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Editors Selection IGR 11-4

Structure and function measurements: FDT versus SAP

Comment by Shaban Demirel on:

20793 Diagnostic accuracy of the matrix 24-2 and original N-30 frequency-doubling technology tests compared with standard automated perimetry, Racette L; Medeiros FA; Zangwill LM et al., Investigative Ophthalmology and Visual Science, 2008; 49: 954-960

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Racette et al. (161) compared the performance of the original N-30 version of FDT and the Matrix to standard auto-mated perimetry (SAP) in their ability to distinguish patients with glaucomatous optic neuropathy (GON) from normals. Tests were compared using area under ROC analysis and the best performing variable for each perimetric method was determined. Interestingly, the best performing parameter was different for each test. Mean deviation was the best performer for SAP, PSD for FDT and the number of total deviation points abnormal at the 5% level for Matrix. Might this finding suggest that early glaucoma damage has a stronger diffuse component when SAP is used vs. either of the FDT platforms? This would perhaps be new finding were it to be true.

Frequency Doubling perimetry, in its initial or more recent incarnation, may outperform SAP for the separation of patients with GON from normals

When the three perimetric methods were compared using their best performing parameter at a fixed specificity of 80%, sensitivities were 46%, 56% and 60% for SAP, FDT and Matrix respectively. There was an expected drop in sensitivities to 38%, 40% and 44% (SAP, FDT, Matrix) when specificity was set to 90%. Matrix was found to be a significantly better performer than SAP when all tests were compared based on their best parameter but Matrix did no better than FDT and FDT did no better than SAP. When all tests were compared based on the PSD index, Matrix and FDT were significantly better than SAP. This is perhaps not surprising given that the best performing parameter for SAP was MD. Once again, Matrix and FDT were not significantly different from one another. This study adds further weight to the suggestion in the literature that Frequency Doubling perimetry, in its initial or more recent incarnation, may outperform SAP for the separation of patients with GON from normals.

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