الفهرس 
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Abstract
Anterior segment optical coherence tomography (AS-OCT) is a valuable, non-invasive and non-contact method to evaluate anterior segment structures quantitatively. Photorefractive keratectomy (PRK) is one of the surface ablation procedures, performed for treat refractive errors in patients not candidates for LASIK. However, eyes with PRK have some notable adverse effects like severe pain, discomfort and prolonged visual recovery due to the process of epithelial wound healing, which usually starts on the day of surgery and may last up to 4 days after surgery.
The aim of the study was to evaluate of corneal epithelial changes after photorefractive Keratectomy by anterior segment Optical coherence.
This study was done at Menoufia University Hospital Ophthalmology department and Tiba eye center. It was a prospective non-randomized clinical study included fifty patients coming for PRK.
All patients were subjected to the following:
1. Full history taking: personal history (age, sex), chronic systemic diseases with special emphasis on diabetes mellitus as regard age of onset, duration and type of treatment, eye diseases as glaucoma, past history of previous ocular inflammation, surgery or trauma.
2. Best corrected visual acuity (BCVA) by decimal chart.
3. Slit lamp bio microscopy (Topcon, Tokyo, Japan) of the anterior segment for examination of the corneal clarity, Lens status.
4. IOP measurement with Goldmannapplanation tonometer (Topcon, Tokyo, Japan).
5. Funds examination by indirect ophthalmoscopy (Heine Omega, Loni, Ghaziabad, Turky) and slit lamp biomicroscopy with auxillary lens (78 D lens)for evaluation of the optic nerve head and retina
Special investigations (Corneal topography), Corneal topography was performed in all cases using pentacamsystem (Wave Light® Allegretto Oculyzer) (Wave Light®, Chicago, USA).
Anterior segment optical coherence tomography(AS-OCTzeiss cirrus –5000 HD-OCT) (Carl zeiss, Oberkochen, Germany) was done in all case to evaluate epithelial thickness.
The surgical technique: one surgeon performed the cases (Abdel RahmanEl-sebaey) All patients under went photorefractive keratectomy (PRK) using wave light Allegero EX-500 Excimerlaser (ALCON, Texas, USA).
Post-operative:After PRK is completed one DROP of moxifloxacin (0.5%) was instilled then we inserted a bandage contact lens to protect the cornea as the epithelial layer grows back over the next 3-4 days. At 2 months and 3 months after surgery, manifest refraction, uncorrected visual acuity UCVA, Best-corrected distance visual acuity BCVA, AS-OCT was assessed.
Follow-up: On the seventh postoperative days, contact lens was removed.Regular follow-up was conducted on the first week, 2 months, 3 months post operatively. In each visit Careful examination of the patients was done with
SUMMARY
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special attention to: 1. Best-corrected distance visual acuity (BCVA).2. Slit-lamp examination (Cornea: corneal clarity).
Intra ocular pressure (IOP) measurement. 4. Any postoperative complications.
Anterior segment OCT:It was done postoperative to evaluate actual epithelial thickness changes at two and three months after PRK.
This study showed that:
Age ranged from 20-40 with mean value 30.79±6.241. Male cases were 15(30%) while female cases were 35(70%).
Sphere diopter ranged from -1.5 – -5.75 with mean value -3.244±1.659 and Cylinder diopter ranged from -1.5– -2.75 with mean value -0.880±1.040 while AXIS ranged from 0 – 180 with mean value 74.60±68.306.
Ablation Depth ranged from 20 – 109 with mean value 62.42±20.911.
Inferior thickness at preoperative ranged from 47 – 60 with mean value 56.50±3.603 and at postoperative time it was increased after 3 months with a mean of 60.81±4.485, Superior thickness at preoperative ranged from 47 – 63 with mean value 53.29±4.207 and at postoperative time it was increased after 3 months with a mean of 59.52±4.868, Temporal thickness at preoperative ranged from 47 – 65 with mean value 55.56±4.105 and at postoperative time it was increased after 3 months more than other with a mean of 63.92±4.685, Nasal thickness at preoperative ranged from 47 – 60 with mean value 53.29±4.037 and at postoperative time it was increased after 3 months with a mean of 59.33±4.764 and Central thickness at preoperative ranged from 49 – 59 with mean value 53.83±3.097 and at postoperative time it was increased after 3 months with a mean of 59.54±3.764. There were statistically significant differences between pre and postoperative. Thickness was more thickening in temporal and inferior.
Spherical Equivalent at preoperative it ranged from-0.625– -6.25 with mean value -3.827±1.523 and there were no differences between spherical equivalent postoperatively after 2 months and 3 months with a mean value -0.495±0.405.
No correlation between changes of epithelial thickness post operatively and spherical equivalent (refraction).
Inferior thickness after 2 months ranged from -1 – 3 with mean value 0.19±0.790 and after 3 months it was increased with a mean of 6.31±2.553, Superior thickness after 2 months ranged from -2 – 3 with mean value 0.35±1.021 and after 3 months it was increased with a mean of 6.23±2.176, Temporal thickness after 2 months ranged from -2 – 4 with mean value 0.63±1.496 and after 3 months it was increased with a mean of 8.35±2.436, Nasal thickness after 2 months ranged from -2 – 7 with mean value 0.38±1.362 and after 3 months it was increased with a mean of 6.06±2.00 and Central thickness after 2 months ranged from -2 – 3 with mean value 0.06±0.810 and after 3 months it was increased with a mean of 5.71±2.221. There were statistically significant differences between postoperative after 2 months and after 3 months.
The epithelial thickness at two month postoperatively returned to its normal thickness preoperatively.
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There was statistically significant positive correlation between Epithelial Thickness and Ablation Depth.
Based on our results we recommend for further studies on higher number of patients and longer period of follow up to emphasize our conclusion.