Effect of intermittent versus continuous patient monitoring on reliability indices during automated perimetry

This prospective, randomized study was undertaken to determine the effect of intermittent versus continuous patient monitoring on reliability indices (fixation losses, false-positive errors, and false-negative errors) during automated static perimetry.

A practice Humphrey Program C30-2 visual field was administered to 169 subjects (mean age +/- standard deviation, 56 +/- 18 years) for 1.5 minutes, during which time trained technicians continuously monitored all subjects and assessed patient fixation as noted on the eye monitor. The computer-generated reliability indices during the 1.5 minute practice test were recorded. After completion of the practice test, the 169 eyes were randomized to either intermittent or continuous monitor for the permanent C30-2 test. During intermittent monitoring, the technician returned periodically to the examination room to assess the subject's performance. For continuous monitoring, the technician continually assessed the subject's performance while remaining in the examination room throughout the test duration.

The mean number of visits per visual field test during intermittent monitoring was 4.0, and mean test duration was 15.8 minutes. There was no difference in the mean deviation, pattern standard deviation, and short-term fluctuation (P = 0.85, 0.98, and 0.41, respectively) of the visual fields for intermittent and continuous monitoring, suggesting similar diffuse depression and localized defects in the visual fields for each group. The mean fixation losses (6.9%), false-positive errors (1.8%), and false-negative errors (5.8%) for the intermittently monitored group were not different from the mean fixation losses (7.8%), false-positive errors, (3.1%) and false-negative errors (5.0%) for the continuously monitored group (P = 0.40, 0.24, and 0.36, respectively).

Although recommended, continuous monitoring does not appear necessary for all patients undergoing automated perimetry. Error-free reliability indices combined with the technician's judgment of patient reliability during the first 1.5 minutes of C30-2 testing may be a guideline for choosing intermittent monitoring.