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Abstract：
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.
CONCLUSIONS: 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.
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.
CONCLUSIONS: 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.
摘要：
背景：当厚度偏离平均值时，准确评估角膜结构状态具有挑战性。偏振敏感光学相干断层扫描（PS-OCT）测量组织特定的偏振变化，为精确分割提供额外的对比度，并有助于相位延迟（PR）测量。先前的研究表明，在不对称病例中，PR在识别亚临床圆锥角膜（KC）方面具有有效性。因此，本研究旨在评估有和没有KC的厚角膜中的PR分布。
方法：在这项回顾性和横断面研究中，来自30个亚洲印度受试者的45个厚角膜，分为健康组（n=26）和KC组（n=19）进行分析。所有的眼睛都接受了标准的临床评估，层析成像评估，和角膜生物力学测量。使用定制设计的超高分辨率PS-OCT测量PR和单个层厚度。生成了PR人脸图。在多个区域中进行单个层厚度和PR分析，延伸到8-10毫米的直径。研究中的所有眼睛都没有经过干预，接受了局部用药,或有角膜疾病史。
结果：在球形和圆柱形屈光力方面发现了显着差异，角膜曲率测量,测厚仪,生物力学指标(均P<0.01)。来自PS-OCT的厚度分布仅在4-8mm区域中显示出显著差异。Bowman的层厚度仅在中心2mm区域存在显着差异（P=0.02）。中位数PR值显示出中央2mm区域的边缘差异（P=0.0565）。此外,在2-4mm和4-6mm区域中观察到显着差异（分别为P=0.0274和P=0.0456）。KC眼表现出不典型的PR分布和角膜变薄，而正常的眼睛保持一个统一的鲍曼的层厚度和PR图与较大的区域更高的PR。
结论：该研究揭示了健康组和KC组的厚角膜中独特的PR分布。使用超高分辨率PS-OCT，还强调了Bowman层厚度在这些组中的重要性。该研究通过增强我们对角膜结构及其改变的功能的理解，为临床诊断提供了潜在的改进。
方法：在这项回顾性和横断面研究中，来自30个亚洲印度受试者的45个厚角膜，分为健康组（n=26）和KC组（n=19）进行分析。所有的眼睛都接受了标准的临床评估，层析成像评估，和角膜生物力学测量。使用定制设计的超高分辨率PS-OCT测量PR和单个层厚度。生成了PR人脸图。在多个区域中进行单个层厚度和PR分析，延伸到8-10毫米的直径。研究中的所有眼睛都没有经过干预，接受了局部用药,或有角膜疾病史。
结果：在球形和圆柱形屈光力方面发现了显着差异，角膜曲率测量,测厚仪,生物力学指标(均P<0.01)。来自PS-OCT的厚度分布仅在4-8mm区域中显示出显著差异。Bowman的层厚度仅在中心2mm区域存在显着差异（P=0.02）。中位数PR值显示出中央2mm区域的边缘差异（P=0.0565）。此外,在2-4mm和4-6mm区域中观察到显着差异（分别为P=0.0274和P=0.0456）。KC眼表现出不典型的PR分布和角膜变薄，而正常的眼睛保持一个统一的鲍曼的层厚度和PR图与较大的区域更高的PR。
结论：该研究揭示了健康组和KC组的厚角膜中独特的PR分布。使用超高分辨率PS-OCT，还强调了Bowman层厚度在这些组中的重要性。该研究通过增强我们对角膜结构及其改变的功能的理解，为临床诊断提供了潜在的改进。
