A Translucent Occluder for Studying Eye Position under Unilateral or Bilateral Cover Test

Bilateral Occlusion Reduces the Ocular Deviation in Intermittent Exotropia

“…We attempted to tease apart the effects of form versus light deprivation by conducting the experiment with filters made of ground glass, similar to the frosted translucent occluders used for cover–uncover testing. 26 Unfortunately, video eye tracking was not possible through ground glass filters. We have no data, therefore, addressing whether obscuration of vision in each eye is sufficient to reduce exotropia or whether darkness is required as well.…”

“…The ocular posture assumed under the latter condition was termed the “static position” by Lancaster, 37 and it was referred to as the “fixation-free” position by Spielmann. 26 She made it easy for the clinician to observe the position of the eyes under fixation-free conditions by introducing the use of translucent occluders. Remarkably, she made the anecdotal comment that “not infrequently” patients with exotropia return to orthoposition under bilateral translucent covers.…”

“…Remarkably, she made the anecdotal comment that “not infrequently” patients with exotropia return to orthoposition under bilateral translucent covers. 26 This prescient observation suggests that simply preventing fixation is enough to reduce exotropia, and light attenuation by the filters is not required. It remains to be determined whether it is the loss of fixation per se or elimination of all high grade form vision that produces this effect.…”

Infantile Strabismus and Dissociated Strabismus Complex

“…In some patients the horizontal angle of deviation increases or decreases when either eye is covered; when this is the main feature it is referred to as DHD (Wilson and McClatchey 1991). Dissociated vertical deviation requires one eye to be fixing (Posner 1944), which was demonstrated by Spielmann (1986) using translucent occluders whereby when one eye was occluded the other eye was elevated behind the occluder but when both eyes were occluded there was no elevation of either eye. Dissociated horizontal deviation is discussed further at the end of this section.…”

Ocular Deviation

“…Spielmann (1986) has developed a translucent occluder made of rigid nonreflective plastic, which allows the examiner to assess the eye position behind the occluder. To perform it accurately and to obtain the maximum information, the test requires the correct fixation targets for use at near distance, distance (≥ 3 m) and in the far distance, and an adequate cover, preferably a matt black 'paddle'.…”