Correlation Between Q-value Changes and Progression of Pediatric Keratoconus.

Study Overview
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Brief Summary
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Keratoconus is a progressive corneal disease characterized by asymmetric corneal thinning and structural changes in corneal collagen which leads to decrease in visual acuity due to myopic shift, irregular astigmatism or corneal scarring. Early detection of the disease in children aids in halting the progression and improve their quality of life. There is no consensus regarding the progression criteria of the disease, we aimed to assess the changes in corneal asphericity in children after corneal collagen crosslinking and investigate any possible correlation with progression criteria widely used.

Detailed Description
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The Keratoconus progression is defined as increasing by 1.0 diopter (D) or more in the maximum keratometry (Kmax), progressive deterioration in Minimal Corneal Thickness is also associated with KC progression, other methods have been investigated to confirm KC progression such as changes in manifest refraction, unaided visual acuity (UAVA), BCVA, posterior keratometric data and higher order aberrations (HOA) which are altered in KC and can aid to confirm disease progression. Q-value (a coefficient of corneal asphericity) reflects the shape of the cornea, its refractive power, and spherical aberration. The mean Q-value in normal cornea is -0.26 ± 0.18, the severity of KC and the Q-value are inversely related. Mean Q-value in KC at 8mm zone is -0.84 and -1.10 for anterior and posterior corneal surfaces, respectively. Until now, no precise criteria of KC progression especially in cases had undergone previous trans-epithelial corneal collagen cross-linking (TE-CXL) to halt the progression of the disease. In the present study we aimed to analyze the correlation between the changes in Q-value and progression of the KC in children had undergone bilateral TE-CXL.

Official Title
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Correlation Between Changes in Corneal Asphericity and Progression of Keratoconus in Children

Conditions
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Keratoconus, Collagen Diseases, Corneal Disease

Intervention / Treatment
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* Procedure: Transepithelial Corneal Collagen Cross-linking
* Diagnostic Test: Scheimpflug camera


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Children that were diagnosed as bilateral progressive KC (stage I-III, according to amsler classification, Kmax change >1D between 2 scanning with at least 2 months apart), and their age were less than 16 years old at time of TE-CXL, topographic parameters were Kmax 47-60D and MCT more than 400μm. Exclusion Criteria: Eyes with central corneal scarring, amblyopic eyes, and other corneal pathologies that may alter Pentacam scanning.

Ages Eligible for Study
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Minimum Age: 6 Years
Maximum Age: 16 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

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Progression Group (P-group)<br>Eyes that showed progression of the disease after trans-epithelial corneal collagen cross-linking during the 5 years of follow-up, (number of eyes = 7 eyes). | Procedure: Transepithelial Corneal Collagen Cross-linking<br>* Bilateral Transepithelial Corneal Collagen Cross-linking was done for all subjects using power of 9mW/cm2 at 55mm from the cornea for 10 minutes, with a total energy of 5.4j/cm2 using the (CCL VARIO, PESCHKE Trade GmbH, Huenenberg Switzerland), in the period between January 2016 to August 2016.<br>* Other names: TE-CXL;Diagnostic Test: Scheimpflug camera<br>* Pentacam (OCULUS Optikgeräte GmbH, Wetzlar, Germany) was done for all subjects at baseline and annually after TE-CXL till 5 years of follow-up.<br>* Other names: Pentacam;|
| No Progression Group (NP-group)<br>Eyes that showed no progression of the disease after trans-epithelial corneal collagen cross-linking during the 5 years of follow-up, (number of eyes = 11 eyes). | Procedure: Transepithelial Corneal Collagen Cross-linking<br>* Bilateral Transepithelial Corneal Collagen Cross-linking was done for all subjects using power of 9mW/cm2 at 55mm from the cornea for 10 minutes, with a total energy of 5.4j/cm2 using the (CCL VARIO, PESCHKE Trade GmbH, Huenenberg Switzerland), in the period between January 2016 to August 2016.<br>* Other names: TE-CXL;Diagnostic Test: Scheimpflug camera<br>* Pentacam (OCULUS Optikgeräte GmbH, Wetzlar, Germany) was done for all subjects at baseline and annually after TE-CXL till 5 years of follow-up.<br>* Other names: Pentacam;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in corneal asphericity (Q-value) in all subjects. | Evaluate the changes in Q-value after Trans-epithelial corneal collagen cross-linking (TE-CXL) using pentacam. | Baseline and annually after TE-CXL till 5 years of follow-up | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Correlation between Q-value changes and disease progression in both groups. | Correlation between the changes in Q-value in different corneal zones and maximum keratometry and minimal corneal thickness in both groups over 5 years of follow-up. | Baseline and annually after TE-CXL till 5 years of follow-up | 
| The Q-value as a predictive value in keratoconus progression. | The possibility of using the Q-value parameters as a predictive values to confirm keratoconus progression in children. | Baseline and annually after TE-CXL till 5 years of follow-up | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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corneal asphericity, corneal collagen cross-linking, Q-value, Pediatric keratoconus, Trans-epithelial