Repeatability of posterior and total corneal curvature measurements with a dual Scheimpflug–Placido tomographer

Kim, Eric J.; de, Ildamaris Montes; Wang, Li; Weikert, Mitchell P.; Koch, Douglas D.; Khandelwal, Sumitra

doi:10.1016/j.jcrs.2015.07.035

Cited by 36 publications

(47 citation statements)

References 15 publications

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“…The worse values were observed for TCA magnitude, whose CoV was 16.58%, but this is not surprising, as the repeatability of corneal astigmatism magnitude measurements is relatively low with all instruments, even in healthy eyes. Our data are similar to those previously reported by other authors [11][12][13][14][15] .…”

Section: Discussionsupporting

confidence: 93%

“…They include the mean Sim-K (calculated using the standard keratometric index of 1.3375), posterior corneal curvature, TCP (obtained by ray tracing through the anterior and posterior surfaces and a 3-mm diameter entrance pupil), total corneal astigmatism (TCA, analyzed with and without vector analysis) 21 , anterior and posterior corneal asphericity in the 8.0 mm zone (calculated as the Q-value), corneal diameter, thinnest corneal thickness, epithelial thickness and aqueous depth (AQD, i.e., the axial distance between the corneal endothelium and the anterior surface of the lens). The details of each measured parameter have been previously described 13 . With the exception of epithelial thickness, the corresponding values provided by the Sirius were analyzed to assess agreement.…”

Section: Measured Parametersmentioning

confidence: 99%

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Repeatability of anterior segment measurements by optical coherence tomography combined with Placido disk corneal topography in eyes with keratoconus

Schiano-Lomoriello

Bono

Abicca

et al. 2020

Sci Rep

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corneal tomography is an important tool to identify and follow up eyes with keratoconus. our study evaluate the repeatability of the automatic measurements provided in keratoconic eyes by a new anterior-segment optical coherence tomographer (AS-oct) combined with placido-disk topography (MS-39, CSO) and assess their agreement with the corresponding measurements taken with a rotating Scheimpflug camera combined with Placido-disk topography (Sirius, CSO). Mean simulated keratometry, posterior and total corneal power, total corneal astigmatism, corneal asphericity, thinnest corneal thickness, epithelial thickness, corneal diameter, and aqueous depth were evaluated. Repeatability was assessed using test-retest variability, the coefficient of variation, and the intraclass correlation coefficient; agreement was assessed by the 95% limits of agreement. Good repeatability was achieved for most parameters. Moderate repeatability was found for total corneal astigmatism measurements. the repeatability of mean simulated keratometry and total corneal power measurements worsened with more severe stages of keratoconus with a statistically significant relationship between the individual coefficient of variation and corneal power values. Agreement with the Scheimpflug camera was moderate for aqueous depth and thinnest corneal thickness and poor for most other measured parameters. the good repeatability of automatic measurements suggests the new AS-oct device to be a viable option in clinical practice of eyes with keratoconus. Keratoconus is a non-inflammatory ectasic disease characterized by progressive thinning and steepening and an apical cone-shaped protrusion of the cornea 1,2. The introduction of corneal topography first and corneal tomography later enabled researchers to develop several methods to identify keratoconic eyes 3-7. Accurate corneal imaging is now highly desirable to diagnose keratoconus, especially in its earlier stages, when visual acuity is still good. Modern anterior segment imaging techniques, such as Scheimpflug photography and optical coherence tomography (OCT), have significantly improved our ability to identify eyes with keratoconus, as they also provide pachymetric data and posterior corneal curvature measurements. Although anterior corneal surface parameters may be sufficient to discriminate between normal eyes and eyes with clinical keratoconus, using the data from both corneal surfaces as well as corneal thickness increases precision, sensitivity, specificity, and accuracy, thus significantly improving the ability to differentiate between normal eyes and subclinical keratoconus suspect eyes 7. One of the main limitations of Scheimpflug imaging is the low resolution and relatively poor quality of anterior segment scans. In this regard, anterior segment OCT (AS-OCT) is known to produce better images with higher definition. The higher resolution has made it possible, for example, to measure the corneal epithelial thickness 8-10. A parameter that has never been evaluated by Scheimpflug cameras. The purp...

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Section: Discussionsupporting

confidence: 93%

Section: Measured Parametersmentioning

confidence: 99%

Repeatability of anterior segment measurements by optical coherence tomography combined with Placido disk corneal topography in eyes with keratoconus

Schiano-Lomoriello

Bono

Abicca

et al. 2020

Sci Rep

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“…Cerviño et al [2] reported ICC values of more than 0.950 for anterior and posterior corneal curvature measurements obtained in normal healthy eyes with the Galilei dual Scheimpflug-Placido analyzer from Ziemer Ophthalmic Systems AG (Switzerland). Kim et al [7] reported for the same dual Scheimpflug-Placido system S w values of 0.08 and 0.09 D for simulated keratometry in normal healthy and postrefractive surgery eyes, respectively. McAlinden et al [12] reported repeatability limits expressed as the within-subject standard deviation ×

