Variability of Different Reference Bodies in Normal, Keratoconus, and Collagen Crosslinked Corneas

Labiris, Georgios; Giarmoukakis, Athanassios; Rampotas, Alexandros; Symeou, Maria; Bougatsou, Panagiota; Sideroudi, Haris; Kozobolis, Vassilios

doi:10.5301/ejo.5000621

Cited by 3 publications

(2 citation statements)

References 26 publications

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“…For instance, some prefer using BFS based on the analysis of 8 mm zone around the corneal apex, especially for refractive surgery screening [6, 7], others keep the device default at 9 mm zone, although there are some concerns about it; that is, it is more difficult to get reliable scans without wide palpebral fissure. On the contrary, BFTE has been recommended for use by other studies, as they concluded that toric ellipsoid reference surface is the most sensitive reference body to compare KC to normal corneas [8–10]. …”

Section: Introductionmentioning

confidence: 99%

Rotating Scheimpflug Imaging Indices in Different Grades of Keratoconus

Wahba

Roshdy

Elkitkat

et al. 2016

Journal of Ophthalmology

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Purpose. To evaluate accuracy of various Keratoconus (KC) screening indices, in relation to Topographic Keratoconus (TKC) grading. Setting. Al Watany Eye Hospital, Cairo, Egypt. Methods. Data of 103 normal (group 1) and 73 KC eyes (group 2), imaged by Pentacam (branded as Allegro Oculyzer), were analysed. Group 2 was divided into 2a: 14 eyes (TKC = 1, early KC), 2b: 25 eyes (TKC = 1 to 2 or 2, moderate KC), and 2c: 34 eyes (TKC = 2 to 3 up to 4, severe KC). Participants were followed up for six years to confirm diagnosis. Area under the receiver operating characteristic curve (AUROC) was calculated for evaluated curvature, elevation, and pachymetry indices with various reference shapes at different diameters. Results. When comparing normal to KC eyes, ten indices had significantly higher AUROC. Only five of them had significantly higher AUROC in early KC compared to normal corneas: Pachymetry Progression Index- (PPI-) Maximum (Max), Ambrósio's Relational Thickness- (ART-) Max, PPI-Max minus PPI-Minimum (Min), central corneal thickness (CCT), and diagonal decentration of thinnest point from the apex (AUROC = 0.690, 0.690, 0.687, 0.683, and 0.674, resp.). Conclusion. Generally, ten pachymetry and elevation-based indices had significantly higher AUROC. Five indices had statistically significant high AUROC when comparing early KC to normal corneas.

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Section: Introductionmentioning

confidence: 99%

Rotating Scheimpflug Imaging Indices in Different Grades of Keratoconus

Wahba

Roshdy

Elkitkat

et al. 2016

Journal of Ophthalmology

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“…FSSC and BSSC were chosen over corneal elevation measurements because they do not rely on reference sphere calculations that may vary between examinations. 30,31 All left eye scans were transposed to right eye format by horizontally transposing data across the vertical midline to allow for direct location-specific comparisons between scans.…”

Section: Methodsmentioning

confidence: 99%

Modeling Changes in Corneal Parameters With Age: Implications for Corneal Disease Detection

Tong

Phu

Kalloniatis

et al. 2020

American Journal of Ophthalmology

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To apply computational methods to model normal age-related changes in corneal parameters and to establish their association with demographic factors, thereby providing a framework for improved detection of subclinical corneal ectasia (SCE).DESIGN: Cross-sectional study. METHODS: One hundred seventeen healthy participants were enrolled from Centre for Eye Health (Sydney, Australia). Corneal thickness (CT), front surface sagittal curvature (FSSC), and back surface sagittal curvature (BSSC) measurements were extracted from 57 corneal locations from 1 eye per participant using the Pentacam HR. Cluster analyses were performed to identify locations demonstrating similar variations with age. Age-related changes were modeled using polynomial regression with sliding window methods, and model accuracy was verified with Bland-Altman comparisons. Pearson correlations were applied to examine the impacts of demographic factors.RESULTS: Concentric cluster patterns were observed for CT and FSSC but not for BSSC. Sliding window analyses were best fit with quartic and cubic regression models for CT and FSSC/BSSC, respectively. CT and FSSC sliding window models had narrower 95% limits of agreement compared with decade-based models (0.015 mm vs 0.017 mm and 0.14 mm vs 0.27 mm, respectively), but were wider for BSSC than decadebased models (0.73 mm vs 0.54 mm). Significant correlations were observed between CT and astigmatism (P [ .02-.049) and FSSC and BSSC and gender (P [ <.001-.049).CONCLUSIONS: The developed models robustly described aging variations in CT and FSSC; however, other mechanisms appear to contribute to variations in BSSC. These findings and the identified correlations provide a framework that can be applied to future model development and establishment of normal databases to facilitate SCE detection.

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