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Himal Kandel, Jyoti Khadka, Konrad Pesudovs; Development and validation of a new measure of convenience in refractive error. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4147.
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© ARVO (1962-2015); The Authors (2016-present)
Inconvenience (e.g. inconvenience handling glasses and contact lenses) is one of the major quality of life (QoL) issues for people with refractive error and it is one of the domains of refractive-error specific QoL item banks. The aim of this study was to validate the Convenience scale.
The 64-item convenience item bank was developed from the issues identified from patient consultation and literature review, followed by an iterative content refinement process. The item bank was interviewer-administered to 305 people with refractive error in Nepal. Rasch analysis was conducted using WinSteps V3.92.1 software applying the Andrich Rating Scale Model. Median convenience scores were compared among various demographic and clinical sub-groups.
Mean age of the participants was 30.5±14.1 years (Range: 18-83 years; Male, 50.6%; Rural, 14.8%). Median visual acuity was 0 (range: -0.08 to +1.18) LogMAR. The mean spherical-equivalent refractive error was -2.40±2.9 (range: -15.0 to +11.0) dioptres. Participants had myopia (n = 227), hyperopia (n=39), astigmatism (n=65) and presbyopia (n=48). They wore glasses (n=257), contact lens (n=37) or underwent refractive surgery (n=25). Rasch analysis revealed that the item-bank had satisfactory psychometric properties: ordered response categories, measurement precision (PSI, 2.9), fit statistics (<1.5 MnSq), targeting (0.96 logits), and unidimensionality.The participants with high refractive error, from rural areas, and female participants had higher inconvenience (Mann Whitney U; p < 0.05). Similarly, the participants wearing contact lenses had the highest inconvenience (0.40 logits) followed by the participants with glasses (0.9 logits), uncorrected refractive error (1.2 logits) and refractive surgery (1.8 logits) [Kurskal Wallis; p = 0.02]. Convenience scores mildly correlated with visual acuity (Spearman’s rho; -0.21; p<0.001) and refractive error (Spearman’s rho; -0.21; p<0.001). Convenience levels between presbyopes (0.88 logits) and non-presbyopes (0.92 logits), myopia (0.91 logits) and hyperopia (0.82 logits), participants with astigmatism (0.82 logits) and without astigmatism (0.99 logits), were not statistically significant (Mann Whitney U; p > 0.05).
The Convenience item bank is a novel measure of inconvenience in refractive error. It has good psychometric properties and known-group validity.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Persons and items calibrated in a common logit scale
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