Influence of corneal shape parameters on corneal deformation responses measured with a Scheimpflug camera

Abstract Background To understand which irregular corneal parameters determine the visual quality in keratoconus subjects. Methods The cross-sectional study examined the eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. We obtained measurements in two ways: (a) by projecting two perpendicular axes onto a cornea (first, through the central point of the cornea and keratoconus apex; second, as the perpendicular axis) to read the elevation values at points on these axes as parameters characterising the corneal surface; (b) by projecting circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined in order to understand which corneal slope parameter has the strongest correlation with visual acuity and contrast sensitivity. Results Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r = 0.25 (p = 0.03) at 3 cpd to r = 0.47 (p < 0.01) at 9 cpd for the highest elevation and from r = 0.33 (p = 0.09) at 5 cpd to r = 0.40 (p < 0.01) at 11 cpd for the lowest elevation in all subjects together, while for visual acuity the parameters were r = 0.30 (p < 0.01) for the highest elevation and r = 0.21 (p = 0.06) for the lowest elevation in all subjects together. The correlation between contrast sensitivity and the highest and lowest corneal point in all measured cornea was stronger for subjects with a peripheral corneal apex than for those with a central apex. In keratoconus subjects, contrast sensitivity displayed a strong correlation with slope in the central part of the cornea (with a radius of 1 mm) ranging from 0.48 (p < 0.01) at 3 cpd to 0.61 (p < 0.01) at 9 cpd. Conclusion Contrast sensitivity has a higher correlation with corneal shape parameters than with visual acuity. Subjects with a peripheral corneal apex had stronger correlations with visual acuity and contrast sensitivity than did subjects with a central apex. In keratoconus subjects, the strongest correlation was for contrast sensitivity and elevation (slope) in the region within a 1 mm radius of the corneal centre in the opposite direction of the keratoconus apex (direction (ax) CB).

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In vivohuman corneal deformation analysis with a Scheimpflug camera, a critical review

Journal of Biophotonics ◽

10.1002/jbio.201500233 ◽

2016 ◽

Vol 9 (5) ◽

pp. 464-477 ◽

Cited By ~ 10

Author(s):

Michele Lanza ◽

Stefania Iaccarino ◽

Mario Bifani

Keyword(s):

Critical Review ◽

Deformation Analysis ◽

Scheimpflug Camera ◽

Corneal Deformation

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First Clinical Impressions on the Integrated Corneal Tomography and Corneal Deformation with Scheimpflug Imaging

International Journal of Keratoconus and Ectatic Corneal Diseases ◽

10.5005/jp-journals-10025-1151 ◽

2017 ◽

Vol 6 (2) ◽

pp. 101-109

Author(s):

Jorge S Haddad ◽

Eliza Barnwell ◽

Karolinne M Rocha ◽

George O Waring IV ◽

Renato Ambrosio Jr

Keyword(s):

Clinical Data ◽

High Speed ◽

Imaging System ◽

Corneal Ectasia ◽

Scheimpflug Camera ◽

Deformation Parameters ◽

Corneal Deformation ◽

Scheimpflug Imaging ◽

Noncontact Tonometer ◽

Corneal Tomography

ABSTRACT The purpose of this study is to report the preliminary findings and the retrospective clinical impressions of the integrated corneal tomography and corneal deformation parameters with a dynamic ultra-high-speed Scheimpflug camera equipped with a noncontact tonometer. Twelve eyes of six patients were evaluated by the Scheimpflug imaging system of the Pentacam HR and Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany) devices. The parameters used were the Belin/Ambrósio deviation (BAD-D) and Corvis biomechanical index (CBI), as well as the recently published tomographic and biomechanical index (TBI), combined with a detailed clinical data and evaluation of normal eyes and patients with different stages of corneal ectasia. How to cite this article Haddad JS, Barnwell E, Rocha KM, Waring IV GO, Ambrosio Jr R. First Clinical Impressions on the Integrated Corneal Tomography and Corneal Deformation with Scheimpflug Imaging. Int J Kerat Ect Cor Dis 2017;6(2):101-109.

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Comparison of Corneal Deformation Parameters in Keratoconic and Normal Eyes Using a Non-contact Tonometer With a Dynamic Ultra-High-Speed Scheimpflug Camera

Journal of Refractive Surgery ◽

10.3928/1081597x-20170621-03 ◽

2017 ◽

Vol 33 (9) ◽

pp. 625-631 ◽

Cited By ~ 9

Author(s):

Ryan N. Mercer ◽

George O. Waring ◽

Cynthia J. Roberts ◽

Vishal Jhanji ◽

Yumeng Wang ◽

...

