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Abstract #6388 Published in IGR 3-2
Variability components of standard automated perimetry and frequency-doubling technology perimetry
Spry PGD; Johnson CA; McKendrick AM; Turpin AInvestigative Ophthalmology and Visual Science 2001; 42: 404-410
PURPOSE: To evaluate and compare intra- and intertest variability components for both standard automated perimetry (SAP) and frequency-doubling technology (FDT) perimetry in a small group of normal individuals and patients with glaucoma. METHODS: The method of constant stimuli (MOCS) was used to examine matched test locations with both SAP and FDT perimetry stimuli in a group of eight normal individuals and seven patients with glaucoma. Subjects were tested weekly at three predetermined visual field loci for five consecutive weeks. Frequency-of-seeing (FOS) curves were generated and used to quantify threshold sensitivity (50% seen on FOS, in dB), intratest variability (FOS interquartile range, in dB), and intertest variability (interquartile range of weekly repeated threshold determinations, in dB). RESULTS: In patients with glaucoma, SAP intra- and intertest variabilities were found to increase with sensitivity reductions, as previously reported. FDT perimetry revealed that both intra- and intertest variability components did not change appreciably with reductions in sensitivity. With the measurement scales used in this investigation, both intra- and intertest variability components were significantly greater for SAP than for FDT perimetry (p < 0.001 and p = 0.003, respectively). Intratest variability exceeded intertest variability for both SAP (p = 0.001) and FDT perimetry (p < 0.001). CONCLUSIONS: For both SAP and FDT perimetry, variability occurring within a single test session contributed more to total variability than between session variability. When the measurement scales available on commercial instrumentation were used, FDT perimetry exhibited significantly less variability than SAP, especially within regions of visual field sensitivity loss. FDT perimetry therefore shows promise as an effective test for detecting progressive glaucomatous visual field loss, although prospective longitudinal validation is still required to determine sensitivity to change.
Dr P.G.D. Spry, Bristol Eye Hospital, Lower Maudlin Street, Bristol BS1 2LX, UK. pgds@hotmail.com
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)
