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

Abstract

PURPOSE: To investigate the appearance and origin of interface particles in the cornea after myopic laser in situ keratomileusis (LASIK) using the confocal microscope. SETTING: Department of Optometry and Neuroscience, UMIST, Manchester, United Kingdom. METHODS: 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. RESULTS: 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.