Session: Poster session A

A convenient method to estimate alignment of eyes under general anesthesia in strabismus subjects

Introduction

This study aims to describe a convenient and reliable method to estimate the alignment of eyes under general anesthesia (GA) in strabismus subjects. It is known that the strabismus angle under GA varies from the angle measured preoperatively. This variation may influence the surgical protocol and guide the operative procedure.



Material and Methods

Through the operating miscroscope, pictures of the eye position of 99 subjects with horizontal strabismus were captured peroperatively under general anesthesia. We placed a curved caliper parallel to the horizontal meridian and measured the distance between the center of cornea and the corneal reflex spot of the axial light of the microscope. The eye position was estimated with a quantified Hirshberg method for each eye and the values were added for the overall angle. To validate this method, four strabismus surgeons blindly estimated the peroperative strabismus angle based on these pictures and the results were compared. Agreement between the four measurements was estimated using the ICC (Intraclass Correlation Coefficient) index.



Results

ICC coefficients and their 95% confidence interval were 0.925 (0.877-0.953) for the overall angle, 0.918 (0.891-0.941) for the right eye and 0.859 (0.774-0.910) for the left eye, indicating good to excellent reliability of these measurements.



Conclusion

The described technique is fast, easy and reliable and provides a tool to encourage surgeons to evaluate the angle under GA.