The Effect of Strabismus Muscle Surgery on Corneal Biomechanics
Heba A. El Gendy, MD; Noha M. Khalil, MD; Iman M. Eissa, MD; Shireen M. Shousha, MD
Kasr Al Ainy Medical School, Faculty of Medicine. Cairo University
Introduction: Studying the early effect of strabismus muscle surgeries on corneal biomechanics
Methods: This is a comparative study, that 42 candidates for elective strabismus surgeries at Cairo university hospitals, aged 14 – 37 years, were recruited. All participants had measuring of the visual acuity, refraction(spherical equivalent(SE),assessment of the EOM motility and muscle balance , sensory evaluation, fundus examination, and assessing the ocular biomechanics using the Ocular response analyzer (ORA, Reichert, INC., Depew, NY) noting the Corneal hysteresis(CH)&Corneal resistance factor (CRF) pre-operatively. Same patients were reassessed using ORA 4 weeks postoperatively following different standard EOM surgery (Recti weakening/strengthening & Inferior oblique weakening either (graded recession ) according to the surgical indication, and ^CH & ^CRF were calculated, each is the preoperative – the postoperative value.
Results: ^CH & ^CRF =-0.78±1.56 & -0.72±2.15 respectively, and a highly significant difference was found between each of the pre and postoperative CH & CRF ( p< 0.001). 18 eyes had single EOM surgery, while 24 had multiple (2 or 3) EOM surgery, ^CH in single group = -1.28±1.5, ^CH in multiple group = 0.4±1.49 (p=0.07). 23 eyes had EOM weakening surgery, while 18 had combined weakening & strengthening EOM surgery, ^CH in weakening group = -1.24±1.77, ^CH in combined group = -0.26±1.07 (p=0.04). A non significant difference was found for ^CRF (p=0.53).
Discussion: The release of anterior traction forces on the sclera is the suggested explanation of postoperative increase of CH
Conclusion: Strabismus surgery has an early tendency for increase of the postoperative CH specially for muscle weakening procedures
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