Purpose: Ocular residual astigmatism (ORA) is the proportion of manifest astigmatism that is not explained by anterior corneal astigmatism. The role of higher order aberrations (HOAs) in the level of ORA has not been profoundly studied. The purpose of this study was to evaluate the effect of different corneal and whole-eye HOAs on levels of ORA using a multivariate modeling approach.Methods: This is a retrospective analytical study including a sample of healthy refractive surgery candidates. One eye of every patient was randomly selected. A total of 294 eyes from an equal number of patients were included. Corneal and whole-eye HOAs were measured with a Pentacam AXL Wave, and subjective manifest refraction was taken. Astigmatism values were converted into power vectors and ORA was calculated. The Spearman rank-order correlation was initially used to explore correlation between HOA and ORA. All variables with a P value under 0.10 were included into a multiple linear regression model to explore this correlation adjusting for confounding variables. Results:The mean age was 28.81 6 5.40 years. Simple bivariate correlation was significant for root mean square (RMS) total, RMS lower order aberrations, RMS HOAs, defocus, and vertical astigmatism. After being included into a multivariate regression model adjusting for confounding variables, the only variable that was significant was RMS total [F (3, 282) = 78.977; P , 0.001; adjusted R 2 = 0.451]. For every mm increase in corneal RMS total, ORA increases by 0.135 diopters. About 45% of variability in ORA can be explained by corneal RMS total, corneal J 0 , and manifest J 0 . No individual HOA correlated with ORA in the multivariate regression model. Conclusions:ORA increases with general corneal irregularity, especially regular astigmatism. Irregular astigmatism expressed by corneal and whole-eye HOAs does not seem to be a significant contributor of ORA in healthy refractive surgery candidates.
Purpose: The keratoconus end-points assessment questionnaire (KEPAQ) is a disease-specific scale designed to evaluate the quality of life in keratoconus patients and provides the measurement of both functional and emotional compromise in keratoconus. It was previously developed, tested, and validated and now we want to evaluate the test-retest reliability of the KEPAQ, in an effort to contribute evidence on its internal consistency and capability of measuring clinical state with minimal inference of random chance. Methods: This is a prospective analytical study, designed to evaluate the test-retest reliability of the KEPAQ through the repeated application of the questionnaire to a group of clinically stable individuals. A number of patients with a confirmed diagnosis of keratoconus underwent double application of the KEPAQ, seven days apart. Mean KEPAQ score was obtained through Rasch analysis, while test-retest reliability was evaluated through Spearman rank-order correlation and intraclass correlation coefficient. Rasch analysis was performed in JMetrik version 4.1.1 (Psychomeasurement Systems LLC; Charlottesville, VA, USA) in a MacBook Air computer running macOS Catalina version 10.15.2 (Apple Inc.; Cupertino, CA, USA). Results: A total of 100 patients were included. For KEPAQ-E, Spearman correlation was R = 0.963 while ICC was 0.981 (95% confidence interval 0.972–0.987). For KEPAQ-F, Spearman correlation was R = 0.921 while ICC was 0.952 (95% confidence interval 0.929–0.968). Conclusion: The KEPAQ is a robust, well-developed, extremely reliable scale which can be confidently used for clinical and research endeavors.
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