The relationship between clinical stereotests.

The stereo-thresholds of 67 normal binocular subjects and two smaller groups of nonbinocular and temporarily occluded subjects were measured using three clinical stereotests and a laboratory two-needle test. The Titmus, Frisby and two-needle tests were found to give a much lower mean threshold than the TNO test. It was found that there is low, but significant, correlation between most pairs of the tests. This suggests they all measure the same underlying function of stereopsis, but other factors must also influence performance in these tests. The non-binocular subjects performed slightly better than the occluded subjects in some of the stereotests.