This article has been reviewed by William J. Johnson, MD
Corneal collagen crosslinking (CXL) appears to be a beneficial therapy that halts the progression of keratoconus in children, according to William J. Johnson, MD, an ophthalmologist in Tifton, Georgia.
This is good news because keratoconus is generally more aggressive in pediatric patients. In addition, he noted that penetrative keratoplasties performed on children are associated with a supervised prognosis.
“CXL has provided a mechanism to stop progression and prevent terminal disease,” he said.
Caveats to CXL include the ability to adequately test pediatric patients preoperatively, sedation requirements, and insurance coverage barriers.
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Erin D. Stahl, MD, department chief and pediatric ophthalmologist at the University of Missouri-Kansas City School of Medicine and associate professor of ophthalmology at the University of Kansas School of Medicine, joined Johnson to conduct the study at the Children’s Mercy Hospital in Kansas City, Missouri.
The medical records of the patients who underwent CXL at Children’s Mercy Hospital were retrospectively reviewed. CXL was performed in all patients using the KXL system (Avedro) with Photrexa riboflavin preparations (Glaukos).
After a superficial keratectomy and topical vitamin B2 administration every 2 minutes for 30 minutes, ultraviolet (UV) -A light (365 nm, 3 mW / cm2) was applied for 30 minutes, with vitamin B2 being applied every 2 minutes during the treatment. applied. Exposure to UV light.
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In patients whose corneas were too thin for endothelial protection despite the application of hypotonic vitamin B2 to induce corneal edema, UV light was blocked for part of the treatment, he explained.
The primary outcomes were best corrected visual acuity (BCVA), complications, treatment failure, and duration of follow-up; where available, tomographic and topographic data were also revised.
In 2015, a 13-year-old patient was diagnosed with keratoconus based on retinoscopy reflex and topography and a marked increase in the cylinder in the left eye (+2.25 x 075).
Later that year the cylinder increased again (-7.50 + 4.00 x 080) and the VA dropped to a BCVA of 20/30. In 2017, the patient underwent bilateral CXL; the thickness of the central cornea was 439 µm and 478 µm in the right and left eye, respectively.
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In 2019, at the age of 19, the cylinder had stabilized, the myopia in the left eye had decreased, and the BCVA was 20/25.
The study included 43 eyes from 27 patients (mean age at surgery 15 years; median follow-up 328 days).
“The logarithm of the minimum resolution angle BCVA improved modestly from 0.3 preoperative to 0.1 postoperative,” said Johnson. This was not statistically significant due to the small sample size.
Postoperatively, many patients were fitted with a scleral contact lens, a particularly useful tool in providing optical rehabilitation and treating often irregular astigmatism in patients with keratometry outside the usual therapeutic ranges of contact lenses.
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Pachymetry, topographic and tomographic data remained broadly stable from preoperative to postoperative measurements overall.
When the researchers evaluated cases with a minimum of 6 months follow-up, 26 eyes were included, the median preoperative and postoperative BCVA showed a similar trend, the pachymetry was stable, and the topographic / tomographic data improved, although not significantly.
Johnson stressed the need to follow the cohort on a long-term basis, despite the encouraging short-term safety and efficacy results. While the treatment is designed to stop the progression of keratoconus, constant observation is needed, he said.
“The goal is to get to a point where penetrating keratoplasty or even partial thickness deep anterior lamellar keratoplasty is not needed at all,” he said. “The idea is to guide them through their younger years, during which time there is a greater risk of corneal transplantation [adverse] Effects. “
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A secondary outcome in these patients was a determination of whether CXL offered a safe and effective treatment that slowed progression to corneal transplantation and also amplified the potential future graft-host junction to reduce the risk of recurrence in future grafts, Johnson explained.
Johnson pointed out that while shorter protocols may be desirable to reduce exposure to anesthesia or use of the operating room, efficiency should not override efficacy in these protocol reviews in the future.
In addition, Johnson believes that the safety of the treatment has been demonstrated. One surgical complication resulted from an aggressive post-operative healing response that caused scarring.
One episode of hydrops was likely keratoconus progression, as it was more than a year after surgery, which may occur in a small percentage of patients after CXL.
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The short-term results suggested the effectiveness of CXL. A patient who lived far from the surgical center did not have access to a doctor who could insert an eyepiece contact lens, so they underwent penetrating keratoplasty to facilitate RGP adjustment.
“There may be a need for more penetrating keratoplasties or partial-thickness transplants in this cohort in the future, but only one has occurred to date,” Johnson said.
Johnson pointed out that in a pediatric population, CXL is a safe procedure in the facility.
“Many of the findings in the FDA-approved CXL studies are similar to our current results, including stability, modest though insignificant BCVA improvement, and few complications,” he concluded. “Clinical judgment is a constant in the management of pediatric keratoconus and CXL due to the difficulty of obtaining definitive data in this patient population.”
William J. Johnson, MD
This article is a modified version of Johnson’s presentation at the 2020 American Academy of Ophthalmology Annual Virtual Meeting. Johnson has no financial interest in this topic.
Erin D. Stahl, MD
Stahl is an advisor to Glaukos.