Differentiating Keratoconus and Corneal Warpage by Analyzing Focal Change Patterns in Corneal Topography, Pachymetry, and Epithelial. Cont Lens Anterior Eye. Sep;26(3) Hydrogel contact lens-induced corneal warpage. Schornack M(1). Author information: (1)Department of. Before the advent of corneal topography, corneal warpage was generally described as a condition that included distorted keratometer mires.
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The novel Anterior Ectasia Index and Warpage Indices can be used to distinguish between keratoconus and warpage. The repetitive local trauma alters the viscosity of the ground substance and initiates a temporary displacement of ground substance from the corneal apex.
The epithelial PSD can distinguish normal from keratoconus or warpage, but does not distinguish between these two conditions. Limited oxygen transmissibility through some hydrogel lenses may lead to chronic hypoxia and acidosis.
The main limitation of this study is that the number of cases is relatively small, which can be addressed in a future study with more cases. Similarly, though Warpage index is positive in all warpage eyes and normal in most keratoconus eyes, it fails in cases where keratoconus and warpage coexist. Certain individuals who wear hydrogel contact lenses can experience corneal warpage.
Ectasia or permanent corneal warpage?
There was no difference in age between groups Table 2. In response to eye rubbing, the buckling and flexure of the corneal fibrils may occur in association with the slippage between collagen fibrils at the cone apex.
Nine of the contact lens-related warpage cases were correctly classified An abnormally high Anterior Ectasia Index is the result of the coincident focal topographic steepening and pachymetric thinning, which is typical in keratoconus and other ectasia i. Our new approach is more closely tailored to the real-world application where a surgeon must distinguish between several different conditions that require different treatment decisions.
Longitudinal data analysis using generalized linear models.
Hydrogel contact lens-induced corneal warpage.
The study included 22 normal, 31 keratoconic, 11 warpage, and 8 FFK eyes. All warpage cases in our study were induced by RGP or soft toric contact lenses instead of regular soft spherical lenses, probably because RGP and soft toric contact lenses had more effect in changing the corneal epithelium.
The pattern deviation PD map was defined as the percent deviation from the normal reference map i. The ectasia map is the product of fitted Gaussian waveforms for the PD maps of anterior topography and pachymetry.
This system projects 40 optical slits, 20 from the right and 20 from the left, onto the cornea corbeal a degree angle. Using just one of the two new indices is not sufficient to distinguish between keratoconus and warpage. This work is licensed under a Creative Commons Attribution 4. Intrinsic position uncertainty impairs overt search performance. Kruskal-Wallis nonparametric tests were used to compare different groups.
Scheimpflug corneal topography revealed the presence of bilateral inferior steepening, more pronounced in the right eye. Evaluation of keratometric, pachymetric, and elevation parameters of keratoconic corneas with pentacam. Given that contact lenses are often used for vision correction in keratoconus, an overall diagnostic scheme is needed to account for this overlap. As a result, he developed chronic ocular irritation, which in turn prompted him to rub his left croneal vigorously with the knuckles of his index finger, often upon awakening.
This prospective observational study was approved by the institutional review board of the Casey Eye Institute, Portland, Oregon, United States. We previously developed diagnostic parameters based on OCT corneal pachymetry and epithelial thickness maps to detect early keratoconus.
In this study, we developed the two warage indices, Anterior Ectasia Index and Warpage Index, to differentiate keratoconus from warpage by combining the focal changes in anterior corneal topography, pachymetry, and epithelial thickness maps. The purpose of this study is to differentiate keratoconus from contact lens-related warpage by combining focal change patterns of several corneal maps: The corneal central zone is flattened larger radius of curvature, lower keratometry to compensate for the inferior third of the corneal surface which is concomitantly steepened shorter radius of curvature, higher keratometry.
The epithelial PSD can distinguish normal from keratoconus or warpage, but does not distinguish between these two conditions. The Warpage Index was designed based on the insight that anterior focal steepening is accompanied by focal epithelial thickening in contact lens-related warpage, but associated with epithelial thinning in keratoconus Table 1. The warpage map is the product of the PD maps of anterior topography and epithelial thickness. Correlation between epithelial thickness in normal corneas, untreated ectatic corneas, and ectatic corneas previously treated with CXL; is overall epithelial thickness a very early ectasia prognostic factor?
The system works at an nm wavelength and has a scanning speed of 26, axial scans per second. Another limitation is that if keratoconic distortion corneap extremely subtle e.
Many cases of keratocon us are reported in corneap website. Those with negative Warpage Index values are diagnosed with keratoconus, while those with positive Warpage Index are diagnosed with warpage. However, topography is not sensitive to very early stages of keratoconus when the topographic steepening is masked by focal epithelial thinning.
Keratoconus subjects included in this study were diagnosed clinically with the following inclusion criteria: We used the Gaussian waveform, which was cone shaped, to fit the focal ectasia. The purple area indicates both conditions coexist.