Corneal High Order Aberrations After Stream Light and Mechanical Photorefractive Keratectomy

Study Overview
=================
Brief Summary
-----------------
Compare corneal high order aberrations before and after stream light trans-PRK and mechanical photorefractive keratectomy including third order aberrations; Trefoil and coma aberrations and forth order aberrations; spherical aberrations

Detailed Description
-----------------
Laser technology has played an important role in promoting the development of ophthalmology, especially corneal refractive surgery.1 Trans-epithelial photorefractive keratectomy (Trans-PRK) has become a highly researched topic in recent years.2 Different epithelial debridement methods with PRK showed favorable results for the surgical treatment of low to moderate myopia3. In mechanical PRK (m-PRK), epithelial debridement is achieved using a blunt spatula, whereas in stream light trans-PRK (t-PRK), there after an excimer laser is used to ablate corneal stroma3. The Stream Light t-PRK is a safe and effective treatment option for the correction of low to moderate myopia.4 Many studies have shown that the corneal asphericity developed significantly after refractive surgeries and introduce higher-order aberrations (HOAs).2 The present study focused on three of the most clinically important HOAs; spherical, coma, and trefoil aberrations, both preoperative and postoperative were recorded from topography over the 6-mm-diameter central corneal zone using Pentacam.

Official Title
-----------------
Comparison of Corneal High Order Aberrations After Stream Light Trans-PRK and Mechanical Photorefractive Keratectomy

Conditions
-----------------
Compare Corneal High Order Aberrations Before and After Stream Light Trans-PRK and Mechanical Photorefractive Keratectomy

Intervention / Treatment
-----------------
* Other: Photorefractive keratectomy


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: • Stable refraction for 1 year (refraction does not exceed 1D more than the last prescribed glasses). Discontinuation of soft contact lens wears at least 1 week before examination. Topography criteria: Corneal thickness equal or more than 470 um Symmetrical bow-tie Back elevation not more than +12 Normal Belin\Ambrosio Enhanced ectasia display Spherical equivalent not more than -6D. Exclusion Criteria: • Previous ocular surgery Concurrent ocular pathology; corneal scar, corneal dystrophy Systemic disease; Uncontrolled diabetes, collagen disease Post-operative complications; sub-epithelial haze.

Ages Eligible for Study
-----------------
Minimum Age: 20 Years
Maximum Age: 40 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Mechanical photorefractive keratectomy<br>Laser photorefractive keratecyomy by Ex500 excimer laser after mannual removal of corneal epithelium | Other: Photorefractive keratectomy<br>* Laser keratectomy by EX500 excimer laser after removal of corneal epithelium either mannually or by laser ablation<br>|
| Stream light trans-PRK<br>Laser photorefractive keratectomy by Ex500 excimer laser after removal of corneal epithelium by stream-light laser technique | Other: Photorefractive keratectomy<br>* Laser keratectomy by EX500 excimer laser after removal of corneal epithelium either mannually or by laser ablation<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Corneal high order aberrations measured before and after the intervention by corneal topography machine | Third order aberrations; Trefoil and coma aberrations Forth order aberrations; spherical aberrations Trefoil, spherical and coma aberrations | 1 monthe after surgery |