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Editors Selection IGR 9-4

Perimetry: Agreement and intraobserver reproducibility of progression

Comment by Chris Johnson on:

27931 Interobserver agreement and intraobserver reproducibility of the subjective determination of glaucomatous visual field progression, Tanna AP; Bandi JR; Budenz DL et al., Ophthalmology, 2011; 118: 60-65

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The determination of visual field progression and rate of progression has remained an enigma for the clinical management of patients with glaucoma and those at risk of developing glaucoma. In this investigation by Tanna et al. (231) five glaucoma specialists with extensive experience provided evaluations of 'none', 'questionable', 'probable' or 'definite' progression for 100 sets of five serial visual fields from 83 patients equally divided between stable and progressed outcomes based on determinations by one of the authors. The determinations were performed on more than one occasion. There was good to excellent agreement for interobserver evaluations, but was moderate to good for intraobserver agreement, even when provided with Glaucoma Progression Analysis (GPA) information. I have several comments with respect to this paper: (1) Most of the patient's visual fields in this study had mild to moderate functional damage, and it is not clear if these findings would also be applicable to individuals with more advanced visual field loss, and hence more test-retest variability. (2) Although the results for intra-observer agreement is a bit disappointing, quantitative mathematical criteria for progression have yielded similar results for inter and intra analysis procedure findings.^1,2 (3) Better intra-observer agreement can be achieved for classification and follow up of visual fields, but the criteria are quite complex and are not amenable to rapid use in a busy clinic.³ (4) Staging the severity of functional loss produced by glaucoma (a part of the progression determination) has also undergone many approaches, with only moderate agreement.⁴ Limitations in the sensitivity, specificity, accuracy, precision, reproducibility and other aspects of the visual field test procedure and subsequent data analysis remains a challenge and an opportunity for investigators to explore.

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