Accuracy and sensitivity analysis of the conical null-screen based corneal topographer

Cossio-Guerrero, Cesar; Campos‐García, Manuel

doi:10.1117/12.2238280

Cited by 1 publication

(1 citation statement)

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“…13,14 Using an inverse ray tracing, the NSM designs a collection of elongated ellipses on the cylinder in order to obtain a set of evenly spaced circles on the detection plane. 15 In previously published works in Refs., [17][18][19][20][21] we proposed a cone topographer, based on the NSM, with the purpose of increasing the evaluation area on the anterior corneal surface and decreasing the size of the topographer. Taking advantage of the above, the cone topographer can use a smartphone to collect the light reflected from the anterior surface of the cornea for analysis.…”

Section: Introductionmentioning

confidence: 99%

Effect of the skew ray error on corneal topography using a cone topographer

Huerta-Carranza,

Campos-García,

Pantoja-Arredondo

et al. 2024

Optical Fabrication and Testing VIII

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Most corneal topographers are based on the Placido disk, which is consists of a set of concentric rings illuminated in black and white. Each luminous ring is projected onto the corneal surface and its image produced by reflection is captured by a camera. When the corneal surface is symmetrical and aligned with respect to the optical axis of the corneal topographer, the image consists of concentric rings; therefore, displacements occur only in the radial direction. However, if the cornea lacks revolution symmetry, the image suffers deformations in both radial and azimuthal directions; therefore, corneal topography depends not only on the radial direction, but also on the azimuthal direction. This is known as the skew ray error. In this work, we present a numerical analysis on the effects on the corneal topography caused by skew ray error and show the advantages of using illuminated elongated ellipses, which are designed using exact ray tracing, to recover the corneal topography considering a conical corneal topographer.

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