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July 1990

Ganzfeld Blankout Occurs in Bowl Perimetry and Is Eliminated by Translucent Occlusion

Author Affiliations

From the School of Optometry/The Medical Center, The University of Alabama at Birmingham.

Arch Ophthalmol. 1990;108(7):983-988. doi:10.1001/archopht.1990.01070090085045

• An intermittent darkening of the visual field (ganzfeld "blankout") is perceived during bowl perimetry. Since this may be a form of rivalry, we hypothesized that occluding the nontested eye with a translucent occluder may eliminate the phenomenon. Ten normal subjects underwent visual field testing with both a translucent and an opaque occluder. Eight of the 10 reported darkening to occur with the opaque patch, while none reported it with the translucent occluder. The darkening occurred with a mean latency of 10.9 seconds, occupied 34.4% of the time, and on average occurred 3.25 times per minute. With the translucent occluder, retest threshold variability was 18.8% less and sensitivity was increased by 0.7 dB. The elimination of this darkening using translucent occluders in bowl perimetry will allow reduced variability and increased sensitivity and comfort.