ANTERIOR CILIARY SCLEROTOMY: Effect on corneal topography, globe integrity, and the role of a novel antifibrotic gel

摘要

Purpose: To (1) quantify changes in corneal topography induced by radial anterior sclerostomy for restoring accommodation and, (2) assess safety and ant fibrosis activity of cross-linked sodium hyaluronic acid (cSHA) based gels in ACS procedures. Methods (ex-vivo study): 6 fresh human Eye-Bank eyes were used. A 15% Dextran solution was injected in the anterior chamber and the vitreous cavity, the corneal epithelium was removed by scraping, and the whole eye was immersed in 15% Dextran solution until corneal thickness reached a physiological value. The conjunctiva and tenon capsule were removed and the eye was mounted on a custom-made holder. Preoperative corneal topography was measured with a PAR corneal topography system. Five to eight 3mm-long linear equidistant anterior radial incisions starting from the limbus were performed in the sclera at 90% depth with a diamond blade. Postoperative corneal topography was measured. The files providing the pre and postoperative tangential curvature along meridians separated by 5 degrees were exported. The axial curvature along the 0 and 90-degree meridians before and after surgery were compared. Methods (in-vivo study): Of 24 rabbits, 4 were operated following Thornton's (90% depth incision) and 20 following Fukasaku's (100% depth) techniques (total peritomy, four 4mm long radial scleral incisions starting 0.5mm from the limbus). In the Fukasaku group, the scleral walls were widened with a modified Fukasaku cross-action forceps. A control group of 6 animals received BSS, a group of 2 received pure cSHA gel (Corneal SA, Paris) and 16 received a cSHA-hydrogel compound (Corneal SA, Paris), applied to each incision. 14 animals of this ongoing long-term study have been euthanized at 1 and 3 months for histology while the remaining cohort are being followed for histology at 6 and 9 months. Results (ex-vivo study): In 4 out of 6 eyes, the cornea flattened in the center by 0.5 to 4D and steepened at the periphery of a 4 mm diameter optical zone by 1 to 4 D. A reverse effect (central steepening) was observed in 2 out of 6 eyes. Results (in-vivo study): The IOP, cornea, iris, lens, vitreous and retina remained normal in all animals. Histology shows the incisions in control eyes to be healed whereas in cSHA eyes, the incisions remained open. Scleral shrinkage in the incision area can be observed in control animals confirming the regression observed in ACS patients that did not receive an implant. Animals that received pure cSHA had open incision but the walls were very close one to another. In animals that received the cSHA-hydrogel compound, at 5 weeks the incisions are wide-open and filled with loose connective tissues ands mall hydrogel particles. No fibrotic contraction could be found in animals that received pure cSHA gel or cSHA-hydrogel compound. Conclusions: Anterior radial sclerostomy induces significant changes in peripheral corneal topography. These changes may have a significant effect on the visual outcome of the procedure. This study confirms the anti-inflammatory/antifibrosis properties of cSHA as well as the potentials for hydrogels to maintain the walls of ACS incision apart avoiding the need for solid plug implants. It also showed the advantage of mechanically widening the incisions during the ACS procedures as it allows for incision of controlled depth and uniformity.