title: Digital analysis of flap parameter accuracy and objective assessment of opaque bubble layer in femtosecond laser-assisted LASIK: a novel technique.
abstract: BACKGROUND
  The purpose of this study was to determine flap parameter accuracy, extent of the opaque bubble layer, and incidence of skip lines in femtosecond laser-assisted stromal in situ keratomileusis (LASIK) using the WaveLight(®) FS200 laser and optoelectronic clinical measurements.
  
  
  METHODS
  Images from 101 flaps were automatically recorded during consecutive routine LASIK procedures performed using the WaveLight FS200 femtosecond laser and the EX500 excimer laser. Digital processing of these images was used to evaluate objectively the diameter of FS200-created flaps, by comparing planned versus achieved procedures and to evaluate the incidence and extent (area) of the opaque bubble layer.
  
  
  RESULTS
  The intended flap diameters were between 8.00 mm and 9.50 mm. The achieved flap diameters showed extremely high precision, and were on average -0.16 ± 0.04 mm smaller for a 8.00 mm intended flap diameter, -0.12 ± 0.03 mm smaller for a 8.50 mm flap, and up +0.06 ± 0.06 mm wider for a 9.50 mm flap. With an average flap area of 72.4 mm(2), the mean area of the opaque bubble layer (4.1 ± 4.3 [range 0-14.34] mm(2)) corresponded to a 6% opaque bubble layer-to-flap area. Specifically, 80% of the femtosecond-created flaps had an essentially zero opaque bubble layer (<2.7% of the flap area).
  
  
  CONCLUSIONS
  In our clinical experience, flaps created using FS200 and this novel highly objective assessment technique demonstrate both precision and reproducibility. The incidence of opaque bubble layer was minimal.
authors: Laservision Eye Institute, Athens, Greece; ; New York University School of Medicine, New York, NY, USA.
authors: A John
authors: AJ
authors: Kanellopoulos
authors: George
authors: G
authors: Asimellis
keywords: WaveLight FS200; bladeless laser-assisted stromal in situ keratomileusis; corneal flap diameter; femtosecond laser precision; opaque bubble layer; skip lines