Quantitative assessment of orbital fractures in Asian patients: CT measurement of orbital volume.

Enophthalmos is caused by an increase of orbital volume after blowout fracture and is one of the most critical complications of such fractures, but is often masked by swelling soon after injury. If surgery is performed after swelling resolves, it becomes more difficult to treat enophthalmos because of atrophy and fibrosis. Accordingly, it is important to estimate the severity of enophthalmos soon after injury. We developed a new criterion for determining whether orbital fractures are indicated for surgery in Asian patients using analysis of orbital volume. We retrospectively calculated the orbital volume of patients treated surgically or conservatively and analyzed the correlation between changes of orbital volume and the severity of enophthalmos. Regression analysis of the correlation between enophthalmos and increased orbital volume (y = 0.8x + 0.2; correlation coefficient: 0.92) showed that enophthalmos of 2.0 mm corresponded to an increase in orbital volume of 2.25 cm3. This result is similar to data reported previously for Caucasian patients - enophthalmos of 2.0 mm is a common surgical indication worldwide. Our results suggest that an increase of orbital volume of >2.25 cm3 could be a new criterion for surgical treatment of blowout fractures in Asians.