1.96 \sqrt{2}

of the anterior flattest and steepest keratometry readings of 0.25 and 0.36 D, respectively, using the Pentacam system from Oculus (Wetzlar, Germany) in a sample of normal healthy eyes.…”

Section: Discussionmentioning

confidence: 99%

Corneal Topographic and Aberrometric Measurements Obtained with a Multidiagnostic Device in Healthy Eyes: Intrasession Repeatability

Piñero

López-Navarro

Cabezos

et al. 2017

Journal of Ophthalmology

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Purpose. To evaluate the intrasession repeatability of corneal curvature, eccentricity, and aberrometric measurements obtained with a multidiagnostic device in healthy eyes. Methods. This study enrolled 107 eyes of 107 patients ranging in age from 23 to 65 years. All of them underwent a complete anterior segment examination with the VX120 system (Visionix-Luneau Technologies, Chartres, France). Three consecutive measurements were obtained. The within-subject standard deviation (Sw), intrasubject precision (1.96 × Sw), and intraclass correlation coefficient (ICC) were calculated. Results. All Sw for corneal power measurements were below 0.26 D, with ICC above 0.982. The Sw for corneal astigmatism at different areas (3, 5, and 7 mm) was below 0.21 D, with ICC above 0.913. Concerning the axis of astigmatism, its Sw was below 11.27°, with ICC above 0.975. The Sw and ICC for corneal eccentricity were 0.067 and 0.957, respectively. The Sw and ICC for high-order aberration root mean square (RMS) were 0.048 µm and 0.901, respectively. For 3rd- and 4th-order aberrometric parameters, all Sw were below 0.037 µm and all ICC were higher than 0.84, except for quadrafoil RMS (ICC: 0.689). Conclusions. The multidiagnostic device evaluated is able to provide consistent measurements of corneal power, eccentricity, and third- and fourth-order aberrations in healthy eyes.

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“…10 Overall, the DRS analyzer provides anterior segment measurements with good repeatability and reproducibility for both normal and postrefractive surgery corneas. 11 There have been numerous studies comparing the clinical outcomes of LASIK and SMILE, but to the best of our knowledge no previous study has compared the anterior segment morphological parameters after FS-LASIK and SMILE using a DRS analyzer. In the present study, we used a DRS analyzer to evaluate changes in the anterior segment following FS-LASIK (Visumax ® & Mel 90 ® ; Carl Zeiss Meditec) and SMILE (Visumax ® ; Carl Zeiss Meditec AG, Jena, Germany) for myopic correction.…”

Section: Introductionmentioning

confidence: 99%

Comparison of anterior segment changes after femtosecond laser LASIK and SMILE using a dual rotating Scheimpflug analyzer

Kim

Mun

Yang

et al. 2019

Preprint

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Purpose To compare the changes in the anterior segment after femtosecond laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE) using a dual rotating Scheimpflug (DRS) analyzer (Galilei®; Ziemer Ophthalmology, Port, Switzerland). Setting Onnuri smile eye clinic, Seoul, South Korea Design Retrospective Method 218 eyes of 109 patients who underwent FS-LASIK or SMILE for myopic correction were retrospectively studied. Ninety-eight eyes of 49 patients who underwent FS-LASIK were compared to 120 eyes of 60 patients treated with SMILE. A DRS analyzer was used for preoperative and 6-month postoperative anterior segment analyses. Measured variables included the central corneal thickness (CCT), anterior chamber depth (ACD), anterior and posterior keratometry (K), anterior and posterior best-fit sphere radius, and maximum posterior elevation (MPE). Results The estimated lenticule thickness (LT; 87.20 ± 22.87 µm) was significantly thicker in the SMILE group than the ablation depth (69.23 ± 22.24 µm) in the FS-LASIK group. However, there was no significant difference in the CCT decrease using the DRS analyzer. The MPE was significantly increased after both procedures, and there was a statistically significant difference in the change in MPE between the two groups (-1.10 ± 2.12 µm after FS-LASIK; -0.75 ± 2.33 µm after SMILE; p = 0.035). Conclusions The preoperative LT was overestimated using SMILE. Regarding changes in the MPE and posterior K, changes in the posterior corneal surface were greater after FS-LASIK than after SMILE.

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Repeatability of posterior and total corneal curvature measurements with a dual Scheimpflug–Placido tomographer

Abstract: Drs. Koch, Weikert, and Wang received research support from Ziemer USA, Inc. No other author has a financial or proprietary interest in any material or method mentioned.

Cited by 36 publications

References 15 publications

Repeatability of anterior segment measurements by optical coherence tomography combined with Placido disk corneal topography in eyes with keratoconus

Repeatability of anterior segment measurements by optical coherence tomography combined with Placido disk corneal topography in eyes with keratoconus

Corneal Topographic and Aberrometric Measurements Obtained with a Multidiagnostic Device in Healthy Eyes: Intrasession Repeatability

Comparison of anterior segment changes after femtosecond laser LASIK and SMILE using a dual rotating Scheimpflug analyzer

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