الفهرس 
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Abstract
The aim of this study is to assess the effect of LASIK on the cornea, and to evaluate it as regard changes of the anterior and posterior corneal curvatures (Rh; horizontal radius, RV; vertical radius, Km; the mean keratometric power), asphericity and changes of the anterior and posterior corneal elevation. Thirty eyes of sixteen patients were included in this prospective study. All eyes were myopic eyes either with or without astigmatism with a mean spherical equivalent of -5.07±2.1 SD. Pediateric patients; patients with history of ocular, corneal or refractive surgery were excluded. Also, patients with central corneal thickness less than 500 micron, patients with too flat (<40) or too steep(> 48) corneas and pregnant patients , patients with autoimmune diseases were also excluded.
LASIK was performed between December2011 and April 2012 and Pentacam was performed preoperatively, and three months postoperatively.
Sstatistically significant decrease of the mean keratometric power of the anterior corneal surface (Km) (P value= 0.001) was detected after three months to its pre-LASIK value. While there was no significant change in keratometric power of posterior surface (p value = 0.836). Also, asphericity(Q-value) of the anterior and posterior surfaces decreased significantly after LASIK (P value=0.001). Corneal thickness (pachymetry) showed significant decrease three months after LASIK (P value = .001). Also refraction revealed significant decrease three months post-LASIK (p=0.001), while there was no significant changes in AC depth and BCVA (p=0.069, p=0.245 respectively)
Forward bulge of the anterior corneal surface at 4mm and 7mm zone from the center was detected three months (significantly with p value of 0.001 for both) after LASIK, while at 4mm and 7 mm zone from the center the posterior elevation increased three months after LASIK ( no significant change with p value of 0.637& 0.26 respectively).But no cases of post-LASIK ectasia were detected.
There was significant changes in anterior radii of curvature (Rv ,Rh) (p=0.001 for both), while there was no significant changes in posterior radii (p=0.695 ,p=0.720 respectively).