الفهرس 
Introduction and Aim of the WorkOnly 14 pages are availabe for public view
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Abstract
Recommendations To understand better the variations of epithelial and stromal changes, further study with a higher number of eyes is required.
• Studying the corneal thickness in males and females separately may add to further information about epithelial and stromal changes together with dividing further groups according to amount of error of refraction to observe the thickness behavior difference and its relation with the laser ablation depth
• Future studies with longer follow-up time, particularly pertaining to changes in epithelial thickness profile extending beyond the 6-mm diameter, are highly recommended.
One limitation of this study is that the inability of the instrument accustomed to measure corneal and epithelial thickness outside the central 6-mm diameter of the cornea so studying larger area of the cornea may give us a wider idea of cellular behavior.
• The validity of our analysis should be viewed by taking the restrictions of the present SD-OCT technology (limited axial resolution and tear film discrimination) with concern. Higher axial resolution instrumentation with higher ability for discrimination of the tear film would be useful.
• Likewise, there’s a requirement to explore the corneal changes for hyperopic and high astigmatism treatments. a lot of enhancements within the study design, like excluding eyes with astigmatism and limiting the spherical refraction groups to distinct small ranges, may additionally be useful in investigating the epithelial response as a result of myopia treated.
• learning the variations in numerous surface ablation techniques would be a 3rd avenue for additional analysis
• Exploring the three-dimensional epithelial morphology following PRK is important to broaden our understanding of corneal wound healing. Information regarding the epithelial contribution to the refraction might improve the programming of the re-treatments. Estimation of the epithelial refractive contribution to the refractive condition in any particular case would represent an excellent improvement com- pared to this use of empirical nomograms for adjusting refractive retreatments that involve epithelial removal. Moreover, an exact epithelial mapping is crucial in designing corneal regularization using topography-guided surface ablation in the treatment of irregular astigmatism and keratoconus.
Summary
This is a prospective, one group, non-randomized, interventional study that aims at evaluation of epithelial and stromal thickness after photo refractive keratectomy. The study was conducted on 50 eyes of 28 patients , 6 were operated on uniocular. 24 eyes were for females ( 48 % ) and 26 eyes were for males (52 % ) with their mean age 28.12 ± 6.22. Patients with myopia of spherical equivalent -6 or less, are prospectively assigned to PRK in which the surgical procedure induces different changes in corneal epithelial and stromal thickness which is measured before and after the procedure using the spectral domain anterior segment OCT technology.
Mean central epithelial and stromal thickness of the studied patients preoperative were : 55.32 ±5.2, 426.42±38.66 respectively. The study showed a generalized pattern of decreased epithelial thickness in the period in the 1st month after performing PRK. In the period from the 1st month postoperative and the 6th month, a generalized pattern of re-increase of the epithelial thickness was observed. Regarding stromal thickness a generalized pattern of decrease was observed among the 6 months period after performing PRK.
Epithelial and stromal wound repair occurs in a manner in which the epithelium seems to behave on reverse the change in stromal thinning and bring back the cornea to its preoperative curvature and integrity by remodeling itself to mirror the amount of stromal tissue removed.
Refraction stability has been achieved in most cases from the 3rd month postoperative which appeared to be stable and to have undergone no further significant changes in the following 5 months. Two eyes developed haze and 5 eyes suffered from regression. The refraction and the keratometry changes have no correlation with central epithelial nor stromal thickness changes after PRK which doesn’t appear to contribute to postoperative refractive regression. However, in high myopic cases this fact is unclear.
To better assess the relation between wound repair, thickness, tissue remodeling and postoperative refractive changes, further studies are being waited.