Confocal microscopic evaluation of particles at the corneal flap interface after myopic laser in situ keratomileusis

To investigate the appearance and origin of interface particles in the cornea after myopic laser in situ keratomileusis (LASIK) using the confocal microscope.

Department of Optometry and Neuroscience, UMIST, Manchester, United Kingdom.

An in vivo slit-scanning, real-time confocal microscope (Tomey ConfoScan P4) fitted with an Achroplan(R) 40X/0.75 NA immersion objective (Zeiss) was used to examine the morphology of the central cornea in 6 patients (12 eyes) at the initial visit (before surgery) and 1 week and 1, 3, and 6 months after LASIK for myopia.

In all eyes, several interspersed particles of variable size and brightness were observed 1 week after surgery at the flap interface. The overall density of these particles decreased with time (F = 14.34, P =.01). For analysis, the particles were divided by density into high brightness and low brightness. The low-brightness particles significantly decreased with time (F = 13.26, P =.02). The high-brightness particles remained constant in density at all postoperative visits (F = 1.3, P =.15). CONCLUSIOINS: The particles of low reflectivity may represent 1 or more types of remains. It is unclear whether the low-reflectivity particles will eventually disappear. The high-reflectivity particles may represent fine metallic debris arising from the mechanical drive mechanism and/or the disposable knife of the microkeratome. If they are metallic and magnetic, they could be cleared during surgery (immediately before flap replacement) using a specially adapted magnet.