A new stereoscopic test for amblyopia screening

A clinical version of the Julesz random dot stereogram, the random dot E (RDE), appears to be a reliable screening test (i.e., no underreferrals) for amblyopia as well as for a variety of potentially amblyopia related visual dysfunctions, including constant large angle and 'micro' tropias, intermittent and accommodative esotropia, anisometropia (>2 diopters), and perhaps high (5 diopter) hyperopic astigmatism. Passing the RDE in the normal range (1 meter card to subject distance or better, equivalent to 250 arc sec disparity or better), on the other hand, appears to be a fairly fail safe indicator that none of these conditions are present (i.e., few or no overreferrals). The RDE test can be routinely and reliably administered by virtually anyone following a few simple instructions, to subjects as young as 3 yr old. The RDE test makes minimal demands on subject cooperation and can, if necessary, be administered nonverbally. Its criterion for detection is basically pass fail, though it can also be used to obtain conservative (and reliable) stereopsis thresholds.