Purpose: To compare the exposure rate of wrapped hydroxyapatite versus unwrapped porous polyethylene orbital implants in enucleated patients. Methods: Medical records of the patients who underwent primary placement of hydroxyapatite (Bio-Eye) or porous polyethylene (Medpor) orbital implants after enucleation between 2002 and 2005 in Farabi Eye Hospital were reviewed, and the occurrence of implant exposure during follow-up visits was recorded. The exclusion criteria were secondary implantation, evisceration, or follow up of less than 1 year unless the exposure had occurred in the year after surgery. In the hydroxyapatite group, the implants were wrapped either in Mersilene mesh (65%) or in donor sclera (35%). Wrapping was not performed for any patient in the porous polyethylene group. Results: A total of 198 cases with hydroxyapatite and 53 cases with porous polyethylene implant were identified. The most common causes of enucleation in both groups were globe trauma and painful blind eye. Rate of exposure was significantly higher [odds ratio (OR) = 7.97, p < 0.001] in patients with porous polyethylene (34.0%) than in those with hydroxyapatite implant (6.1%). This association remained significant after adjustment for potential confounders. Mean time of exposure after surgery was significantly (p < 0.001) longer in patients with porous polyethylene implant. Kaplan-Meier plots depicted a significantly (p < 0.001) higher rate of exposure in patients with porous polyethylene implant during the follow-up time. Conclusion: Unwrapped porous polyethylene implants demonstrated a higher rate of exposure, and longer time interval to exposure, compared with wrapped hydroxyapatite implants.
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