A comparison between Humphrey and frequency doubling perimetry for chiasmal visual field defects

To evaluate and compare the diagnostic ability of frequency doubling technology perimetry (FDT) with standard automated perimetry (SAP) using Humphrey Field Analyser for the detection of visual field defects produced by chiasmal lesions.

Fifteen patients with documented chiasmal disease and previously diagnosed of bitemporal hemianopia with Humphrey perimetry were prospectively evaluated. All of them underwent a new SAP (SITA 24-2) followed by FDT tests (C-20 threshold). Diagnostic criteria for hemianopia were established according to the total deviation plot and the threshold values of FDT. A patient was diagnosed with hemianopia if one or both criteria were met. Based on these criteria, FDT sensitivity was calculated. Testing time and global indexes for both perimetric strategies were compared.

The sensitivity of FDT was 75.0% (18 out of 24 eyes); the criterion based on threshold values was met more often (70.83%) than the criterion based on the total deviation plot (50.0%). Linear correlation was better for the external column than for the internal column of the visual field. Testing time with FDT was 122.16 seconds shorter than with SAP (p<0.001). The mean value for mean deviation (MD) was -13.62 dB (SD 6.88) for SAP and -8.83 dB (SD 5.94) for FDT (p<0.001).

Compared with standard automatic perimetry, FDT has a low sensitivity for detecting temporal hemianopias and also has more difficulty in defining the vertical limits of the defects. Therefore, it does not appear to be an adequate method for the detection of chiasmal visual field defects.