Corneal surface morphology following excimer laser ablation with humidified gases
R. R. Krueger, M. Campos, X. W. Wang, M. Lee and P. J. McDonnell
Doheny Eye Institute, Los Angeles.
OBJECTIVE: To compare the effects of blowing dry (nitrogen or helium) and
humidified gases over the corneal surface during photorefractive
keratectomy. METHODS: Excimer laser myopic ablations were performed on
porcine eyes (10 per group) using humidified and dry nitrogen and helium
gas under ambient conditions. Surface smoothness was quantified with light
and electron microscopy. RESULTS: Corneas that were ablated using
humidified gas were smooth and equivalent to those ablated under ambient
conditions. Dry nitrogen and helium blowing resulted in increased surface
irregularity evident on light and electron microscopy (P < .001). The
pseudomembranes in the humidified gas and ambient air groups had fewer
surface discontinuities than did those in the nonhumdified gas groups and
appeared to have a thinner electron-dense surface layer. CONCLUSIONS: The
blowing of humidified gas during excimer laser corneal ablation produces a
smoother surface than does the blowing of dry gas and is comparable to that
produced under ambient (no blowing) conditions. Maintaining corneal
moisture is important in photorefractive keratectomy. If blowing gas is
necessary to remove debris from the surface, the gas should be humidified.
