Intraocular and intraorbital compartment pressure changes following orbital bone grafting: A clinical and laboratory study

Visual loss is an uncommon but catastrophic complication after intraorbital bone grafting for the reconstruction of acute traumatic defects or long-st anding enophthalmos. Increased intraocular or intraorbital compartment pres sure may be pathogenic in this setting. A two-part study was designed to te st the null hypothesis that intraocular and intraorbital compartment pressu re values remain constant despite orbital volume reduction with graft mater ial. Laboratory study: Intraocular and intraorbital compartment pressures were m easured during sequential orbital volume reduction in New Zealand White rab bits that had been randomized to one of three groups: intact orbits (n = 10 ), acute orbital wall defects (n = 8), and chronic (3 months) orbital wall defects (n = 11). Intraocular pressure was significantly (p < 0.05) elevate d in all three groups of orbits undergoing orbital volume reduction compare d with control, nonoperated orbits. Intraorbital compartment pressure value s did not change significantly from control levels throughout the grafting sequence. Although no significant differences existed between groups in the maximum levels of intraocular pressure attained, the chronic group demonst rated a greater rate of rise and slower rate of decline. Clinical study: Using applanation tonometry, intraocular pressure was measu red before and serially after orbital floor exploration and intraorbital pl acement of split calvarial bone grafts in 19 patients who presented with or bital-zygomatic complex fractures that required surgery. A separate group o f 16 patients with orbital-zygomatic complex fractures that required explor ation of the orbital floor but not bone grafting was used for comparison. A significant (p < 0.05) elevation of intraocular pressure was observed imme diately after bone grafting compared with nongrafted orbits, but values ret urned to normal within 30 minutes and remained stable through the third pos toperative day. There were no cases of visual impairment in any patients in either group as the result of surgical treatment. These data indicate that orbital volume reduction with graft material resul ts in significant, temporary elevation of intraocular pressure. No signific ant elevations of intraorbital compartment pressure were detected in the ra bbit orbits. Data from this study may have direct relevance in defining gui delines for "tolerable" changes in orbital tissue and globe pressures after surgery.