الفهرس 
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Abstract
br>SUMMARY
Laser -assisted in situ keratomileusis (LASIK) is becoming widely accepted as an effective method for the correction of myopia and astigmatism.
The maximum refraction in the eye occurs at the anterior surface of cornea due to its high curvature and due to the large difference between the refractive indices of media on its two sides, namely air and corneal substance (1 and 1.37).
Higher-order aberrations (HOAs) are small optical irregularities or imperfections of the eye which cannot be corrected by simple sphere and cylinder corrections. Many authors believe that HOAs are the reason many patients complain of halo, glare and decreased contrast sensitivity after successful corneal refractive surgery. In the normal eye, 90% of total aberrations are caused by the cornea.
Many techniques for measuring the eye’s aberrations have been described the most common technique is Shack-Hartmann aberrometry, it became possible to measure the low and high order aberrations of the optical system.
This study compares between the effect of different types of LASIK (proscan ablation and Zyoptix HD ablation) in correction of higher order abberations
Personalized refractive surgery based on wavefront analysis aims to correct or minimize high order eye aberrations while correcting low order aberrations. Thus, by providing a more homogeneous posto perative ocular surface, it offers a better postoperative visual quality
So, Zyoptix custom HD treatment is superior to Proscan conventional treatment in the correction of low and high order eye aberrations.