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Angelique Pillar, Osamah Saeedi; Choroidal Vessel Cross-Sectional Area Before and After Trabeculectomy. Invest. Ophthalmol. Vis. Sci. 2014;55(13):918.
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© ARVO (1962-2015); The Authors (2016-present)
We have previously shown that choroidal thickness has an inverse linear relationship with intraocular pressure (IOP) after trabeculectomy. As current methods to isolate choroidal vessels rely on complex algorithms and customized software, our purpose was to develop a simple method of identifying choroidal vessels in ImageJ to understand the relationship between large choroidal vessel area and IOP after trabeculectomy.
21 eyes of 20 patients undergoing trabeculectomy were studied in this case series. Patients were examined pre-operatively, then post-operatively at 1 week and 1, 3, and 6 months with IOP checks and Enhanced Depth Imaging SD-OCT (Spectralis, Heidelberg Instruments) centered on the posterior 6 mm surrounding the fovea. Using ImageJ software (NIH Bethesda), the choroid was manually outlined extending from the retinal pigment epithelium to the choroidal-scleral interface. The image was contrast enhanced with histogram equalization and compared to a color gradient-map to determine the extent of the choroidal vessels. A threshold value was set, above which the large choroidal vessels were outlined. The outlined vessel area was then averaged over the 6 mm choroid to obtain choroidal vessel thickness. Interstitial thickness outside of the major vessels was calculated by subtracting the choroidal vessel thickness from the choroidal thickness. The relationship between the change in vascular thickness and change in IOP after trabeculectomy was analyzed using univariate regression analysis and a linear regression model to calculate the coefficient of determination (R2).
58 OCT image in 16 patients were deemed sufficient for analysis. The average large vessel thickness was 96+/-56 µm and the average choroidal thickness was 220+/-73 µm. The change in vessel thickness statistically significantly correlated with change in IOP after trabeculectomy at one month (P < 0.01). Conversely, change in interstitial thickness was not correlated with change in IOP (P = 0.053). Neither the change in vessel thickness (slope -2.190, R2 0.397) nor the interstitial thickness (slope -1.35, R2 0.241) respected a linear relationship with IOP.
Our data suggest that choroidal vessel cross-sectional area increases with IOP lowering after trabeculectomy, but this relationship is not linear. Furthermore, using our method, interstitial cross-sectional area does not change with IOP lowering trabeculectomy surgery.
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