Abstract
Purpose: :
To determine the optimum time for biodegradation of a hyaluronic acid scaffold during lens regeneration in the rabbit.
Methods: :
Endocapsular lens extraction by phacoemulsification and irrigation/aspiration of the lens through a 2 mm capsulorrhexis was performed in 19 New Zealand white rabbits. Following removal of the lens, a collagen patch was inserted into the capsule bag and maneuvered behind the anterior capsulotomy. Thirty-seven eyes were injected with approximately .04 to .09 cc of cross linked hyaluronic acid (HA) gel to distend the capsule bag and maintain capsule tautness. Due to a tear in the posterior capsule, 1 eye was not injected with HA gel. Postoperatively, hyaluronidase was injected intravitreally in one eye at Days 0 (n=6), 3(n=5), 5(n=6), 7(n=5), 9(n=4) or 10(n=5) to break the HA bonds and aid in dissolution of the HA gel. Six eyes were not injected with hyaluronidase. The animals were followed for three months postoperatively by slit lamp biomicroscopy and photography. The clarity of the regenerated lens was graded on a scale of 0 to 4 with 0 equaling opaque and 4 equaling a normal clear lens.
Results: :
Immediately postoperative, the capsule bag was distended and filled with the cobblestone appearance characteristic of the cross-linked HA gel. Following intravitreal hyaluronidase, the cobblestone appearance of the HA gel dissolved, and the capsule contents appeared clear in all eyes. Lens regrowth was first noted at 2-4 weeks in all groups. Lens regrowth gradually filled the capsule bag and had replaced the HA gel by Day 42--67 in the Day-0, Day-3, Day-5 and Day-10 groups and by Day 109 in the Day-7 and Day-9 groups. The longer time for full lens regrowth in the Day-7 and Day-9 groups may be related to the slightly larger HA gel dose given (.06-.09cc compared to .04-.06 cc). While lens clarity was greatest in the Day-0, Day-3 and Day-5 groups compared to the Day-7, Day-9, and Day-10 groups, the nucleus of the lens was more spheroid and the cortical structure and clarity of the lens were better in the Day-5, Day-7, and Day-10 groups.
Keywords: regeneration • posterior capsular opacification (PCO) • differentiation