Three-dimensional vector analysis after decompression surgery in thyroid-associated ophthalmopathy

Abstract

Objective: To analyze the change of globe position after different orbital decompression in thyroid-associated ophthalmopathy (TAO). Methods: It was a retrosective case series study. Twenty-nine TAO patients (33 eyes) underwent orbital decompression were collected between October 2014 and December 2016 at Eye & ENT Hospital of Fudan University. There were 17 males and 12 females, and the average age was 46 years (ranging from 21 to 66 years). Fifteen patients (17 eyes) underwent balanced decompression, 11 patients (11 eyes) underwent deep lateral decompression, and 4 patients (5 eyes) underwent medial decompression. CT scan was performed pre and postoperatively for each patient and a reference coordinate system was established on the three-dimensional reconstructed image. The eyeball vector EC from the eyeball center to the corneal apex was defined and the coordinates (X(E), Y(E), Z(E))(X(C), Y(C), Z(C)) were calculated. The angle M between EC and the midsagittal plane and the angle F between EC and the Frankfort plane were also calculated. Paired t test and one way ANOVA were used for statistical analysis. Results: The average value of X(C) before and after deep lateral decompression was 19.53 mm and 17.25 mm (t=10.87, P<0.05) and average value of X(E) was 7.73 mm and 5.69 mm (t=12.22, P<0.05). The average value of X(C) before and after medial decompression was 20.24 mm and 18.17 mm (t=7.93, P<0.05) and average value of X(E) was 7.14 mm and 5.52 mm (t=9.24, P<0.05). The average value of X(C) before and after balanced decompression was 22.16 mm and 18.83 mm (t=12.71 , P<0.05) and average value of X(E) was 10.20 mm and 6.67 mm (t=11.91, P<0.05). The average value of horizontal deviation angle M before and after medial decompression was 6.48° and 13.34° (t=- 8.41, P<0.05). The average value of angle M before and after balanced decompression was 1.42° and 6.76° (t=- 2.86, P<0.05). The average value of angle M before and after deep lateral decompression was 5.18° and 1.39° (t=2.57, P<0.05). Conclusions: The proptosis reduction was significant after deep lateral decompression, balanced decompression and medial decompression. Additionally, the horizontal deviation tended to increase after medial and balanced decompression, whereas the horizaontal deviation tended to decrease after deep lateral decompression. (Chin J Ophthalmol, 2017, 53: 424-429).