[FDT versus automated standard perimetry in healthy subjects]

To assess the frequency of visual field defects in frequency doubling technology (FDT) perimetry performed in healthy volunteers and the correlations between FDT and standard automated perimetry (SAP).

A transversal study that included 57 healthy volunteers who were subject to visual field testing in both FDT and SAP (randomly effectuated in the same day). The studied parameters were: the frequency of visual field defects in the two techniques, the correlation of the quantitative parameters (MD, PSD) with the C/D ratio and also between techniques, the test reliability and the test duration. The subjects have been questioned about their preference for one test or another.

The frequency of visual field defects was 47.35% in FDT and 22.8% in SAP. The MD values were significantly higher in FDT (MD FDT= -1.45+/-1.91, MD SITA= -0.77+/-1.58, p< 0.0001). Also the PSD values were higher in FDT (PSD FDT= 3.76+/-0.96, PSD SITA= 1.94+/-1.05). The correlation of quantitative parameters between the two techniques was low (r = 0.369 for MD and 0.206 for PSD). The correlation between the PSD value and the C/D ratio was extremely weak in both methods (because the subjects were healthy). The mean duration of a FDT test (4 '29") was significantly lower than that of a SITA test (5'18") - p < 0.00001. The reliability indices (fixation losses, false negative and false positive errors) were significantly better in FDT, and 3/4 of subjects declared that they preferred the FDT test.

In normal subjects the frequency of visual field defects was greater in FDT than in SAP. There was a low correlation of quantitative parameters (MD, PSD) between SAP and FDT, and also with the C/D ratio. Better reliability indices, shorter test duration and better patient compliance are arguments for using FDT as a screening test for glaucoma.