1Weeber H. A., 2Martin H.

1Pharmacia Groningen B.V., van Swietenlaan 5, 9728 NX Groningen, Nederland; 2Institut für Biomedizinische Technik, Universität Rostock, Ernst-Heydemann-Strasse 6, D-18055 Rostock

Objective: The change of lens power during accommodation is related to deformations in the lens material and the capsular bag. The objective of this study was to find the interaction between capsule and crystalline lens and show their relative importance for the accommodative ability.
Methods: Since measurements of the forces is not yet possible, the forces and deformations are estimated by calculations using a finite elements (FE) computer model. After extensive testing of the computer model, parameters of the lens and capsule are varied and the forces and stresses are calculated.
Results: Extensive testing of the computer model was performed. The model was challenged by changing the number of elements, the type of elements, changing from a 2 dimensional model to a 3 dimensional model and by changing the software. In all situations, the amount of accommodation for a 40-year-old subject was about 4 diopters. The calculations show that the capsule plays an important role in the mechanism of accommodation. The crystalline lens material, though elastic, mainly functions as a filling material. Even modeling the lens as a fluid results in a realistic amount of accommodation. Stiffening of the lens as a uniform material has a relative small effect on accommodation.
Conclusion: The FE model shows to be very robust and results in realistic values for the amount of accommodation. Fluctuations in the mechanical properties of the crystalline lens have only a limited effect on accommodation. This indicates that the lens plays a minor role in the accommodative ability.

Copyright © Deutsche Ophthalmologische Gesellschaft, 2001. All rights reserved.

Last updated: 

Webdesign: SPALLEK.COM