Perimetric sensitivity and response variability in glaucoma with single-stimulus automated perimetry and...

To measure perimetric sensitivity and response variability of glaucomatous patients with single-stimulus automated perimetry (SSAP) and multiple-stimulus perimetry (MSP) with verbal feedback.

Frequency-of-seeing (FOS) data were collected from the same four visual field locations (normal and reduced sensitivity) in one eye of 10 glaucoma patients, using SSAP and MSP. The SSAP technique was similar to that used in routine clinical perimetry while the MSP technique required the patient to verbally report the positions of the seen stimuli (0-4, with no more than 1 in each quadrant) after each presentation. At each test location, stimuli (0.5 degrees , 200 ms) were repeatedly presented at five or more intensities around the estimated threshold. FOS curves (logistic) were determined using a maximum likelihood method and the threshold sensitivity (50% seen) and response variability (20-80% seen range) were compared between the two perimetric techniques.

There was an increase in sensitivity (mean = 1.9 dB, P < 0.01, Wilcoxon) and reduction in variability (mean range reduced from 3.7 to 2.5 dB, P < 0.01, Wilcoxon) with MSP. The increase in sensitivity with MSP varied between patients (P < 0.001, one-way anova) with the mean MSP-SSAP sensitivity per eye ranging from 0.1 to 4.8 dB.

Patients have a higher sensitivity and less variability in their visual field when tested with MSP with verbal feedback than with SSAP. These differences vary between patients and a likely explanation is the better maintenance of attention with MSP and verbal feedback. This finding demonstrates how the variability found in routine clinical perimetry can be reduced through changes to the way in which the stimuli are presented and the way in which the patient responds.