Department of Ophthalmology, Antwerp University Hospital, Edegem, Belgium.
Department of Medicine and Health Sciences, University of Antwerp, Wilrijk, Belgium.
Ophthalmic Physiol Opt. 2019 May;39(3):183-193. doi: 10.1111/opo.12616.
To study the corneal and internal astigmatism and the age-related changes underlying the known refractive shift with-the-rule (WTR) towards against-the-rule (ATR) astigmatism.
Refractive and corneal biometry data were collected for a total of 1195 healthy Caucasian subjects, recruited by ophthalmological centres across Europe. After conversion of refractive and corneal surface astigmatism to power vectors J and J , the total corneal and internal astigmatism were calculated.
Both refractive power vectors had leptokurtic distributions with a narrow peak at zero, and a broader, secondary distribution at its base, corresponding to eyes without balanced components. This may be fitted with a bigaussian function (J : r² = 0.87; J : r² = 0.98). Statistically significant changes in these distributions are seen with age: for refractive J the narrow peak shortens progressively, while the broad peak shifts positive from to negative values, corresponding to increased astigmatism and a shift from with-the-rule towards against-the-rule. For J the narrow peak shortens with age as well, while the broad peak flattens. These changes in refractive J result from statistically significant negative shifts in both the corneal and internal components with age (Kruskal-Wallis, p < 0.05).
In young participants corneal and internal astigmatism partially cancel each other out. This balance between both is gradually lost after age 50, leading to larger amounts of refractive astigmatism, as well as a reorientation of the axis. Given the small amplitude of these changes, they are unlikely to have repercussions for long term stability toric cataract or refractive surgery outcomes.
研究角膜和内在散光以及与规则性散光（WTR）向逆规性散光（ATR）的已知屈光漂移相关的年龄变化。
共收集了来自欧洲各地眼科中心的 1195 名健康白种人受试者的屈光和角膜生物测量数据。在将角膜表面散光和角膜表面散光转换为 J 和 J 力向量后，计算了总角膜和内部散光。
两种屈光力向量均具有尖峰偏态分布，在零处有一个狭窄的峰，在其底部有一个更宽的二次分布，对应于没有平衡分量的眼睛。这可以用双峰函数（J ：r²=0.87；J ：r²=0.98）拟合。随着年龄的增长，这些分布会发生统计学上显著的变化：对于屈光 J，狭窄的峰值逐渐缩短，而宽峰从正值转移到负值，对应于散光增加和从规则性向逆规性的转变。对于 J，随着年龄的增长，狭窄的峰值也会缩短，而宽峰会变平。屈光 J 的这些变化是由于角膜和内部成分随年龄的统计显著负向变化所致（Kruskal-Wallis，p<0.05）。
在年轻参与者中，角膜和内部散光部分相互抵消。这种平衡在 50 岁后逐渐丧失，导致更大的屈光性散光，以及轴的重新定向。鉴于这些变化的幅度较小，它们不太可能对长期稳定性有影响。
