Frequency-doubling matrix perimetry not superior to SAP

This prospective study found no evidence that frequency-doubling matrix perimetry (FDT2) is more sensitive than standard automated perimetry (SAP) in identifying visual field deterioration.

The study’s authors investigated visual field deterioration in 64 glaucoma patients and 36 healthy controls with FDT2 and SAP using a new analytical technique called permutation of pointwise linear regression (PoPLR). This measures the significance of deterioration over time at each visual field location, combining values into a single overall statistic and determining the likelihood of that statistic existing because of chance alone. Because the outcome is a single P value independent of the scale of original measurement, the method is well suited for comparison of techniques with different stimuli and measurement scales.

They write that direct comparisons between FDT2 and SAP in measuring glaucomatous visual field damage and its progression are problematic for several reasons, including differences in the stimulus area, imperfect matching of stimulus locations and variations between thresholding algorithms (which in turn lead to variations in the number and arrangement of possible sensitivity levels analyzed by the techniques), as well as different measurement scales.

Therefore, they compared FDT2 and SAP solely on the basis of the statistical significance of deterioration derived from PoPLR rather than on the magnitude (in decibels) or the rate of deterioration (in decibels per year).

Progression was identified in fewer glaucoma patients with FDT2 compared with SAP in both total deviation and pattern deviation analyses. Controls were also identified as having deterioration with both techniques but particularly by SAP with total deviation analysis. Agreement between techniques in the identification of deterioration was moderate with total deviation analysis and poor with pattern deviation analysis.

It is noteworthy that SAP identified about twice as many participants with progression than FDT2 using total deviation. Also, SAP identified 31 percent of healthy controls as having statistically significant progression, whereas FDT2 only identified 8 percent. However, magnitude of change, while significant, was less in controls than in patients found to have progression.