A patient with a painful right eye after a crash shows a visual acuity of 20/200. What is the most likely cause of his symptoms?

In this case, the symptoms of painful vision loss in the right eye following trauma can be attributed to a retrobulbar hematoma. This condition occurs when blood accumulates behind the eye, often as a result of blunt trauma. The patient's significant reduction in visual acuity to 20/200 indicates a serious compromise to the integrity of the eye or its surrounding structures. Retrobulbar hematoma can lead to increased intraocular pressure and result in optic nerve compression, which can severely affect vision.

The mechanism of trauma in this scenario suggests that a blow to the eye can easily cause such bleeding, thus making retrobulbar hemorrhage a plausible and likely diagnosis. The presence of pain in conjunction with the visual symptoms further supports this diagnosis, as the pain often stems from the increased pressure or the irritation of surrounding tissues.

While other conditions like hyphema (bleeding in the anterior chamber) or orbital fractures may also cause pain and visual changes, the specific details of this scenario—especially the marked decrease in visual acuity and acute pain—align more closely with the presentation of a retrobulbar hematoma.