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W.M. Stapleton, R.R. Mohan, W.J. Dupps, S. Sinha, M.V. Netto, S.E. Wilson; Decreased Stromal Cell Death With the Model III 30 Khz Femtosecond Laser and the Effect of the Side Cut on Stromal Cell Death and Monocyte Infiltration . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2733.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate stromal cell death and immune cell infiltration with the model III femtosecond laser (Intralase) and to determine the effect of the side cut on stromal cell death and immune cell infiltration.
Rabbits were anesthetized and underwent flap formation (9 mm diameter and 100 micrometer thickness) with either the model I 15 kHz or model III 30 kHz femtosecond laser (Intralase, Irvine, CA) (110 µm thickness, 9.0 mm diameter, 0.9 uJ raster stromal energy, 0.9 uJ side–cut energy). A second group of corneas had intrastromal ablation without the transepithelial side cut. Corneas were removed at 24 hours after surgery and evaluated for stromal cell apoptosis with the TUNEL assay and monocyte infiltration detected by immunocytochemistry for CD11b.
After complete flap formation, intrastromal cell death was markedly reduced (P<0.01) with the 30kHz laser (15.0 dead cells/400X field ± 2.9 S.E.M.) compared with the 15 kHz model 1 laser (48.2 ± 9.2). Corneas that had intrastromal cut alone with the 30 kHz femtosecond laser had markedly reduced stromal cell death (8.3 cells/400X field ± 2.1) compared to corneas that had both the intrastromal and side cut (p< 0.05) with the 30 kHz laser. Monocyte infiltration was also significantly greater in corneas that had both the intrastromal and side cut (14.0 cells/400X field ± 0.9) compared to corneas with no side cut (4.8 ± 0.1).
The 30 kHz model III Intralase femtosecond laser is associated with much less intrastromal cell death, and therefore a diminished wound healing response, compared to the 15 kHz model I Intralase femtosecond laser. The side cut through the epithelium contributes to increased intrastromal keratocyte death and inflammatory cell infiltration. Minimizing side cut energy and, therefore, epithelial injury is likely an important strategy to decrease the wound healing response and diffuse lamellar keratitis associated with femtosecond flap formation.
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