Purpose: This article aims to illustrate the principles of bearing fixing, a new computer-controlled procedure for subjective determination of astigmatism, and to compare it with conventional clinician-controlled Jackson crossed-cylinder refraction.
Methods: The principles and method for bearing fixing are described. Astigmatism was measured using bearing fixing and Jackson cross-cylinder twice on 20 visually normal participants aged between 18 and 34 years. After final sphere adjustment, acuity measurements were made with each refraction estimate.
Results: Bearing fixing results could be obtained for all participants. Mean bearing fixing cylinder magnitude was slightly higher than Jackson cross-cylinder measures of cylinder magnitude, by 0.05D. Using vector analysis to take into account cylinder power and axis, mean bearing fixing astigmatism was not significantly different from cross-cylinder astigmatism, but did have higher test-retest variability (p < 0.05). Acuity with bearing fixing and cross-cylinder corrections did not significantly differ in average value or repeatability.
Conclusions: Bearing fixing is a feasible method for subjective determination of astigmatism, and there are a number of potential improvements to the method which could make it faster and more precise.
Keywords: astigmatism; computer controlled refraction; optics; refraction algorithm.
© 2021 The Authors Ophthalmic and Physiological Optics © 2021 The College of Optometrists.