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Evaluation of the High-Specificity Screening Program (C-20-1) of the Frequency Doubling Technology (FDT) Perimeter in Clinical Practice

¹ Optometry & Vision Sciences Cardiff University Cardiff United Kingdom
² Ophthalmology University of Wales College of Medicine Cardiff United Kingdom

Commercial Relationships:  R.V. North, None; J.M. Wild, Humphrey Systems, Inc. R; E. Hunter, None; A.L. Jones, None; J.E. Morgan, None.

Abstract

Purpose: The efficacy of the FDT Program C-20-1, which has high specificity, has received relatively little attention. We compared the efficacy of this program for detecting patients with glaucoma in a busy ophthalmological clinic to that of conventional white-on-white static threshold perimetry. Methods: One hundred consecutive patients attending a glaucoma clinic at the Department of Ophthalmology, University Hospital of Wales, were examined with Program C-20-1 of the FDT and with Program 24-2 and the SITA Fast algorithm of the Humphrey Field Analyzer (HFA). Both examinations were undertaken on the same day and the order of examination was randomised between patients. The diagnosis for each patient was made by JEM, a glaucoma specialist trained to fellowship standard, and was based upon IOP, optic nerve head appearance and visual fields. The data for one eye only of each patient was analyzed. Results: Ten patients were diagnosed as normal, 68 as glaucomatous, 8 as ocular hypertensives and 13 others as exhibiting non-glaucomatous conditions. Of the 68 patients, 49 exhibited high tension glaucoma, 9 normal tension glaucoma and 10 were glaucoma suspects. The visual fields from the HFA were independently classified as normal or glaucomatous by JMW masked to the ophthalmological findings and diagnosis. Of the 68 patients with glaucoma 60 manifested glaucomatous field loss. The field loss, classified using a grading system modified from that of Hodapp et al. (1993), comprised 26 patients with early, 14 with moderate and 20 with severe loss. The assessment of the HFA fields gave a sensitivity of 92.6% and specificity of 83.3% compared to the ophthalmological diagnosis. The FDT fields were considered to be abnormal if one or more stimulus locations exhibited visual field loss. When compared to the outcome with the HFA the FDT gave a sensitivity of 71.4% and specificity of 86.4%. Conclusion: The results confirm that the C-20-1 screening test possesses high specificity in the detection of glaucoma.

Keywords: 624 visual fields • 511 perimetry • 498 optic disc

© 2002, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. For permission to reproduce any part of this abstract, contact the ARVO Office at arvo{at}arvo.org.