Optical Coherence Tomography Guided Transepithelial Phototherapeutic Keratectomy

Study Overview
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Brief Summary
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Optical Coherence Tomography (OCT) machines are non-contact instruments that can measure the depth of scars and other causes of cloudiness in the front of the cornea. The purpose of this study is to determine whether OCT-guided settings for the lasers used for removal of corneal scars and other partial-thickness corneal defects result in improved vision in patients receiving these procedures.

Detailed Description
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The long-term goal of this project is to utilize newly available very high-speed OCT technology to guide surgical treatments of corneas with superficial opacities and irregularities. OCT is well known for its exquisite resolution, but until recently it has not had sufficient speed to capture the shape of the cornea because of eye motion during OCT scanning. The development of Fourier-domain OCT (FD-OCT) technology has made the requisite speed possible. Eyes with superficial opacities (corneal scars and stromal dystrophies) can be treated by phototherapeutic keratectomy (PTK). Currently, many surgeons rely on subjective slit-lamp impression of opacity depth to guide PTK and repeat slit-lamp examinations during surgery to determine if the opacity has been sufficiently reduced. Unpredictable hyperopic shifts can occur after PTK. The aim of this project is to develop methods for imaging the cornea with an FD-OCT system that will precisely measure corneal shape and use this information to guide surgery. Patients with irregularly shaped corneas could have their vision restored by reshaping the corneas with a procedure that combines the precision of OCT and lasers.

Official Title
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Optical Coherence Tomography Guided Transepithelial Phototherapeutic Keratectomy

Conditions
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Corneal Opacity

Intervention / Treatment
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* Drug: OCT-guided laser phototherapeutic keratectomy


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients with vision primarily limited by superficial opacities and irregularities that could be removed by PTK while leaving at least 250 µm. Exclusion Criteria: Inability to give informed consent Inability to maintain stable fixation for OCT imaging Inability to commit to required visits to complete the study Deep corneal opacities and irregularities Cataracts, retinal disease, glaucoma, or other eye conditions that may limit the visual outcome after surgery

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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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Surgery<br>OCT is assisting in surgery guidance. | Drug: OCT-guided laser phototherapeutic keratectomy<br>* Preoperative measurements from the OCT are used to assist the calculation in deciding the laser depth settings for removal of anterior corneal opacities and defects in the phototherapeutic PTK procedure. The surgeon uses the OCT data to plan a range of treatment parameters to remove most of the opacity while preserving at least 250 microns of residual corneal stroma.<br>* Other names: Zeiss/Visante Time-domain K051789;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Improvement in best spectacle-corrected visual acuity (BSCVA) after PTK | The primary goal of the trial is to determine the efficacy of the OCT-guided PTK treatment of corneal opacities. During the course of the trial, we will compare the predictive accuracy of the original OCT-guided PTK planning system to the OCT topography-guided system. BSCVA will be measured in typical Snellen acuity notation as 20/xx (feet) | 12 months post-procedure | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Improvement in uncorrected visual acuity (UCVA), refractive error, and higher order aberrations | A second goal is to develop a more sophisticated OCT guidance system incorporating OCT topography of anterior and posterior corneal surfaces and to develop a mathematical model that relates epithelial thickness variation to corneal mean curvature. During the course of the trial, we will compare the predictive accuracy of the original OCT-guided PTK planning system to the OCT topography-guided system. UCVA will be measured in typical Snellen acuity notation as 20/xx (feet) | 12 months post-procedure | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Phototherapeutic keratectomy, Optical coherence tomography, Corneal opacity, Corneal dystrophy