Clinical Evaluation of Two Absorbable Non Penetrating Deep Sclerectomy Implants in a Rabbit Model

Abstract

Purpose: : To compare biocompatibility of absorbable thiolated hyaluronic acid (HA-Cys) and chitosan (C-NAC) as implants for non penetrating deep sclerectomy (NPDS).

Methods: : 8 healthy NZW rabbits underwent NPDS with intrascleral implantation of 2 materials in one eye while the other served as control in a 3 months study. 4 animals received HA-Cys implant (A) and 4 animals received C-NAC implant (B). After peritomy 2 hours wide, a 1/3 thickness limbal scleral flap dissection was performed up to 1 mm into the cornea tissue, a secondary 1/3 thickness scleral flap was dissected, Schlemm’s canal was unroofed, aqueous humor percolating through the remaining trabeculo-Descemet membrane was observed, secondary flap was excised and the implant was placed over scleral bed, scleral flap was repositioned and sutured with 10-0 nylon. Conjunctiva was sutured with 10-0 nylon. Biomicroscopy, tonometry, gonioscopy, funduscopy and ultrabiomicroscopy (UBM) were performed in pre and postop at POD 1, 7, 14, 21, 28, 45, (A&B) and 60, 90, 120 (A). Thus far, 2 animals were euthanized at POD 28 (A, B), and 3 at POD 45 (B) for histology analysis

Results: : All rabbits remained healthy and increased in weight. No intraoperative difficulties, no implant extruded; no conjunctival erosion or intraocular infection. No clinical or histological changes were observed in retina, iris, vitreous and lens. No blebs were observed during the study. Scleral flap thinning was present in all animals after a week. No biodegradation was observed until POD 45 in both groups and very little at POD 120 in the HA-Cys group. Until POD 45 there were not significant differences in IOP (Perkins tonometer) between the groups (p=0.272). HA-Cys implants showed less inflammatory reaction with a thin fibrovascular tissue around the implant and histiocytic infiltrate. The capsule was 2 cell layers thick on margins. Data at POD 180 will be shown. C-NAC implants showed mixed acute and chronic inflammation. The implant showed sharp edges with inflammation around it and the capsule was 10 cell layers thick.

Conclusions: : Both implants were easy to place, safe and biocompatible. Clinical exam, UBM and histology showed no biodegradation of both implants at POD 45. HA-Cys implants showed a very slow biodegradation at POD 120. Inflammatory reaction was much stronger in the C-NAC implant group. HA-Cys implant showed better biocompatibility.Support: Florida Lions Eye Bank, CromaPharma; NIH Center Grant P30-EY01480; Henri and Flore Lesieur Foundation (JMP)

Keywords: aqueous • trabecular meshwork • anterior chamber