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RL Goodman, DA Johnson, H Dillon, HF Edelhauser, SG Waller; Laser in Situ Keratomileusis (LASIK) Flap Stability During Simulated Cockpit Ejection in a Rabbit Model . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2083.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine LASIK flap stability in a rabbit model when subjected to vertical acceleration at 9 times the force of gravity (9 G's) in a cockpit seat ejection simulator. Methods: Twenty-five New Zealand white (Oryctolagus cunniculus) rabbits underwent LASIK flap creation with an InnovatomeTM microkeratome without laser photoablation. Five rabbits had unilateral surgery to allow comparison with the untreated eye and then 20 rabbits had bilateral LASIK flap creation. After healing for 1 month the rabbits were anesthetized and mounted in a cockpit ejection seat simulator used to train United States Air Force pilots. They then underwent a controlled rapid-sequence ejection at 9 G's. The rabbits were then euthanized and the corneas harvested for microscopic examination. Measurements of corneal curvature with autokeratometry, autorefraction, and portable slit lamp examination were made before LASIK flap creation, before ejection simulation and after the 9G ejection. Determination of LASIK flap dislocation was based on clinical slit-lamp examination or a significant change in pre-ejection to post-ejection refraction. Results: Of the 25 rabbits, 40 eyes with LASIK flaps had data useful for statistical analysis. Five eyes were left untreated as controls and showed no significant corneal or refractive effect of ejection. Five eyes had flap irregularities prior to ejection and were excluded from analysis. The average refraction for the rabbit eye was 2.39D + 2.84D x 092. The average change from pre-ejection to post ejection for sphere was 0.27D, cylinder 0.05D, axis 1.1, spherical equivalent 0.29D. None of these changes were statistically significant. There was no clinical observation of LASIK flap dislocation or ejection-induced corneal folds or striae. Conclusion: Healed LASIK flaps as created in this rabbit model without laser ablation are stable when subjected to a rapid vertical ejection at 9 times the force of gravity.
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