Document Detail

Mathematical models for describing the shape of the in vitro unstretched human crystalline lens.
MedLine Citation:
PMID:  19647765     Owner:  NLM     Status:  MEDLINE    
We developed orthogonal least-squares techniques for fitting crystalline lens shapes, and used the bootstrap method to determine uncertainties associated with the estimated vertex radii of curvature and asphericities of five different models. Three existing models were investigated including one that uses two separate conics for the anterior and posterior surfaces, and two whole lens models based on a modulated hyperbolic cosine function and on a generalized conic function. Two new models were proposed including one that uses two interdependent conics and a polynomial based whole lens model. The models were used to describe the in vitro shape for a data set of twenty human lenses with ages 7-82years. The two-conic-surface model (7mm zone diameter) and the interdependent surfaces model had significantly lower merit functions than the other three models for the data set, indicating that most likely they can describe human lens shape over a wide age range better than the other models (although with the two-conic-surfaces model being unable to describe the lens equatorial region). Considerable differences were found between some models regarding estimates of radii of curvature and surface asphericities. The hyperbolic cosine model and the new polynomial based whole lens model had the best precision in determining the radii of curvature and surface asphericities across the five considered models. Most models found significant increase in anterior, but not posterior, radius of curvature with age. Most models found a wide scatter of asphericities, but with the asphericities usually being positive and not significantly related to age. As the interdependent surfaces model had lower merit function than three whole lens models, there is further scope to develop an accurate model of the complete shape of human lenses of all ages. The results highlight the continued difficulty in selecting an appropriate model for the crystalline lens shape.
George Smith; David A Atchison; D Robert Iskander; Catherine E Jones; James M Pope
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-08-06
Journal Detail:
Title:  Vision research     Volume:  49     ISSN:  1878-5646     ISO Abbreviation:  Vision Res.     Publication Date:  2009 Oct 
Date Detail:
Created Date:  2009-10-05     Completed Date:  2009-12-14     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0417402     Medline TA:  Vision Res     Country:  England    
Other Details:
Languages:  eng     Pagination:  2442-52     Citation Subset:  IM    
Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia.
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MeSH Terms
Aged, 80 and over
Aging / physiology
Lens, Crystalline / physiology*
Middle Aged
Models, Biological*
Young Adult

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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