Artefacts of computerized perimetry may simulate glaucomatous defects

Computerized perimetry has improved the quality and standardization of perim-rety. There is however a certain percentage of patients that does not interact with computerized strategies as we would desire. The incomprehension of the task that the computerized examination expects them to perform, may lead to artefactual visual field defects. It may also lead to excessive long-term fluctuation. We have collected twenty examples of such artefacts or pseudo-defects, after examining the patients both with fully-automated and with semi-automated perimetry (Peritest-Rodenstock). Clearly these pseudodefects have to be differentiated from glaucomatous defects and in many cases this is possible because: the pseudo-defects are bilateral, they have typical features, there is an optic disc-visual field discrepancy. These pseudo-defects: are usually more outspoken in the upper half than in the lower half, usually spare the central 10°-visual field, can be found in both eyes though not exactly symmetrical, may simulate a central island, an be differentiated from a glaucomatous central island because of the equal distance to the center in the nasal and temporal field and because of the absence of a nasal step.