الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 153 |  |  |
| | | from | 153 | | |
Abstract
The eye, like any other optical system, suffers from a number of specific optical aberrations. The optical quality of the eye is limited by optical aberrations, diffraction and scatter.(1) Correction of spherocylindrical refractive errors has been possible for nearly two centuries following Airy’s development of methods to measure and correct ocular astigmatism. It has possible to measure the aberrations of the eye and with the advent of refractive surgery it might be possible to correct certain types of irregular astigmatism. The appearance of visual complaints such as halos, glare and monocular diplopia after corneal refractive surgery has long been correlated with the induction of optical aberrations. Several mechanisms may explain the increase in the amount of higher-order aberrations with conventional eximer laser refractive procedures: a change in corneal shape toward oblateness or prolateness (after myopic and hyperopic ablations respectively),insufficient optical zone size and imperfect centration. These adverse effects are particularly noticeable when the pupil is large.(2)In normal population the dominant aberrations are the ordinary second-order spherocylindrical focus errors, which are called refractive errors .Higher order aberrations are a relatively small component, comprising about 10% of theeye’s tota laberrations.(3)High order aberrations increase with age and minor symmetry exists between the right and the left eyes.(4)In our study cases from Beni-Suef University Hospital were done in clear vision laser center in Cairo from May 2019 till January 2022.Study was designed as a prospective randomized intervention study including 40 myopic eyes of 20 patients (12 females /8 males in LASIK group and 6 females / 14 males in PRK group). The eyes were divided into two randomized groups A &B. - group A: 20 myopic eyes corrected with laser-assisted in situ keratomileusis. -group B: 20 myopic eyes corrected with Photorefractive keratectomy. In our study there are significant visual acuity and spherical equivalent improvement in both LASIK and PRK with no significant different between them, there is clinically significant increase in higher order aberrations 5mm and 6mm of LASIK group and no significant changes in PRK group with no significant different between them. There is Ho w/o z400 5mm and 6mm clinically significant increase in LASIK group and no significant changes in PRK group with significant different between them in 5mm and non-significant in 6mm, there is significant Total abrasion 5mm and Total abrasion 6mm improvement in both LASIK and PRK with no significant different between them. There is insignificant increase in spherical aberration in PRK and LASIK groups with no significant different between them there is significant improvement in PRK vertical trefoil and vertical coma while there are no significant changes in LASIK with no significant different between LASIK and PRK, there are no significant changes or different in LASIK and PRK horizontal coma, quadrafoil z441, 2nd astigmatism z421, 4th order sph aberration, 2nd astigmatism z420, quadrafoil z440,pentafoil 2551, 2nd vertical coma, 2nd horizontal coma, 2nd horizontal trefoil and pentafoil z550. There is non-significant increase in LASIK and PRK horizontal trefoil with significant different between them. There is significant improvement in 2nd vertical trefoil PRK with no significant different between PRK and LASIK.