The validity and reliability of the handheld SW-100 autokeratometer

Iyamu, Eghosasere; Amiebenomo, Onyeka Mary-Anne

Abstract

Background: The agreement of new instruments or clinical tests with other instruments or tests defines the possibility of these being used interchangeably. Aim: To investigate the validity and reliability of the SW-100 autokeratometer using a Bausch & Lomb (B&L) keratometer as the 'gold standard'. Methods: Eighty subjects (80 right eyes) aged between 21 and 38 years were recruited. For intra-test repeatability, two measurements of the corneal radius of curvature were taken with the SW-100 and B&L keratometers. Forty of the 80 subjects participated in the inter-test repeatability measurement. Results: Corneal radius of curvature was found to be statistically different between the two instruments (p < 0.001), with the SW-100 providing slightly flatter values of 0.11 mm and 0.05 mm for the horizontal and vertical meridians, respectively, than the B&L keratometer. The average corneal curvature was 0.07 mm flatter with the SW-100 autokeratometer than with the B&L device. Agreement between the SW-100 and B&L keratometers' axes was 45% within ± 5°, 60.3% within ± 10°, 78.8% within ± 15°, 80.3% within ± 20°, and 88.7% within ± 40°. Inter-test repeatability was better for the B&L device than the SW-100 and showed no significant difference between the two sessions. Both instruments demonstrated comparable intra-session repeatability. As such, both instruments were comparatively reliable (per coefficients of repeatability). The range of limits of agreement of ± 0.14 mm (horizontal meridian) and ± 0.17 mm (vertical meridian) between the SW-100 and B&L devices showed good agreement. Conclusion: The results suggest that the SW-100 autokeratometer is a reliable and objective instrument that, however, provides flatter radii of curvature measurements than the B&L keratometer. A compensating factor incorporated into the instrument could reduce the difference between the two instruments and make them more interchangeable.

• Journal Article Type: Article
• Online Publication Date: Mar 26, 2015
• Publication Date: Jul 23, 2015
• Deposit Date: Nov 6, 2024
• Publicly Available Date: Nov 6, 2024
• Journal: African Vision and Eye Health
• Print ISSN: 2413-3183
• Electronic ISSN: 2410-1516
• Publisher: AOSIS
• Peer Reviewed: Peer Reviewed
• Volume: 74
• Issue: 1
• Article Number: a26
• DOI: https://doi.org/10.4102/aveh.v74i1.26
• Public URL: https://uwe-repository.worktribe.com/output/13403011