Purpose
This study was performed to evaluate the changes of corneal astigmatism in patients undergoing orbital decompression surgery.
Methods
This retrospective, nonrandomized comparative study comprised 42 eyes from 21 patients with thyroid ophthalmolpathy who underwent orbital decompression surgery between September 2011 and September 2014. The 42 eyes were divided into three groups: control (9 eyes), two wall decompression (24 eyes), and three wall decompression (8 eyes). Control was defined as the contralateral eyes of 9 patients who underwent orbital decompression surgery only in one eye. Corneal topography (Orbscan II), Hertel exophthalmometry, and intraocular pressure were measured at 1 month before and 3 months after surgery. Corneal topographic parameters analyzed were the total astigmatism(TA), steep axis(SA), central corneal thickness(CCT), and anterior chamber depth(ACD).
Results
Exophthalmometry values and intraocular pressure were significantly decreased after the decompression surgery. The change (the absolute value (|x|) of the difference) of astigmatism at 3mm zone was significantly different between the decompression group and the control (P = .0250). There was also significant change of the steepest axis at 3mm zone between the decompression group and the control (P = .0331). An analysis of relevant changes in astigmatism showed that there is a dominant tendency of incyclotorsion of the steepest axis in eyes which underwent decompression surgery. Using Astig PLOTTM, the mean surgically induced astigmatism (SIA) was 0.21±0.88D with the axis of 46±22° which suggest that decompression surgery did change the corneal shape and induced incyclotorion of the steepest axis.
Conclusions
There is a significant change in corneal astigmatism after orbital decompression surgery and this change is sufficient to affect the optical function of the cornea. Surgeons and patients should be aware of these changes.