Document Detail

Evaluation of Goldmann applanation tonometry using a nonlinear finite element ocular model.
MedLine Citation:
PMID:  17006754     Owner:  NLM     Status:  MEDLINE    
Goldmann applanation tonometry (GAT) is the internationally accepted standard for intra-ocular pressure (IOP) measurement, which is important for the diagnosis of glaucoma. The technique does not consider the effect of the natural variation in the corneal thickness, curvature and material properties. As these parameters affect the structural resistance of the cornea, their variation is expected to lead to inaccuracies in IOP determination. Numerical Analysis based on the finite element method has been used to simulate the loading conditions experienced in GAT and hence assess the effect of variation in corneal parameters on GAT IOP measurements. The analysis is highly nonlinear and considers the hyper-elastic J-shaped stress-strain properties of corneal tissue observed in laboratory tests. The results reveal a clear association between both the corneal thickness and material properties, and the measured IOP. Corneal curvature has a considerably lower effect. Similar trends have been found from analysis of clinical data involving 532 patients referred to the Glaucoma Unit at Moorfields Hospital, and from earlier mathematical analyses. Nonlinear modelling is shown to trace the behaviour of the cornea under both IOP and tonometric pressure, and to be able to provide additional, and potentially useful, information on the distribution of stress, strain, contact pressure and gap closure.
Ahmed Elsheikh; Defu Wang; Aachal Kotecha; Michael Brown; David Garway-Heath
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Publication Detail:
Type:  Evaluation Studies; Journal Article     Date:  2006-09-28
Journal Detail:
Title:  Annals of biomedical engineering     Volume:  34     ISSN:  0090-6964     ISO Abbreviation:  Ann Biomed Eng     Publication Date:  2006 Oct 
Date Detail:
Created Date:  2006-10-25     Completed Date:  2006-12-05     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0361512     Medline TA:  Ann Biomed Eng     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1628-40     Citation Subset:  IM    
Division of Civil Engineering, Faculty of Engineering, University of Dundee, Dundee, DD1 4HN, UK.
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MeSH Terms
Biomedical Engineering
Cornea / anatomy & histology,  physiology,  ultrasonography
Glaucoma / diagnosis,  pathology,  physiopathology
Intraocular Pressure
Models, Biological
Nonlinear Dynamics
Tonometry, Ocular / methods*,  standards,  statistics & numerical data

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