Thesis (M.Optom.)--University of Melbourne, Dept. of Optometry and Vision Sciences, 2009. / Typescript. Includes bibliographical references.

No / To explore the performance of patient-specific prior information, for example, from structural imaging, in improving perimetric procedures. Computer simulation was used to determine the error distribution and presentation count for Structure–Zippy Estimation by Sequential Testing (ZEST), a Bayesian procedure with prior distribution centered on a threshold prediction from structure. Structure-ZEST (SZEST) was trialled for single locations with combinations of true and predicted thresholds between 1 to 35 dB, and compared with a standard procedure with variability similar to Swedish Interactive Thresholding Algorithm (SITA) (Full-Threshold, FT). Clinical tests of glaucomatous visual fields (n = 163, median mean deviation −1.8 dB, 90% range +2.1 to −22.6 dB) were also compared between techniques. For single locations, SZEST typically outperformed FT when structural predictions were within ± 9 dB of true sensitivity, depending on response errors. In damaged locations, mean absolute error was 0.5 to 1.8 dB lower, SD of threshold estimates was 1.2 to 1.5 dB lower, and 2 to 4 (29%–41%) fewer presentations were made for SZEST. Gains were smaller across whole visual fields (SZEST, mean absolute error: 0.5 to 1.2 dB lower, threshold estimate SD: 0.3 to 0.8 dB lower, 1 [17%] fewer presentation). The 90% retest limits of SZEST were median 1 to 3 dB narrower and more consistent (interquartile range 2–8 dB narrower) across the dynamic range than those for FT. Seeding Bayesian perimetric procedures with structural measurements can reduce test variability of perimetry in glaucoma, despite imprecise structural predictions of threshold. Structural data can reduce the variability of current perimetric techniques. A strong structure–function relationship is not necessary, however, structure must predict function within ±9 dB for gains to be realized.

Thesis (Ph. D.)--University of California, San Diego, 2009. / Title from first page of PDF file (viewed July 23, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

Background : Frequency Doubling Perimetry ( FDP ) is a recently developed form of perimetry, which may be more sensitive for detecting visual field loss from glaucoma than conventional Achromatic Automated Perimetry ( AAP ). This thesis was undertaken to study aspects of FDP for the detection of early glaucoma. Method : FDP was compared with other forms of perimetry at one point in time using one dataset ( n = 83 ) and longitudinally over a four - year period with another dataset ( n = 62 ). Several aspects were studied : ( 1 ) the ability of FDP to detect visual field loss earlier than AAP, ( 2 ) its ability to detect early functional abnormality in the presence of mild glaucomatous structural abnormality ( 3 ) visual field topography compared with other perimetry and ( 4 ) its ability to predict future field loss when only the nasal quadrants were considered. Results : When subjects at risk of glaucoma with initial visual field loss on FDP were followed over a three - year period, a significant proportion developed field loss with AAP, whilst those without initial FDP loss did not. FDP detected cases of early glaucomatous optic disc damage, which had not been detected using AAP ; however, there was still a proportion of those with abnormal optic discs which remained normal on FDP. FDP field topography was hill - shaped with the most sensitive point centrally ; however, it was considerably flatter and more sensitive than AAP. Finally, if FDP field loss was only considered significant when it occurred within the nasal step location of the visual field, then this may improve the accuracy of glaucoma diagnosis. Conclusion : This thesis has demonstrated that FDP is not only more sensitive than AAP in the detection of glaucomatous optic disc damage, but it is able to predict future field loss on AAP. FDP may therefore be useful in the early detection and management of glaucoma. / Thesis (Ph.D.)--School of Medicine, 2006.

Glaucoma is defined as a progressive optic neuropathy, characterized by loss of visual function and often associated with high intra-ocular pressure. Testing the patients' visual function with Standard Automated Perimetry (SAP) is currently the clinical standard for detecting glaucomatous visual field loss. A new test algorithm using the Frequency Doubling illusion has been introduced on the Matrix perimeter (Humphrey Matrix; Carl Zeiss Meditech, Dublin CA) that measures the central 10° using a 2°x 2° square flickering stimulus. This stimulus has the theoretical advantage of being both a large target, with good repeatability, and being perceptually selective, by preferentially stimulating the magnocellular projecting ganglion cells. <br /><br /> The purpose of this thesis was to determine the within-technique, between-visits repeatability and the within-visit, between-technique comparison of several techniques available to measure the central 10° visual field in patients with late stage glaucoma. In particular, to examine test-retest variability and compare sensitivity threshold values, visual field indices, and total and pattern deviation probability maps among the following techniques: Full Threshold SAP 10-2 size III (SAP III), Full Threshold SAP size V (SAP V), SITA SAP 10-2 size III (SS III), and Matrix 10-2 2° stimulus (M2). <br /><br /> Forty nine patients with advanced glaucomatous visual field defects attended 3 visits. During each visit, 1 eye was examined with each of the 4 techniques mentioned above. Data from the first visit was discarded to eliminate bias that may occur from the learning effect. Coefficient of Repeatability values of SAP III, SAP V, SS III, and M2 were calculated to be 10. 33, 9. 00, 9. 90, and 12. 04%dB respectively, relative to the average difference in threshold estimates between visits. M2 had the most uniform test-retest characteristics across the full range of sensitivities; however the 90% confidence interval was the widest of all techniques in the normal to near normal range (24 to 38dB). M2 showed the greatest defects in both total and pattern deviation probability plots. Threshold estimates of SAP III and SS III were shown to be similar and slightly more variable than SAP V. M2 showed greater defects than SAP III in both total and pattern deviation probability plots. Compared to SAP III and SS, M2 estimated sensitivity as less severe. Estimates of 20 dB and above on M2 were estimated at approximately 30 dB with SAP V. In the moderate to abnormal sensitivity range, Matrix estimated points to be shallower than that estimated by SAP V. <br /><br /> This thesis showed that test-retest variability of the SAP techniques decreased with increasing sensitivity whereas; variability was constant throughout the dynamic range for M2 and smaller in the moderate to severe range. However M2 was worst in the normal to near-normal sensitivity range. This suggests that M2, compared to all SAP techniques, will be disadvantaged for the detection of early visual field loss but better positioned to repeatably detect and follow moderate to severe loss in the central 10° of patients with late stage glaucoma.

