CHARACTERISTICS OF FREQUENCY-OF-SEEING CURVES IN NORMAL SUBJECTS, PATIENTS WITH SUSPECTED GLAUCOMA, AND PATIENTS WITH GLAUCOMA

Purpose. The authors performed this study to determine factors that af fect the characteristics of frequency-of-seeing curves in normal subje cts, patients with suspected glaucoma, and patients with glaucoma. Met hods. The sample consisted of 70 subjects (22 normal subjects, 12 pati ents with suspected glaucoma, and 36 patients with glaucoma). A progra m was written to interface with the Humphrey Field Analyzer (Humphrey Instruments, San Leandro, CA) to measure frequency-of-seeing curves. T he authors presented stimuli 8 dB either side of the estimated thresho ld in 1-dB intervals with five repetitions at each stimulus intensity. The authors tested four to six locations in each subject, with random ization of the stimulus intensity and location. Fixation was monitored with the Heijl-Krakau method. Using a probit program, the authors cal culated the threshold and slope (estimated by the interquartile range) of each curve. Results. The authors obtained 124 curves from the norm al subjects, 71 from the patients with suspected glaucoma, and 183 fro m the patients with glaucoma. In all three groups, the slope of the fr equency-of-seeing curve was correlated highly with the threshold or th reshold deviation, although the correlation was significantly higher i n the normal subjects compared with the patients with suspected glauco ma and patients with glaucoma, even after controlling for the range of the threshold and threshold deviation. For this reason, the authors f ound considerably different frequency-of-seeing cur-ves, between subje ct groups and also within the group of patients with glaucoma, in loca tions with the same threshold. Conclusions. There may be fundamental d ifferences in areas of normal subjects and patients with glaucoma with similar thresholds or threshold deviations. These differences also ma y exist within patients with glaucoma.