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Susan A. Strenk, Bosco S. Tjan, Liliana Werner, Nick Mamalis, Lawrence M. Strenk, Kenneth L. Lu; In Vivo and In Vitro MRI of the Uvea in Pseudophakic Human Eyes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6618.
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© ARVO (1962-2015); The Authors (2016-present)
MRI is not impeded by the iris or optical distortions and has the unique ability to visualize the entire intraocular lens (IOL) and its relationship to the surrounding uveal tissue in any desired plane. The purpose is to determine the effect of cataract surgery on the uvea and its implications for IOL design.
Donor eyes (N=100, ages 10-99) were imaged 1.5T (General Electric) using custom RF coils (MRI Research) and T1 weighting. Several donor eyes underwent gross and histopathological evaluation in order to further characterize the uvea, most notably the presence of connective tissue within the ciliary muscle. Cataract patients that had either single-piece acrylic or three-piece silicone IOLs (N=50, ages 45-87) were imaged at 3T (Siemens) to allow shorter scans, an important consideration for geriatric volunteers. The location, size, and nature of uveal tissue were measured in the donor eyes and cataract patients.
MRI revealed that the uvea, which is displaced anteriorly by lens growth, returns to a more youthful anteroposterior location after cataract surgery. Conversely, the ciliary muscle diameter, which decreases with age in the phakic eye, remains so after cataract surgery. Gross and histopathological analysis confirmed the presence of connective tissue within the ciliary muscle. In-vivo images were at a lower in-plane resolution (156 vs 39 microns) but were otherwise consistent with in-vitro findings.
This study cross-validates MRI of cataract patients with MRI of donor eyes, and gross and histopathological analysis. It extends our previous in vivo findings, which were limited to a small cohort of cataract patients (n=8) with single-piece acrylic IOLs. The current study included silicone three-piece IOLs, thus covering the two most commonly used IOL types. The age range was also significantly expanded which is relevant as accommodating IOLs may be implanted in people younger than the typical cataract patient. We have previously reported undiminished ciliary muscle contraction in both phakic and pseudophakic eyes, yet the overall effect of cataract surgery on the uvea must be taken into account; for example, diminished ciliary muscle diameter with advancing age may reduce zonular tension. Posterior movement of the uvea after cataract surgery in glaucoma patients may open the angle and reduce tension throughout the uvea.
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