Change in the eye position under general anesthesia: Is it related to the etiology in intermittent exotropia?

Abstract

Purpose : The position of the eyes under general anesthesia (GA) can be useful as a measurement of the resting eye position without innervational vergence tonus. We conducted the study to evaluate the eye position under GA in subjects with intermittent exotropia (IXT) with or without lateral incomitance (LI) and normal subjects using a three-dimensional (3D) strabismus photo analyzer.

Methods : This case-control study included 52 subjects with IXT and 25 normal subjects who underwent epiblepharon surgery. The eye position under GA was assessed using a 3D strabismus photo analyzer based on 3D eye models generated from corneal lights and limbi on pre- and post-anesthetic infrared images, and it was compared among the control and IXT with or without LI groups. In addition, the correlation between the preoperative angle of deviation and the change in the eye position under GA was analyzed.

Results : Eye positions under GA were divergent in all subjects with IXT and normal subjects, with no significant differences among the three groups. The change in the eye position (Y) was strongly correlated with the preoperative angle of deviation (X) in all subjects with IXT (Y = −1.35*X + 35.02, r² = 0.599, p < 0.001). In small preoperative exodeviations, the eye position was primarily divergent, whereas in large exodeviations, a convergent tendency was observed.

Conclusions : Eye positions under GA were not significantly different between controls and subjects with IXT with or without LI. Subjects with IXT may exhibit a tendency for a change in the eye position in different directions under GA, and this tendency correlates with the preoperative angle of deviation.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Figure 1. Measurement of the eye position following GA by pre-and post-anesthetic photographs.
(A) Pre-anesthetic infrared image was obtained when the subject’s fusion occurred. The corneal light reflex and limbus were detected. Two separate spheres, the spheres of the eye and cornea, were simulated. (B) Post-anesthetic image was registered. (C) Operator rotated the left eyeball of the 3D model manually until its visual axis matched that of the processed image (black arrowhead in Figure B). (D) The same procedure was repeated on the right eye (white arrow in Figure B). Added angle of deviation of each eye was defined as the angle of deviation under GA.