Document Detail

Depth-dependent cohesive tensile strength in human donor corneas: implications for refractive surgery.
MedLine Citation:
PMID:  18269156     Owner:  NLM     Status:  MEDLINE    
PURPOSE: To determine the cohesive tensile strength throughout the stroma of normal human donor corneas and evaluate the relevance of these findings within the context of current excimer laser surgical techniques. METHODS: Twenty normal corneoscleral buttons from 11 donors were obtained from the Georgia Eye Bank. The corneas were cut into 3-mm strips, dissected at varying stromal depths, mechanically separated through the dissection plane using a motorized extensometer, and measured for cohesive tensile strength. Central corneal thickness and dissection depth were measured by routine light microscopy and correlated with cohesive tensile strength measurements. RESULTS: A strong negative correlation was noted between stromal depth and cohesive tensile strength (r = -0.93). The anterior corneal stroma directly adjacent to Bowman's layer followed by the underlying anterior 40% of the corneal stroma had the highest cohesive tensile strength. Cohesive tensile strength plateaued from 40% to 90% corneal stromal depth and then declined rapidly from the posterior 10% of the stroma to Descemet's membrane. The anterior 40% of the corneal stroma had significantly higher cohesive tensile strength than the posterior 60% (33.3 g/mm vs 19.6 g/mm, P < .00001). Within the central 40% to 60% depth, a positive correlation was found between increased age and increased tensile strength (r = 0.67), with corneal tensile strength increasing 38% from ages 20 to 78 years. CONCLUSIONS: The anterior 40% of the central corneal stroma is the strongest region of the cornea, whereas the posterior 60% of the stroma is at least 50% weaker. The risk for ectasia may therefore be greater with ablations into the posterior stroma. Increasing age is associated with increased corneal cohesive tensile strength.
J Bradley Randleman; Daniel G Dawson; Hans E Grossniklaus; Bernard E McCarey; Henry F Edelhauser
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of refractive surgery (Thorofare, N.J. : 1995)     Volume:  24     ISSN:  1081-597X     ISO Abbreviation:  J Refract Surg     Publication Date:  2008 Jan 
Date Detail:
Created Date:  2008-02-13     Completed Date:  2008-05-15     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9505927     Medline TA:  J Refract Surg     Country:  United States    
Other Details:
Languages:  eng     Pagination:  S85-9     Citation Subset:  IM    
Emory University, Department of Ophthalmology, Atlanta, GA, USA.
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MeSH Terms
Compressive Strength / physiology
Corneal Stroma / physiology*
Middle Aged
Refractive Surgical Procedures*
Tensile Strength / physiology*
Tissue Donors
Grant Support

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