Effects of General Anesthesia on Ocular Refraction

Abstract

ABSTRACT Purpose General anesthesia alters the autonomic nervous system. This study aimed to investigate the effects of general anesthesia on objective ocular refraction. Methods A total of 57 patients (112 eyes) under 15 years of age who underwent strabismus surgery under general anesthesia were included in this study. Objective refraction values, corneal refraction values, and pupil diameter were measured using a HandyRef-K, a hand-held refractive keratometer, in the operating room before and during general anesthesia before strabismus surgery. Results The spherical power of the myopic eye increased from −0.75 D to −2.29 D (diopter); the cylindrical power increased from −0.90 D to −1.39 D (p < .01 for all). The corneal refractive power decreased by an average of 0.25 D (p < .01). The spherical refractive power was negatively correlated with the age and the amount of change between cycloplegia before general anesthesia and during general anesthesia (r = −0.32, p < .05). Conclusions General anesthesia resulted in manifestation of myopia as noted by the objective refraction values. Corneal refractive values flatten under the same conditions, suggesting that the contraction of the ciliary muscles was the main cause of myopia. We speculate that this change was due to parasympathetic dominance and contraction of the ciliary muscles during general anesthesia.