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Lawrence M Strenk, Suqin Guo, Kenneth Lu, Bosco Tjan, Liliana Werner, Susan Strenk; The force of lens growth on the uvea. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2211.
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© ARVO (1962-2015); The Authors (2016-present)
We hypothesize MRI’s unique ability to show the entire crystalline lens, intraocular lens (IOL), or Soemmering’s ring and its relationship to the uvea can be used to estimate the force applied to the uvea by life-long lens growth.
Spin-echo, T1-weighted images were collected from both eyes of subjects with monocular IOL implantation or from the same eye before/after cataract surgery (N = 15, ages 46-83) using a 1.5T (GE) or a 3T (Siemens) imager and custom eye coils (MRI Research). The force acting on the uvea due to lens/iris contact was estimated by comparing measurements from phakic/pseudophakic eye pairs from each subject. Strain was calculated from the measured differences in choroidal circumferential perimeters and multiplied by published Young’s modulus values to obtain stress. Choroidal cross-sectional area was calculated from the measured choroidal thickness and multiplied by the stress, to estimate the lens force applied to the uvea.
Force linearly increases with age: slope = 0.0366±0.005 grams/year (P<0.00001); intercept = -1.4796 ±0.344 grams (P=0.00092); and power = 0.75.
We have reported life-long crystalline lens growth displaces the uvea anteriorly and cataract surgery returns it to a relatively youthful antero-posterior position. Here we find the age-enlarged crystalline lens applies ever-increasing forces to the uvea. This may initiate a mechanical traumatic insult to: 1) the elastic layer of Bruch’s membrane, 2) retinal vessels, and 3) retinal nerves. Specifically, this insult may damage the meshwork of Bruch’s membrane, trigger cross-linking growth factors resulting in phospholipid walls, and ultimately leading to drusen. Similarly, this insult may stretch retinal vessels, creating connective tissue at the artery/arteriole junctions and thinning vessel walls while decreasing their diameter thus leading to retinal ischemia. These vessels may also ultimately break, triggering angiogenesis. Finally, this insult may stretch the axons of the ganglion cells with longer ganglion cells necessarily breaking first. While uneventful cataract surgery cannot negate initial mechanical insults, it removes any further force applied by the lens to the uvea, and thus has the potential to positively affect the trajectory of retinal diseases. Unfortunately, post-surgical Soemmering’s ring often develops and, when abundant, will contact the iris and similarly apply force and any associated traumatic insult to the uvea.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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