False-negative responses in glaucoma perimetry: Indicators of patient performance or test reliability?

PURPOSE. To study whether false-negative answers in computerized glaucoma p erimetry indicate the patient's ability to perform perimetry or test result reliability. METHODS. A retrospective evaluation was performed of visual field test resu lts obtained with a perimetry program (Humphrey 30-2 Sita Standard; Humphre y Instruments, San Leandro, CA) in 70 consecutive patients with unilateral glaucomatous field loss. Frequencies of false-negative answers were compare d between the two eyes of each patient and related to amount of visual fiel d damage in the glaucomatous eyes using linear regression analysis. RESULTS. Frequencies of false-negative answers were higher in eyes with fie ld loss. The intrapatient intereye difference was 6.6% on average (P < 0.00 01). In seven subjects with false-negative frequency of 5% or more in both eyes, the mean difference was 12.7% between eyes. The differences in false- negative answers depended significantly on the amount of field loss in the glaucomatous eyes (P = 0.0003). Larger differences were seen in patients wi th advanced field loss in the affected eye. CONCLUSIONS. The increased frequencies of false-negative answers in eyes wi th field loss were strongly associated with held status. The higher false-n egative frequencies in eyes with glaucomatous field loss compared with unaf fected eyes may be explained by the increased variability in threshold valu es typically found in such eyes. False-negative answers in patients with gl aucoma therefore represent eye rather than patient status.