A Surgical Cryoprobe for Targeted Transcorneal Freezing to Treat Corneal Endothelial Dysfunction

Abstract

Purpose : To examine the effects on corneal tissue of localized freezing induced by a new surgical cryoprobe. The machine was designed to remove endothelial cells from the posterior surface of the cornea in a reproducible and targeted manner to aid the treatment of corneal endothelial dysfunction.

Methods : A freezing console was designed and manufactured based on the use of nitrous oxide as a cryogen. The console was connected to one of four different cryoprobes, each with a different freezing tip (1.8 mm-diameter, flat profile; 2.4 mm-diameter, flat profile; 2.4 mm-diameter concave profile; 3.4 mm-diameter, concave profile) at which temperatures below -50°C were achieved. In vitro studies were conducted on 426 porcine corneas, followed by a small number of in vivo investigations on rabbit corneas. After treatment the epithelial basement membrane, corneal stroma, and corneal endothelium were investigated by slit-lamp microscopy, ultrasound pachymetry, and light and electron microscopy.

Results : In vivo and in vitro the corneal epithelium was destroyed by freezing, but the epithelial basement membrane remained intact. In vitro, reproducible corneal endothelial damage was achieved using the 3.4 mm-diameter cryoprobe tip with the concave profile. The damage occurred after a short, 3-sec freeze, and was confined to a circular region of the endothelium located directly under the surface application position of the cryoprobe tip. Corneal edema was seen in vivo 24-hrs after freeze injury and was accompanied by alterations to the arrangement of collagen fibrils, but this resolved by 10-days and 1-month concurrent with endothelial repopulation of the wound area.

Conclusions : Surface corneal freezing using a 3.4 mm-diameter concave cryoprobe induces transient stromal edema, but leaves the epithelial basement membrane intact which likely aids epithelial resurfacing. Localized destruction of the endothelial monolayer was achieved in a consistent manner, and represents a potentially useful approach to help treat corneal endothelial dysfunction.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.