Stereotest artifacts and the strabismus patient.

A new use of nonstereoscopic cues in stereopsis testing is described. It consists of alternation of fixation while observing for image jump in the disparate portions of the test target. This may enable some stereoblind strabismus patients to achieve artifactually good stereotest scores and explain those patients who appear to have gross stereopsis on the Titmus test, but are unable to perform any random-dot test of stereopsis. A new stereotest is described which does not resort to a random-dot format and yet is free from lateral displacement and alternation cues.