Evaluation of the EyeSys Model II Computerized Videokeratoscope. Part II: The Repeatability and Accuracy in Measuring Convex Aspheric Surfaces

Dave, Trusit; Ruston, David; Fowler, Colin

doi:10.1097/00006324-199809000-00020

Cited by 21 publications

(7 citation statements)

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“…13 The accuracy of this technique in measuring the central and peripheral radius of curvature is dependent on the shape of the cornea; measurement accuracy is reduced for aspheric surfaces that show sudden flattening, although this appears to be clinically acceptable. 14 Next, Orbscan II (Bausch & Lomb Surgical) scanning-slit corneal topography was used. This system provides a complete analysis of the corneal surface.…”

Section: Methodsmentioning

confidence: 99%

Effect of keratoconus grades on repeatability of keratometry readings: Comparison of 5 devices

Hashemi

Yekta

Khabazkhoob

2015

Journal of Cataract and Refractive Surgery

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Section: Methodsmentioning

confidence: 99%

Effect of keratoconus grades on repeatability of keratometry readings: Comparison of 5 devices

Hashemi

Yekta

Khabazkhoob

2015

Journal of Cataract and Refractive Surgery

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“…This results in a decrease and an increase in the calculated radius of curvature, respectively. Dave et al. (1998) presented a table for the EyeSys II displaying sagittal (axial) radius of curvature error for several ellipsoids, with a p value of 0.80, ranging from −0.1 to +0.072 mm.…”

Section: Discussionmentioning

confidence: 99%

“…respectively. Dave et al (1998) presented a table for the EyeSys II displaying sagittal (axial) radius of curvature error for several ellipsoids, with a p value of 0.80, ranging from )0.1 to +0.072 mm. Comparing these results with Figure 6, only two peripheral ring edges from surface 5 (worst) fall outside the range determined by Dave et al The work of these investigators was selected, because they used a similar reflecting surface and presented their results in sagittal (axial) radius of curvature error.…”

Section: Analysis Ofmentioning

confidence: 99%

The effect of videokeratoscope faceplate design on radius of curvature maps

Monteiro

Hull²

2007

Ophthalmic Physiologic Optic

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Citation: Monteiro, P.M.L. & Hull, C.C. (2007). The effect of videokeratoscope faceplate design on radius of curvature maps. OPHTHALMIC AND PHYSIOLOGICAL OPTICS, 27(1), pp. 76-84. doi: 10.1111/j.1475-1313.2006.00426.x This is the accepted version of the paper.This version of the publication may differ from the final published version. and 75 in 15 intervals at the corneal vertex. Image quality was assessed by adding the geometrical blurs of the 5 image points. Differences (error) between accurate sagittal radius of curvature and sagittal radius of curvature calculated by the van Saarloos algorithm were calculated for selected surfaces at the same corneal points. The calculations were repeated for the tangential radius of curvature. Differences equal or bigger than 0.02 mm were regarded as clinically significant. The surface that provided the sharpest image for an average cornea was a cylinder with the base 120 mm away from the corneal vertex and a diameter of 26 mm. Changing the faceplate design results in clinically significant differences for an average cornea. Permanent

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“…An additional limitation (of all placido-based corneal topographers) is that the apical corneal curvature (R o ) is not measured by the instrument but is extrapolated from paracentral data (i.e., from the innermost ring data). 31 This may introduce uncertainty in deriving apical corneal curvature, particularly when unusual corneal shapes are created. Finally, as already discussed, there are significant uncertainties concerning the derivation of corneal shape indices, such as e and Q, in terms of the algorithms used and the area or chord across which the shape factor is calculated.…”

Section: Discussionmentioning

confidence: 99%