Echographic detection and classification of posterior hyphemas.

A 'posterior hyphema' (in analogy to the classic hyphema seen in the anterior chamber) is a collection of liquid blood at the bottom of a fluid-filled space in the posterior segment of the eye. The horizontal surface of a posterior hyphema produces strong signals echographically which, at first glance, may be confused with signals from a retinal detachment or a preretinal membrane. With the patient being examined in a supine position, a retinal detachment of the inferior posterior fundus involving the macula is suggested. Such a misdiagnosis would have serious consequences for the management of a patient and must be avoided. A simple, quick and effective (both highly sensitive and specific) echographic (A-scan and B-scan) shift technique clearly differentiates a posterior hyphema from a retinal detachment and a preretinal membrane. This shift method has been applied successfully in 62 consecutive cases of posterior hyphema. These represent 20% of 304 cases with severe posterior segment hemorrhages examined echographically in a 3-year period. With echography, the height of a posterior hyphema can be measured precisely and its consistency ranging from very liquid ('thin' hyphemas) to highly viscous ('thick' and 'sticky' hyphemas) can be determined. Thus, echography contributes important information about this special kind of posterior segment hemorrhage, particularly useful in previtrectomy evaluations.