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C.A. Johnson, S.K. Gardiner, G.A. Cioffi; Structure–Function Relationships in Glaucoma: A Comparison of Different Functional Tests . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1123.
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Glaucoma is diagnosed on the basis of a combination of optic nerve structural features, functional tests, and additional clinical information including past medical history. However, the spatial relationship between structure (optic nerve head [ONH] properties) and function (visual fields) is not well defined. This study investigates whether that relationship is dependant on the particular functional test used.
In a previous study (Gardiner et al 2005, IOVS 46:3712–7) normalized rim area measurements using the Heidelberg Retina Tomograph (HRT) were compared to perimetric sensitivities measured using white–on–white Standard Automated Perimetry (SAP), in order to derive a map relating regions of the ONH to SAP test locations. This study uses the same analysis technique for Short Wavelength Automated Perimetry (SWAP) and Frequency Doubling Technology perimetry (FDT, Humphrey Matrix), using a 24–2 test pattern in each. 165 eyes of 165 subjects with early glaucoma or glaucomatous optic neuropathy were included in the study, with all four tests being carried out within one month.
For SAP and FDT, 37 of the 52 non–blind spot locations exhibited a correlation >0.25 with the normalized rim area of at least one sector of the ONH, and 35 did so for SWAP. The best perimetry location – ONH sector correlations were 0.486, 0.450 and 0.417 for SAP, SWAP and FDT respectively.
The topographical map appeared similar for all three functional tests. The graphical representation produced using SWAP was less clear than those using SAP or FDT, which may be indicative of increased variability. Correlations in the locations near fixation were noticeably poorer for FDT than for SAP or SWAP, which may be caused by the lower proportion of magnocellular mechanisms around the fovea compared with the periphery.
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