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Euna Koo, Jing Hou, Ying Han, Jeremy Keenan, Robert Stamper, Bennie Jeng; Effect of glaucoma tube-shunt position on corneal thickness and endothelial cell density. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1650.
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To investigate post-operative changes in corneal thickness and endothelial cell density (ECD) after tube-shunt implantation
Twenty-eight eyes of 24 glaucoma patients with superotemporal tube-shunts, but without prior corneal transplantation or previous tube-shunt placement, were evaluated at University of California, San Francisco. Superotemporal (ST), central, and inferonasal (IN) ECD and corneal thickness were measured by non-contact specular microscopy (CellChek XL™ Specular Microscope, Irvine, CA) and ultrasound pachymetry (DGH™ Pachette 2, Exton, PA), respectively. The angle of the tube relative to the cornea, tube length, and distance between the tip of the tube and cornea, were measured with anterior segment optical coherence tomography (Visante™ OCT Anterior Segment Imaging, Dublin, CA). Linear regression analyses were used to assess effects of tube position on ECD and corneal thickness.
The average time lag from tube implantation to time of cornea and anterior segment measurements was 45±40.4 months (range 1-156 months). Mean ST, central, and IN ECD (cells/mm2) were 1649.7±800.0, 1940.1±862.0, and 1963.6±856.7, respectively. Mean ST, central, and IN corneal thicknesses (μ) were 640.6±103.6, 536.3±86.8, and 650.8±83.6, respectively. ST ECD was lower than central ECD (P=0.0001) and IN ECD (P=0.003, paired t-test). There was no difference in ECD between central and IN cornea (P=0.97). ST and IN cornea were thicker than central cornea (P<0.0001, paired t-test), but ST and IN thickness were comparable. For each additional degree in angle of tube away from the cornea, there were 21.6 (-12.1-55.2, 95% CI) more ST endothelial cells, though this was not significant (P=0.20). There was no relationship between ST ECD and tube length (P=0.30) or tube-corneal distance (P=0.80).
The presence of a tube shunt drainage device in the anterior chamber causes significant local endothelial cell loss compared to central cornea or cornea furthest away from the tube. Endothelial cells near the tube may be better preserved with tubes angled further away from the cornea, but a larger study is needed to answer this question.
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