Abstract
Purpose: :
The authors performed a statistical correlation between Visual Field Index (VFI) and the reliability indices provided by modern campimetric tests: false positive responses (FP), false negative responses (FN) and loss of fixation (LF).
Methods: :
It was based on a retrospective analysis from 52,742 Visual Fields (VFs) made consecutively from 01-01-1995 to 01-01-2011. All tests were performed in the Department of Glaucoma, Hospital das Clinicas in Sao Paulo, with the same Humphrey Perimetry, always using the same program (SITA 30-2, 24-2 or Full Threshold). Like all these indices are provided in percentages from 0 to 100%, it was possible to correlate the average of each index (FL, FP and FN) for each level of VFI (0 to 100%).
Results: :
This study was based on a computerized statistical analysis of 23.506 tests campimetric were selected and performed in 8.853 patients, according to the inclusion and exclusion criteria, giving us an average of 4.0 VF per patient. The mean age was 60.05 years, ranging from 41 to 83 years (SD: 18.96). The average of FN responses was 6.6% (SD: 9.1). The FP average was 2.5% (SD: 4.3) and the FL average was 10.1% (SD: 14.7). Our results showed that both that the greater variability and the highest percentage of FN were associated with low VFI, and that there was an association between loss fixation and false negative indexes with the level of damaged, assessed by the VFI. The causal relationship could not be determined by the design of this study. It was also noted that the rate of FP responses did not vary significantly with the levels of VFI and may be considered as a measurement of the reliability of the perimetric examination
Conclusions: :
There is an inverse relationship between VFI and the FN, FL indices: with reduced levels of VFI (progression of glaucomatous damage) there is an increased rate of FN responses and LF.
Keywords: visual fields • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • imaging/image analysis: clinical