Document Detail

The in vitro inflation response of mouse sclera.
MedLine Citation:
PMID:  20868685     Owner:  NLM     Status:  MEDLINE    
The purpose of this research was to develop a reliable and repeatable inflation protocol to measure the scleral inflation response of mouse eyes to elevations in intraocular pressure (IOP), comparing the inflation response exhibited by the sclera of younger and older C57BL/6 mice. Whole, enucleated eyes from younger (2 month) and older (11 month) C57BL/6 mice were mounted by the cornea on a custom fixture and inflated according to a load-unload, ramp-hold pressurization regimen via a cannula connected to a saline-filled programmable syringe pump. First, the tissue was submitted to three load-unload cycles from 6 mmHg to 15 mmHg at a rate of 0.25 mmHg/s with ten minutes of recovery between cycles. Next the tissue was submitted to a series of ramp-hold tests to measure the creep behavior at different pressure levels. For each ramp-hold test, the tissue was loaded from 6 mmHg to the set pressure at a rate of 0.25 mmHg/s and held for 30 min, and then the specimens were unloaded to 6 mmHg for 10 min. This sequence was repeated for set pressures of: 10.5, 15, 22.5, 30, 37.5, and 45 mmHg. Scleral displacement was measured using digital image correlation (DIC), and fresh scleral thickness was measured optically for each specimen after testing. For comparison, scleral thickness was measured on untested fresh tissue and epoxy-fixed tissue from age-matched animals. Comparing the apex displacement of the different aged specimens, the sclera of older animals had a statistically significant stiffer response to pressurization than the sclera of younger animals. The stiffness of the pressure-displacement response of the apex measured in the small-strain (6-15 mmHg) and the large-strain (37.5-45 mmHg) regime, respectively, were 287 ± 100 mmHg/mm and 2381 ± 191 mmHg/mm for the older tissue and 193 ± 40 mmHg/mm and 1454 ± 93 mmHg/mm for the younger tissue (Student t-test, p<0.05). The scleral thickness varied regionally, being thickest in the peripapillary region and thinnest at the equator. Fresh scleral thickness did not differ significantly by age in this group of animals. This study presents a reliable inflation test protocol to measure the mechanical properties of mouse sclera. The inflation methodology was sensitive enough to measure scleral response to changes in IOP elevations between younger and older C57BL/6 mice. Further, the specimen-specific scleral displacement profile and thickness measurements will enable future development of specimen-specific finite element models to analyze the inflation data for material properties.
Kristin M Myers; Frances E Cone; Harry A Quigley; Scott Gelman; Mary E Pease; Thao D Nguyen
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Publication Detail:
Type:  Journal Article     Date:  2010-09-22
Journal Detail:
Title:  Experimental eye research     Volume:  91     ISSN:  1096-0007     ISO Abbreviation:  Exp. Eye Res.     Publication Date:  2010 Dec 
Date Detail:
Created Date:  2010-11-29     Completed Date:  2010-12-30     Revised Date:  2014-09-15    
Medline Journal Info:
Nlm Unique ID:  0370707     Medline TA:  Exp Eye Res     Country:  England    
Other Details:
Languages:  eng     Pagination:  866-75     Citation Subset:  IM    
Copyright Information:
Copyright © 2010 Elsevier Ltd. All rights reserved.
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MeSH Terms
Aging / physiology*
Eye Enucleation
Glaucoma / physiopathology
Intraocular Pressure / physiology
Mice, Inbred C57BL
Myopia / physiopathology
Sclera / physiopathology*
Scleritis / physiopathology*
Stress, Mechanical
Grant Support
P30 EY001765/EY/NEI NIH HHS; R01 EY002120/EY/NEI NIH HHS; R01 EY002120-30/EY/NEI NIH HHS

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