Displacements of eyeball in orbital blowout fractures

Thirty-two cases of orbital blowout fracture, excluding those of linear fracture with trap-door variety, were selected to study the changes of the eyeball position: posterior displacement or enophthalmos, medial and inferior displacement. Two-millimeter slices of computed tomographic scans were taken, and the eyeball positions were measured with the contralateral eye as a control. Intraorbital edema, if present, at least 10 days after injury had little effect on the position of the eyeball, nor was there any evidence to suggest the late onset of enophthalmos. Enophthalmos remains around 1 mm before total orbital enlargement reaches 2 ml in volume, thereafter increases proportionally with total orbital enlargement until 4 ml, then remains on a plateau. Enophthalmos increases proportionally with the increase of medial orbital wall enlargement when the inferior orbital wall enlargement is less than 2 ml. With inferior wall enlargement more than 2 ml, 3 to 4 mm of enophthalmos is seen irrespective of the increase of medial wall enlargement. The medial displacement of the eyeball increases proportionally with the increase of medial wall enlargement when inferior wall enlargement is less than 2 ml. The inferior displacement of the eyeball has little proportional relationship with medial or inferior wall enlargement when the former exceeds 2 ml. Relatively good proportional relationship is found between the enophthalmos and the medial displacement of the eyeball, but not between the enophthalmos and the inferior displacement of the eyeball.