instrument is available in English and in French and the translation was shown to be reliable. Conclusions: The acceptability, reliability, and interpretability of the in strument, as well as its ease of administration, were shown to be adequate. This questionnaire appears clinically useful to document patient satisfact ion after excimer laser photorefractive keratectomy. Ophthalmology 2000; 10 7:1783-1789 (C) 2000 by the American Academy of Ophthalmology.