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Editors Selection IGR 17-4
Visual function: SITA versus FDT
Comment by Chris Johnson on:
16946 Comparison of visual field defects using matrix perimetry and standard achromatic perimetry, Patel A; Wollstein G; Ishikawa H et al., Ophthalmology, 2007; 114: 480-487
Patel et al. (134) performed a comparison of visual field results obtained using the Swedish Interactive Threshold Algorithm(SITA) Standard 24-2 test procedure for conventional automated perimetry (Humphrey Field Analyzer II) and Frequency Doubling Technology (FDT) perimetry using the 24-2 test procedure of the Humphrey Matrix in 50 eyes of 50 glaucoma patients with visual field loss. Most of the glaucoma patients had mild to moderate visual field loss. The authors report that the average test time was shorter for the Matrix than for SITA Standard, that there was good congruence in the visual field loss when both devices detected the visual field deficits, that 36% of SITA deficits were missed by the Matrix, and that deficits tended to be smaller and deeper with the Matrix than with SITA. The authors interpret the differences to be due to the large stimulus size of the Matrix or differences in the normative database.
36% of SITA deficits were missed by the MatrixAlternatively, because one of the inclusion criteria was the presence of visual field loss for SITA Standard testing, a selection bias may also have affected the results. It would be of interest to repeat the test, but to use presence of a deficit on the Matrix as an inclusion criterion to see if the findings are comparable. The authors are to be commended because the study was thorough and was performed carefully. It is particularly noteworthy that the authors provide a distribution of threshold sensitivity measures for both devices, and that they indicate that both devices use a dB scale, but that the physical properties that they represent are substantially different. These are hallmarks of a well-planned and thoroughly analyzed investigation.
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