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M. Figus, S. Lazzeri, A. Ferreras, F. Oddone, M. Iester, P. Frezzotti, M. Nardi, P. Fogagnolo; Short-Term Changes in the Optic Nerve Head and Visual Field After Trabeculectomy in Advanced Glaucoma. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4921.
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To determine the short-term relationship between changes in optic nerve head (ONH) topography and functional parameters following a sudden intraocular pressure (IOP) reduction.
A prospective study was performed on 56 patients (56 eyes) with uncontrolled primary open angle glaucoma, who underwent filtration surgery. ONH parameters, measured with the Heidelberg Retina Tomograph (HRT), and standard automated perimetries were performed preoperatively, and at 3 and 6 months after surgery. Differences in IOP, visual field (VF) and HRT measurements were evaluated with the t-test for paired data. A linear regression model was calculated to analyze the relationship between IOP reduction and VF and ONH changes.
Mean IOP decreased from 24.36 ± 5.00 mmHg to 12.07 ± 3.12 mmHg (month 3) and 10.64 ± 2.84 mmHg (month 6) after trabeculectomy. The average preoperative Mean Deviation (MD) and Pattern Standard Deviation (PSD) were -13.05 ± 9.37 dB and 7.58 ± 3.79, respectively. VF indices did not show significant changes (p=0.059 and p=0.063) compared with baseline values. Cup area, cup volume, cup/disc area ratio, maximum cup depth and mean retinal nerve fiver layer (RNFL) thickness did not show any significant change (p=0.053; p=0.064; p=0.131; p=0.188; and p=0.053, respectively). Changes in rim parameters (area and volume) did not show statistically significant association with IOP change (Rim Area r2=0.1656 and r2=0.2518 respectively at 3 and 6 months after surgery; Rim Volume r2=0.0014 and r2=0.0440).The linear regression model demonstrated an increase of RNFL thickness, rim area and rim volume for each 1 mmHg of IOP reduction at both follow-up time points (p=0.053; p=0.058 and p=0.060). Changes in RNFL had a mild association with changes in IOP (r2=0.0084) 3 months after surgery (p=0.046) even if it was not statistically significant at month 6 (p=0.054).
Morphological changes were pointed out before functional modifications, but both of them, which were related to IOP reduction, were not statistically significant after glaucoma filtration surgery. However, IOP reduction was correlated with a trend of improvement of the ONH morphological and functional parameters in short-term in advanced glaucoma patients.
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