Dynamic point shifting in null screen videokeratometry

In this paper, the use of three liquid crystal displays (LCDs) as targets for an experimental corneal topographer is proposed. The main advantage is that the geometrical pattern in the target can be modified without moving any mechanical part to apply the dynamic point shifting (DyPoS) method. Some results on the capabilities of the LCDs, obtained with photo frames, for measuring a 6.37 mm radius of curvature calibration sphere, and applying the DyPoS method, are presented. It is shown that the error in measuring the radius of curvature with DyPoS is reduced to 3% of the real value and the RMS in elevation or sagitta differences is around 15 μm, 30% or 66% of the values obtained without DyPoS, respectively.

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Dynamic point shifting with null screens using three LCDs as targets for corneal topography

Rodríguez-Rodríguez

Jaramillo-Núñez

Díaz-Uribe

2015

Appl. Opt.

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Corneal topographer using null-screen patterned within a quadrangular acrylic prism

Rodriguez-Rodriguez,

Gonzalez-Utrera,

Aguirre-Aguirre

et al. 2023

Opt. Continuum

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In this paper, the use of four flat-null-screens forming a quadrangular prism setup is employed as a target for an experimental corneal topographer. Topographic maps of three reflective calibration spheres with different radii of curvature: 7.70 mm, 9.42 mm, and 6.20 mm, and the corneal surface evaluation of a volunteer subject are presented. The experimental setup is based on the null-screen method. Zonal reconstruction of the surface shape of the human cornea is obtained by numerical integration of the normal vectors. The corresponding elevation map was found fitting an spherical model to the recovered data. The differences obtained in radius of curvature were 0.02% or less for the calibration spheres, and the cornea under test showed a difference of 1.39% (0.6 diopters) compared to the value obtained with ORBSCAN topographer.

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Dynamic point shifting in null screen videokeratometry

Cited by 2 publications

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Dynamic point shifting with null screens using three LCDs as targets for corneal topography

Dynamic point shifting with null screens using three LCDs as targets for corneal topography

Corneal topographer using null-screen patterned within a quadrangular acrylic prism

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