To investigate the effects of strabismus surgery on corneal biomechanical parameters and surgically induced astigmatism after strabismus surgery

Purpose: To investigate the effects of strabismus surgery on corneal biomechanical parameters and surgically induced astigmatism after strabismus surgery. Metods: The study included 69 eyes of 49 patients who have undergone strabismus surgery from January 2015 to August 2015. Patients were divided into 3 groups according to strabismus surgery performed; Group 1: 36 eyes of 22 patients lateral rectus recession, Group 2: 26 eyes of 20 patients medial rectus recession and Group 3: 7 eyes of 7 patients medial rectus resection and lateral rectus recession. Corneal hysteresis, (CH) and corneal resistance factor (CRF), intraocular pressure correlated with Goldmann (IOPg) and corneal-compensated IOP (gibcc) were measured with Ocular Response Analyzer (ORA, Ocular Response Analizer, ReiKHert Depew, N.Y. USA) preoperative, 1 week and 1 month postoperatively. Central corneal thickness (CCT) was measured with the ultrasonic Pacimetry (NIDEK-UP 1000). Keratometry were measured by autorefractometer device preoperative, 1 week and 1 month postoperatively for analysis of surgically induced astigmatism. Surgically induced astigmatism was calculated with vector analysis program of Egrilmez et al Results: The preoperative and postoperative first week CH, CRF, IOPg, GIBcc and keratometry measurements showed no significant difference in group 1 and group 2; however in group 3 CRF measurements showed statistically significant differences (p= 0,043). Post-operative first week surgically induced astigmatism, regular component and irregular component values were 0,42±0,21, 0,25±0,24, 0,17±0,20 in Group 1; 0,45±0,28, 0,30±0,29, 0,15±0,23 in Group 2; 0,74±0,49, 0,60±0,51, 0,14±0,19 in Group 3, respectively. The preoperative and postoperative first month CH, CRF, IOPg, GIBcc and keratometry measurements showed no significant difference in all groups. Post-operative first month surgically induced astigmatism, regular component and irregular component values were 0,40±0,25, 0,32±0,25, 0,07±0,12 in Group 1; 0,39±0,25, 0,28±0,26, 0,10±0,11 in Group 2; 0,59±0,40, 0,40±0,26, 0,19±0,23 in Group 3, respectively. When first week and first month post-operative surgery induced astigmatism rate were compared in group 1 (p>0,615) and group 2 (p>0,348) surgically induced astigmatism reduced but it was no statistically significant. In Group 3 the reduction was statistically significant (p< 0,003). Conclusions: Strabismus surgery does not cause significant changes in corneal biomechanical parameters in late postoperative period. Only in cases of surgeries include two rectus muscles simultaneously, early postoperative period CRF showed a significant decrease but has been observed that this is a temporary impairment. In addition surgically induced astigmatism can develop after strabismus surgery but clinically significant change in astigmatism was observed only in group three which surgery ınclude two rectus muscles simultaneously.