Myopia ≤ -6 Diopters or Myopic Astigmatism ≤ -4 Diopters
Conditions
Keywords
Photorefractive Keratectomy PRK, Phototherapeutic Keratectomy PTK, Trans-epithelial PRK, Laser Vision Correction LVC
Brief summary
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
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.
Interventions
PROCEDUREPhotorefractive keratectomy (PRK)
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.
Sponsors
Assiut University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
SINGLE (Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
* Inclusion Criteria: Candidates for Laser vision correction (LVC) with 1. Myopia up to -6 diopters 2. Myopic astigmatism up to -4 diopters 3. Corneal thinnest location ≥ 500 um and a residual stromal bed ≥ 300um. *
Exclusion criteria
1. Patients not candidates for LVC. 2. Hyperopic patients. 3. Systemic disease that contraindicates LVC. 4. Intra- or post-operative complications.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Uncorrected distant visual acuity (UDVA) | 6 months | Visual acuity measurement using Snellen's Acuity Chart and will be expressed as decimal notation |
| Postoperative Refraction (Spherical equivalent) | 6 months | Measured by Topcon Auto-Keratorefractometer |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Epithelial healing duration | 2 weeks | Time for the epithelium to heal reported in days after PRK procudre |
| Postoperative pain | 1 week | 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) |
| Postoperative Haze | 3 months | 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 1. Haze not interfering with visibility of fine iris details 2. Mild obscuration of iris details 3. Moderate obscuration of the iris and lens 4. Complete opacification of the stroma in the area of the scar, anterior chamber is totally obscured |
Countries
Egypt
Outcome results
None listed