Glaucoma is defined as a progressive optic neuropathy, characterized by loss of visual function and often associated with high intra-ocular pressure. Testing the patients' visual function with Standard Automated Perimetry (SAP) is currently the clinical standard for detecting glaucomatous visual field loss. A new test algorithm using the Frequency Doubling illusion has been introduced on the Matrix perimeter (Humphrey Matrix; Carl Zeiss Meditech, Dublin CA) that measures the central 10° using a 2°x 2° square flickering stimulus. This stimulus has the theoretical advantage of being both a large target, with good repeatability, and being perceptually selective, by preferentially stimulating the magnocellular projecting ganglion cells. <br /><br /> The purpose of this thesis was to determine the within-technique, between-visits repeatability and the within-visit, between-technique comparison of several techniques available to measure the central 10° visual field in patients with late stage glaucoma. In particular, to examine test-retest variability and compare sensitivity threshold values, visual field indices, and total and pattern deviation probability maps among the following techniques: Full Threshold SAP 10-2 size III (SAP III), Full Threshold SAP size V (SAP V), SITA SAP 10-2 size III (SS III), and Matrix 10-2 2° stimulus (M2). <br /><br /> Forty nine patients with advanced glaucomatous visual field defects attended 3 visits. During each visit, 1 eye was examined with each of the 4 techniques mentioned above. Data from the first visit was discarded to eliminate bias that may occur from the learning effect. Coefficient of Repeatability values of SAP III, SAP V, SS III, and M2 were calculated to be 10. 33, 9. 00, 9. 90, and 12. 04%dB respectively, relative to the average difference in threshold estimates between visits. M2 had the most uniform test-retest characteristics across the full range of sensitivities; however the 90% confidence interval was the widest of all techniques in the normal to near normal range (24 to 38dB). M2 showed the greatest defects in both total and pattern deviation probability plots. Threshold estimates of SAP III and SS III were shown to be similar and slightly more variable than SAP V. M2 showed greater defects than SAP III in both total and pattern deviation probability plots. Compared to SAP III and SS, M2 estimated sensitivity as less severe. Estimates of 20 dB and above on M2 were estimated at approximately 30 dB with SAP V. In the moderate to abnormal sensitivity range, Matrix estimated points to be shallower than that estimated by SAP V. <br /><br /> This thesis showed that test-retest variability of the SAP techniques decreased with increasing sensitivity whereas; variability was constant throughout the dynamic range for M2 and smaller in the moderate to severe range. However M2 was worst in the normal to near-normal sensitivity range. This suggests that M2, compared to all SAP techniques, will be disadvantaged for the detection of early visual field loss but better positioned to repeatably detect and follow moderate to severe loss in the central 10° of patients with late stage glaucoma.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 106-108). Also available via the Internet.

