Comparison between Stimulus and Response AC/A Ratios for Each Phoria with Additional Spherical Power

Abstract

Purpose: The accommodative response and the near horizontal phoria were examined with additional spherical power to analyze the stimulus and response AC/A ratios that suggest reference data for the binocular vision.Methods: The open-field autorefractometer (Nvision-K 5001, Shin nippon) and modified thorington method (MIM card; Muscle Imbalance Measure card, Bernell) at 40 cm were utilized to measure the accommodative response and the near horizontal phoria for 81 persons (20.89±1.92 years old) with additional spherical power. The stimulus and the response AC/A ratios were calculated by gradient AC/A method. Results: The exophoria group showed the highest accommodative response (1.92±0.26 D) at 40 cm, followed by orthophoria group and esophoria group(1.72±0.26 D and 1.62±0.42 D, respectively) Meanwhile, the esophoria group showed the biggest ocular deviation for the near (23.24 ∆) followed by the orthophoria group and exophoria group (19.76 ∆ and 15.14 ∆, respectively). The biggest difference of the stimulus and the response AC/A ratios was 1.72 ∆ for the exophoria group with −2.00 D, while the one was 3.43 ∆ for the esophoria group with +1.00 D. There was a significant difference between AC/A ratios for the exophoria group with −2.00 D, −1.00 D and the esophoria group with +3.00 D, +2.00D, +1.00D and −1.00D. Conclusions: The difference between stimulus and response AC/A was greater when increased minus spherical power for the exophoria group, while it was greater when increased plus spherical power for the esophoria group. Furthermore, the difference for the esophoria group was a greater than the one for the exophoria group.