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A Heijl

Publications and source records attributed to A Heijl.

15 recordsLinked to original sources
PubMed1992

Glaucoma Hemifield Test. Automated visual field evaluation.

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.

Adult↗
PubMed1992

Evaluation of methods for automated Hemifield analysis in perimetry.

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.

Adult↗
PubMed1992

Weighting according to location in computer-assisted glaucoma visual field analysis.

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.

Adult↗
PubMed1992

Spatial analyses of glaucomatous visual fields; a comparison with traditional visual field indices.

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.

Adult↗
PubMed1978

Automatic computerized perimetry in the detection of neurological visual field defects. A pilot study.

Forty-seven eyes from 25 patients with neurological disease were examined with an automatic computerized perimeter primarily intended for glaucoma. Manual kinetic and static perimetry with Goldmann's instrument was used for comparison. In 32 fields, the automatic method disclosed all defects that had been found by manual perimetry. Furthermore, it detected three small defects that had been missed in the initial manual examination. The remaining 12 fields were normally using both methods. Consequently, in detecting field defects, the automatic perimeter was superior to the manual method.

Amblyopia↗
PubMed1977

Time changes of contrast thresholds during automatic perimetry.

Contrast thresholds were continuously recorded in six points of the visual field through a repetitive up-and-down staircase method using the automatic perimeter developed by Heijl & Krakau (1975b). The uninterrupted sessions lasted about 30 min. Nineteen patients with a verified diagnosis of glaucoma, or in whom glaucoma was suspected, and twelve healthy normal subjects were tested. With increasing test time, a decreased contrast sensitivity was found. In most subjects the mean threshold increment was small (less than 1.5 dB). The threshold increments were larger in the patient group than in the normal subjects--many test points showing increments of 6-10 dB during the test session. Such a large deterioration of sensitivity was most common in eyes with visual field defects. Test points which showed large threshold increments were often situated in the vicinity of documented visual field defects. In eyes with pathological visual fields, the short-term variation increased with increasing test time. An impairment of fixation with increasing test time was found in the patient group.

Adult↗
PubMed1977

Computer test logics for automatic perimetry.

Using an automatic computerized perimeter developed by Heijl & Krakau (1975b) three different perimetric test logics, one simple (I) and two more complicated and time-consuming (II & III) were investigated in practical experiments on healthy normal test subjects and patients and in computer simulated tests. The patients either had a verified diagnosis of glaucoma or glaucoma was suspected. The best consistency in measured thresholds was obtained with test logic II, in which an averaging procedure is used. The variation of the results was larger in pathological than in normal visual fields. All test logics investigated readily detected the pathological field defects, but blind spots could easier pass unrecognized with the simplest logic than with the other two logics. The conclusion is drawn that a simple test logic can be used for perimetry in glaucoma suspects if no visual field defect has previously been documented. For the follow-up of pathological fields a fairly complicated test logic, e.g. using averaging, is preferable.

Adult↗
PubMed1977

A note of fixation during perimetry.

Small eye movements in the direction of the disappearing stimulus can be observed at kinetic perimetry when the test object enters a scotomatous area. These may be responsible for the fact that several field defects, missed at routine manual perimetry, are spotted at automatic perimetry. In the latter case the patient cannot predict the position of next test light, since these are illuminated at random, whereas at kinetic perimetry they are exposed in systematic order. By using two specially designed logics in automatic perimetry, it was shown that there may be a reduction of the scotoma size if the lights are exposed in an ordered sequence. This effect is avoided by using a logic with randomly exposed stimuli. It is most likely that the difference can be attributed to "malfixation".

Adult↗
PubMed1976

Automatic perimetry in glaucoma visual field screening. A clinical study.

Automatic computerized perimetry was compared to careful manual selective perimetry (a variant of that proposed by Armaly) in 181 eyes of 100 patients from a glaucoma open-care unit. The results of the two methods were very similar. Thus all defects found were identified by the automatic perimeter, and one pathologic field was missed by the manual selective perimetry. The automatic examination gave 16% false positive results and the manual 11% when optimally performed. The false positives could be greatly reduced (to 4.4% and 3.3% respectively) by rescreening. In a comparison with "routine" perimetry, the automatic screening is shown to be superior.

Adult↗
PubMed1976

A portable hemianopsia tester.

A pocket-size static perimeter provided with four test lights, one for each quadrant of the visual field, has been constructed and applied to 190 visual fields in 97 patients. The main advantage of the instrument is its ability to disclose hemianopic defects in bedridden and certain sick patients unable to co-operate with other methods, including the confromtation test. This was performed in 12 fields in 7 patients.

Adolescent↗
PubMed1975

An automatic perimeter for glaucoma visual field screening and control. Construction and clinical cases.

An apparatus for static perimetry of the central visual field at 64 points is described. The testing is fully automatic: the test logic is programmed into a mini-computer and the results are plotted as a diagram in polar coordinates. A few cases with small or medium sized visual field defects have been analyzed by conventional methods and by the automatic instrument with satisfying results.

Adult↗
PubMed1975

An automatic static perimeter, design and pilot study.

An instrument for automatic static perimetry at 14 points across a meridian was constructed and used in a pilot study. The machine was controlled by a computer and the subjects responded to the light stimuli by pressing one of two push-buttons. Most people investigated readily understood the rules at testing. "Blunders" made by the subject were, however, so common, that allowance had to be made in the test programme for a number of mistakes. The test stimuli should be exposed in random order. When the zone of uncertain seeing is wide - this occurs especially in untrained subjects - a simple test logic gives a fairly large variation. An improvement in reproducibility is then obtained by applying a more complicated logic, though at the cost of an increased duration of the test session.

Adult↗