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A corneal model for slit-scanning elevation topography.

G Cairns·A Collins·C N J McGhee
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Abstract

Computerised videokeratography is increasing in sophistication and accuracy. The Orbscan II Videokeratographer combines the advantages of Placido derived and slit-scanning derived topography, to acquire shape information on the posterior surface of the cornea. The purpose of this paper is to construct a model of slit-scanning elevation topography and highlight potential sources of variation in this methodology. Ray tracing calculations were performed on a defined, theoretical, spherical model to obtain a pachymetric measurement. These calculations were tested by comparing the pachymetry measurement derived from the model, over a refractive index shift from 1.376 to 1.400 with the pachymetry measurement obtained by Orbscan II, of a human eye, with an identical alteration in refractive index. The two methods of measurement differed by only 0.157 microm, suggesting that the model is a good representation of slit-scanning elevation topography, and that refractive index variations have only a minimal effect on Orbscan II pachymetry measurement.

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Corneal DiseasesCorneal TopographyHumansModels, BiologicalRefraction, OcularSensitivity and SpecificityJournal Article

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BibTeXRIS

G Cairns, A Collins, C N J McGhee. 2003. A corneal model for slit-scanning elevation topography.. https://doi.org/10.1046/j.1475-1313.2003.00107.x

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