Comparison of Corneal Stromal Tissue Consumption (LATAC)

Study Overview
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Brief Summary
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In refractive surgery, stromal ablation depth is fundamental because it determines the thickness of the residual posterior wall. The posterior wall is an essential element that guarantees the refractive stability and the long term prevention of corneal ectasia after corneal refractive surgery. A minimum thickness of more or less 300 microns is universally accepted. Its calculation is based on well-known formulas, such as Munnerlynn ones. With the excimer laser platform last generation WaveLight® Allegretto® EX-500 of Alcon, a new treatment option called wavefront optimized is offered for myopia, astigmatism and hyperopia. The ablation profile has been developed to save stromal tissue consumption and to favor the quality of vision, by optimizing connections between the optical zone and the transition zone of the photoablation. Alongside the theoretical formulas, evaluation of the depth of ablation may be defined by differential ultrasonic pachymetry or by topographical analysis pre and postoperatively. The latter is currently the method of reference to assess the corneal thickness.

Official Title
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Comparison of Corneal Stromal Tissue Consumption Values Estimated When Programming the Intervention Versus the Values Measured by Pre and Postoperative Topography

Conditions
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Disorders, Refractive

Intervention / Treatment
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* Device: Measurement of stromal tissue ablation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients having a refractive disorder and for whom a refractive surgery is programmed. Exclusion Criteria: Patient opposed to participation in the study Another refractive surgery technique Hyperopic patient Pregnant or lactating woman Patient under a measure of legal protection Absence of affiliation to social security or universal health coverage (CMU)

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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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Device: Measurement of stromal tissue ablation|Stromal tissue consumption will be estimated preoperatively by WaveLight Allegretto EX-500 laser and central corneal thickness will be measured by Pentacam. One month after refractive surgery, during follow-up,central corneal thickness will be again measured by Pentacam.|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Difference between stromal tissue consumption, expressed in micrometers, estimated before surgery by WaveLight Allegretto EX-500 laser and measured one month after surgery by Pentacam | Stromal tissue consumption will be estimated preoperatively by WaveLight Allegretto EX-500 laser and central corneal thickness will be measured by Pentacam. One month after refractive surgery, during follow-up,central corneal thickness will be again measured by Pentacam. The difference between the estimated and the measured tissue consumption will be calculated. | One month |