Ultrastructure of clear corneal incisions - Part I: Effect of keratomes and incision width on corneal trauma after lens implantation

purpose: To examine the ultrastructure of clear corneal incisions (CCls) performed with diamond keratomes and steel blades as well as the corneal trauma after implantation of a foldable intraocular lens (IOL) through two incision widths. Setting: University Eye Clinic and Institute of Histology and Embryology II, University of Vienna, Austria. Methods: Twenty-four human cadaver eyes without prior ocular surgery were obtained from the University Eye Bank, Vienna. Single-plane CCls were performed with 3.0 and 3.2 mm Alcon steel blades and with a 3.0 mm Huco diamond keratome. The AMO PhacoFlex ii lens was implanted with a Fine II folder. During the entire procedure, the eye pressure was kept between 26 and 30 mm Hg by infusing balanced sail solution into the anterior chamber. Specimens were prepared for light microscopy, transmission electron microscopy, and scanning electron microscopy according to standard procedures. Results: The diamond keratome produced cleaner cuts than the steel blade. After IOL implantation, 3.0 mm steel blade incisions exhibited extensions at their lateral ends. Within these extensions, the collagen lamellae were displaced and torn. This was not true with 3.2 mm tunnels. Because of the thickness of a 3.0 mm diamond keratome, the extent of corneal trauma was between that found with 3.0 and 3.2 mm steel keratome tunnels. Conclusions: implantation of the SI-30 through 3.0 mm CCls produced by the steel blade led to more severe corneal trauma than implantation through 3.2 mm steel blade incisions or 3.0 mm diamond keratome incisions. Thus, IOL implantation through incisions that are too small intensifies corneal trauma.