Accommodative Facility and Accommodative Response of Intermittent Exotropia

Abstract

Objective: To evaluate the accommodative facility and accommodative response in patients with intermittent exotropia. Methods: Thirty-five patients with basic intermittent exotropia and 24 normal controls were recruited for a case control study at Eye Hospital, Wenzhou Medical University from October 2016 to January 2017. Binocular and monocular accommodative facility were tested using a ± 2.00 diopter (D) flip. Accommodative responses under binocular and monocular viewing conditions at 40 cm were tested by an open-field autorefractor WAM-5500. Data were analyzed using t-tests. Results: The binocular accommodative facility of intermittent exotropia was 8.8 ± 4.1 cycles per minute (cpm), which was significantly lower than the normal control, 10.9 ± 3.1 cpm (t=-2.165, P=0.035). The fixating eye of intermittent exotropia had higher monocular accommodative facility than the non-fixating eye (t=4.657, P<0.001). Under binocular viewing conditions, the fixating eye of the intermittent exotropia had a higher accommodative response than the fixating eye of the normal control (t=-2.163, P=0.035). The binocular accommodative response was also higher than the accommodative response under monocular viewing conditions (t=3.801, P=0.001). Conclusions: Patients with intermittent exotropia have low binocular accommodative facility. They also have asymmetric monocular accommodative facility and asymmetric accommodative responses between the fixating eye and the deviating eye. Patients with intermittent exotropia have a higher accommodative response under binocular viewing conditions than under monocular viewing conditions. Key words: intermittent exotropia; accommodative facility; accommodative response