97th DOG Annual Meeting 1999

V668

CONSISTENT CALCULATIONS OF INTRAOCULAR LENSES AND QUANTIFICATION OF ACCOMMODATION MECHANISMS

J. Wahl, P.-R. Preußner


Background: Calculations of intraocular lenses are mostly described by approximative formulae (e.g. SRK II). Their validity range is limited and rather poor in higher myopia or hyperopia. Even more precise formulae (e.g. after Holladay) still contain approximations so that their results are not absolutely secure. In addition, they are not very illustrative and moreover troublesome in practical handling.

Method: In a computer program, the optical ray tracing is calculated exactly except for negligible numerical rounding errors. No approximations are made, neither for thin lenses nor for paraxial rays. The calculation is uniquely determined by the refractive indices of the cornea, the anterior chamber, the intraocular lens and of the vitreous, and by the radii of curvature and the positions of the refractive surfaces. By the same calculation, also different mechanisms of accommodation can be quantified. Changes of the anterior or posterior radius of the lens as well as shifts of the lens on the optical axis appertain for this. All calculations are performed interactively and vividly. Therefore, also proposals from the auditory are welcome in the discussion.

Conclusion: The interactive presentation of the calculations increases the clearness and therefore the understanding of the coherencies. The physical consistence eliminates doubts against the method.

University Eye Hospital, Langenbeckstr. 1, D-55101 Mainz


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