Keyword(s):

High Speed ◽

Scheimpflug Camera ◽

Deformation Parameters ◽

Ultra High Speed ◽

Corneal Deformation

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The Impact of Irregular Corneal Shape Parameters on Visual Acuity and Contrast Sensitivity

10.21203/rs.2.23099/v5 ◽

2020 ◽

Author(s):

Sanita Liduma ◽

Artis Luguzis ◽

Gunta Krumina

Keyword(s):

Visual Acuity ◽

Contrast Sensitivity ◽

Cross Sectional Study ◽

Shape Parameters ◽

Corneal Surface ◽

Cross Sectional ◽

Corneal Shape ◽

Different Diameters ◽

The Impact ◽

Corneal Apex

Abstract Background: To understand which irregular corneal parameters determine the visual quality in keratoconus subjects.Methods: The cross-sectional study examined the eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. We obtained measurements in two ways: (a) by projecting two perpendicular axes onto a cornea (first, through the central point of the cornea and keratoconus apex; second, as the perpendicular axis) to read the elevation values at points on these axes as parameters characterising the corneal surface; (b) by projecting circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined in order to understand which corneal slope parameter has the strongest correlation with visual acuity and contrast sensitivity.Results: Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r=0.25 (p=0.03) at 3 cpd to r=0.47 (p<0.01) at 9 cpd for the highest elevation and from r=0.33 (p=0.09) at 5 cpd to r=0.40 (p<0.01) at 11 cpd for the lowest elevation in all subjects together, while for visual acuity the parameters were r=0.30 (p<0.01) for the highest elevation and r=0.21 (p=0.06) for the lowest elevation in all subjects together. The correlation between contrast sensitivity and the highest and lowest corneal point in all measured cornea was stronger for subjects with a peripheral corneal apex than for those with a central apex. In keratoconus subjects, contrast sensitivity displayed a strong correlation with slope in the central part of the cornea (with a radius of 1 mm) ranging from 0.48 (p<0.01) at 3 cpd to 0.61 (p<0.01) at 9 cpd.Conclusion: Contrast sensitivity has a higher correlation with corneal shape parameters than with visual acuity. Subjects with a peripheral corneal apex had stronger correlations with visual acuity and contrast sensitivity than did subjects with a central apex. In keratoconus subjects, the strongest correlation was for contrast sensitivity and elevation (slope) in the region within a 1 mm radius of the corneal centre in the opposite direction of the keratoconus apex (direction (ax) CB).

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Scheimpflug camera in the quantitative assessment of reproducibility of high-speed corneal deformation during intraocular pressure measurement

Journal of Biophotonics ◽

10.1002/jbio.201400137 ◽

2015 ◽

Vol 8 (11-12) ◽

pp. 968-978 ◽

Cited By ~ 10

Author(s):

Robert Koprowski ◽

Renato Ambrósio ◽

Sven Reisdorf

Keyword(s):

Intraocular Pressure ◽

Pressure Measurement ◽

High Speed ◽

Quantitative Assessment ◽

Scheimpflug Camera ◽

Corneal Deformation

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The Impact of Irregular Corneal Shape Parameters on Visual Acuity and Contrast Sensitivity

10.21203/rs.2.23099/v2 ◽

2020 ◽

Author(s):

Sanita Liduma ◽

Artis Luguzis ◽

Gunta Krumina

Keyword(s):

