Risk factors for orbital implant exposure after evisceration: A case control study of 93 patients

Purpose: The study aims to analyze risk factors for exposure of orbital implants after evisceration by comparison of patients with and without exposure of implants. Methods: This is a case control study in retrospective interventional case series; Group A- implant exposures after evisceration, Group B - Patients on follow up after evisceration with implant, without exposure, with matched duration of follow up. The sample size is calculated for a power of 80. Results: Group A comprised 32 sockets with implant exposure, presenting at median 18 months after surgery; Group B included 61 eviscerated sockets, without implant exposure, with follow up median 36 months. Odds Ratio (OR) was calculated; infected eyes -OR 1.3, P = 0.6; phthisical eye - OR 1.4, P = 0.43; multiple prior surgeries- OR 1.55, P = 0.33. Group A had 59.3% porous implants, Group B 55.7%, - OR 1.3, P = 0.5. Mean implant size in Group A 19.06 mm, Group B 18.78 mm- showed no statistical difference. Multiple logistic regression analysis showed no significant risk factor for exposure. Surgeon factor was not analyzed since there were multiple surgeons. Conclusion: This is the first study with calculated sample size, comparing implant exposure patients to a control group. Porous implant material, presence of infection, phthisical scleral shell, and prior surgery showed higher trend of exposure (Odds ratio >1), but none was conclusive. Larger size of implant was not a risk factor for exposure. Eliminating the role of several factors in implant exposure allows the surgeon to make better surgical choices: such as place an implant of appropriate size, of a material of surgeon's choice, and do primary placement of implant in a patient with evisceration post-corneal ulcer or endophthalmitis. A hypothesis and a recommendation is that meticulous attention be paid to surgical technique.