Study on the difference of binocular accommodative response between atients with intermittent exotropia under different viewing condition

Objective To evaluate the accommodative response of patients with intermittent exotropia (IXT) objectively, and study the changes of accommodative response of intermittent exotropia patients when maintaining binocular fusion. Methods The prospective cohort study was used in this study. Twenty-four patients diagnosed with basic intermittent exotropia who visited the eye hospital of Wenzhou Medical University during October 2016 through January 2017 together with 24 normal volunteers were included, the 48 participants aged from 10 to 27 years old. The participants were divided into the case group and the control group. There were 11 males and 13 females in the case group, and 7 males and 17 females in the control group. The Open-filed autorefractor WAM-5500 (Grand Seiko, Japan) was used to measure the accommodative response of each eye under binocular and monocular viewing conditions at 5 m and 40 cm respectively. During the measurement, patients wore full correction spectacles to achieve distant best-corrected visual acuity of both eyes. The accommodative responses of each eye under binocular and monocular viewing conditions at distance or near between fellow eyes and groups were compared. Results Under near fixation (40cm) binocular viewing conditions, the accommodative response of the fixating eye (-1.915±0.301)D was different from the deviating eye -1.649(-2.020, -0.304)D in the case group (Z=-3.714, P 0.05). Besides, the asymmetric values of accommodative response between groups were not significantly different (Z=-1.433, P=0.152. Z=-0.938, P=0.348). Under distance viewing conditions, the changes in accommodative response of each eye during both monocular viewing and binocular viewing were not significantly different between case group and normal controls (Z=-0.041, P=0.967. Z=-1.433, P=0.152). Conclusions The accommodative responses of the fixating eye and deviating eye of patients with intermittent exotropia were asymmetric under near fixation binocular viewing conditions, and the accommodative response of the deviating eye tends to decrease. Besides, the change of accommodative response of the patients with intermittent exotropia when maintaining binocular fusion is more significant than that of the normal controls. (Chin J Ophthalmol, 2018, 54: 55-61) Key words: Exotropia; Fixation, ocular; Vision disparity; Accommodation, ocular; Visual field tests