Corneal wound integrity and architecture after phacoemulsification: Comparative analysis of corneal wounds created by silicon and steel blades

Abstract

Little is known about the effect of keratome type on postoperative wound integrity and architecture. Studies comparing metallic blades and diamond blades show conflicting results in terms of which type creates a less traumatized wound. 1,2 Recently, a new line of surgical blades composed of silicon material was introduced. Studies of the quality of corneal wounds created by silicon blades are needed but difficult to find in the peer-reviewed literature.We compared the postoperative architecture and integrity of corneal wounds created by metallic and silicon keratomes by observation of wound leakage, scanning electron microscopy (SEM) of the wounds and blades, and histopathologic analysis of the wounds in an ex vivo setting. Each of 10 human cadaver eyes (2 groups of 5 eyes) had a 2.8 mm clear corneal incision by a silicon blade (BD Atomic Edge safety slit knife [BD Medical]) or a metallic blade (Sharpoint slit knife [Surgical Specialties Corp.]). Care was taken to ensure that all eyes were of similar firmness before wound creation. A small amount of balanced salt solution was injected into the anterior chamber of softer eyes to prevent bias in wound construction.All incisions were created in a standard biplanar fashion with a length approximately equal to the initial width of 2.8 mm. A new blade was used for each eye.Simulated phacoemulsification was performed for 2 minutes in each eye using the Legacy Everest system (Alcon Laboratories). After phacoemulsification, each wound was examined for evidence of initial leakage. Then, intraocular pressure (IOP) was cycled between 0 mm Hg and 125 mm Hg 3 times in each eye and the wound was again examined for leakage (IOP was cycled and monitored using an arterial line dynamometer connected to an electronic pressure sensor, which was the design used by Berdahl et al. 3 ). In 2 eyes in each group, India ink was placed above the wound prior to IOP cycling. Those eyes were examined for leakage as well as ingress of fluid. Corneas with India ink were sent for histopathologic analysis to determine whether there was evidence of penetration. All other corneas in each group, along with a representative blade from each group, were sent for SEM examination using a Philips XL30 ESEM TMP electron microscope (FEI Co.).No eye had leakage immediately after phacoemulsification. In the metallic blade group, spontaneous leakage during IOP cycling was evident in 3 eyes (60%) and 8 of 15 total cycles (53%). In the silicon blade group, no eye displayed leakage during IOP cycling. India ink penetration was not evident in any eye in either group. On SEM, wounds in the metallic blade group displayed more stromal disruption than wounds in the silicon blade group (Figure 1). Scanning electron microscopy of the blades showed the silicon blade to have a smoother surface texture and sharper point than the metallic blade.As keratome technology advances, the interest in providing alternative blade designs and materials that have the potential to create better wounds will Figure 1. Scanning electron mic...

Comparing consistency of clear corneal incisions using a traditional diamond keratome and a newly designed diamond keratome

“…This does not happen in surgery where even with a retaining ring, the eye often moves in the direction of the blade movement, perhaps making blade tilt more difficult to avoid. In addition, while there has been significant research examining the effect of wound architecture on leakage, 11 – 15 most of these studies have focused on the technique or instrument material used to create the incision and not on actual consistency in incision length or width.…”

Quantitative measurement of wound architecture in microincision cataract surgery

“…Current techniques to consider include coaxial small-incision cataract surgery (SICS), in which the incision sizes (widths) generally range between 2.6 mm and 3.2 mm; bimanual microincision cataract surgery (MICS), in which an unsleeved phacoemulsifying aspiration tip is used in tandem with a second irrigating tool through a pair of incisions ranging between 1.2 mm and 1.5 mm; and coaxial MICS, in which the primary incision ranges between 2.0 mm and 2.4 mm. [2][3][4] Further considerations include which phacoemulsification tip is optimum (eg, tapered versus flared versus sleeved), A which blade type is optimum (eg, metallic versus diamond versus silicone), 5 and how the outcome of the phacoemulsification procedure might benefit from the selected techniques and equipment. 3,6 All surgical techniques and phacoemulsification tips cause some amount of wound trauma.…”

“…2,5,6,11 If the usefulness of SEM could be extended from qualitative to quantitative analysis, the results could provide evidence-based medicine to guide decisions about which techniques, tips, and blades are best. The purpose of this analysis was to show that changes in internal wound architecture after phacoemulsification can be successfully measured quantitatively and comparatively by analysis of scanning electron micrographs.…”