The Effect of Strabismus Muscle Surgery on Corneal Biomechanics.

Heba A El Gendy,Iman M Eissa,Noha M Khalil,Shireen Ma Shousha

doi:10.1155/2018/8072140

Abstract

Purpose Studying the early effect of different extraocular muscle (EOM) surgeries on corneal biomechanics. Subjects and methods This is a prospective, nonrandomized, interventional study, in which 42 eyes of 29 candidates for EOM surgery for strabismus correction 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) and corneal resistance factor (CRF) preoperatively. Same patients were reassessed using ORA 4 weeks postoperatively following a different standard EOM surgery (recti weakening/strengthening and inferior oblique weakening either (graded recession) according to the surgical indication, and ∆CH and ∆CRF were calculated, each is the preoperative − the postoperative value. Results ∆CH and ∆CRF = −0.78 ± 1.56 and −0.72 ± 2.15, respectively, and a highly significant difference was found between each of the pre- and postoperative CH and CRF (p < 0.001). 18 eyes had single EOM surgery, while 24 had multiple (2 or 3) EOM surgery; ∆CH in the single group = −1.28 ± 1.5, and ∆CH in the multiple group = 0.4 ± 1.49 (p=0.07). 23 eyes had EOM weakening surgery, while 18 had combined weakening and strengthening EOM surgery: ∆CH in the weakening group = −1.24 ± 1.77 and ∆CH in combined group = −0.26 ± 1.07 (p=0.04). A nonsignificant difference was found for ∆CRF (p=0.53). Conclusion A different EOM surgery has an early tendency for increase of the postoperative CH specially for muscle weakening procedures (recti recession/inferior oblique muscle weakening).

Highlights

Corneal and ocular biomechanics have been a topic of increasing interest in ophthalmology over the last two decades.e eye has been commonly thought of as an optical rather than a mechanical system; biomechanics can still play an important role in a number of different ophthalmic pathologies [1, 2].Corneal biomechanical properties, namely, corneal hysteresis (CH), corneal resistance factor (CRF), and corneal compensated intraocular pressure (IOPcc), generally reflect corneal deformation and equilibrium under the application of external force
CH, CRF, and intraocular pressure Goldmann (IOPg) were all found to increase significantly early after strabismus surgery, a finding which supports our hypothesis that, if forces applied to the global wall by the extraocular muscles are changed, the corneal biomechanics are likely to change
Ere was a tendency for an increase in IOPcc after surgery (p 0.06); it was not statistically significant. e significant increase in IOPg could be partially attributed to steroid-induced rise of IOP in three cases which went back to normal with follow-up after cessation of topical steroids

Summary

Introduction

Corneal and ocular biomechanics have been a topic of increasing interest in ophthalmology over the last two decades. Data collection conformed to all local laws, and the study followed the guidelines of the Declaration of Helsinki 1964 [13] In this prospective, nonrandomized, interventional study, 29 patients, aged 14–37 years, who presented with manifest heterotropias and who met the inclusion criteria for the current study, were scheduled for elective strabismus muscle surgery. All patients who met the predetermined inclusion criteria or their guardians were requested to sign a full informed consent regarding their acceptance of participation in the current study, the surgical procedure, the follow-up protocol regimen, and the possible complications. Corneal hysteresis (CH), corneal resistance factor (CRF), intraocular pressure Goldmann (IOPg), and cornea compensated intraocular pressure (IOPcc) were measured using Reichert Ocular Response Analyzer (ORA, Reichert Instruments, Depew, New York, USA). Bivariate correlations were performed between different parameters using Pearson’s correlation coefficient (r), and Δ for a variable was calculated by subtracting the preoperative value from the postoperative value

Results

ΔCH ΔCRF

Discussion