title: Effect of Horizontal Strabismus Surgery on the Refractive Status.
abstract: OBJECTIVE
  To evaluate the effects of horizontal strabismus surgery on the refractive and astigmatic status of eyes following horizontal muscle surgery using double-angle vector analysis.
  
  
  METHODS
  This was a retrospective analysis of 137 patients (250 eyes) conducted between February 1997 and October 2010 in patients who had unilateral or bilateral recession or monocular recession and/or underwent resection of horizontal muscles by a single surgeon. Refraction data were obtained at 1-2 weeks preoperative and at 4-6 weeks and 4-6 months postoperative. Surgically induced refractive changes were calculated using double-angle vector analysis.
  
  
  RESULTS
  The mean change in the spherical equivalent (SE) of the refraction was 0.23 ± 0.78 D for surgically induced refractive changes at 4-6 weeks postoperative (SIRC1; p < 0.0001) and 0.14 ± 0.85 D (p = 0.018) for surgically induced refractive changes at 4-6 months postoperative (SIRC2), indicating a small shift in the myopic direction with regression at 4-6 months. The mean amplitudes of the induced cylinders were 0.072 ± 1.22 D (p = 0.262) in SIRC1 and 0.20 ± 1.14 D (p = 0.012) in SIRC2, and the mean axis of the induced plus cylinder was 21.74° in SIRC1, indicating a small shift in the with-the-rule direction, but no statistically significant difference from zero (p = 0.331). The changes in the surgically induced refraction over time (SIRC d), ie, 0.05 ± 0.64 in SE (p = 0.255) and 0.09 ± 0.65 in the cylinder (p = 0.049), were stable. There was no significant correlation between the amounts of horizontal rectus muscle recession and/or resection and the cylinder power of individual induced astigmatism at 4-6 weeks after surgery (p = 0.266) and the myopic shift (p = 0.345). Moreover, there were no significant correlations between the ages of the patients and the spherical equivalent for SIRC1 (p = 0.858) and the induced cylinder for SIRC1 (p = 0.750).
  
  
  CONCLUSIONS
  Horizontal rectus muscle surgery tended to induce a transient, statistically significant change in the spherical equivalent of refraction, with a myopic shift that was clinically not important. Our findings did not strongly support that the astigmatism induced changes. There was no correlation between the amount of recession and/or resection and the amount of induced refractive error.
authors.affiliation: a Department of Ophthalmology , University of Dammam, Consultant Ophthalmologist at King Fahd Hospital of the University , Saudi Arabia and.
authors.forename: Elham
authors.initials: E
authors.lastname: Al-Tamimi
authors.affiliation: b Consultant Ophthalmologist at Dammam Medical Tower , Saudi Arabia.
authors.forename: Ghadah
authors.initials: G
authors.lastname: Al-Nosair
authors.affiliation: a Department of Ophthalmology , University of Dammam, Consultant Ophthalmologist at King Fahd Hospital of the University , Saudi Arabia and.
authors.forename: Sanaa
authors.initials: S
authors.lastname: Yassin
mesh_terms: D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000503:physiopathology / Q000601:surgery*; D013508:Ophthalmologic Surgical Procedures; D011184:Postoperative Period; D012029:Refraction, Ocular / Q000502:physiology; D012030:Refractive Errors / Q000503:physiopathology*; D012189:Retrospective Studies; D013285:Strabismus / Q000503:physiopathology / Q000601:surgery*; D014787:Vision Tests
keywords: Astigmatism; horizontal muscle surgery; horizontal strabismus surgery; refraction; surgical induced refractive error