Outcomes of a New Trans-epithelial Photorefractive Keratectomy (Streamlight PRK) Compared to Conventional PRK Procedures

Study Overview
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Brief Summary
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Photorefractive keratectomy (PRK) involves mechanical or alcohol assisted debridement of the epithelium that leads to potential basement membrane (BM) injury ,with resultant more significant haze and pain compared to laser assisted epithelial removal known as 2 step trans-epithelial PRK (PTK-PRK). Our study is focusing on comparing the outcomes of the conventional 2 step trans-epithelial PTK-PRK to the new single step trans-epithelial PRK (StreamLight PRK, Alcon lab, TX, USA).

Detailed Description
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Photorefractive keratectomy (PRK) is nowadays one of the commonest refractive procedures in laser vision correction (LVC). PRK differs from laser in situ keratomileusis (LASIK) in that it's a flapless procedure involving the removal of corneal epithelium with different techniques including manual removal , alcohol assisted removal or excimer laser assisted removal with phototherapeutic keratectomy (PTK). Mechanical or alcohol assisted debridement of the epithelium may lead to potential basement membrane (BM) injury ,with resultant more significant haze and pain compared to laser assisted epithelial removal known as 2 step trans-epithelial PRK (PTK-PRK). Single step trans-epithelial PRK allows removing the epithelium and stroma in a single step with a single ablation profile. Previous studies paid particular attention for comparing the 2 step PTK-PRK procedure or the new single step PRK procedure to the conventional PRK procedures involving epithelial removal whether manual or alcohol assisted. The aim of this study is to focus on comparing the different outcomes of the new single step Trans-epithelial PRK (StreamLight Technology) versus the routine 2 step PTK-PRK in terms of postoperative vision, epithelial healing, pain scoring and haze evaluation.

Official Title
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Outcomes of a New Trans-epithelial Photorefractive Keratectomy (Streamlight PRK) Compared to Conventional PRK Procedures

Conditions
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Myopia ≤ -6 Diopters or Myopic Astigmatism ≤ -4 Diopters

Intervention / Treatment
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* Procedure: Photorefractive keratectomy (PRK)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Candidates for Laser vision correction (LVC) with Myopia up to -6 diopters Myopic astigmatism up to -4 diopters Corneal thinnest location ≥ 500 um and a residual stromal bed ≥ 300um. Exclusion criteria Patients not candidates for LVC. Hyperopic patients. Systemic disease that contraindicates LVC. Intra- or post-operative complications.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Patients planned to undergo conventional 2 step trans-epithelial PTK-PRK<br>Patients planned to undergo: Epithelial removal using Phototherapeutic Keratectomy PTK as a separate step. Laser Vision Correction using Excimer laser wavefront optimized technology. | Procedure: Photorefractive keratectomy (PRK)<br>* Photorefractive keratectomy (PRK) is a surgical procedure used by ophthalmic surgeons to treat patients presented with refractive errors and involves corneal epithelial removal followed by application of excimer laser to correct different refractive errors including Myopia, Hyperopia and Astigmatism.<br>|
| Active Comparator: Patients planned to undergo the new single step trans-epithelial (StreamLight) PRK.<br>Patients planned to undergo: Epithelial removal and Excimer wavefront optimized Laser Vision Correction in a single step using the new StreamLight Technology. | Procedure: Photorefractive keratectomy (PRK)<br>* Photorefractive keratectomy (PRK) is a surgical procedure used by ophthalmic surgeons to treat patients presented with refractive errors and involves corneal epithelial removal followed by application of excimer laser to correct different refractive errors including Myopia, Hyperopia and Astigmatism.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Uncorrected distant visual acuity (UDVA) | Visual acuity measurement using Snellen's Acuity Chart and will be expressed as decimal notation | 6 months | 
| Postoperative Refraction (Spherical equivalent) | Measured by Topcon Auto-Keratorefractometer | 6 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Epithelial healing duration | Time for the epithelium to heal reported in days after PRK procudre | 2 weeks | 
| Postoperative pain | Verbal Rating Scale(a series of words commonly used to describe pain (0: no pain, 1: mild pain, 2: moderate pain, 3: severe pain, 4: disabling pain) | 1 week | 
| Postoperative Haze | Corneal Haze scoring using slit lamp bio-microscopy according to Fantes scoring system: 0: No haze, completely clear cornea 0.5: Trace haze seen with careful oblique illumination Haze not interfering with visibility of fine iris details Mild obscuration of iris details Moderate obscuration of the iris and lens Complete opacification of the stroma in the area of the scar, anterior chamber is totally obscured | 3 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Photorefractive Keratectomy PRK, Phototherapeutic Keratectomy PTK, Trans-epithelial PRK, Laser Vision Correction LVC