Visual Acuity ◽

Contrast Sensitivity ◽

Strong Correlation ◽

Visual Quality ◽

Main Axis ◽

Shape Parameters ◽

Visual Axis ◽

Corneal Shape ◽

The Impact ◽

Corneal Apex

Abstract Background: To understand which irregular corneal parameters determine the visual quality in keratoconus subjects. Methods: The cross-sectional study examined thecovered eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. To characterize the shape of cornea, wWe obtained measurements in two ways: (a) by projectinged two perpendicular axes onto a cornea (– the main axis passed first, through the central point of the cornea (visual axis projection) and keratoconus apex; second, as , while the second axis was perpendicular to the main axis) to – and read the elevation values at points on theses axeis as parameters characterising the corneal surface; (b) by projectinged circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined The measurements were used to calculate various elevation change (slope) parameters, in order to understand which corneal slope parameter has the strongest correlation with visual acuityquality and contrast sensitivity.Results: According to the acquired data, the visual acuity of a corrected eye does not have a strong correlation with the measured keratoconus apex slope. Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r=0.25 (p=0.03) at 3 cpd to r=0.47 (p<0.01) at 9 cpd for the highest elevation and from r=0.33 (p=0.09) at 5 cpd to r=0.40 (p<0.01) at 11 cpd for the lowest elevation in all subjects together, while for visual acuity the parameters were r=0.30 (p<0.01) for the highest elevation and r=0.21 (p=0.06) for the lowest elevation in all subjects together. The correlation between contrast sensitivity and the highest and lowest corneal point in all measured cornea was stronger for subjects with a peripheral corneal apex than for those with a central apex. In keratoconus subjects, Ccontrast sensitivity displayed a strong correlation with keratoconus slope in the central part of the cornea (with a radius of 1 mm). Correlations in different spatial frequencies ranging from 0.48 (p<0.01) at 3 cpd to 0.61 (p<0.01) at 9 cpd.Conclusion: Contrast sensitivity has a higher correlation with corneal shape parameters than with is more important parameter which describes the visual quality of keratoconus subjects than visual acuity. Subjects with a peripheral corneal apex had stronger correlations with visual acuity and contrast sensitivity than did subjects with a central apex. In keratoconus subjects, Tthe strongest correlation was for contrast sensitivity and elevation (slope) in the region most important region which determines the visual quality in keratoconus subjects is the region within a 1 mm radius of the corneal centre in the opposite direction of the keratoconus apex (direction (ax) CB).

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The Impact of Irregular Corneal Shape Parameters on Visual Acuity and Contrast Sensitivity

10.21203/rs.2.23099/v3 ◽

2020 ◽

Author(s):

Sanita Liduma ◽

Artis Luguzis ◽

Gunta Krumina

Keyword(s):

Visual Acuity ◽

Contrast Sensitivity ◽

Cross Sectional Study ◽

Shape Parameters ◽

Corneal Surface ◽

Cross Sectional ◽

Corneal Shape ◽

Different Diameters ◽

The Impact ◽

Corneal Apex

Abstract Background: To understand which irregular corneal parameters determine the visual quality in keratoconus subjects. Methods: The cross-sectional study examined the eyes of 44 subjects, graded from the first to third keratoconus stages by Amsler-Krumeich classification. We obtained measurements in two ways: (a) by projecting two perpendicular axes onto a cornea (first, through the central point of the cornea and keratoconus apex; second, as the perpendicular axis) to read the elevation values at points on these axes as parameters characterising the corneal surface; (b) by projecting circles with different diameters around the central part of the cornea (1, 2, and 3 mm) and reading elevation values at points equally displaced on these circles as parameters characterising an anterior surface slope. Irregular corneal shape parameters’ correlations with visual acuity and contrast sensitivity were determined in order to understand which corneal slope parameter has the strongest correlation with visual acuity and contrast sensitivity.Results: .Parameters characterising the corneal surface’s correlations with contrast sensitivity were from r=0.25 (p=0.03) at 3 cpd to r=0.47 (p<0.01) at 9 cpd for the highest elevation and from r=0.33 (p=0.09) at 5 cpd to r=0.40 (p<0.01) at 11 cpd for the lowest elevation in all subjects together, while for visual acuity the parameters were r=0.30 (p<0.01) for the highest elevation and r=0.21 (p=0.06) for the lowest elevation in all subjects together. The correlation between contrast sensitivity and the highest and lowest corneal point in all measured cornea was stronger for subjects with a peripheral corneal apex than for those with a central apex. In keratoconus subjects, contrast sensitivity displayed a strong correlation with slope in the central part of the cornea (with a radius of 1 mm) ranging from 0.48 (p<0.01) at 3 cpd to 0.61 (p<0.01) at 9 cpd.Conclusion: Contrast sensitivity has a higher correlation with corneal shape parameters than with visual acuity. Subjects with a peripheral corneal apex had stronger correlations with visual acuity and contrast sensitivity than did subjects with a central apex. In keratoconus subjects, the strongest correlation was for contrast sensitivity and elevation (slope) in the region within a 1 mm radius of the corneal centre in the opposite direction of the keratoconus apex (direction (ax) CB).

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