Clustering of fixation targets in multifixation campimetry.

The multifixation campimeter has a central test stimulus and a series of numbered fixation targets and uses the patient's eye movements to position the stimulus in the visual field. The stimulus is constantly exposed so that the patient reads the numbers and identifies any which are associated with its disappearance. The aim of this study is to identify the effect of clustering fixation targets on sensitivity. Two hundred and seventy-two eyes of 139 normal individuals were tested with a multifixation campimeter in which either one or two of the fixation targets corresponded to the physiological blind spot. Sixty-nine individuals (138 eyes) were tested with chart A and 70 individuals (134 eyes) with chart B. The second fixation target increased the blind spot detection rate from 65% to 85% of the eyes respectively. In 10% of eyes the blind spot was detected on only one of two examinations. The performance of multifixation campimetry is improved if fixation targets are clustered in vulnerable parts of the field and distributed so as to test the blind spot repeatedly during the examination. Inconsistent results are an indication for re-examination of selected points, with intermittent stimulus presentation.