Evaluation of an Integrated Orbital Tissue Expander in an Anophthalmic Feline Model

Purpose To evaluate the anatomical effects and tissue biocompatibility in a feline model of an integrated orbital tissue expander (OTE) designed to stimulate bone growth in an anophthalmic socket. Design An animal study was performed in cats to assess orbital bone growth with and without an OTE. Methods The OTE is an inflatable (0.5 to >6.0 cm 3 ) polymeric globe sliding on a titanium T plate secured to the lateral orbital rim with screws. Eight cats had left eye enucleation at age two weeks, with five orbits receiving an OTE and the remaining three serving as nonimplanted controls. Serial transconjunctival implant inflation was performed by injecting normal saline solution into the OTE to a final volume of 3.5 ml. Serial computed tomographic scans were obtained to assess socket growth. All eight cats were euthanized at 18 weeks and dry skulls prepared. The effective orbital volume was measured by inflating an OTE in the orbit of a dry skull until it filled the cavity completely. Results Three cats periodically scratched open the tarsorrhaphy and conjunctiva to rupture the OTE, which resulted in implant exchanges. At 18 weeks, the OTE expanded orbital volume was approximately 18% smaller than the normal contralateral side. In the control animals, the anophthalmic orbital volume was approximately 66% smaller than the contralateral orbit. Histopathology of orbital tissues showed no evidence of foreign body reaction. Conclusions This proof-of-concept pilot study demonstrated implant efficacy in cats, and no implant-related adverse effects were observed. OTE has the potential to stimulate bone growth in human anophthalmic orbits.