Perimetry is essential to identify visual field defects in disorders of the visual pathways. In compliant adults, automated static perimetry (ASP) is the preferred method of visual field assessment. However, children under 10 years have difficulty with the visuo-motor task and constant fixation required. Manual kinetic perimetry is often used for children as it can be adapted to a child’s age. However, it suffers from many of the problems inherent to ASP. In infants perimetry is limited to the “confrontation” technique which can be imprecise and does not generate quantitative data. The lack of reliable ASP in children and quantitative perimetry in infants is a longstanding clinical problem. The aims of this research were to (i) develop, and (ii) clinically evaluate, a technique for ASP in children which utilises “eye tracking”. The first part of this research was concerned with the development of the technique, termed “Saccadic Vector Optokinetic Perimetry” (SVOP). The system comprises a personal computer, display screen, and an X50 eye tracker (Tobii Technology, Sweden). The eye tracker is noncontact and provides data on (i) eye position in 3D space, and (ii) the point of gaze. This allows the screen position of “test stimuli” to be calculated, and eye gaze responses to the “test stimuli” to be assessed in “real time”. A software algorithm was developed to determine if “test stimuli” have been perceived based on the direction, amplitude and latency of a subject’s gaze response. A feasibility study was conducted with 29 subjects comprising 4 groups: (i) healthy adults, (ii) healthy children, (iii) adult patients with visual field defects, and (iv) child patients with visual field defects. Subjects performed SVOP tests which replicated the Humphrey Field Analyser (HFA) C-40 screening test with a stimulus size of Goldmann III and intensity of 14dB. Subjects able to do so also performed equivalent HFA C-40 tests for comparison. In healthy subjects 99.1% of SVOP test points were in agreement with a healthy visual field. In patients with visual field defects, 89.8% of test points were in agreement with HFA equivalent tests. The visual field defects identified using SVOP in the child patients were consistent with their clinical findings. A clinical evaluation of SVOP was undertaken in the second stage of this research with 122 subjects comprising the same four subject groups as in the feasibility trial. An “ideal” test protocol resulted in 8 uniocular visual field tests for each subject comprising 4 SVOP tests and 4 HFA tests. In children where uniocular testing was not tolerable, two binocular SVOP tests were performed. The sensitivity and specificity of the SVOP tests were computed using a direct comparison with reliable HFA tests, and repeatability of SVOP and HFA tests were assessed using Cohen’s kappa coefficient. In child patients unable to provide a reliable HFA test, their clinical history, other clinical findings and the repeatability of their SVOP tests were used to assess the SVOP results. The overall sensitivity and specificity of the SVOP testing was 72.7% and 96.8% respectively. The sensitivity had a greater variation than the specificity amongst the different subject groups. The repeatability of SVOP tests was slightly reduced as compared to the HFA tests across all groups with kappa coefficient’s of 0.65 and 0.74 for SVOP and HFA respectively. In child patients without reliable HFA equivalent tests the SVOP results could commonly be associated with other clinical findings and repeatable testing added to the confidence in the reliability of these cases. The developed SVOP technique performs well with accurate eye tracking data and an attentive child. It has proved extremely useful in identifying and monitoring visual field defects in several child patients who required regular visual field assessment.

This study investigated the variability of response associated with various perimetric techniques, with the aim of improving the clinical interpretation of automated static threshold perirnetry. Evaluation of a third generation of perimetric threshold algorithms (SITA) demonstrated a reduction in test duration by approximately 50% both in normal subjects and in glaucoma patients. SITA produced a slightly higher, but clinically insignificant, Mean Sensitivity than with the previous generations of algorithms. This was associated with a decreased between-subject variability in sensitivity and hence, lower confidence intervals for normality. In glaucoma, the SITA algorithms gave rise to more statistically significant visual field defects and a similar between-visit repeatability to the Full Threshold and FASTPAC algorithms. The higher estimated sensitivity observed with SITA compared to Full Threshold and FASTPAC were not attributed to a reduction in the fatigue effect. The investigation of a novel method of maintaining patient fixation, a roving fixation target which paused immediately prior lo the stimulus presentation, revealed a greater degree of fixational instability with the roving fixation target compared to the conventional static fixation target. Previous experience with traditional white-white perimetry did not eradicate the learning effect in short-wavelength automated perimetry (SWAP) in a group of ocular hypertensive patients. The learning effect was smaller in an experienced group of patients compared to a naive group of patients, but was still at a significant level to require that patients should undertake a series of at least three familiarisation tests with SWAP.

Visual field testing, or perimetry, measures peripheral visual loss in eye diseases such as glaucoma. Rarebit Perimetry (RBP) is a new and novel perimetric method, introduced in 2002 by Lars Frisén (2002), with the aim of detecting low degrees of neural damage within the retina. / RBP is unlike conventional perimetric methods that measure levels of retinal sensitivity, but instead uses very bright (i.e. suprathreshold) and very small targets to detect tiny areas of absolute blindness within otherwise normal areas of vision. RBP thus claims to locate miniscule gaps in the receptive field matrix of neurons in the retina, with the assumption that dead neurons leave gaps in this matrix. The most useful application of this idea is to detect progressive eye disease in the earliest stages (Frisén, 2002). Current research shows that RBP correlates with other standard visual field tests (Brusini, Salvetat, et al., 2005; Frisén, 2003; Gedik, Akman, et al., 2007; Martin & Wanger, 2004), but may afford greater sensitivity by detecting very mild visual losses missed by other tests (Martin, Ley, et al., 2004; Martin & Nilsson, 2007; Nilsson, Wendt, et al., 2007). / To date, there are no studies that definitively test the theoretical basis of RBP, so in this thesis I aim to explore the proposed underlying mechanisms and assumptions of this test. In particular, the proposed mechanism of RBP leads to specific predictions as to how responses will alter when the luminances of the RBP targets are systematically decreased. I therefore compared RBP responses of mean hit rate as a function of target luminance and found results to be inconsistent with the proposed RBP mechanism. Mathematical simulations were performed to explore reasons for the differences between the two groups (Chapter Seven).