A prospective three-year study of response properties of normal subjects and patients during automated perimetry

The purpose of this study is to evaluate prospectively the reliability characteristics of patients undergoing automated perimetry over a 3-year period and compare these results with the results of previous investigations.

The subjects included 48 normal observers, 32 ocular hypertensive subjects, and 19 patients with early glaucomatous visual field loss. Both eyes were tested annually for 3 years with automated perimetry, using the standard procedures for the Humphrey Field Analyzer. Fixation losses, false-positive errors, false-negative errors, and short-term variability (double determinations) were evaluated.

Short-term variability was slightly higher for the early glaucoma group than for the normal observer and ocular hypertensive groups, but there were no meaningful changes in short-term variability over 3 years. False-positive errors were very low in all three groups throughout the investigation. False-negative errors were slightly higher in the early glaucoma group, but all three groups had relatively low false-negative error rates throughout the study. Fixation losses were the most common source of unreliable results. The number of fixation losses decreased for the second and third years of the study.

Contrary to a previous report, a relatively low number of unreliable tests were found for both initial and follow-up visits. The majority of unreliable visual field tests were sporadic events. Only a few subjects repeatedly produced unreliable test results. The authors conclude that automated perimetry can provide a reliable means of following patients over extended periods of time.