A note of fixation during perimetry.

Small eye movements in the direction of the disappearing stimulus can be observed at kinetic perimetry when the test object enters a scotomatous area. These may be responsible for the fact that several field defects, missed at routine manual perimetry, are spotted at automatic perimetry. In the latter case the patient cannot predict the position of next test light, since these are illuminated at random, whereas at kinetic perimetry they are exposed in systematic order. By using two specially designed logics in automatic perimetry, it was shown that there may be a reduction of the scotoma size if the lights are exposed in an ordered sequence. This effect is avoided by using a logic with randomly exposed stimuli. It is most likely that the difference can be attributed to "malfixation".