Corneal Cross-linking and Refractive Surface Ablation in Patients With Asymmetric Corneas

Study Overview
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Brief Summary
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The purpose of this study is to evaluate safety and efficacy of corneal cross-linking and photorefractive keratectomy for refractive correction in patients with bilateral asymmetric topography.

Detailed Description
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Corneal cross-linking (CXL) by the photosensitizer, riboflavin (vitamin B2), and ultraviolet A (UVA) light increases corneal rigidity and has been described as an effective method for stabilizing the cornea in patients with progressive keratoconus. The photochemical reaction in this procedure causes the collagen to form additional covalent connections between its fibers, which stabilizes the stromal collagen fibers, improving the collagen's structure and the cornea rigidity. It is a relatively safe procedure with low rates of complications Photorefractive keratectomy (PRK) it is a traditional technique for refractive surgery. In cases of irregular corneas or re-operation normally the favorite ablation profile chosen is the guided surgery, topography guided or wavefront guided, showing better results. This technique is also relatively safe procedure with low rates of complications. One of the most unwanted complications of this surgery and also rare is corneal ectasia. Combining PRK and CXL is already done in patients with keratoconus and suspected keratoconus. This combined procedure uses the principle that CXL stiffen the cornea making it possible to reduce corneal thickness with PRK without weakening corneal strength. Literature show better results, in keratoconus, with simultaneous procedures. Guedj et al performed PRK in keratoconus suspects and within 5 years he did not found any corneal ectasia.

Official Title
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Two Years Follow up of Corneal Cor Cross-linking and Refractive Surface Ablation in Patients With Asymmetric Corneal Topography

Conditions
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Surgical Procedure, Unspecified

Intervention / Treatment
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* Procedure: CXL + PRK group
* Procedure: PRK group


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: bilateral asymmetric topography with inferior steepening corneal thickness of 440 micra at the thinnest point inferior-to-superior index (I-S) between 1.0D and 1.4D maximum keratometric steepness < 47.00D stable refraction more than 1 year. Exclusion Criteria: forme fruste keratoconus and keratoconus previous eye surgery previous eye trauma confirmed pregnancy

Ages Eligible for Study
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Minimum Age: 23 Years
Maximum Age: 51 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: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: CXL + PRK group<br>Corneal cross-linking surgery is perfomed in one eye : deepithelization of the cornea and instillation of 0,1% riboflavin (ophthalmos - Brazil) for 30 minutes and UVA for irradiated for 30 minutes with ultraviolet-A of 365nm light with an irradiance of 3 mW/cm2 using Xlink (Opto - São Carlos) Photorefractive keratotomy will be perfomed in the same eye using excimer laser Ladarvision (Alcon - USA) with 0,02 % mitomicin for 30 seconds (Ophthalmos - Brasil) simultaneously with the other eye. Both procedures will have the same post operative treatment : gatifloxacin 0,3% 6/6h for 10 days prednisolone acetate 0,12% 6/6h por 14 days | Procedure: CXL + PRK group<br>* Corneal cross-linking with subsequent photorefractive keratotomy after 6 months was performed in one eye<br>|
| Active Comparator: PRK group<br>Photorefractive keratotomy will be perfomed in the fellow eye using excimer laser Ladarvision (Alcon - USA) with 0,02 % mitomicin for 30 seconds (Ophthalmos - Brasil) simultaneously with the other eye. Both procedures will have the same post operative treatment : gatifloxacin 0,3% 6/6h for 10 days prednisolone acetate 0,12% 6/6h por 14 days | Procedure: PRK group<br>* Photorefractive keratotomy alone was performed in contra lateral eyes<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Refractive results - spherical equivalent in diopters |  | 30 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Biomicroscopy findings with the slit lamp |  | 30 months | 
| Visual acuity in logMar |  | 30 months | 
| Aberrometric Results in root mean square | Only coma and spherical aberration | 18 months | 
| Topographic results in diopters | we will measure the increase in diopters with time | 30 months | 
| Pachymetric results in micra |  | 30 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Refractive Surgical Procedures, Photorefractive Keratectomy, Aberrometry