Effects of General Anesthesia on Ocular Refraction

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.

KEYWORDS:

• General anesthesia
• ocular refraction
• ciliary muscle
• pupil
• autonomic nervous system

Acknowledgments

We would like to thank Wakako Ando, CO at the Department of Ophthalmology, Kitasato University Hospital for the comments provided regarding the corneal SIA tool, and Editage (www.editage.com) for English language editing.

Disclosure statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: [Nobuyuki Shoji: TOMEY CORPORATION, RE Medical Inc.]