FIELDS OF DREAMERS AND DREAMED-UP FIELDS - FUNCTIONAL AND FAKE PERIMETRY

Purpose: Hysterical and malingering patients can manifest visual field defects on perimetry (visual field testing), including defects sugges tive of true visual pathway pathology. It has been shown that control subjects can easily imitate some pathologic defects with automated, co mputed perimetry. The authors sought to determine whether subjects cou ld imitate the same pathologic defect with manual and automated perime try. Method: Six subjects posed as patients with neurologic problems. They had manual perimetry with both an experienced and an inexperience d technician followed by automated perimetry. They were later intervie wed about the methods of the technicians and the difficulty of the exe rcise. Results: Four of six subjects easily imitated the assigned defe cts with both technicians on manual perimetry and with automated perim etry. These included quadrantic, altitudinal, hemianopic, and enlarged blind-spot defects. Two subjects who were assigned cecocentral and pa racentral scotomas instead produced enlarged blind spots by manual per imetry and defects suggestive of chiasmal pathology by automated perim etry. Paradoxically, some subjects found that experienced technicians were easier to fool than inexperienced technicians because of the syst ematic way in which experienced technicians defined defects. Conclusio ns: With minimal coaching, some subjects can imitate visual fields wit h enlarged blind spots, quadrantic, hemianopic, and altitudinal defect s with ease and reproducibility by both automated and manual perimetry . Cecocentral and paracentral scotomas are harder to imitate but may b e mistaken as representing chiasmal pathology, Paradoxically, experien ced technicians may not be better at detecting hysterical or malingeri ng individuals.