CROSSLINKING

Corneal crosslinking is effective in arresting progressive keratoconus and improving or stabilising vision in children for three years or more, presenters told the XXX Congress of the ESCRS. Though it is less successful in reducing astigmatism than in adults, the procedure appears to be as safe for children as it is for adults, and may help reduce the need for corneal transplants due to keratoconus. “Keratoconus in children is more severe at diagnosis and progresses faster than in adults. it is one of the most common causes of corneal transplantation in children, after congenital corneal opacities, accounting for 15 per cent to 20 per cent of all corneal transplants in children,†noted Hemlata Gupta MD, Centre for sight, New Delhi, India.

Children also have a higher risk of transplant rejection. Early identification is crucial, and crosslinking in these patients might prevent many transplants, she added. in a prospective study involving 33 eyes in 25 progressive keratoconus patients under age 18, progression was arrested in every eye, reported Beatrice Frueh MD, of the University of Bern, switzerland. Mean patient age was 14.8 years, ranging from five to 17. Four were girls, three had previous penetrating keratoplasty in the fellow eye and two had Down’s syndrome. All were treated with the Dresden protocol, receiving epithelial abrasion followed by 30 minute riboflavin application and 30 minutes UVA irradiation. Topical anaesthesia was used in all but the two Down’s syndrome patients, who received general anaesthesia. intraoperative pachymetry was used in all cases.

At the last follow-up, which ranged from 12 months to 36 months after surgery with a mean of 26.2 months, eight eyes had gained two lines or more of best corrected visual acuity, 25 eyes were unchanged and none lost two or more lines, Dr Frueh said. Topographic indices, including average K, surface activity index and surface regularity index, did not change significantly and cylinder and spherical equivalent remained stable out to three years. Corneas thinned significantly during the first year and then stabilised, while Kmax flattened from a mean of 55.5 D preoperative to 53.9 D at 12 months and 52.9 D at 24 months, findings consistent with other studies, Dr Frueh added.

However, Kmax increased at 12 months in two eyes, boys aged 11 and 8. These apparent progressions both were due to acute keratoconjunctivitis, and regressed when treated. One other eye also underwent lamellar keratoplasty, though this was a very advanced case with poor vision, she said. “Be aware of pseudoprogression in case of active vernal keratoconjunctivitis,†Dr Frueh said. And as with adults, corneal crosslinking should not be performed in children with advanced keratoconus cases, such as those with scarring, she cautioned.

Continuous improvement

Similar results were observed in a 36-month retrospective study by Denise Wajnsztajn MD, Joseph Frucht-Pery MD and colleagues at hadassah-hebrew University Medical Center, Jerusalem, israel. in 42 eyes of 36 keratoconus patients with a mean age of 16 ranging from 11 to 18, of whom five were female, best corrected visual acuity improved for 62 per cent, remained the same for 30 per cent and declined for eight per cent. Two eyes lost one line of vision while one eye, in a Down’s syndrome patient, lost two lines. Gains were statistically significant at 12, 24 and 36 months.

Other topographic and refractive parameters also suggested crosslinking arrested keratoconus progression. Kmax improved or was stable in 94.5 per cent of eyes overall, falling from a mean of 55 to 52.6 in 25 eyes at 12 months (p<0.0001), Dr Wajnsztajn reported. Kmax continued to decline in the second year and levelled off in the third, but the difference was not statistically significant, possibly due to a small sample. Topographic cylinder was improved or stable in 91.4 per cent, refractive cylinder in 73.3 per cent and refractive spherical equivalent in 65.6 per cent.

Four ocular surface complications were observed. These were a hypertrophic epithelium eight weeks after surgery which progressed to a culture-negative microbial keratitis two weeks later, contact lens-induced sub-epithelial infiltrates four days after surgery and a non-healing epithelial defect for seven weeks after crosslinking that progressed to severe stromal oedema. Three eyes also experienced corneal haze with no loss of visual acuity. “in the paediatric age and adolescents, crosslinking is a safe and efficacious procedure to stop or delay keratoconus progression. Further studies are required to confirm our findings,†Dr Wajnsztajn said.

Dr Gupta also reported a retrospective corneal crosslinking study involving 20 eyes of 15 children aged nine to 16. All had documented ectasia progression with no active surface inflammation. Eight of the 15 had vernal keratoconjunctivitis-associated keratoconus. All were treated with 0.1 per cent with one drop every 2.5 minutes for 30 minutes before irradiation. Mean follow-up was 18.5 months, ranging from 12 to 25 months.

At the last follow-up, improvement of one line or more in best corrected visual acuity was observed in all eyes, with six, or about 30 per cent, gaining more than three lines, Dr Gupta said. Kmax fell from a mean of 59.64 preoperative to 56.53, sim K fell from 51.96 to 48.73, and thinnest pachymetry from 455 microns to 400 microns. Mean preoperative aberrations also fell from 2.6 to 2.42 after treatment. Postoperative complications were limited to mild corneal haze and corneal scarring.

“The results show a stabilisation and improvement in keratoconus in terms of corrected visual acuity and corneal curvature after collagen crosslinking in children,†Dr Gupta concluded. Larger cohort studies with longer follow-up are needed to derive stronger conclusions, she said.