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A. Kesler–Diaz, R. Kurtz, N. Morishige, T. Juhasz, M. Sarayba, J.V. Jester; Corneal Response to Femtosecond Laser Disruption in Rabbit . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2731.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate corneal response to femtosecond laser photodisruption in LASIK flap creation using different energy levels.
A modified commercial femtosecond surgical laser was used to create a 7.5 mm diameter, 110 µm thick central corneal flap in rabbits. Three groups of flap parameters were used: 1.5 µJ/pulse with 10 µm spot separation and complete side cut (Group 1; n = 5), 3.5 µJ/pulse with 14 µm spot separation and complete side cut (Group 2; n = 5), 3.5 µJ/pulse with 14 µm spot separation and partial (50 µm) side cut that avoided the epithelium (Group3; n = 4). Flaps were not lifted or manipulated after laser treatments to investigate specific effects of photodisruption. Rabbits were evaluated pre– and post–operatively by in vivo confocal microscopy (CM) to measure epithelial, stromal and flap thickness as well as stromal haze. Animals were humanely sacrificed at 8 weeks and tissue evaluated by laser CM to evaluate cell and collagen organization.
The achieved flap thickness 1 week after surgery averaged 88.9 + 12.8, 90.8 + 6.9 and 86.5 + 6.8 µm for Groups 1–3 respectively. No significant differences between groups or time were noted. The region of stomal acellularity was significantly thicker (p<0.043) in the higher energy groups averaging 40.0 + 11.2 and 37.7 + 5.7 µm for Groups 2–3 compared to 28.6 + 4.5 µm for Group 1. Corneal haze was barely detectible and not significantly different between groups. No changes in stromal or epithelial thickness were noted. Laser CM showed the presence of small diameter cells within the flap interface that were not detected by in vivo CM. Additionally, evaluation of collagen organization by second harmonic imaging showed loss of collagen signal in punctate regions at the flap interface.
Photodisruption of the corneal stroma alone without flap elevation regardless of laser energy does not induce significant corneal haze in the rabbit. However, a thicker region of stromal acellurity was seen with the higher energy suggesting greater stromal effects. Additional studies involving flap elevation may suggest other factors leading to more pronounced responses following femtosecond photodisruption.
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