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A. Panarelli, J. P. S. Garcia, Jr., R. B. Rosen; Glaucoma Implant Imaging: Anterior Segment OCT versus UBM. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1187.
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The purpose of this study is to compare the ability of anterior segment optical coherence tomography (OCT) and ultrasound biomicroscopy (UBM) to effectively image glaucoma implants.
A retrospective review was made of patients with glaucoma implants who were imaged using the non-contact technique of anterior segment OCT and the water-immersion technique of UBM (AC Cornea OCT prototype and OTI Scan 35-50MHz Ultrasound System, Ophthalmic Technologies Inc. [OTI], Toronto, Ontario, Canada). Similar views were obtained utilizing anterior segment OCT and UBM consecutively, and images were compared.
Twelve eyes were included in the study. Anterior segment OCT imaged glaucoma implants under the conjunctiva better than UBM because UBM images were less clear due to echoes from the implant's plastic structural material resulting in artifacts. Anterior segment OCT also provided better quality images of glaucoma tubes in the anterior chamber but not in the posterior chamber or anterior vitreous, as OCT was limited by shadowing brought about by the pigmented posterior layer of the iris, and/or light-scattering effect of the overlying sclera. UBM, however, provided better images of tubes in the posterior chamber and anterior vitreous despite the presence of echoes. The coronal images provided by the AC Cornea OCT demonstrated the implant's position relative to other ocular structures in a spatial manner not obtainable through classic cross sectional images, and also provided better assessment of the tube's patency.
Anterior segment OCT is more effective at imaging glaucoma implants beneath the conjunctiva and in the anterior chamber. UBM is more effective at imaging glaucoma implants in the posterior chamber and anterior vitreous. By means of coronal imaging, the AC cornea OCT is uniquely able to depict the patency of glaucoma implants, as well as their spatial positioning relative to other ocular structures.
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