gms | German Medical Science

102. Jahrestagung der DOG

Deutsche Ophthalmologische Gesellschaft e. V.

23. bis 26.09.2004, Berlin

Refractive indices of ocular media for optical biometry

Meeting Abstract

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  • corresponding author W. Haigis - Universitäts-Augenklinik Würzburg
  • H. Hasche - Universitäts-Augenklinik Würzburg
  • M. M. Much - Universitäts-Augenklinik Würzburg

Evidenzbasierte Medizin - Anspruch und Wirklichkeit. 102. Jahrestagung der Deutschen Ophthalmologischen Gesellschaft. Berlin, 23.-26.09.2004. Düsseldorf, Köln: German Medical Science; 2004. Doc04dogDO.04.05

Die elektronische Version dieses Artikels ist vollständig und ist verfügbar unter: http://www.egms.de/de/meetings/dog2004/04dog037.shtml

Veröffentlicht: 22. September 2004

© 2004 Haigis et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielf&aauml;ltigt, verbreitet und &oauml;ffentlich zug&aauml;nglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Objective

With a novel biometry device (Zeiss ACMaster) it has now become possible to perform laser interference measurements of the anterior ocular segment. Since the primary measurement parameters in laser biometry are optical path lengths, the group refractive indices of the respective ocular media are needed for the translation into geometrical distances. By comparative measurements using well-established precision ultrasound methods, we determined these indices for cornea, anterior chamber and crystalline.

Methods

For the measurement of corneal thickness a Tomey AL 2000 pachometer (ultrasound frequency: 20 MHz) was applied, while a Grieshaber Biometric System GBS (ultrasound frequency: 10 MHz) was used for the comparison of anterior chamber depth and lens thickness. Patients and volunteers were examined prospectively by ultrasound and laser interference (ACMaster prototype).

Results

The following group refractive indices were determined for the applied wavelength of λ=850 nm: cornea: 1.3616 ± 0.0015, n=104, R=98.5%; lens: 1.3669 ± 0.0051, n=50, R=97.4%; anterior chamber: 1.3873 ± 0.0049; n=56, R=99.1%. In this context, anterior chamber depth is defined from the anterior corneal surface to the anterior lens surface.

Conclusions

The Zeiss ACMaster allows highly precise measurements of the anterior ocular segment. By means of the refractive indices deduced it is easily possible to relate laser interference results to those of clinically well-established ultrasound methods.