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D. H. Su, R. Maldonado, C. M. Santiago-Turla, S. Stinnett, R. R. Allingham; Change in Optic Nerve Morphology Following Reduction in Intraocular Pressure - An SD-OCT Study. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2254.
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To determine if lowering intraocular pressure (IOP) induces changes in optic nerve morphology detectable by spectral domain optical coherence tomography (SD-OCT).
Subjects undergoing trabeculectomy or glaucoma tube surgery were enrolled after informed consent was obtained. The optic nerves were imaged with the Spectralis SD-OCT before and 1 week after surgery. Optic nerve cup volume, nasal cup depth and temporal optic cup depth were measured using Amira 5 (Visage Imaging GmbH., Berlin, Germany) software. Descriptive statistics were computed for all variables at each visit and for change from the pre-operative visit. The significance of the change from baseline was assessed using the Wilcoxon signed rank test of median difference equal to zero. The Spearman rank correlation was computed to assess the relationship between the change in intraocular pressure (IOP) and the measured parameters. Plots of the change in the SD-OCT variables versus the change in IOP were produced and a regression line was fit to the data. The significance of the slope of the line was assessed using the t-test of the equality of the slope to zero.
7 eyes of 7 subjects underwent glaucoma surgery and the mean reduction in IOP was 11.43 (SD 6.95) mmHg (57.55%). The difference in nasal cup depth before and after surgery was 0.017 (SD 0.019) mm which approached statistical significance (p=0.078). Optic cup volume and temporal cup depth were also lower after surgery but the difference did not reach statistical significance. Reduction in optic cup volume and nasal cup depth measured by SD-OCT was weakly correlated with change in IOP (Rho = 0.143, 0.286 respectively; R2 = 0.088, 0.115 respectively) but the trend was not statistically significant.
SD-OCT is a powerful new imaging technology. In this study we found that optic cup volume, nasal and temporal cup depth were reduced following surgery. These findings did not reach statistical significance, which may be due in part to small sample size. The dataset is being expanded and alternative strategies for image analysis will be employed to further investigate the effect of IOP lowering on optic nerve head parameters using this technology.
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