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E.S. Loft, J.B. Randleman, C.S. Banning, R.D. Stulting; The Effect Of Microkeratome Parameter Adjustment On Interface Quality . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3613.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the effect of microkeratome oscillation rates and head–advance speeds on the quality of LASIK interface surfaces.
Corneal flaps were created on 9 porcine eyes using the Amadeus I microkeratome. Only eyes with a smooth cornea and intact epithelium were used. One microkeratome blade was used per cornea. Eyes were held during flap creation with the Mastel "Practice EyeBox" fixating device. The flaps were created using a thickness setting of 140 µm with varying head–advance speeds (1.5, 2.5, and 4.0 mm/s) and oscillation rates (8000, 13000, and 18000 rpm) used in 9 different combinations. The central and peripheral residual stromal bed, along with the posterior surface of 2 flaps, was examined using a scanning electron microscope. Representative photomicrographs of each specimen were taken at specified magnifications for comparison of the cut quality. The photos were examined in a blinded fashion by trained corneal specialists. The surface smoothness was graded on a scale of 1 to 3 (1 being the smoothest surface and 3 being the roughest), with particular attention paid to linear striations and overall surface regularity.
The 9 microkeratome parameter combinations along with the central and peripheral stromal bed grading were as follows: 1) 8000 rpm, 1.5 mm/s: central=1.0 peripheral=1.0; 2) 13000 rpm, 1.5 mm/s: central=1.25 peripheral=2.25; 3) 18000 rpm, 1.5 mm/s: central=2.75 peripheral=3.0; 4) 8000 rpm, 2.5 mm/s: central=1.75 peripheral=2.0; 5) 13000 rpm, 2.5 mm/s: central=2.0 peripheral=2.0; 6)18000 rpm, 2.5 mm/s: central=2.5 peripheral=3.0; 7) 8000 rpm, 4.0 mm/s: central=1.5 peripheral=2.5; 8) 13000 rpm, 4.0 mm/s: central=2.75 peripheral=2.25; 9) 18000 rpm, 4.0 mm/s: central=1.75 peripheral=1.75. The grading of the central portion of 2 representative posterior flap surfaces matched exactly with their stromal bed counterparts.
At fixed head–advance speeds increases in oscillation rates reduced central interface cut quality, while at fixed oscillation rates changes in head–advance speeds did not predictably affect central interface cut quality. A combination of 1.5mm/s head– advance speed and 8000 rpm oscillation rate produced the smoothest central interface. Surface changes induced by the microkeratome correlate between posterior flap and stromal bed. Neither variations in oscillation rate nor head–advance speed significantly affected peripheral cut quality.
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