Comparison Between Standard Deep Anterior Lamellar Keratoplasty (S-DALK) and Intralase Enabled Deep Anterior Lamellar Keratoplaty (IE-DALK)

Study Overview
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Brief Summary
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A prospective comparison between standard deep anterior lamellar keratoplasty (S-DALK) performed manually using a blade (trephine) and femtosecond laser-enabled deep anterior lamellar keratoplasty (IE DALK), where incisions are performed using the femtosecond laser.

Detailed Description
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Even though corneal transplants have been around for more than 100 years, and tools to improve their surgical technique keep getting perfected, both regular and irregular postoperative astigmatism continue to be major concerns in achieving predictable visual results. Femtosecond laser technology allows for the creation of more precise incisions with more reproducible patterns, which could lead us to believe that astigmatism management and visual results should be improved with this technology. This would be the first study to prospectively analyze standard versus femtosecond laser-enabled deep anterior lamellar keratoplasties in order to elucidate their relative advantages in the quest for a gold standard.

Official Title
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Comparison Between Standard Deep Anterior Lamellar Keratoplasty (S-DALK) and Intralase Enabled Deep Anterior Lamellar Keratoplaty (IE-DALK)

Conditions
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Scar, DALK Corneal Transplant, Keratoconus

Intervention / Treatment
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* Procedure: Standard Deep Anterior Keratoplasty (S-DALK)
* Procedure: IE-DALK (femtosecond)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age between 18 and 70 years Either advanced keratoconus or corneal scarring requiring a deep anterior lamellar keratoplasty Exclusion Criteria: Previous keratoplasty Advanced glaucoma Any other retinal or optic nerve pathology that could potentially affect visual outcome Strabismus or amblyopia Significant limbal stem cell deficiency (invlolving > 3 limbal clock hours) Active autoimmune disease.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 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
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: This is a randomize study, in which half of the participants will be receiving either the standard deep anterior lamellar keratoplasty (DALK) (with a blade) technique or the femtosecond laser technique that creates the initial incisions instead of a blade.
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Standard DALK<br>Standard (with the use of a blade) deep anterior lamellar keratoplasty (DALK), which is a partial thickness corneal transplant, which has been shown to be a safe and effective procedure. | Procedure: Standard Deep Anterior Keratoplasty (S-DALK)<br>* Standard (with the use of a blade) deep anterior lamellar keratoplasty (DALK), which is a partial thickness corneal transplant, which has been shown to be a safe and effective procedure.<br>|
| Active Comparator: IE-DALK (femtosecond)<br>Femtosecond deep anterior lamellar keratoplasty (DALK). The femotosecond laser technology allows for the creation of precise and reproducible corneal incisions. | Procedure: IE-DALK (femtosecond)<br>* Femtosecond deep anterior lamellar keratoplasty (DALK). The femotosecond laser technology allows for the creation of precise and reproducible corneal incisions.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from preoperative topographical corneal astigmatism | Corneal astigmatism is the difference (expressed in Diopter units) of refractive power between the steep and flat corneal meridians and is measured using corneal topography. Values range between 0 and 20 diopters. Lower values represent a better outcome. | preoperatively, 6, 12 and 15 months postoperatively | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from preoperative best-corrected distance visual acuity (BCVA) | BCVA will be measured using an ETDRS acuity chart and recorded in logMAR (logarithm of the minimal angle of resolution) units. Value range is between -0.125 and 3 logMAR. Lower values represent a better outcome. | preoperatively, 6, 12 and 15 months postoperatively. | 
| Change from preoperative uncorrected distance visual acuity (UCVA) | UCVA will be measured using an ETDRS acuity chart and recorded in logMAR (logarithm of the minimal angle of resolution) units. Value range is between -0.125 and 3 logMAR. Lower values represent a better outcome. | preoperatively, 6, 12 and 15 months postoperatively. | 
| Big-bubble success rate | This outcome represents the number of procedures where the deep anterior lamellar keratoplasty (DALK) procedure was completed using the big bubble surgical technique. This can either be Yes for successful or No for unsuccessful completion of this technique. Higher big-bubble success rates represent a better outcome. | 6 months postoperatively. | 
| Rate of conversion to penetrating keratoplasty | This outcome represents the number of failed DALK procedures (using any of the possible DALK techniques) that needed to be converted to a procedure other than DALK (a penetrating keratoplasty procedure). This can either be Yes for DALK failure and conversion to penetrating keratoplasty or No for a successful DALK procedure. Higher penetrating keratoplasty conversion rates represent a worse outcome. | 6 months postoperatively. | 
| Change from preoperative endothelial cell count | This is the density of corneal endothelial cells (measured as cells per square millimeter). Value range is between 300 and 3500 cells/square millimeter. Higher values represent a better outcome. | preoperatively, 6, 12 and 15 months postoperatively. | 
| Change from preoperative pachymetry | This represents corneal thickness, measured in microns. Value ranges are between 200 and 800 microns. Values between 500 and 600 micron represents a good outcome. | preoperatively, 6, 12 and 15 months postoperatively. | 
| Change from preoperative higher-order optical aberrations | Values of total higher-order optical aberrations and coma higher-order optical aberration measured in RMS (root mean square) units. Value range is between -20 and +20 RMS. Lower absolute value represents a better outcome (values closer to zero on both the negative and positive ends). | preoperatively, 6, 12 and 15 months postoperatively. |