Background An orbital implant is used after enucleation or evisceration surgery to replace the volume lost and to aid in prosthesis fitting and movement. Different materials have been used through the years. The authors noted that with bone-derived hydroxyapatite orbital implants, some patients lose their orbital volume.

Methods The operating theatre record was searched to find patients who had their hydroxyapatite orbital implant removed at Dunedin Hospital, New Zealand, between 2011 and 2015. The original implant size and size at removal were noted. Histological results were noted. Medical notes were reviewed.

Results A total of six patients had hydroxyapatite orbital implants removed during this time. Four patients had implants that were smaller than their original sizes. All specimens had fibrovascular infiltration noted, three had chronic inflammatory cells and one had osteoclastic activity.

Conclusions Bone-derived hydroxyapatite orbital implants can reduce in size, and this may occur due to osteoclastic activity. The surgeon must consider this scenario when choosing the type of implant to be used after enucleation or evisceration.