A Novel Orbital Tissue Expander (OTE): Feasibility Study in the Feline Model

Abstract

Abstract: : Purpose: To evaluate the anatomical and tissue biocompatibility in a feline model of an Orbital Tissue Expander (OTE) implant designed to treat congenital anophthalmic and microphthalmic patients. Methods: The OTE implant (Innovia LLC, Miami) is an inflatable (0.5 to >6cm³) polymeric globe sliding on a titanium T–shaped bone plate secured to the lateral orbital rim with titanium screws. Inflation is performed by injection of BSS with a 30ga needle through the conjunctiva during the postoperative period. 8 kittens had one eye enucleated at 2 weeks of age, 5 received an OTE implant while 3 did not (controls). The conjunctiva was closed with sutures and a tarsorrhaphy performed. OTE inflations with BSS injection were done step–wise: 0.5cc at 2–4w, 1–1.5cc at 7w, 0.5–1cc at 9w, 0.5cc at 12w and 0.5cc at 14 to16 weeks. CT scans were taken at weeks 3, 7, 9, 15 and 18. The 8 cats were euthanized at 18 weeks, the OTE removed for shadowphotogrammetry and surface analysis, the normal contralateral eyes enucleated for size measurements, the orbital tissue of OTE and control animals exenterated for histology analysis and the skulls prepared for morphometry of the orbit. Results: The presence of the OTE implant facilitated normal growth of orbital bone structure and there was almost no difference in facial appearance. The cats periodically opened the tarsorrhaphy as well as the conjunctiva necessitating surgical repairs and on a few occasions, they were even able to pierce the OTE globe requiring implant exchange. The OTE had no adverse effects in the normal maturation of the cats; weight gain and food intake remained normal throughout. At 18 weeks the diameter of the implants were 3.1+/–0.1cc smaller than the normal contralateral eyes (3.5+/–0.1cc) due to the insufficient inflation based on the 3cc volume published in Prince's textbook, whereas in the control animal, the enucleated orbit was one third the volume of the normal contralateral orbit. Histology showed no signs of foreign body reaction Conclusions: This pilot study demonstrates the safety and efficacy of the OTE implant in the feline model and shows the implant's potential for treatment of anophthalmic and microphthalmic babies. Support: NIH–1R43–EY015016, Florida Lions Eye Bank, NIH center grant P30–EY014801; Research to Prevent Blindness; Innovia LLC; the Henri and Flore Lesieur Foundation.

Keywords: orbit