Laser Stromal Keratomileusis using the Berlin Microkeratome

Abstract

OBJECTIVE: Laser keratomileusis leads to the development of superficial corneal clouding. To reduce corneal scar formation, a laser lathing procedure has been performed on the stromal side of corneal discs which have been removed using a microkeratome. STUDY DESIGN: The Berlin microkeratome used for keratokyphosis permits the severance of circular lamellae from the cornea and, through its two suction-ring systems, their subsequent completely fold-free fixation. The corneal lamella thus smoothly stretched out in the microkeratome is accessible to laser keratomileusis.The Berlin microkeratome was used to separate corneal lamellae parallel to the surface of freshly enucleated pig eyes with fully intact epithelia. With the aid of an argon fluoride excimer laser (Lambda Physik Co.) laser keratomileusis was performed with a repetition rate of 25 Hz and an energy density of 180 mJ/cm2. After fixation, the corneal lamellae were embedded and subsequently bisected with a fine saw in the feed direction of the microkeratome. SETTING: Department of Ophthalmology, Klinikum Steglitz, Free University of Berlin, Germany. MAIN OUTCOME MEASURES: The axial sections were measured under the universal measuring microscope (UMM) in an embedded state. RESULTS: The measuring data were printed as a layer thickness over a straight line and showed a mean concavity of about 100 wm, but the mean-value curve was asymmetrical, which is ascribed to the inadequate centering afforded by the preconnected microscope. CONCLUSION: This laser stromal keratomileusis has the following advantages over laser keratomileusis with regards to the corneal surface:(1) elimination of the potentially cataractogenic secondary radiation; (2) restriction of the potentially mutagenic side effects to the corneal lamella; (3) no shock wave; (4) no fixation problems during tissue ablation, and possibly less scar formation. Centration of the laser beam still needs further improvement before clinical application can start.