FS200 femtosecond laser LASIK flap digital analysis parameter evaluation: comparing two different types of patient interface applanation cones

A John Kanellopoulos,1,2 George Asimellis1 1LaserVision.gr Eye Institute, Athens, Greece; 2New York University School of Medicine, NY, USA Purpose: To evaluate the safety and efficacy of a novel LASIK flap patient interface (PI) cone with our reported digital analysis and compare for potential differences with the standard metal and glass PI in flap parameters when used with the Alcon/WaveLight FS200 femtosecond laser. Patients and methods: Thirty-six consecutive LASIK patients (72 eyes) subjected to a bilateral femtosecond assisted LASIK procedure with the novel clear cone PI FS200 1505 were examined for flap diameter and flap thickness over the entire flap area via digital analysis performed on intraoperation image (flap diameter) and anterior-segment optical coherence tomography image (flap thickness). This group was compared with an age- and procedure-matched group B from our practice, in which the standard metal and glass PI was employed. Results: Horizontal flap diameter for group A (clear cone) was 7.87 mm ± 0.02 mm (range 7.89–7.84 mm) for 8.00 mm programmed, whereas for group B (metal and glass cone) was 7.85 mm ± 0.04 mm (range 7.93–7.80 mm). Likewise, along the vertical line, flap diameter for group A was 7.84 mm ± 0.02 mm (range 7.85–7.80 mm) and for group B was 7.83 mm ± 0.03 mm (range 7.87–7.80 mm). Central flap thickness for group A was 113.29 µm (±1.19 µm) for 110 µm planned, 122.1 µm (±2.10 µm) for 120 µm planned, and 133.50 µm (±0.71 µm) for 130 µm planned. Group B central flap thickness was, accordingly, 112.8 µm (±1.25 µm), 122.4 µm (±2.15 µm), and 132.50 µm (±0.90 µm). The data evaluated (paired group comparisons) between group A and group B did not show statistically significant differences. Conclusion: This study indicates that two PIs in use with the FS200 femtosecond laser are safe and have highly reproducible and accurate flap parameter results, such as achieved diameter and flap thickness. The paired group comparisons between the two PIs’ respective data do not show statistically significant differences. Keywords: femtosecond laser precision, bladeless LASIK, corneal flap diameter, flap thickness, Alcon/WaveLight FS200, clear cone, patient interface, applanation cone, myopic laser correction, hyperopic laser correctio