Computer Test Logics for Automatic Perimetry

Abstract

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.

A new generation of algorithms for computerized threshold perimetry, SITA

“…The methods used in currently available test algorithms were developed during the 197Oies (Heijl & Krakau 1975;Bebil et al 1976;Heijl 1977). The methods used in currently available test algorithms were developed during the 197Oies (Heijl & Krakau 1975;Bebil et al 1976;Heijl 1977).…”

“…The relation for traditional threshold strategies between quality of test result and test time is apparent; more time-consuming tests are more accurate than shorter ones (Heijl 1977;Johnson et al 1992). Thus, threshold strategies that use shorter stimulus steps and more reversals produce longer staircase sequences resulting in more accurate, but longer tests.…”

“…Threshold variability is large in glaucomatous fields, even when ambitious test algorithms are used (Heijl 1977;Holmin & Krakau 1979;Flammer et al 1984;Werner et al 1987;). To accept increased measurement errors would make interpretation of tests results even more difficult and could lead to errors in patient management.…”

“…glaucoma, and computerized threshold perimetry is the most precise clinical method to measure the visual field. The methods used in currently available test algorithms were developed during the 197Oies (Heijl & Krakau 1975;Bebil et al 1976;Heijl 1977). Stimulus intensities are altered up and down in staircases at predetermined test point locations.…”

“…Thus, threshold strategies that use shorter stimulus steps and more reversals produce longer staircase sequences resulting in more accurate, but longer tests. The relation for traditional threshold strategies between quality of test result and test time is apparent; more time-consuming tests are more accurate than shorter ones (Heijl 1977;Johnson et al 1992). Long tests are impractical in clinical settings, however, and often difficult for elderly glaucoma patients.…”