Comparison of corneal lenticules produced for keratokyphosis and keratophakia.

Apart from the original freezing technique, there are three non-freeze keratomileusis procedures, in which the cornea is first deformed before a tissue lens is severed from the side. Two measuring procedures were used to measure corneal lamellae separated from pig eyes by means of the microkeratome. The following parameters were determined: the size of the severed lamellae, given as the two diameters in the feed direction of the microkeratome and perpendicular to it, and the profiles of the axial sections of these lamellae as determined by means of the universal measuring microscope (UMM). Both measuring procedures had a precision of +/- 3 microns. The results obtained with different blade types were compared, and an optimized blade was developed. The corneal lamellae separated parallel to the surface using the optimized blade were of higher quality than those cut with the Barraquer microkeratome. The variation coefficient was 0.9% for the Berlin microkeratome and 6.0% for the Barraquer microkeratome. The profile studies demonstrated that rotationally symmetrical tissue sections can be obtained with the Berlin microkeratome. The lens-shaped tissue sections separated from pig cornea showed an undercorrection. Further studies are needed to determine whether a higher refraction precision can be achieved in lamellae cut from human donor cornea.