Reliability of the response AC/A ratio determined using nearpoint autorefraction and simultaneous heterophoria measurement

Abstract

Background: Clinicians frequently assess the accommodative convergence to accommodation (AC/A) ratio using near phoria measurements and accommodative stimuli. The purpose of this study was to evaluate the repeatability of AC/A ratio measurements and to compare the response AC/A ratio to stimulus AC/A ratios determined two different ways.Methods: Heterophorias and accommodative responses to different stimuli were measured simultaneously on eight subjects at two visits. A Canon Auto Ref R‐1 autorefractor was used to measure accommodative response, while vergence posture was measured using the modified Thorington heterophoria technique. These results were used to calculate response‐slope, stimulus‐slope and stimulus‐gradient AC/A ratios and the means of these ratios for each session were compared. Correlations between the response AC/A ratios and the stimulus AC/A ratios were calculated.Results: The mean response AC/A ratios for the two sessions were 3.8 prism dioptres per dioptre for each session. The correlation between the slope‐determined ratios was 0.56, and between the response‐slope and the stimulus‐gradient AC/A ratios the correlation was ‐0.03. The regression equation for the slope‐determined AC/A ratios was calculated.