Keratoconus is a complex disease with a genetic component. Keratoconus is a slowly progressive, noninflammatory corneal dystrophy characterized by changes in the structure and organization of corneal collagen. It results in asymmetrical thinning of the cornea and causes severe refractive error.
When its onset is early, keratoconus progresses quickly during the pediatric years, often resulting in the need for early penetrating keratoplasty (PK). When PK is performed in children, the rate of graft failure is higher and visual prognosis is worse than in adults undergoing the procedure. The most frequent complications occurring in pediatric PK include expulsive choroidal hemorrage (2Ð3%), wound leakage or dehiscence (2Ð10%), inadvertent lens loss (1Ð2%), corneal ulcer and/or infection (4Ð9%), endophthalmitis (2%), new onset glaucoma (5Ð9%), cataract (2Ð7%), retinal detachment (3Ð5%), and phthisis (4Ð13%).1
After observing pachymetry loss of 186 µm over a span of 5 months in one of our young patients with progressive keratoconus (Figure 1), we decided to treat pediatric patients with corneal collagen crosslinking (CXL). This relatively new technique in ophthalmology slows the progression of keratoconus, stabilizing the disease and avoiding the need for early PK. We are currently following 15 pediatric patients (three girls and 12 boys) between the ages of 12 and 17 years.2
Preoperative keratoconus progression was confirmed by serial differential corneal topographies and differential optical pachymetry analysis in all eyes. Progression was defined as a change in either myopia and/or astigmatism of at least 3.00 D in the previous 6 months, a change of at least 1.50 D in the mean central keratometry observed in three consecutive topographies during the preceding 6 months, or a decrease in mean central corneal thickness of at least 5% in three consecutive tomographies performed in the previous 6 months.
Inclusion criteria were documented keratoconus progression in the previous 6 months, corneal thickness of at least 400 µm at the thinnest point, and age under 18 years. Of the treated eyes, graded stage two to three according to Amsler-Krumeich classification, six were right and nine were left eyes. Exclusion criteria included corneal thickness less than 400 µm at the thinnest point, a history of herpetic keratitis, severe dry eye, concurrent corneal infections, concomitant autoimmune diseases, previous ocular surgery, and patients with central or paracentral opacities. Poor compliance or those who wore rigid gas permeable contact lenses for at least 4 weeks before baseline were also excluded. Parents signed the informed consent form before surgery.
Topical anesthesia was used during CXL. We performed corneal deepithelialization, followed by the application of 0.1% riboflavin in 20% dextran solution to the corneal stroma for 30 minutes. The solution was again applied every 5 minutes for an additional 30 minutes under UV-A irradiation.
At 12 months, no ocular or systemic adverse events were observed, and no significant intraocular pressure changes were seen; however, 62% of eyes developed CXL-specific golden striae. Although patients complained of nighttime glare and halos for the first 3 months, they subjectively perceived an improvement of UCVA during the first 6 postoperative months and reported a continuing increase in BCVA between 6 and 12 months. Contact lens tolerance also increased after CXL.
Mean BCVA improved from 0.4 at baseline to 0.6 at 12 months, a statistically significant difference (P<.05), and mean spherical equivalent refraction significantly decreased (0.36 D). Mean baseline simulated keratometry (SimK) at the flattest and steepest meridians and the average SimK were 64.87 D, 47.71 D, and 42.73 D, respectively; at 12 months, they were 63.06 D, 46.88 D, and 41.28 D, respectively (Figure 2). The difference was significant for all three indices (P<.05). Mean apical keratometry changed significantly, from 52.00 D at baseline to 50.51 D at 12 months (P<.05). For a 3-mm pupil, there was a significant reduction (P<.05) in total, corneal, higher-order, and astigmatic wavefront aberrations. No statistically significant changes in endothelial cell count were seen (P>.05), indicating that CXL did not induce endothelial damage at 1-year follow-up.
In conclusion, at 1 year, CXL does not appear to induce any harmful side effects in pediatric eyes with keratoconus. As demonstrated in adult eyes, CXL appears to effectively improve UCVA and BCVA by significantly reducing corneal apical keratometry and corneal and total wavefront aberrations.
Our results appear promising and suggest that it would be worthwhile to perform CXL in early onset keratoconus to avoid further loss of visual acuity at an amblyogenic age, improve the fit of contact lenses, and reduce the need for early PK as well as the side effects related to the young age of the patients.
Elena Albé, MD, is a Consultant in the Department of Ophthalmology, Cornea Service, Istituto Clinico Humanitas Ophthalmology Clinic, Milan, Italy. Dr. Albé states that she no financial interest in the products or companies mentioned. She may be reached at e-mail: email@example.com.
Paolo Vinciguerra, MD, is the Chairman of the Department of Ophthalmology, Istituto Clinico Humanitas, Milan, Italy. Dr. Vinciguerra is a member of the CRST Europe Editorial Board. He states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: firstname.lastname@example.org.