Histological Equivalence of a Hyper-Dry Amniotic Membrane and the Ambio2TM after Implantation in the Rabbit Conjunctiva

Abstract

Purpose: A hyper-dry amniotic membrane (HDAM) has been used clinically for ocular surface reconstruction, but sufficient evidence of the histological dynamics and long-term safety have not been obtained. We examined the histological changes in an HDAM after its subconjunctival implantation in rabbit eyes, and we compared these changes to those in the Ambio2^TM Amniotic Membrane Graft (IOP Ophthalmics, Costa Mesa, CA, USA) after the same surgery. Design: A prospective controlled animal study. Methods: We used 27 rabbits in two groups: the HDAM group (36 eyes of 18 rabbits) and the Ambio2 group (18 eyes of 9 rabbits). The HDAM or Ambio2 was transplanted on the bare sclera and covered with a conjunctival autograft. The histological changes were determined by evaluating the amniotic membrane graft, inflammatory cells, and foreign body granulomas in hematoxylin/eosin-stained sections at 30 days, 93 days, and 184 days postoperatively. Results: In all cases, the amniotic membrane graft was completely absorbed without scarring at 184 days postoperatively. The positive rate of inflammatory cells was significantly higher in the HDAM group compared to the Ambio2 group at 30 days postoperatively. The positive rate of foreign body granulomas decreased with time, with no significant difference between the two groups. Conclusions: Both the HDAM and Ambio2 were completely absorbed without scarring within 6 months after surgery. The two types of membranes showed histologically equivalent responses. Translational Relevance: Since the HDAM was completely absorbed without scarring within 6 months after surgery, we could confirm its long-term safety.