High false-positive response in perimetry

BACKGROUND: In Humphrey visual field analyzer, the false-positive (FP) responses imply that the patient has pressed the response button despite no stimulus being seen at the time of response and FP rates >15% are flagged. The classical “Trigger happy” visual field has increased fixation loss, very high threshold retinal sensitivity with the values in supernormal range, “white scotoma” on grayscale map, high positive mean deviation (MD), glaucoma hemifield test (GHT) gives classification of “abnormally high sensitivity, ‘Excessive high false positive’ message is displayed,” and pattern deviation probability plot has more defects than total deviation probability plot known as “reverse cataract pattern.” However, these classical findings are not seen in all the cases of FP as the same thumb rule cannot be applied to all the visual fields with high FP. PURPOSE: This video emphasizes the significance of careful examination of all the parameters in a visual field printout of high FP to interpret the test results and the caution needed when an FP response is seen in a patient with advanced glaucoma. SYNOPSIS: The video presents some interesting visual fields in normal and glaucoma patients and the effect of high FP responses on MD, the different classification messages displayed for GHT, patterns of total deviation probability plot and pattern deviation probability plot, and how to identify the hidden FP. HIGHLIGHTS: This video highlights the importance of careful examination of all the parameters in a visual field printout to interpret the test results. One should be especially cautious when an FP response is noted in a patient with advanced glaucoma, as the retinal sensitivity values may not be in supernormal range but are significantly affected by the increased FP. Clinician should be able to identify this and repeat the test as high FP reponses can lead to underestimation of visual field loss. VIDEO LINK: https://youtu.be/T2SGZf16UzA