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Abstract #13201 Published in IGR 7-3
Detecting glaucoma with frequency-doubling technology perimetry: a comparison between N-30 and C-20 screening programs
Fogagnolo P; Mazzolani F; Rossetti L; Orzalesi NJournal of Glaucoma 2005; 14: 485-491
PURPOSE: To evaluate the ability of frequency-doubling technology (FDT) perimetry in detecting glaucoma with N-30 and C-20 screening programs. METHODS: Eighty eyes of 80 patients were enrolled (40 glaucomatous, 40 controls). Humphrey achromatic perimetry (standard automated perimetry, SAP) was considered as the 'gold standard' for diagnosis. To assess whether N-30 screening program could detect more initial glaucomatous defects than C-20, glaucomatous patients included 20 cases with nasal step at SAP (pre-selected by medical chart inspection). Patients underwent two SAP examinations to confirm diagnosis; then two N-30 and two C-20 screening tests with frequency-doubling technology were performed in a randomized sequence. Finally, a frequency-doubling technology N-30 full-threshold examination was performed. Several criteria to define abnormality at frequency-doubling technology screening programs were evaluated. RESULTS: For both C-20 and N-30 screening programs, the best parameter to detect glaucoma was the presence of at least 1 point with P < 5% (sensitivity = 87.5% for both tests and specificity of 90% and 95% for C-20 and N-30, respectively). Both screening procedures obtained a lower sensitivity (75%) in patients with a nasal step, whereas frequency-doubling technology full-threshold program was able to detect the initial defects in all cases. CONCLUSIONS: N-30 and C-20 screening procedures obtained similar results in well-defined glaucoma patients in terms of sensitivity and specificity. In the presence of a standard automated perimetry nasal step, diagnostic ability with both frequency-doubling technology screening strategies decreased and one quarter of nasal steps went undetected.
Dr. P. Fogagnolo, Eye Clinic, Department of Medicine, Surgery, and Odontoiatry, San Paolo Hospital, University of Milan, Milan, Italy. fogagnolopaolo@libero.it
Classification:
6.6.3 Special methods (e.g. color, contrast, SWAP etc.) (Part of: 6 Clinical examination methods > 6.6 Visual field examination and other visual function tests)
