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Frequency doubling technology perimetry for neuro-ophthalmological diseases
  1. C A Johnson
  1. Correspondence to: C A Johnson Discoveries in Sight, Devers Eye Institute, Legacy Health Systems, 1225 NE Second Avenue, Portland, OR 97208, USA; cajohnsondiscoveriesinsight.org

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It will be beneficial to all eye care practitioners if investigations of a wide variety of ocular and neurological diseases are evaluated with FDT perimetry

In the past decade, there have been many advances in diagnostic test procedures for evaluation of structural and functional changes affecting the visual pathways. Perimetry and visual field testing have undergone improvements that allow tests to be performed more efficiently and accurately, detect earlier signs of pathological changes, quantitatively evaluate progressive losses, and provide enhanced diagnostic information.1–3 One of these emerging visual field test procedures is frequency doubling technology (FDT) perimetry, which has been shown to be effective in detecting visual field loss produced by glaucoma and other visual disorders,4 and may detect early perimetric changes before standard automated perimetry.5 Because of its clinical value and importance, an improved second generation of FDT instrumentation, known as the Humphrey Matrix, has recently become available.6 This new device attests to the significance and success of FDT perimetry as a clinical diagnostic tool.

The emphasis of FDT perimetry has been directed towards the detection and evaluation of glaucomatous visual field loss, and some papers have alluded to FDT perimetry as a procedure to be used predominantly for glaucoma patients and individuals at risk of developing glaucoma. However, FDT perimetry, like most visual field test procedures, was designed to evaluate peripheral sensitivity loss produced by a variety of disorders affecting the visual system, including neuro-ophthalmological diseases.4,7–9 It is unfortunate that only a few investigators have reporting FDT findings for visual dysfunction other than glaucoma. In this view, it is most encouraging to observe the article by Girkin et al in this issue of the BJO (p 1274) on FDT perimetry in non-arteritic ischaemic optic neuropathy with altitudinal defects.

In their study, the authors of this investigation report that FDT perimetry, in comparison with standard automated perimetry, is able to provide very good detection and characterisation of visual field loss in non-arteritic ischaemic optic neuropathy. FDT perimetry reveals more extensive damage that standard automated perimetry for some cases, and demonstrates a strong correlation with structural optic disc changes. These findings provide important clinical information for practitioners and augment our existing knowledge pertaining to the clinical value of FDT perimetry. Additionally, this report indicates that FDT perimetry may be helpful in future investigations of this type for determining insights and added information about the pathophysiological basis for the damage resulting from non-arteritic ischaemic optic neuropathy.

FDT perimetry is a relatively new visual field test procedure that has been available for approximately 7 years, has demonstrated clinical value and usefulness, and has resulted in development of a new device (the Humphrey Matrix) that appears to have many enhanced features. It will be beneficial to all eye care practitioners if investigations of a wide variety of ocular and neurological diseases are evaluated with FDT perimetry. The study of FDT findings in patients with non-arteritic ischaemic optic neuropathy and altitudinal defects, as reported here, is an excellent example of this type of research. The authors are to be congratulated for conducting such a careful, well designed, and timely study. Through these and similar efforts we will gain a better understanding of the clinical capabilities and limitations of FDT perimetry, enhance our understanding of the underlying pathophysiological basis of visual pathway disorders, and obtain an improved awareness of the association between structural and functional damage produced by ocular and neurological diseases. Hopefully, this work may serve as a source of motivation and inspiration for other researchers to pursue these types of studies pertaining to the clinical utility of FDT perimetry.

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It will be beneficial to all eye care practitioners if investigations of a wide variety of ocular and neurological diseases are evaluated with FDT perimetry

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