Binocular accommodative function in patients with intermittent exotropia

Abstract

Objective To investigate the binocular accommodative function of patients with intermittent exotropia.Methods Seventy-six patients aged 18 to 40 years with intermittent exotropia and 40 normal controls were recruited for a prospective case control study.Accommodative responses in dominant and nondominant eyes were tested using MEM (monocular estimate method) dynamic retinoscopy.The testing measured positive relative accommodation/negative relative accommodation (PRA/NRA) and deviation to a 40 cm target with binocular viewing.The data were analyzed by a nonparametric test,t-test and correlation analysis.Results During binocular viewing at the 40 cm target,the accommodative response was asymetric between the two eyes in patients with intermittent exotropia.Forty-eight of the dominant eyes (63％) showed an accommodative lead.Sixty-two of the nondominant eyes (81％) showed an accommodative lag.The mean accommodative response in the dominant and nondominant eyes in patients and normal control dominant eyes were-0.32±0.57 D,+0.36±0.44 D and +0.34±0.28 D,respectively.The accommodative response was asymetric in patients between dominant and nondominant eyes (Z=-7.01,P＜0.01).There was significant difference between the dominant eyes in patients and normal controls (Z=-6.36,P＜0.01).The accommodative responses in the dominant eyes were significantly correlated with the angle of exotropia (r=-0.67,P＜0.01).The mean PRA was-4.03±0.82 D in patients and-3.09±0.74 D in normal controls (t=6.05,P＜0.01).The mean NRA was +1.96±0.56 D in patients and +2.23±0.34 D in normal controls (t=-2.82,P＜0.01).Conclusion During binocular viewing at the near target,the accommodative response in patients with intermittent exotropia was asymetric between dominant and nondominant eyes with a hyperactive response in the dominant eye. Key words: Intermittent exotropia; Accommodation; Dominant eye