Amadeus II microkeratome: optimizing microkeratome settings for high flap accuracy using optical low coherence reflectometry

To investigate the impact of various experimental microkeratome settings and blade reuse on the accuracy of the flap thickness created with the new Amadeus II microkeratome (SIS, Ziemer Ophthalmic, Port, Switzerland).

In this prospective study, 120 porcine eyes were used to create corneal flaps with the Amadeus II using 2 different cutting heads (140 microm, 160 microm) with the Surepass blade. Using each blade twice, a head advance speed of 1.5 mm/s and 3.5 mm/s and oscillation rates of 8000 rpm, 10,000 rpm, and 13,000 rpm were used. Flap thickness was measured by optical low coherence reflectometry (OLCR). Descriptive statistical analysis was based on means, medians, and quartiles, with graphical representation on box plot. Pearson correlation test and Mann-Whitney U-test for unpaired samples were employed to identify the impact of different settings.

Using the 140 microm cutting head, highest precision of the flap thickness was achieved with a head advance rate of 1.5 mm/s and an oscillation rate of 10,000 rpm (mean 132.1+/-10.0 microm; range 120.2-147.2 microm). Reusing the blade, highest accuracy (mean 130+/-6.9 microm; range 118.5-135 microm) was achieved with 8000 rpm. Using the 160 microm cutting head, an optimum flap thickness was reached with a head advance rate of 3.5 mm/s and an oscillation rate of 13,000 rpm (mean 162.4+/-7.7 microm; range 151.9-169.8 microm). Reusing the blade with the 160 microm cutting head, an adjustment to 3.5 mm/s and 10,000 rpm was necessary (mean 157.4+/-7.7 microm; range 153.7-161.8 microm).

Optimized microkeratome settings lead to minimized deviation from the intended flap thickness and are mandatory to improve flap accuracy. OLCR is an ideal method to proof individualized settings.