Abstract
Purpose: :
Aim of this study was to evaluate the longterm–reproducibility of FDT screening procedures in patients of the 'erlangen glaucoma registry' in a 5 years survey.
Methods: :
Longitudinal data of 231 patients have been included: 172 ocular hypertensive eyes, 107 preperimetric open–angle glaucoma eyes (glaucomatous optic disc atrophy, normal standard perimetry), and 72 perimetric open angle glaucoma eyes (glaucomatous optic disc atrophy and visual field defects). All patients had yearly tests with the FDT perimeter and thorough opthalmological examination (i.a. conventional perimetry, optic disc inspection, tonometry, lens opacity measurement). Patients with progression of glaucoma and patients with elevated lens density had been excluded. The present screening strategies of the FDT perimeter (procedure: C–20–5 and N–30–5) start testing at the normal 5% probability level. If a stimulus is not detected further targets are presented. The present analysis uses case–wise recalculation of all missed localized probability levels to create an overall screening score for 17 central test–positions (Horn 2002). Thus the score ranges from 0 to 68. We analyzed longterm variability by correlation analysis and limits of agreement (Altman and Bland). All subjects had 2 or more yearly tests with the C–20 procedure and another year later at least one additional test with the N–30 protocol. Seventy–nine eyes had 2 or more tests with the N–30 protocol. Dependencies between left and right eyes were statistically adjusted for.
Results: :
Analyses of repeated measurements in patients revealed significant learning effect (p<0.001) between first and second examination but no significant difference between second and following tests with the C–20 protocol (p>0.6). In addition, there was no significant difference between second C–20 and N–30 tests (p>0.5). Limits of agreement were between –7 and 10 for the present screening score. Correlation coefficients: all eyes: 0.85, oht: 0.6, preperimetric glaucomas: 0.69, perimetric glaucomas: 0.9.
Conclusions: :
Longitudinal FDT–results in a clinical study show high reproducibility if the first test is discarded. The FDT screening N–30 protocol (which is faster and offers information for two additional test–positions) is comparable with the C–20 procedure.
Keywords: clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • learning • perimetry