School of Health Sciences and Social Work, University of Portsmouth, Portsmouth, PO1 2DT, United Kingdom.
Division of Optometry and Visual Science, City University London, Northampton Square, London, EC1V 0HB, United Kingdom.
Cont Lens Anterior Eye. 2020 Aug;43(4):333-337. doi: 10.1016/j.clae.2020.02.007. Epub 2020 Feb 22.
There is a clear benefit in defining internal (IA) and corneal astigmatic error (CA) prior to surgical and other refractive interventions, such as orthokeratology, to minimise risk of unsatisfactory refractive outcomes. Such data would also be of relevance to broader areas of ophthalmic care such as spectacle dispensing and other types of rigid lens fitting. This study offers a detailed characterisation of astigmatic error in a group of university students and specifically investigates compensation of corneal astigmatism by the eye's internal optics.
For 176 young-adult participants, objective measurements of refractive error were obtained using the open-view Grand Seiko WAM-5500 autorefractor; corneal curvature and axial length were measured using the Aladdin biometer. Clinical measurements of corneal and refractive astigmatism were converted into vector components J0 and J45; followed by an assessment of corneal astigmatism compensation.
Mean total refractive astigmatism (RA), CA, and IA were 0.24 ± 0.32D, 0.46 ± 0.27D and -0.21 ± 0.25D respectively for J0 and -0.05 ± 0.20D, 0.01 ± 0.16D, and -0.06 ± 0.18D for J45. Significant linear correlations were noted between RA, CA, and IA for both J0 and J45 (P < 0.01). A significant linear regression was also noted between axial length and J45 RA and IA, but not CA. Levels of full compensation were low, 7% and 9% for J0 and J45 respectively, however, a complete absence of compensation was also uncommon particularly for J45 (2%).
In general, partial compensation for corneal astigmatism by the eye's internal optics is noted, but it is unclear whether this is an active compensatory mechanism. Further, larger scale, studies would be required to characterise differences in corneal astigmatic compensation with respect to ethnicity.
在进行手术和其他屈光干预（如角膜塑形术）之前，明确定义内部（IA）和角膜散光误差（CA），以最大程度降低屈光效果不满意的风险，这具有明显的优势。此类数据对于眼科护理的其他领域也具有重要意义，如配镜和其他类型的硬性隐形眼镜适配。本研究对一组大学生的散光误差进行了详细的描述，并特别研究了眼球内部光学对角膜散光的补偿。
对 176 名年轻成年人参与者，使用开放式 Grand Seiko WAM-5500 自动验光仪获得客观的屈光误差测量值；使用 Aladdin 生物测量仪测量角膜曲率和眼轴。将临床测量的角膜和屈光散光转换为矢量分量 J0 和 J45；随后评估角膜散光的补偿情况。
总散光（RA）、角膜散光（CA）和眼内散光（IA）的平均值分别为 J0 方向的 0.24 ± 0.32D、0.46 ± 0.27D 和-0.21 ± 0.25D，J45 方向的 0.05 ± 0.20D、0.01 ± 0.16D 和-0.06 ± 0.18D。J0 和 J45 方向的 RA、CA 和 IA 之间均存在显著的线性相关性（P < 0.01）。也观察到眼轴与 J45 RA 和 IA 之间存在显著的线性回归，但与 CA 无关。完全补偿的水平较低，J0 和 J45 分别为 7%和 9%，但完全无补偿也不常见，尤其是 J45（2%）。
总体而言，眼球内部光学对角膜散光存在部分补偿，但尚不清楚这是否是一种主动的补偿机制。此外，还需要进行更大规模的研究，以确定种族差异对角膜散光补偿的影响。
