Diamond-tip versus blunt-tip caliper enlargement of clear corneal incisions

Purpose: To assess corneal trauma after clear corneal incision (CCI) enlargement with a diamond-tip versus a blunt-tip caliper, Setting: University of Vienna, Austria. Methods: Human bulbi obtained from the eye bank of the University of Vienna had a 3.0 mm single-plane CCI enlarged to 5.0 mm using either a diamond-tip or a blunt-tip adjustable caliper. During the process, eye pressure was kept between 22 and 25 mm Hg by infusing balanced salt solution using an anterior chamber maintainer. Light, scanning electron, and transmission electron microscopy were performed according to standard procedures. Results: Incisions enlarged with the diamond-tip caliper were well-defined and allowed good closure of the wound lips. In contrast, the blunt-tip caliper produced widened, drumstick-shaped recesses at the lateral ends of the incisions. Adjacent to these recesses, the collagen lamellae were severely dislocated and torn. Conclusion: Cutting the corneal tissue with diamond tips caused less tissue damage than expanding it with blunt tips. It was not possible to temporarily widen incisions using a blunt-tip caliper without significantly intensifying tissue damage.