Does the Howard-Dolman really measure stereoacuity?

The Howard-Dolman (H-D) is a version of Howard's stereoacuity test (H) which has almost completely eclipsed the original. However, there is reason to believe that the H-D is not as good a test as the H. To find out whether or not the H-D gave results similar to the H, 34 subjects were tested by both procedures with the same stereoacuity tester. This was fully automated and programmable. There are at least four ways of relating H-D findings to stereoacuity. None of these gave results comparable to those found with the H. Therefore, the H-D may be of questionable worth for clinical and scientific use. The same conclusion can be drawn regarding the relation between the H-D constant error and aniseikonia.