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Editors Selection IGR 7-1

Visual function: Progression

Comment by Catherine Boden on:

11790 Glaucomatous visual field progression with frequency-doubling technology and standard automated perimetry in a longitudinal prospective study, Haymes SA; Hutchison DM; McCormick TA et al., Investigative Ophthalmology and Visual Science, 2005; 46: 547-554

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Newer perimetric tests may be valuable in monitoring visual field loss by overcoming some properties of standard automated perimetry (SAP) that may hinder detection of visual field deterioration (e.g., high variability). Frequency-doubling technology perimetry (FDT) is a newer test with variability characteristics that may be more amenable to detecting progression. Haymes et al. (189) compared FDT and SAP using two progression analyses (Glaucoma Change Probability (GCP) and linear regression analyses (global, by hemifield, by quadrant)) with various combinations of the number of field locations and the number of examinations required for confirmed progression. Participants were primary open-angle glaucoma patients from a longitudinal prospective study who had a minimum of six exams with both FDT and SAP. Overall, the agreement between FDT and SAP on which eyes progressed was poor. FDT did not consistently identify more progressed eyes or detect progression earlier. Rather, the results depended upon the analysis and criteria employed. The influences of test type (FDT vs SAP) and progression criteria were inseparable. As the authors note, true comparison of tests requires equalization of progression criteria across test types. Moreover, there is currently no gold-standard for glaucomatous progression against which to validate accuracy. Two nasal locations of the FDT were excluded from analyses because testing early in the study did not include those points. Thus, the ability of FDT to detect progression in the nasal regions may have been disadvantaged. The relatively recent availability of FDT meant short follow-up times (maximum of 4.5 years). With longer follow-up times, there could be sufficient numbers of progressed eyes to compare adequately FDT and SAP using stricter progression criteria. The primary contribution of this paper is to show that selection of progression analysis and criteria is a critical factor in determining which perimetric tests appears to identify more progression and, presumably, time to progression.

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