| 1. |
- Asman, P, et al.
(författare)
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Evaluation of methods for automated Hemifield analysis in perimetry
- 1992
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Ingår i: Archives of Ophthalmology. - : American Medical Association (AMA). - 0003-9950. ; 110:6, s. 6-820
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Tidskriftsartikel (refereegranskat)abstract
- A new aid to perimetric analysis, the Glaucoma Hemifield Test, primarily evaluates up-down differences in automated static visual field tests. We analyzed the visual fields of 163 eyes of 163 normal subjects and 77 eyes of 77 patients with glaucoma diagnosed on bases other than perimetry using the Glaucoma Hemifield Test and a similar, previously developed, hemifield analysis method. The performance of the Glaucoma Hemifield Test was compared with that of the earlier method and the differences in test design were evaluated individually. The Glaucoma Hemifield Test allowed significantly improved separation between the normal group and the group with glaucoma than did the earlier method. This improvement was due to an increase in sensitivity, and was associated with the use of test point significances instead of threshold values, and a large normal database alone in the determination of normal limits.
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| 2. |
- Asman, P, et al.
(författare)
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Glaucoma Hemifield Test. Automated visual field evaluation
- 1992
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Ingår i: Archives of Ophthalmology. - : American Medical Association (AMA). - 0003-9950. ; 110:6, s. 9-812
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an algorithm, the Glaucoma Hemifield Test (GHT), for automated evaluation of single static threshold visual field test results in glaucoma. The GHT uses empirically determined limits of normality for up-down differences in the Statpac probability maps of the Humphrey Field Analyzer to detect localized visual field loss. It is also constructed to detect field loss that is symmetric around the horizontal meridian. Analysis is done in five corresponding pairs of sectors that are based on the normal anatomy of the retinal nerve fiber layer. Deviations from the age-corrected normal threshold in the most sensitive portions of the visual field are used to detect general reductions of sensitivity or abnormally high sensitivities. The GHT provides brief visual field evaluations printed on the field chart as plain text. The aim of this article is to describe the fundamentals of the analysis program and to provide clinical examples.
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| 3. |
- Asman, P, et al.
(författare)
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Spatial analyses of glaucomatous visual fields; a comparison with traditional visual field indices
- 1992
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Ingår i: Acta Ophthalmologica. - 0001-639X. ; 70:5, s. 86-679
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Tidskriftsartikel (refereegranskat)abstract
- Interpretation of numeric automated threshold visual field results is often difficult. A large amount of data is obtained for every single field tested. Various approaches to summarize this data have been suggested, most commonly the mean and standard deviation of departures from age-corrected normal threshold values. These visual field indices differ substantially from subjective field interpretation where spatial relationships are important. We have previously devised two methods for automated field interpretation which take spatial information into account--regional up-down comparisons and arcuate cluster analysis. We now studied the merits of using these new spatial methods and compared them to traditional visual field indices for discrimination between normal and glaucomatous field results. Central static 30 degree field results in 101 eyes of 101 normal subjects and 101 eyes of 101 patients with glaucoma were discriminated using logistic regression analysis. The best field classification was obtained with a spatial visual field model combining up-down differences and arcuate clusters. The advantages of the spatial model were confirmed in an independent material of 163 eyes of 163 normal subjects and 76 eyes of 76 patients with glaucoma where eyes with large field defects had been removed. In this material the spatial model gave 87% sensitivity and 83% specificity while the best non-spatial model gave 82% sensitivity and 80% specificity. Visual field interpretation in glaucoma may be significantly enhanced if detection is focused on circumscribed field loss rather than on averages of differential light sensitivities and similar indices which do not take spatial relationships into consideration.
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| 4. |
- Asman, P, et al.
(författare)
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Weighting according to location in computer-assisted glaucoma visual field analysis
- 1992
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Ingår i: Acta Ophthalmologica. - : Wiley. - 0001-639X .- 1755-375X. ; 70:5, s. 8-671
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Tidskriftsartikel (refereegranskat)abstract
- In recent years several aids for automated interpretation of visual field data have been suggested. We believed that incorporation of thorough knowledge of normal visual field variability would allow improvements in the performance of such aids since more attention would be paid to field results in areas with low physiological variability. Two visual field models for classification of fields in glaucoma based on comparisons of sensitivity values in the upper and lower hemifields and on analysis of test point clusters with diminished sensitivity were compared. Both models were constructed using logistic regression analysis in 101 normal eyes and 101 eyes with glaucoma. The first, more traditional model assumed Gaussian distributions of deviations from age-corrected normal thresholds and constant variability across the field (non-weighted model). The second model took into account empirically determined variability of pointwise threshold results and of cluster volumes in various visual field regions (weighted model). The two models were subsequently tested on an independent material of 163 normal eyes and 76 eyes with glaucoma. The weighted model gave significantly better classification of the fields in both materials. Accounting for physiological threshold variability can offer significant advantages in the construction of perimetric analysis aids for detection of glaucoma.
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