Comparison of long-term variability for standard and short-wavelength automated perimetry in stable glaucoma patients

PURPOSE: To quantify and compare, on a point-by-point basis, the long-term variability of standard and short-wavelength automated perimetry in a group of stable glaucoma patients. METHODS: From a group of 53 glaucoma patients experienced in visual field t esting, we identified one eye, randomly chosen, from each of 25 glaucoma pa tients whose condition was found to be stable, based on both standard and s hort-wavelength automated perimetry visual field criteria. On each of three visits during a period of up to 3 months, each patient performed one stand ard and one short-wavelength automated perimetry 24-2 visual field in a ran dom order on a Humphrey visual field analyzer. The long-term variability (a lso referred to as test-retest variability) was defined as the SD of the th ree threshold decibel values at each test location. The longterm variabilit y for each test point (mean +/- SD) was determined separately for both stan dard visual fields and short-wavelength automated perimetry. RESULTS: With all 52 test locations of the 24-2 field averaged, the global long-term variability, mean (+/- SD) for standard visual fields and short-w avelength automated perimetry was 2.37 +/- 2.03 dB (95% confidence interval , 2.26-2.48 dB) and 2.92 +/- 2.03 dB (95% confidence interval, 2.81-3.03 dB ), respectively (P < .0001). In 16 of the 52 visual field locations, long-t erm variability on short-wavelength automated perimetry was significantly h igher than long-term variability on standard visual fields. In addition, th e long-term variability increased with greater distance from the point of f ixation for both standard visual fields and short-wavelength automated peri metry. The long-term variability decreased closer to fixation, more for sta ndard visual fields than for short-wavelength automated perimetry. CONCLUSIONS: In a group of stable glaucoma patients, mean long-term variabi lity was 0.55 dB higher for short-wavelength automated perimetry than for s tandard visual fields. This needs to be taken into consideration when seria l visual fields are evaluated for change. (C) 2000 by Elsevier Science Inc, All rights reserved.