Accuracy of Orbscan II slit-scanning elevation topography

Cairns, Gerard, McGhee, Charles N. J., Collins, Michael J., Owens, Helen, & Gamble, Greg D. (2002) Accuracy of Orbscan II slit-scanning elevation topography. Journal of Cataract and Refractive Surgery, 28(12), pp. 2181-2187.

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Purpose: To establish the accuracy of Orbscan II (Orbtek Inc.) slit-scanning elevation topography in analyzing the anterior surface of complex test objects.

Setting: Discipline of Ophthalmology, University of Auckland, Faculty of Medical and Health Sciences, Auckland, New Zealand.

Methods: Six test objects were created from 2 materials: standard calibration poly(methyl methacrylate) (PMMA) (Orbtek Inc.) and a research PMMA material. The test objects were produced with spherical (radii of curvature 6.00 mm, 7.67 mm, and 8.88 mm), aspherical (apical radius 7.67, eccentricity 0.5, Q _0.25), and toroidal (7.67/7.92 mm radii of curvature) surfaces. The accuracy of the test surfaces was established by Form Talysurf Analysis. A single calibrated Orbscan II device was used to obtain 20 separate anterior elevation maps of each test object. The data obtained from Orbscan II, at 0.2 mm intervals along the chosen meridian, were directly compared with the Talysurf values for each test surface.

Results: Orbscan II measurements of all test objects were statistically significantly different from the Talysurf values (P _ .001). The test objects produced from standard calibration material were more accurately measured by Orbscan II than the objects produced from the research material. Data obtained by Orbscan II from the central 3.5 mm of all test objects were more accurate than peripheral data when compared with the Talysurf values (P _ .001).

Conclusions: Orbscan II anterior surface elevation measurements differed significantly from Form Talysurf Analysis of complex test surfaces. However, the magnitude of the errors in the measurement of standard test objects was small, less than 0.20 _m centrally and 0.70 _m peripherally. Clinically, if similar accuracy of measurement is confirmed in the human eye, anterior surface elevation maps can be considered accurate representations of corneal shape.

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39 citations in Web of Science®
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ID Code: 885
Item Type: Journal Article
Refereed: Yes
Additional Information: For more information, please refer to the journal’s website (see hypertext link) or contact the author. Michael Collins, email:,.au
DOI: 10.1016/S0886-3350(02)01504-3
ISSN: 0886-3350
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: Copyright 2002 Elsevier
Deposited On: 30 Jun 2005 00:00
Last Modified: 10 Aug 2011 16:02

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