The Optical Nature of Myopic Changes in Retinal Vessel Caliber

IF 3.2 Q1 OPHTHALMOLOGY

Ophthalmology science Pub Date : 2024-10-10 DOI:10.1016/j.xops.2024.100631

Fabian Yii BSc , Niall Strang MCOptom, PhD , Colin Moulson BSc, MCOptom , Baljean Dhillon FRCPS, FRCOphth , Miguel O. Bernabeu PhD , Tom MacGillivray PhD

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Abstract

Purpose

Dimensional measures of retinal features are subject to the optical influence of ocular magnification. We examined the impact of ocular magnification on the association between axial length (AL) and measurements of retinal vessel caliber in fundus photographs.

Design

Cross-sectional study.

Participants

Eighty-two normal right eyes from healthy participants aged 16 to 31 years.

Methods

Central retinal arteriolar and venular equivalents (CRAE and CRVE) were derived from color fundus photographs using semiautomated software. Ordinary least squares linear regression was used to assess the influence of AL (independent variable) on CRAE and CRVE, controlling for age, sex, and ethnicity, both before and after magnification correction using different formulae. These formulae estimate magnification based on different ocular parameters: AL only (Bennnett’s formula), refractive error only (Bengtsson’s formula), and refractive error combined with keratometry (Littmann’s formula). Previous research has primarily relied on Bengtsson’s formula, which is less accurate than Bennett’s formula. We also examined the impact of treating the nontelecentric fundus camera used in this study as telecentric when applying these magnification correction formulae.

Main Outcome Measures

Central retinal arteriolar and venular equivalents (in pixels).

Results

Before magnification correction, increasing AL was associated with decreasing CRAE (β: −0.49, 95% confidence intervals: −0.89 to −0.09, P = 0.02) and CRVE (β: −0.91, 95% confidence intervals: −1.62 to −0.20, P = 0.01). After magnification correction, this observation was no longer evident, regardless of the correction formula applied. When inappropriately assuming the fundus camera to be telecentric, we observed a bias toward increasing magnification-corrected CRAE and CRVE with increasing AL (β coefficients were positive or became more positive), reaching statistical significance (P < 0.05) for CRAE corrected using Bennett’s or Littmann’s formula, and for CRVE corrected using Bennett’s formula.

Conclusions

Failing to correct for ocular magnification results in apparent narrowing of vessels in longer eyes, while inappropriate assumptions about telecentricity during magnification correction introduce an optical artifact that causes apparent widening of vessels. These findings suggest that myopic changes in retinal vessel caliber are optical (not biological) in nature. Proper correction of this effect to accurately derive dimensional measures is a crucial—yet often overlooked—methodological consideration in “oculomics” research investigating retinal biomarkers of systemic conditions.

Financial Disclosure(s)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

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视网膜血管口径近视变化的光学性质

目的视网膜特征的尺寸测量受眼球放大倍数的光学影响。我们研究了眼球放大倍数对轴向长度（AL）和眼底照片中视网膜血管口径测量值之间关联的影响。方法使用半自动软件从彩色眼底照片中得出视网膜中央动脉和静脉等值（CRAE 和 CRVE）。使用普通最小二乘法线性回归评估 AL（自变量）对 CRAE 和 CRVE 的影响，同时控制年龄、性别和种族，并在使用不同公式进行放大校正之前和之后进行校正。这些公式根据不同的眼参数估算放大倍数：仅 AL（Bennnett 公式）、仅屈光不正（Bengtsson 公式）和屈光不正与角膜测量相结合（Littmann 公式）。以往的研究主要依赖 Bengtsson 公式，但其准确性不如 Bennett 公式。结果在放大校正前，AL 的增加与 CRAE（β：-0.49，95% 置信区间：-0.89 至 -0.09，P = 0.02）和 CRVE（β：-0.91，95% 置信区间：-1.62 至 -0.20，P = 0.01）的减少相关。放大校正后，无论采用何种校正公式，这一观察结果都不再明显。当不适当地假设眼底照相机为远心时，我们观察到随着 AL 的增加，放大校正后的 CRAE 和 CRVE 有所增加（β 系数为正或变得更正），使用 Bennett 或 Littmann 公式校正的 CRAE 和使用 Bennett 公式校正的 CRVE 达到了统计学意义（P < 0.05）。结论未对眼球放大率进行校正会导致长眼血管明显变窄，而在放大率校正过程中对远心的不恰当假设则会引入光学假象，导致血管明显变宽。这些发现表明，近视眼视网膜血管口径的变化本质上是光学的（而非生物的）。在研究全身性疾病的视网膜生物标志物的 "眼科组学 "研究中，适当纠正这种效应以准确得出尺寸测量值是一个至关重要但却经常被忽视的方法学考虑因素。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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