To quantify the inter-test variability (dB) for the Optopol automated perimeter, Glaucoma Fast Treshold program, in normals and glaucoma patients.Methods
A prospective study was performed on 204 glaucoma patients and a control group of 30 normal subjects, tested by complete ophthalmological exam and automated perimetry (Optopol PTS-910). The visual field was tested weekly for 4 consecutive weeks, using the Glaucoma Fast Threshold strategy. The visual field defects were classified according to the Aulhorn-Karmeyer descriptive scale.Results
For the control group, the average inter-test variability was of 1.57+/- 0.24 dB, lower next to fixation and increasing towards the 50 degree isopter. The average inter-test variability increases along with the perimetric stage: 1.57+/-0.66 dB for pre-perimetric glaucoma, 2.13+1.04 dB for non-specific defects group, 3.23 + 1.01dB for the stage 1, 3.52 + 2.61dB, for the stage 2, 3.65 + 1.19dB for the stage 3 and 5.82 +/- 1.67dB for the stage 4. For the cases of preperimetric glaucoma and non-specific defects, a similar profile of variability as for the normal subjects could be observed. For the stages 2-4, the profile of the areas with maxim inter-test variability moves towards the relative scotoma and the surrounding area.Conclusion
A better description of the inter-test variability and the evolution of this intricate parameter of the retinal light sensitivity is useful for the differential diagnostic between the real change and the « background noise » in early detection of the functional progression in glaucoma.