Correlation Between Q-value Changes and Progression of Pediatric Keratoconus.
Condition: Keratoconus; Collagen Diseases; Corneal Disease
MeSH terms: Rheumatic Diseases; Keratoconus; Corneal Diseases; Collagen Diseases
Study type: Observational

Summary: 
      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: 
      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.
    

Intervention name(s): Transepithelial Corneal Collagen Cross-linking; Scheimpflug camera
Intervention type(s): Procedure; Diagnostic Test
Intervention description(s): 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.; Pentacam (OCULUS Optikgeräte GmbH, Wetzlar, Germany) was done for all subjects at baseline and annually after TE-CXL till 5 years of follow-up.
Other intervention name(s): TE-CXL; Pentacam
Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        This retrospective observational study was performed at Ophthalmology department, Benha
        University, EGYPT using the medical records of 9 children diagnosed as bilateral
        progressive KC that was confirmed by Pentacam according to amsler criteria, patients had
        undergone bilateral TE-CXL in the period from January 2016 to August 2016 and completed
        annual visits till 5 years of follow-up.
      
Keywords: corneal asphericity; corneal collagen cross-linking; Q-value; Pediatric keratoconus; Trans-epithelial