Corneal Stress Distribution Evolves from Thickness-Driven in Normal Corneas to Curvature-Driven with Progression in Keratoconus.

Autor: Roberts CJ; Department of Ophthalmology & Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio.; Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio., Knoll KM; Department of Ophthalmology & Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio.; College of Optometry, The Ohio State University, Columbus, Ohio., Mahmoud AM; Department of Ophthalmology & Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio.; Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio., Hendershot AJ; Department of Ophthalmology & Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio., Yuhas PT; College of Optometry, The Ohio State University, Columbus, Ohio.
Jazyk: angličtina
Zdroj: Ophthalmology science [Ophthalmol Sci] 2023 Jul 20; Vol. 4 (2), pp. 100373. Date of Electronic Publication: 2023 Jul 20 (Print Publication: 2024).
DOI: 10.1016/j.xops.2023.100373
Abstrakt: Purpose: To introduce the novel parameter of Corneal Contribution to Stress (CCS) and compare stress distribution patterns between keratoconus (KCN) and normal corneas.
Design: Prospective, observational, cross-sectional study.
Participants: The study included 66 eyes of 40 subjects diagnosed with KCN and 155 left eyes from 155 normal control (NRL) subjects.
Methods: Tomography was obtained to calculate the newly proposed CCS, defined according to the hoop stress formula without intraocular pressure, R/2t, where R is the radius of curvature and t is the thickness. CCS maps were calculated from pachymetry and tangential curvature maps. Custom software identified the 2-mm-diameter zones of greatest curvature (Cspot-max), thinnest pachymetry (Pach-min), greatest stress (CCSmax), and lowest stress (CCSmin). Stress difference (CCSdiff) was calculated as CCSmax - CCSmin. Distances between Cspot-max vs. Pach-min, vs. CCSmax, and vs. CCSmin, as well as between Pach-min vs. CCSmax and vs. CCSmin, were calculated. t tests were performed between cohorts, and paired t tests were performed within cohorts. Univariate linear regression analyses were performed between parameters and distances. The significance threshold was P < 0.05.
Main Outcome Measures: Corneal stress parameters, corneal features of maximum curvature, minimum thickness, and distances between corneal stress parameters and corneal features.
Results: CCSmax was significantly closer to Pach-min (0.79 ± 0.92) and Cspot-max (2.04 ± 0.85) than CCSmin (3.17 ± 0.38, 2.73 ± 1.53, respectively) in NRL, P < 0.0001, whereas CCSmin was significantly closer to Cspot-max (1.35 ± 1.43) than CCSmax (2.52 ± 0.72) in KCN, P < 0.0001. Cspot-max (severity) was significantly related to CCSdiff in KCN ( P < 0.0001; R 2  = 0.5882) with a weak relationship in NRL ( P < 0.0080, R 2  = 0.0451). Cspot-max was significantly related to the distance from Pach-min to CCSmax ( P < 0.0001; R 2  = 0.3737) without significance in NRL ( P  = 0.8011).
Conclusions: Corneal stress is driven by thickness in NRL, with greatest stress at thinnest pachymetry and greatest curvature. However, maximum stress moves away from thinnest pachymetry with progression in KCN, and minimum stress is associated with maximum curvature. Severity in KCN is significantly related to greater difference between maximum and minimum stress, consistent with the biomechanical cycle of decompensation.
Financial Disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.
(© 2023 by the American Academy of Ophthalmology.)
Databáze: MEDLINE
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