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Joel M. Miller, Ethan A. Rossi, Martin Wiesmair, Danielle E. Alexander, Orazio Gallo; Stability of gold bead tissue markers. Journal of Vision 2006;6(5):6. doi: 10.1167/6.5.6.
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© ARVO (1962-2015); The Authors (2016-present)
Significant soft tissue features in the orbit and elsewhere are not resolved by MRI or any other imaging method. We describe a new method that uses tiny (∼0.1 mm diameter) gold beads as markers to visualize movements of such tissues with high spatial resolution (∼100 μm) and moderate temporal resolution (∼100 ms). We describe bead fabrication, implantation, imaging, and image processing to extract three-dimensional bead coordinates. We then present results of an experiment to determine the stability of gold bead tissue markers (GBTMs) over time in normally moving orbital tissues. Most beads (76%) implanted in sclera, muscle, tendon, and connective tissue were highly stable over the 6-month measurement period. Beads that were judged unstable drifted only a few 100 μm. Bead flows with gaze suggested that posterior Tenon's capsule moves with the globe, that the lateral rectus belly may sideslip, producing “bridle forces,” and that the posterior medial rectus pulley sling moves freely anteriorly and posteriorly, but hardly vertically, as required by the “coordinated active pulley” hypothesis. The GBTM method seems applicable to study such short time course phenomena as extraocular muscle (EOM) and connective tissue movement as a function of gaze and such long time course phenomena as myopic eye growth.
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