ANALYSIS OF RELIABILITY INDEXES FROM HUMPHREY VISUAL-FIELD TESTS IN AN URBAN GLAUCOMA POPULATION

Purpose: Visual field assessment is extremely important in glaucoma ma nagement, but interpretation is affected by the quality of the patient 's performance, The authors have investigated the reliability of visua l field performance by a randomly selected sample of the chronic glauc oma population at an urban tertiary care practice. Methods: Patient re liability in Humphrey automated visual field testing was studied in 10 6 randomly selected chronic open-angle glaucoma patient charts, which provided 768 tests (mean, 7.2 +/- 4.8 fields; range, 2-18 fields). Rel iability criteria were established as less than 20% fixation losses, l ess than 33% false-negative error, and less than 33% false-positive er ror, as recommended by Humphrey Instruments, Inc (San Leandro, CA). Re sults: Patients performed reliably in 61% of right eye fields, 58% of left eye fields, and 59.5% overall. Of the 106 patients, only 35 (33%) were always reliable in both eyes, whereas 8 (7.5%) were always unrel iable in both eyes, The most common cause of unreliability was fixatio n loss (39%), whereas false-positive error (5%) and false-negative err or (9%) were less frequent. A more severely depressed mean deviation c orrelated significantly with poorer performance on the three reliabili ty indices, with false-negative error having the greatest correlation, followed by fixation loss and false-positive error. Corrected pattern standard deviation correlated closely only with false-negative error. Prolonged test time also correlated with all three reliability indice s. Age was a significant factor for fixation loss but not for false-ne gative or false-positive error. Conclusions: The authors conclude that fewer than two thirds of the Humphrey visual fields were reliable wit h the authors' urban tertiary care population of patients with glaucom a. Relaxing the fixation loss criterion to less than 33% improved the rate of reliability to approximately 75%. The severity of glaucomatous visual field defects, test time, and age were identified as factors i nfluencing the reliability of the Humphrey visual fields.