Pocket Versus Tunnel ICRS for Treatment of Keratoconus

Study Overview
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Brief Summary
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Keratoconus is a corneal degenerative disease associated with loss of best-corrected visual acuity. The use of intrastromal corneal ring segment implants is indicated to regularize the cornea and to reduce aberrations.

Detailed Description
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Keratoconus is a corneal degenerative disease characterized by corneal thinning and subsequent development of irregular astigmatism, diminution of vision and loss of best-corrected visual acuity. Management of keratoconus includes halting disease progression through a corneal strengthening procedure called corneal collagen cross-linking (CXL) which usually results in stabilizing the condition but with no improvement in visual acuity or quality. Intrastromal corneal ring segment (ICRS) implantation is a well-established procedure for the management of moderate keratoconus with a corneal flattening effect that is associated with improvement of visual acuity and reduction of optical aberrations. The aim of the study is to evaluate and compare the visual, refractive and topographic outcomes of two different femtosecond laser assisted surgical techniques to create a corneal stromal pocket or a tunnel for implantation of ICRS for the management of central keratoconus

Official Title
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Pocket Versus Tunnel Intrastromal Corneal Ring Segment Implantation (KeraRing) for the Management of Central Keratoconus

Conditions
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Keratoconus

Intervention / Treatment
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* Procedure: Intrastromal corneal ring segment implantation (Pocket)
* Procedure: Intrastromal corneal ring segment implantation (Tunnel)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients with progressive keratoconus with maximum keratometry (Kmax) between 50-65 diopters Central keratoconus (Keratoconus with steepest corneal point within the central 3 mm zone). Clear corneal with a minimum pachymetry of 400 μm. Exclusion Criteria: Corneal scars Patients with advanced keratoconus with Kmax > 65 diopters. Non-central keratoconus (para-central or peripheral keratoconus with steepest corneal point outside the central 3 mm zone). Previous corneal cross-linking and/or ocular surgery. Systemic diseases such as diabetes mellitus and autoimmune diseases

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 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: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Pocket ICRS<br>Patients in this group are planned to undergo KeraRing implantation through a femtosecond laser-assisted corneal pocket creation for the management of their central keratoconus. | Procedure: Intrastromal corneal ring segment implantation (Pocket)<br>* Patients in this group are planned to undergo ICRS implantation through a femtosecond laser-assisted pocket creation. The device creates an intrastromal corneal pocket of 8-mm diameter and a depth of nearly 80% of the corneal thickness at the thinnest location with a superior tunnel incision at 90° of 4-mm width.<br>|
| Active Comparator: Tunnel ICRS<br>Patients in this group are planned to undergo KeraRing implantation through a femtosecond laser-assisted corneal tunnel creation for the management of their central keratoconus. | Procedure: Intrastromal corneal ring segment implantation (Tunnel)<br>* Patients in this group are planned to undergo ICRS implantation through a femtosecond laser-assisted tunnel creation. The device creates an intrastromal tunnel with a depth of nearly 80% of the corneal thickness at the site of implantation. The tunnel inner and outer diameters are at 5 and 6 mm from the corneal center, respectively with the incision located at the steepest keratometry axis.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Uncorrected distance visual acuity (UDVA) | Uncorrected distance visual acuity measurement using Snellen's Acuity Chart expressed as logMAR notation | 6 months | 
| Corrected distance visual acuity (CDVA) | Corrected distance visual acuity measurement using Snellen's Acuity Chart expressed as logMAR notation | 6 months | 
| Postoperative Refraction | Spherical equivalent refraction measured by Topcon Auto-Keratorefractometer | 6 months | 
| Postoperative keratometry | Postoperative keratometry as measured by Scheimpflug imaging Pentacam | 6 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Keratoconus, Femtosecond laser-assisted ICRS, Central keratoconus, KeraRing