Testing for Functional Total Blindness

Abstract

A patient with organic bilateral blindness rarely has a pupillary response to light, optokinetic nystagmus in response to the rotating striped OKN drum, an intact menace reflex, or blinking with strong focal illumination. The examiner should also observe the patient's responses to obstacles in the walking pathway, ridiculous facial expressions, or a humorous or startling test card. Functional patients may guess the expected response of a blind person to requests to position hands or fingers with the eyes closed, but perform incorrect maneuvers because they do not understand that spatial orientation is still intact. In addition, a seeing eye has specific responses to various prism tests. There is a selective role for electrophysiologic testing with electroencephalograms, electroretinograms, visual evoked responses to visual stimulation, and galvanic skin reflex monitors.