Modification of the Accommodative-Convergence over Accommodation (AC/A) Ratio, in Response to Different Stimulus Lenses

Abstract

The amount of accommodation modified by convergence is called the AC/A ratio and it canaffect the magnitude of ocular deviation in the sensory and motor state diagnosis, as well as inthe patient’s treatment plan. There are some disagreements on whether the measurement of theAC/A gradient is the same with other accommodative responses. <em><strong>Objective</strong><em> To determine if thegradient stimulus AC/A ratio had a similar response when using different stimulus lenses. <em>Materials and methods:</em> One hundred and thirty-two (132) individuals were evaluated, who had regularand induced heterophoria with +3.00, +2.00, +1.00, -1.00, -2.00 and -3.00 dioptry stimulus lensesmeasured through the Thorington technique, with a modified phoria card (for 0.33 m). <em><strong>Results:</strong><em>The mean gradient AC/A for the stimulus lens was +3.00 (1.39), +2.00 (1.67), +1.00 (1.84), -1.00(1.42), -2.00 (1.48), -1.00 (1.42), and the slope AC/A ratio (AC/Ap1.49). The comparison of theAC/A did not show any significant differences (ANOVA p=0.0132), but a higher variability in theresults with the +/-1.00D (COA ±2.98 and ±2.56) lenses. <em><strong>Conclusions:</strong><em> The mean gradient stimulusAC/A was similar when calculated with the different lenses, but the variability of the informationindicates that it should be measured and calculated with several accommodation stimuli.