Iris contour is critical in angle-closure, pigment dispersion syndrome, and pigmentary glaucoma. Although many studies have examined iris contour under various conditions, the basic mechanical interactions between the iris and its surroundings remain poorly elucidated. We therefore propose to perform both computational and clinical studies of iris contour under different dynamic circumstances. The word """"""""dynamic"""""""" is emphasized as central to our hypothesis that the anterior segment is a dynamic system, and the iris contour is determined largely by dynamic effects. The effects of accommodation, blinking, and pupil diameter are not due to the position of the relevant tissues but rather to the motion thereof. For example, our hypothesis implies that the posterior bowing of the iris seen following accommodation is the result of the movement of the lens, not the final shape of the lens. Similar ramifications exist for blinking and pupil dilation and miosis, each of which is a dynamic event. The computational studies will involve extension of our previous models of the aqueous humor- iris system to include the following: dynamic active tension of the iris sphincter (already included in steady-state simulations), combines lens and iris motion during accommodation, and the dynamic mechanical effect of blinking on the anterior segment. In addition to extending our models, we will apply them to a series of periodic and random events including accommodation, blinking, and pupil diameter changes. We will compute the dynamic iris contour and will use the results to assess the mechanisms underlying angle closure and pigmentary glaucoma. The clinical studies will involve ultrasound biomicroscopy of the anterior segment during and for three minutes following accommodation. The accommodation studies will be critical because they will separate lens position (unchanged) from lens dynamics (during vs. after accommodation), We will also perform a retrospective study of dark-room angle closure tests, which will provide insight into the role of pupil dynamics in angle closure.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY015795-03
Application #
7122442
Study Section
Special Emphasis Panel (ZRG1-AED (01))
Program Officer
Araj, Houmam H
Project Start
2004-09-30
Project End
2008-08-31
Budget Start
2006-09-01
Budget End
2007-08-31
Support Year
3
Fiscal Year
2006
Total Cost
$223,765
Indirect Cost
Name
University of Minnesota Twin Cities
Department
Biomedical Engineering
Type
Schools of Engineering
DUNS #
555917996
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
Amini, Rouzbeh; Jouzdani, Sara; Barocas, Victor H (2012) Increased iris-lens contact following spontaneous blinking: mathematical modeling. J Biomech 45:2293-6
Amini, Rouzbeh; Whitcomb, Julie E; Al-Qaisi, Muhammad K et al. (2012) The posterior location of the dilator muscle induces anterior iris bowing during dilation, even in the absence of pupillary block. Invest Ophthalmol Vis Sci 53:1188-94
Amini, Rouzbeh; Barocas, Victor H; Kavehpour, H Pirouz et al. (2011) Computational simulation of altitude change-induced intraocular pressure alteration in patients with intravitreal gas bubbles. Retina 31:1656-63
Whitcomb, Julie E; Amini, Rouzbeh; Simha, Narendra K et al. (2011) Anterior-posterior asymmetry in iris mechanics measured by indentation. Exp Eye Res 93:475-81
Powell, Tracy A; Amini, Rouzbeh; Oltean, Alina et al. (2010) Elasticity of the porcine lens capsule as measured by osmotic swelling. J Biomech Eng 132:091008
Amini, Rouzbeh; Barocas, Victor H (2010) Reverse pupillary block slows iris contour recovery from corneoscleral indentation. J Biomech Eng 132:071010
Trastman-Caruso, Elyse; Dorairaj, Syril; Barocas, Victor H et al. (2010) Pigment dispersion syndrome patients do not have larger-than-normal irides. J Glaucoma 19:493-6
Amini, Rouzbeh; Barocas, Victor H (2009) Anterior chamber angle opening during corneoscleral indentation: the mechanism of whole eye globe deformation and the importance of the limbus. Invest Ophthalmol Vis Sci 50:5288-94
Prata, Tiago Santos; Palmiero, Pat-Michael; Angelilli, Allison et al. (2009) Iris morphologic changes related to alpha(1)-adrenergic receptor antagonists implications for intraoperative floppy iris syndrome. Ophthalmology 116:877-81
Whitcomb, Julie E; Barnett, Vincent A; Olsen, Timothy W et al. (2009) Ex vivo porcine iris stiffening due to drug stimulation. Exp Eye Res 89:456-61

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