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C. F. Gomi, I. Debert, F. A. Medeiros, M. Polati, D. B. Granet; Effect of Horizontal Strabismus Surgery in Refraction. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1125.
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The importance and mechanisms of the refractive changes after strabismus surgery has been subject of debate. The purpose of this study was to evaluate the refractive changes that follow unilateral horizontal strabismus surgery and their clinical relevance.
A retrospective chart review was performed of all patients who underwent unilateral surgery for horizontal strabismus from Jan-2000 to Dec-2005. Patients with vertical deviation or who underwent surgery on vertical rectus or oblique muscles were excluded. Refractive error was assessed pre and at least 45 days after surgery, with cycloplegic retinoscopy in all patients. The non-operated eye served as control.
Two-hundred and four charts were reviewed and 59 patients met the inclusion criteria. There were 27 males and 32 females, with mean age ± SD of 16.6 ± 10.6 years. The mean pre operative values in surgical eyes were: +0.20 ± 3.91 D for sphere, +0.96 ± 1.21 D for cylinder and +0.68 ± 3.77 D for spherical equivalent. The mean pre operative values in control eyes were: +0.61 ± 2.22 D for sphere (p=0.284), +0.60 ± 0.75 D for cylinder (p=0.002) and +0.92 ± 2.12 D for spherical equivalent (p=0.790). The absolute change in these three refractive components were calculated for the operated and control eyes and then compared. Surgical eyes showed no significant difference in mean change of sphere and spherical equivalent values when compared to control eyes (+0.85 ± 1.13D vs. +0.52 ± 0.50D, respectively for sphere; p= 0.056 and +0.63 ± 0.92D vs. +0.44 ± 0.45D, respectively for spherical equivalent; p= 0.210). For cylinder measurements, surgical eyes showed more significant changes than control eyes (+0.57 ± 0.72D vs. +0.28 ± 0.29D, respectively; p= 0.001). A change of equal or greater than 0.50D in sphere occurred in 38 eyes (64.4%) of the surgical group and in 28 eyes (47.5%) in the control group. For cylinder, a change of equal or greater than 1.00D was found in 17 surgical eyes (28.8%) and in only 2 control eyes (3.4%). For spherical equivalent, a change of at least 0.5D was observed in 28 surgical eyes (47.5%) and in 23 control eyes (39.0%).
Significant changes in cylindrical measurements were observed before and after horizontal strabismus surgery. Clinically significant changes in refraction affect a large portion of eyes undergoing this type of surgery.
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