Purpose

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.

Methods

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.

Results

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%).

Conclusions

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.

中文翻译：

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英国大学生群体内部散光、屈光和角膜散光的表征。

目的

在手术和其他屈光干预（例如角膜塑形术）之前定义内部 (IA) 和角膜散光误差 (CA) 有明显的好处，可以最大限度地降低屈光结果不满意的风险。此类数据还将与更广泛的眼科护理领域相关，例如配镜和其他类型的刚性镜片装配。这项研究提供了一组大学生散光误差的详细特征，并专门研究了眼睛内部光学对角膜散光的补偿。

方法

对于 176 名年轻参与者，使用开放式 Grand Seiko WAM-5500 自动验光仪获得了屈光不正的客观测量值；角膜曲率和轴向长度使用阿拉丁生物计测量。角膜和屈光散光的临床测量值被转换成矢量分量 J0 和 J45；其次是评估角膜散光补偿。

结果

J0 的平均总屈光散光 (RA)、CA 和 IA 分别为 0.24±0.32D、0.46±0.27D 和 -0.21±0.25D，而 J0 的平均总屈光度为 -0.05±0.20D、0.01±0.16D 和 -0.08±0.16D。 J45。J0 和 J45 的 RA、CA 和 IA 之间均存在显着的线性相关性（P < 0.01）。在轴向长度和 J45 RA 和 IA 之间也注意到显着的线性回归，但没有 CA。J0 和 J45 的完全补偿水平较低，分别为 7% 和 9%，然而，完全没有补偿也并不常见，尤其是 J45 (2%)。

结论

一般来说，眼睛的内部光学系统对角膜散光进行了部分补偿，但尚不清楚这是否是一种主动补偿机制。此外，需要更大规模的研究来表征角膜散光补偿的种族差异。