Dutt Deepaysh D C S, Yazar Seyhan, Charng Jason, Mackey David A, Chen Fred K, Sampson Danuta M
Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute), The University of Western Australia, Perth, WA, Australia.
Garvan Institute of Medical Research, Sydney, Australia.
Eye Vis (Lond). 2022 Aug 1;9(1):29. doi: 10.1186/s40662-022-00299-x.
To generate and validate a method to estimate axial length estimated (AL) from spherical equivalent (SE) and corneal curvature [keratometry (K)], and to determine if this AL can replace actual axial length (AL) for correcting transverse magnification error in optical coherence tomography angiography (OCTA) images using the Littmann-Bennett formula.
Data from 1301 participants of the Raine Study Gen2-20 year follow-up were divided into two datasets to generate (n = 650) and validate (n = 651) a relationship between AL, SE, and K. The developed formula was then applied to a separate dataset of 46 participants with AL, SE, and K measurements and OCTA images to estimate and compare the performance of AL against AL in correcting transverse magnification error in OCTA images when measuring the foveal avascular zone area (FAZA).
The formula for AL yielded the equation: AL = 2.102K - 0.4125SE + 7.268, R = 0.794. There was good agreement between AL and AL for both study cohorts. The mean difference [standard deviation (SD)] between FAZA corrected with AL and AL was 0.002 (0.015) mm with the 95% limits of agreement (LoA) of - 0.027 to 0.031 mm. In comparison, mean difference (SD) between FAZA uncorrected and corrected with AL was - 0.005 (0.030) mm, with 95% LoA of - 0.064 to 0.054 mm.
AL is more accurate than AL and hence should be used preferentially in magnification error correction in the clinical setting. FAZA corrected with AL is comparable to FAZA corrected with AL, while FAZA measurements using images corrected with AL have a greater accuracy than measurements on uncorrected images. Hence, in the absence of AL, clinicians should use AL to correct for magnification error as this provides for more accurate measurements of fundus parameters than uncorrected images.
生成并验证一种从等效球镜度（SE）和角膜曲率[角膜曲率计（K）]估算眼轴长度（AL）的方法，并确定该估算的AL是否可替代实际眼轴长度（AL），使用利特曼 - 贝内特公式校正光学相干断层扫描血管造影（OCTA）图像中的横向放大误差。
将莱恩研究第二代20年随访的1301名参与者的数据分为两个数据集，用于生成（n = 650）和验证（n = 651）AL、SE和K之间的关系。然后将开发的公式应用于46名有AL、SE和K测量值以及OCTA图像的参与者的单独数据集，以估计并比较估算的AL与实际AL在测量黄斑无血管区面积（FAZA）时校正OCTA图像中横向放大误差的性能。
AL的公式得出方程：AL = 2.102K - 0.4125SE + 7.268，R = 0.794。两个研究队列中估算的AL与实际AL之间具有良好的一致性。用估算的AL和实际AL校正后的FAZA之间的平均差异[标准差（SD）]为0.002（0.015）mm，95%一致性界限（LoA）为 - 0.027至0.031 mm。相比之下，未校正的FAZA与用估算的AL校正后的FAZA之间的平均差异（SD）为 - 0.005（0.030）mm，95% LoA为 - 0.064至0.054 mm。
估算的AL比实际AL更准确，因此在临床环境中校正放大误差时应优先使用。用估算的AL校正后的FAZA与用实际AL校正后的FAZA相当，而使用用估算的AL校正的图像测量的FAZA比未校正图像的测量更准确。因此，在没有实际AL的情况下，临床医生应使用估算的AL校正放大误差，因为这比未校正的图像能提供更准确的眼底参数测量。
