Interchangeability between Placido disc and Scheimpflug system: quantitative and qualitative analysis

Stefano, Vinícius Silbiger De; Melo, Luiz Alberto S.; Mallmann, Felipe; Schor, Paulo

doi:10.1590/s0004-27492010000400013

Cited by 14 publications

(12 citation statements)

References 24 publications

(36 reference statements)

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“…These results are consistent with the findings of previous studies. Stefano et al [32] compared the keratometry values obtained by EyeSys with those obtained by the Pentacam. Although they found a high correlation between the measurements obtained with both devices, the 95% LoA range from −1.06 to 1.26 D and −0.87 to 0.85 D for Kf and Ks, respectively, suggests that these limits were too large to consider both instruments are interchangeable.…”

Section: Discussionmentioning

confidence: 99%

A Comprehensive Assessment of the Precision and Agreement of Anterior Corneal Power Measurements Obtained Using 8 Different Devices

et al. 2012

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PurposeTo comprehensively assess the precision and agreement of anterior corneal power measurements using 8 different devices.MethodsThirty-five eyes from 35 healthy subjects were included in the prospective study. In the first session, a single examiner performed on each subject randomly measurements with the RC-5000 (Tomey Corp., Japan), KR-8000 (Topcon, Japan), IOLMaster (Carl Zeiss Meditec, Germany), E300 (Medmont International, Australia), Allegro Topolyzer (Wavelight AG, Germany), Vista (EyeSys, TX), Pentacam (Oculus, Germany) and Sirius (CSO, Italy). Measurements were repeated in the second session (1 to 2 weeks later). Repeatability and reproducibility of corneal power measurements were assessed based on the intrasession and intersession within-subject standard deviation (Sw), repeatability (2.77Sw), coefficient of variation (COV), and intraclass correlation coefficient (ICC). Agreement was evaluated by 95% limits of agreement (LoA).ResultsAll devices demonstrated high repeatability and reproducibility of the keratometric values (2.77Sw<0.36D, COV<0.3%, ICC>0.98). Repeated-measures analysis of variance with Bonferroni post test showed statistically significant differences (P<0.01) among mean keratometric values of most instruments; the largest differences were observed between the EyeSys Vista and Medmont E300. Good agreement (i.e., 95%LoA within ±0.5D) was found between most instruments for flat, steep and mean keratometry, except for EyeSys and Medmont. Repeatability and reproducibility of vectors J0 and J45 was good, as the ICCs were higher than 0.9, except J45 of Medmont and Pentacam. For the 95% LoAs of J0 and J45, they were all ≤ ±0.31 among any two paired devices.ConclusionsThe 8 devices showed excellent repeatability and reproducibility. The results obtained using the RC-5000, KR-8000, IOLMaster, Allegro Topolyzer, Pentacam and Sirius were comparable, suggesting that they could be used interchangeably in most clinical settings. Caution is warranted with the measurements of the EyeSys Vista and Medmont E300, which should not be used interchangeably with other devices due to lower agreement.Trial RegistrationClinicalTrials.gov NCT01587287

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Section: Discussionmentioning

confidence: 99%

A Comprehensive Assessment of the Precision and Agreement of Anterior Corneal Power Measurements Obtained Using 8 Different Devices

et al. 2012

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“…Having a common reference centre is equally important to study the relationship between the ocular and corneal wavefront aberrations of the normal and diseased eyes. In fact, the pupil centroid was used as the reference point to centralize the corneal maps measured by the Pentacam and a Placido disk‐based corneal topography system, the EyeSys, when keratometric values were analyzed 1 . For this type of study, knowledge about the match of the pupil centres between the two systems is obviously important.…”

Section: Discussionmentioning

confidence: 99%

“…For example, the Pentacam HR (http://www.pentacam.com/sites/hr.php) is capable of measuring the posterior corneal surface and corneal thickness due to its Scheimpflug principle, and it is also capable of accessing the anterior corneal surface with a function equivalent to that of the conventional Placido‐ring corneal topography. Because different techniques accomplish the same function, it becomes important to ensure that measurements of corneal properties are compatible and exchangeable across different modalities in clinical applications 1 …”

Section: Introductionmentioning

confidence: 99%

An indirect method to compare the reference centres for corneal measurements

Bao

Liu

et al. 2011

Ophthalmic Physiologic Optic

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“…As in [9, 10, 20], (8) ascribes irregular astigmatism to distinct principal powers along meridians that are significantly off-perpendicular or off-parallel detected on a small zone on a cornea. One needs to sample larger corneal zones to detect the other contributors.…”

Section: Methodsmentioning

confidence: 99%

“…Depending on the progression of growth, the pterygium may cause the anterior surface to vary [12] irregularly of which the irregular astigmatism in (8) is a processed measure. Topography should confirm the nature of the local or general variation of the corneal surface and irregular astigmatism should be diagnosed (outside of the paraxial) by different segments of the same meridian having different powers [9, 10, 20]. When the cornea heals after refractive laser surgery and leaves a discontinuous anterior surface, irregular astigmatism may manifest.…”

Section: Methodsmentioning

confidence: 99%

Paraxial Ocular Measurements and Entries in Spectral and Modal Matrices: Analogy and Application

Abelman

2014

Computational and Mathematical Methods in Medicine

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Lensometers and keratometers yield powers along perpendicular meridians even if the principal meridians of the lens and the cornea are oblique. From each such instrument, multiple raw data represented on optical crosses require conversion to determine elementary statistics. Calculations for research decisions need to be authentic. Principles common to meridians generalize formulaic methods for oblique meridians. Like a lens or a cornea, matrix latent quantities are represented on a matrix cross. Our problem is to determine the matrix whose cross represents quantities on the optical cross. All measurements on an optical cross that include corneal and lens powers and oblique meridians can be considered. Once determined, a portfolio of matrix calculations applies and is justified for ophthalmic calculation. Matrices can be unique and, like a cornea before it is measured, contain latent observations. Asymmetric power component matrices quantify a deviation of a corneal surface from smoothness and toricity. Entries may identify those measurements causing irregular astigmatism that may stem from surgical or other external intervention. Irregular astigmatism is detected primarily from significant measurements in the paraxial range. Measurements are assimilated with matrix factors in a holistic way in order to support choices with calculations and statistics.

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Interchangeability between Placido disc and Scheimpflug system: quantitative and qualitative analysis

Cited by 14 publications

References 24 publications

A Comprehensive Assessment of the Precision and Agreement of Anterior Corneal Power Measurements Obtained Using 8 Different Devices

A Comprehensive Assessment of the Precision and Agreement of Anterior Corneal Power Measurements Obtained Using 8 Different Devices

An indirect method to compare the reference centres for corneal measurements

Paraxial Ocular Measurements and Entries in Spectral and Modal Matrices: Analogy and Application

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