PEDIATRIC AND TEEN CL CARE

PEDIATRIC CORNEAL COLLAGEN CROSS-LINKING

MELANIE FROGOZO, OD

Keratoconus is a non-inflammatory corneal dystrophy characterized by progressive steepening and thinning of the paracentral cornea, resulting in high irregular astigmatism. This dystrophy typically manifests during adolescence and progresses until the age of 40 years (Rabinowitz, 1998; Tuft et al,1994). Keratoconus develops more aggressively in children and adolescents than in adults. Moreover, a younger age of diagnosis is associated with corneal opacities and rapid progression to advanced-stage disease (Chatzis and Hafezi, 2012).

Corneal collagen cross-linking (CXL) is a well accepted and widely performed procedure that decreases the progression of keratoconus. This should be considered as a treatment option in cases of pediatric and adolescent keratoconus. The Avedro KXL system is currently the only FDA-approved CXL system for patients aged 14 and older; use in younger ages and other CXL procedures would be considered off-label.

How It Works

CXL can halt the progression of keratoconus in adults (Wollensak et al, 2003; Vinciguerra et al, 2009; Wittig-Silva et al, 2008) and shows the same promise for children and adolescents (Godefrooij et al, 2016). Because the disease tends to progress faster and the risk for requiring keratoplasty is much greater in pediatric versus adult patients, it has been suggested to perform CXL in young patients as soon as the diagnosis is made (Chatzis and Hafezi, 2012).

CXL is accomplished through a polymerization reaction that results from combining riboflavin and ultraviolet A (UVA) irradiation. Riboflavin acts a photosensitizer and, when combined with UVA, increases the cross-links between and within the corneal collagen fibers (Spörl et al, 1997; Ziaei et al, 2015). This creates reactive oxygen species that promote the formation of covalent bonds between collagen fibers, which increases corneal rigidity, collagen fiber thickness, and resistance to enzymatic degradation (Spoerl et al, 1998; Wollensak et al, 2003).

Procedure Types

Since the establishment of the original Dresden protocol, there have been several variations of the procedure. A table that reviews the different types of CXL techniques that are currently being performed on children and adolescents is available with the online version of this article at www.clspectrum.com.

Regarding pediatric patients, the original epithelium-off protocol has demonstrated improvement of uncorrected and best-corrected visual acuity and improvement of keratometry values (flat, steep, average, and max readings) during long-term follow-up (Godefrooij et al, 2016).

Additionally, accelerated epithelial-on (ionophoresis) and epithelial-off techniques may also show promise in decreasing the progression of pediatric keratoconus. The benefits of epithelium-on techniques for children include less pain, faster visual recovery, and fewer complications such as corneal haze (Buzzonetti et al, 2015). Overall, children may better tolerate the reduced treatment time of accelerated CXL techniques.

Summary

Keratoconus diagnosed at a younger age progresses more aggressively compared to adult disease. CXL should be considered as a treatment option because it has the potential to decrease or even halt the progression in children. CLS

For references, please visit www.clspectrum.com/references and click on document #253.

Dr. Frogozo specializes in adult and pediatric specialty contact lenses. She is the director of the Contact Lens Institute of San Antonio and the owner of Alamo Eye Care in San Antonio, Texas. She also is a consultant to CooperVision and Visionary Optics. You can contact her at contactlensinstitutesa@gmail.com.