LASEK Safety

As with adults, excimer laser energy in children undergoing laser subepithelial keratomileusis, or LASEK, has no apparent effect on endothelial cell density or morphology, Adam K Muzychuk MD told the XXXI Congress of the ESCRS. His study suggests that LASEK, which has been shown effective for treating refractive amblyopia unresponsive to standard therapy, is safe and unlikely to increase long-term risks of corneal oedema or other problems related to endothelial cell damage.

The result was hardly surprising, said Dr Muzychuk, of the University of Calgary, Alberta, Canada, who is a resident under the supervision of William F Astle MD, FRCSC, Dipl ABO, at the Alberta Children’s Hospital, University of Calgary, Canada. He pointed to studies in adults, showing that 200 microns of residual stroma protects endothelial cells (Kim et al. 1997; Advances in Corneal Research, Springer:329-342), and that refractive surgery shows no effect on endothelial cell density or morphology long term (Woodward et el. J Cataract Refract Surg. 2011; 37(4):767-777).

Also, the safety and efficacy of PRK and LASEK for treating amblyopia in a subset of children not responsive to glasses, contact lenses, eye patches or atropine has been demonstrated in follow-up studies ranging up to 15 years with Dr Astle’s patients at the Alberta Children’s Hospital, in Calgary, Canada (Astle et al. J Cataract Refractive Surg. 2008; 34(3):411-6), Dr Muzychuk said. “We anticipated there would be no effect on the endothelium from excimer laser treatment.”

Still, no paediatric studies existed, Dr Muzychuk said. It could be because assessing endothelial cell condition involves confocal microscopy, requiring several seconds of absolute stillness. This is difficult with any paediatric population let alone this subset of amblyopia patients, who usually have poor vision and often neurodevelopmental deficits. But given the potential for devastating long-term complications if endothelial cells are damaged by laser refractive surgery in children, Dr Astle and his colleague, Dr Peter T Huang, felt a study was warranted. Dr Muzychuk explained: “The concern has been raised in the literature over the years and has yet gone unanswered.” (Paysse, E. A., L. Tychsen, et al. (2012.) 'Paediatric refractive surgery: corneal and intraocular techniques and beyond.' J AAPOS 16(3): 291-297.)

The retrospective study involved 15 eyes of 11 patients under age 18 receiving LASEK for amblyopia. The group included five males and six females with a mean age of 12.2 +/- 3.7 years, ranging from 6.8 to 17.1. Refractive error ranged from -17 D to +6.9 D with four hyperopic, five astigmatic and six myopic corrections. No complications were observed in any patient, and there were no signs of endothelial cell dysfunction.

Endothelial cell density and morphology were analysed manually and automatically using confocal microscopy before surgery and at a mean 145 days after surgery, ranging from 62 days to 302 days. Mean density fell by 25 cells per square mm from 3,493 to 3,468 measured manually, and by 32 from 2,954 to 2,922 measured automatically, neither of which was statistically significant, Dr Muzychuk reported. No correlation between change in cell density and spherical equivalent correction was found. Similarly, no significant differences were found in cell area or percentages of cells with polymorphism or polymegathism by either manual or automated analysis.

Dr Muzychuk acknowledged that the study’s retrospective nature, small sample, single follow-up and difficulties imaging patients limit its power. However, its consistency with adult studies and longterm observations of patients operated as children lend credence to the conclusion that LASEK does not harm the endothelium in paediatric patients.