A comparison of the pattern- and total deviation-based Glaucoma Change Probability programs.

PURPOSE To compare the rates of progression of visual field defects in glaucoma patients, by using the Glaucoma Change Probability program based on pattern deviation and total deviation probability maps. METHODS The incidence of progression of visual field loss among 67 eyes of 56 glaucoma patients with an average of 6 years of follow-up was estimated by applying the criteria set by the Early Manifest Glaucoma Treatment study, which uses the output from the Glaucoma Change Probability (GCP) program of the Humphrey Field Analyzer (San Leandro, CA) based on pattern deviation probability maps. This incidence estimate was compared with one obtained by applying the same criteria but using the GCP program based on total deviation probability maps. RESULTS The 6-year incidence of progression among patients with glaucoma was 23.2% and 35.7% using the GCP program based on pattern deviation and total deviation probability maps, respectively. Not all patients in whom visual field loss progressed according to pattern deviation also showed progression according to total deviation. CONCLUSIONS The GCP program based on pattern deviation probability maps appears to screen out patients in whom progression of visual field defects may be due to diffuse loss from cataract, but the pattern deviation maps may also be identifying other types of field loss not detected by the total deviation maps.