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C. Ajtony, Z. Bernad, R. Fustos, A. Horvath, Z. Biro; Visual Field Changes in the Progression of Preperimetric Glaucoma. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4393.
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To evaluate the rate and pattern of visual field (VF) changes in preperimetric glaucoma patients during a median of 3.7 years of follow-up.
Observational cohort study including 75 eyes of 75 patients with optic nerve head changes typical for glaucoma but no detectable VF defects. Anually obtained retinal nerve fiber layer (RNFL) thickness measurements with optical coherence tomography (StratusOCT) along with standard automated perimetry visual fields performed every 4 to 6 months were evaluated. VF progression was definied as a glaucoma hemifield test outside normal limits and/or a pattern standard deviation with P<.05 on three consecutive tests. Independent samples T-test for means comparisons was employed using SPSS 16.0 statistical software. The change of RNFL thickness over time was defined by regression analysis.
14 eyes (18%) had VF progression during follow-up. Eight cases of 14 (57%) developed in those with average (AVG) RNFL thickness below 80 µm at baseline (mean:73.5±6.9) together with -0.46 µm/year (R2=0.93) rate of AVG RNFL loss, mainly in 7, 8 and 10 o’clock segments (-3.0, -2.1, -2.1 µm/year, respectively).Subjects with thicker AVG RNFL (baseline mean: 96±6.1) had -2.44 µm/year decline (R2=0.95) with a more diffuse pattern of RNFL loss. There was no significant age difference between the groups (66.2±8.3 vs. 61.3±12.5 years).
No constant RNFL decline can be suspected in the process of glaucoma. In preperimetric glaucoma patients with thinner RNFL thickness at baseline, a more subtle structural change may precede the appearance of glaucomatous visual field loss. These data might also support our previous finding that a mean value of RFNL thickness around 70 µm measured by OCT - even considering its wide range of interindividual variability - can represent a profound threshold value in glaucomatous structural changes.
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