COMPARISON OF 2 MICROKERATOME SYSTEMS

BACKGROUND: Microkeratomes are currently used for keratomiluesis in si tu (automated lamellar keratoplasty) for myopia and hyperopia and for laser in situ keratomileusis (LASIK), Visual and refractive complicati ons have been reported with these refractive surgical procedures. We c ompared two microkeratomes in their ability to resect corneal lamellae to gain insight into possible mechanism(s) of refractive and visual c omplications following lamellar refractive procedures. METHODS: Using an eyebank eye model, we performed automated lamellar keratoplasty to theoretically correct 10.00 diopters (D) of myopia using the Automated Corneal Shaper, manufactured by Chiron, Inc. and the MicroPrecision m icrokeratome, manufactured by Eye Technology, Inc. Diameters before (w et) and after fixation, thicknesses of excised tissue, and scanning el ectron microscopy were measured in a masked evaluation to compare inst ruments. Ultrasonic corneal pachymetry and a mechanical tissue compres sion gauge were also used to assess thickness of excised tissue. RESUL TS: The Chiron automated corneal shaper created blade chatter marks at the edges of all excisions, smaller than anticipated excision diamete rs, and a wide range of tissue thicknesses. In contrast, the MicroPrec ision microkeratome created smoother resections of all tissues without creating blade marks; tissue diameters and thicknesses were closer to the intended dimensions compared to the Chiron automated corneal shap er. CONCLUSION: Different microkeratomes create different morphologic features as they excise corneal tissue. Differences in instrument desi gn, mechanics of the tissue excision and blade oscillation, and instru ment traverse combined with surgical skill influence the configuration of lamellar keratotomies.