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Title: Variability of the automated perimetric threshold response
Author: Djiallis, Caroline Helen
ISNI:       0000 0004 2746 5676
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2005
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The thesis investigated aspects of the perimetric threshold estimate with the aim of facilitating the outcome of the visual field examination. The difference in performance of the three current short-duration commercially available algorithms, SITA Standard, SITA Fast and TOP was investigated, relative to their respective 'gold standards' and to each other, in two separate studies of normal individuals and of patients with open angle glaucoma (OAG). The results for the normal individuals suggested that the TOP algorithm will overestimate the severity of the field loss relative to the Octopus Threshold and SITA Fast algorithms. However, for the patients with OAG, SITA Fast represented a good compromise between performance and examination duration. The inherent differences within- and between-algorithm for TOP suggests that an alternative should be utilised in clinical practice. The characteristics of the Frequency-of-seeing (FOS) curves for W-W perimetry and for SWAP were investigated for varying eccentricities in normal individuals and in patients with OAG. In the normal individuals, the slope of the FOS curve flattened and the magnitude of the 50th percentile decreased with increase in eccentricity for W-W perimetry and for SWAP. The magnitude of the slope was flatter at any given eccentricity for SWAP than for W-W perimetry. In patients with OAG, the magnitude of the slope was moderately correlated with the severity of field loss for W-W perimetry and for SWAP. The flatter slope of the FOS curve will always yield greater variability for SWAP than for W-W perimetry. The number of incorrect responses to the False-negative catch trials was investigated in patients with OAG as a function of the fatigue effect. No significant difference was found in the prevalence of incorrect responses with increase in fatigue. The prevalence of incorrect responses was modestly correlated with increasing severity of field loss. W-W perimetry, SWAP, SITA, TOP, FOS, False-negative catch trials.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available