Insights into atypical segmental layer thicknesses and phase retardation in thick corneas using ultrahigh-resolution polarization-sensitive optical coherence tomography.

Autor: Patil RP; Imaging, Biomechanics and Mathematical Modelling Solutions Lab, Narayana Nethralaya Foundation, Narayana Nethralaya, Bangalore, India.; University Eye Clinic Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands., Shetty R; Department of Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore, India., Khamar P; Department of Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore, India., Patel YG; Imaging, Biomechanics and Mathematical Modelling Solutions Lab, Narayana Nethralaya Foundation, Narayana Nethralaya, Bangalore, India., Narasimhan RR; Imaging, Biomechanics and Mathematical Modelling Solutions Lab, Narayana Nethralaya Foundation, Narayana Nethralaya, Bangalore, India., Bhatkal AA; Department of Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore, India., Hitzenberger CK; Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria., Pircher M; Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria., Nuijts RMMR; University Eye Clinic Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands., Sinha Roy A; Imaging, Biomechanics and Mathematical Modelling Solutions Lab, Narayana Nethralaya Foundation, Narayana Nethralaya, Bangalore, India. asroy27@yahoo.com.
Jazyk: angličtina
Zdroj: Eye and vision (London, England) [Eye Vis (Lond)] 2024 Jul 15; Vol. 11 (1), pp. 30. Date of Electronic Publication: 2024 Jul 15.
DOI: 10.1186/s40662-024-00391-4
Abstrakt: Background: Accurately assessing corneal structural status is challenging when thickness deviates from the average. Polarization-sensitive optical coherence tomography (PS-OCT) measures tissue-specific polarization changes, providing additional contrast for accurate segmentations and aids in phase retardation (PR) measurements. Previous studies have shown PR's effectiveness in identifying sub-clinical keratoconus (KC) in asymmetric cases. Thus, this study aims to assess PR distribution in thick corneas with and without KC.
Methods: In this retrospective and cross-sectional study, 45 thick corneas from 30 Asian-Indian subjects, categorized into healthy (n = 26) and KC (n = 19) groups were analyzed. All eyes underwent standard clinical evaluations, tomographic assessments, and corneal biomechanics measurements. PR and individual layer thicknesses were measured using custom-designed ultrahigh-resolution PS-OCT. PR en-face maps were generated. Individual layer thicknesses and PR analysis was conducted across multiple zones, extending up to 8-10 mm in diameter. All eyes in the study had not undergone interventions, received topical medications, or had previous corneal disease history.
Results: Significant differences were found in spherical and cylindrical powers, keratometry, pachymetry, and biomechanical indices (all P < 0.01). Thickness profiles from PS-OCT showed significant differences in the 4-8 mm zones only. Bowman's layer thickness significantly differed only in the central 2 mm zone (P = 0.02). The median PR values showed marginal differences in the central 2 mm zone (P = 0.0565). Additionally, there were significant differences observed in the 2-4 mm and 4-6 mm zones (P = 0.0274 and P = 0.0456, respectively). KC eyes exhibited an atypical PR distribution and corneal thinning, while normal eyes maintained a uniform Bowman's layer thickness and PR maps with larger areas of higher PR.
Conclusion: The study revealed distinctive PR distribution in thick corneas among healthy and KC groups. Using an ultrahigh-resolution PS-OCT the significance of Bowman's layer thickness in these groups was also emphasized. The study offered potential improvements in clinical diagnostics by enhancing our understanding of corneal structure and its altered function.
(© 2024. The Author(s).)
Databáze: MEDLINE
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