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D Jackson Coleman, Ronald H. Silverman, Harriet O. Lloyd, Dan Z. Reinstein; High Definition Ultrasound Imaging of the Lens. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3077.
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High frequency (30-50 MHz) ultrasound provides fine-resolution images of the anterior segment of the eye. Its ability to penetrate optically opaque tissues enables visualization of the retroiridal structures such as the crystalline lens, lens implants and the ciliary body. The ability of single-element transducers to image specular surfaces (e.g., the crystalline lens), however, is affected by angle of incidence. Our aim was to evaluate a compound high-frequency ultrasound imaging technique for improved visualization of the lens contour.
We imaged a series of 10 phakic human subjects with the Artemis-3 (Arcscan, Morrison, CO) prototype. The instrument includes a system for optical visualization of the ocular surface during scanning and an optical fixation target. A focused single-element 40 MHz transducer is moved under computer-control to image the anterior segment in either an arc motion of user-selected radius, or linear translation (in 3 axes). While arc-scanning is ideal for imaging the cornea and anterior lens surface, this geometry is inappropriate for the posterior lens. To address this, we tested a compound scanning protocol consisting of an arc scan and two linear scans at oblique incidence. The three scans were acquired in approximately one second, and then combined to form a single image.
Compound high frequency ultrasound images of the anterior segment enabled depiction of the full anterior segment (sulcus-to-sulcus) and virtually the entire contour of the crystalline lens with high-resolution. In addition, the zonule can be seen to be posteriorly oriented and largely by passes the ciliary processes.
Higher imaging speed and registered imaging in serial meridians will permit 3D depiction of lens geometry and anterior segment anatomy. The ability to image lens surfaces will allow investigation and modeling of the accommodative lens changes. Determination of lens volume and position relative to scleral landmarks may allow more accurate estimation of post-cataract extraction expected lens position.
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