Differences between accommodative-convergence ratios as determined by the gradient (delta phoria/delta sphere) method and the phoria (delta phoria/delta diopters) method are studied in order to investigate the validity and reliability of these tests clinically. Comparisons of these two methods were performed using the Badal optometer/haploscope (laboratory method), and an American Optical phoropter (clinical method), in order to establish the correlation between As and Ar measurements when determining the accommodat.i veconvergence ratio. The results of this study show that the coefficient of correlation for ACA values obtained between clinical and laboratory methods is low, indicating a significant discrepancy between the two methods. It was concluded that measurement of ACA is dependent upon many factors, rendering valid and reliable measurement difficult over time. Recommendations for appropriate ACA measurement include cognizance of the complexity andvariability of the ACA relationship, as well as maintaining consistency of and between test methods.
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