الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Strabismus is a well-known ocular disorder and it should be treated early to restore normal ocular alignment and prevent amblyopia. Treatment is by refractive error correction, orthoptic exercises, occlusive patching, topical medications and extraocular muscle surgery. Surgery is a major treatment of choice for strabismus and its basic goal is to align the eyes to their primary position. Multiple studies have shown that corneal topography and corneal refractive power can change after strabismus surgery. Some of the refractive changes were found to be mild and regress with time, but others were significant and lasted for long time. Most of them reported a postoperative myopic shift, although some showed a hyperopic shift or no significant change in spherical equivalent. As with the spherical equivalent, an increase in with-therule (WTR) astigmatism has been reported in the majority of studies. Various imaging techniques have been developed for corneal curvature assessment, including corneal topography devices combining a Placido disc and a Scheimpflug camera The cornea is responsible for the majority of the eye’s refractive power, so its topography is important in determining the quality of vision and corneal health. Corneal topography is a non-invasive imaging technique for mapping the surface curvature of the cornea. The aim of our study is to evaluate the effect of strabismus surgery on the corneal topographic changes This is a prospective interventional randomized study included 40 eyes of 20 patients diagnosed with horizontal strabismus. . The patients were divided into four groups with five patients in each group. First group performed bilateral lateral rectus recession, second group performed bilateral lateral rectus resection, third group performed bilateral medial rectus recession and the last group performed bilateral medial rectus resection. Corneal topography was performed preoperative, one and six months after the surgery. The preoperative and postoperative data were subtracted and statistically analyzed. Data included K1, K2, corneal astigmatism power and the axis. The effect of surgery on spherical equivalent and BCVA was also evaluated. The four groups were well matched in baseline data, as there were no statistically significant differences between the studied groups as regard age, sex and side. In this study, 6 months postoperatively there were significant changes of K1, K2 and the astigmatism power in group I and group III. Different strabismus surgeries have different effects on corneal topography and the refraction. According to our study, horizontal muscle recession (MR or LR) has significant effect on corneal topographic parameters K1, K2 and astigmatism that persists to at least six months after the operation, on the other hand horizontal muscle resection has no significant effect on these parameters. There was no significant change in the axis in all groups. There was significant myopic shift in the spherical equivalent and significant improvement in BCVA.