Myopia is a worldwide major public concern, aside from the visual disturbance needing optical correction, myopia may be associated with open angle glaucoma, retinal detachment and myopic maculopathy. The higher the myopia the higher the risk for retinal associated comorbidities, and the axial length is the more important measure to estimate risk of visual impairment. Recently a formula to predict axial length using spherical equivalent and keratometry was proposed, with the intention of categorizing the risk of visual impairment with Tideman et al. classification.

Purpose

To evaluate the accuracy of an axial length prediction formula in a Colombian population 8–17 years old.

Methods

Children from MIOPUR study with optical biometer axial length measure (AL), manifest refraction and keratometry were included in the analysis. Predicted axial length (PAL) was calculated with the prediction formula. A Bland-Altman assessment was conducted, and the concordance correlation coefficient was measured. Proposed classification of AL to establish risk of visual loss was used with measured AL and with PAL. The percentage of eyes misclassified was then established.

Results

A total of 2129 eyes were included in the analysis. Mean difference of axial length (actual AL minus PAL) was −0.516 mm (−1.559 mm – 0.528 mm). Concordance correlation coefficient (CCC) of 0.656 (IC95 0.636-0.675) was found between the real AL and PAL. PAL differed from measured AL by 1 mm or more in 16.58 %, and by 2 mm or more, in 0.61 % of the eyes. In myopic eyes, PAL was in average 0.426 mm longer than the AL actually measured with CCC of 0.714 (IC95 0.666−0.761). PAL differed from measured AL by 1 mm or more in 21.92 %, and by 2 mm or more, in 0.45 % of the myopic eyes. The study revealed that 15.03 % of all eyes, and 29.81 % of myopic eyes, were misclassified when PAL was used.

Conclusions

The proposed axial length prediction formula was not accurate, and it did not adequately classify risk of visual impairment in myopic eyes in a group of Colombian children. We consider that it is not possible to predict the axial length based only on optometric data, such as the corneal radius of curvature and the spherical equivalent. This is very possibly related to the variability of crystalline lens power within a population.

中文翻译：

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用验光参数估计眼轴长度不准确

近视是世界范围内的主要公众问题，除了需要光学矫正的视力障碍外，近视还可能与开角型青光眼、视网膜脱离和近视性黄斑病变有关。近视度数越高，视网膜相关合并症的风险就越高，而眼轴长度是评估视力障碍风险的更重要指标。最近提出了一种使用等效球面和角膜曲率测量来预测眼轴长度的公式，目的是使用 Tideman 等人对视力障碍的风险进行分类。分类。

目的

评估 8-17 岁哥伦比亚人群中轴长预测公式的准确性。

方法

来自 MIOPUR 研究的儿童采用光学生物计轴向长度测量 (AL)、明显屈光度和角膜曲率计被纳入分析。用预测公式计算预测轴向长度（PAL）。进行了 Bland-Altman 评估，并测量了一致性相关系数。为确定视力丧失风险而提出的 AL 分类与测量的 AL 和 PAL 一起使用。然后确定被错误分类的眼睛的百分比。

结果

共有 2129 只眼睛被纳入分析。轴向长度的平均差（实际 AL 减去 PAL）为 -0.516 毫米（-1.559 毫米 - 0.528 毫米）。实际 AL 和 PAL 之间的一致性相关系数 (CCC) 为 0.656 (IC95 0.636-0.675)。在 16.58% 的眼睛中，PAL 与测量的 AL 相差 1 毫米或更多，在 0.61% 的眼睛中相差 2 毫米或更多。在近视眼中，PAL 平均比实际测量的 AL 长 0.426 mm，CCC 为 0.714 (IC95 0.666−0.761)。在 21.92 % 的近视眼中，PAL 与测量的 AL 相差 1 毫米或更多，在 0.45 % 的近视眼中相差 2 毫米或更多。研究表明，当使用 PAL 时，15.03% 的眼睛和 29.81% 的近视眼被错误分类。

结论

所提出的眼轴长度预测公式不准确，并且没有对一组哥伦比亚儿童的近视眼视力障碍风险进行充分分类。我们认为仅根据验光数据（例如角膜曲率半径和等效球面）是不可能预测眼轴长度的。这很可能与人群中晶状体屈光度的可变性有关。