Original article
Relationship of Axial Length and Retinal Vascular Caliber in Children

https://doi.org/10.1016/j.ajo.2007.07.023Get rights and content

Purpose

Previous studies in older adults suggest that longer axial length is associated with narrower arteriolar caliber. In this study, we re-examined this relationship in a cohort of children, while controlling for the effects of ocular magnification.

Design

Cross-sectional study of 767 children aged 7 to 9 years.

Methods

Retinal vascular calibers were measured from retinal photographs using a computer-based program. Ocular magnification was corrected using the Bengtsson formula. Standardized examination of refraction and ultrasound ocular biometry was performed for all children.

Results

In models that adjusted for age, gender, ethnicity, body mass index, blood pressure, and birth weight, longer axial length was associated strongly with narrower retinal arteriolar caliber (3.18-μm decrease per standard deviation increase in axial length; P < .001) and venular caliber (4.62-μm decrease standard deviation increase in axial length; P < .001) before correction for ocular magnification. However, after correction, these associations no longer were significant (0.44 μm; P = .31, change for arteriolar caliber; and 0.70 μm; P = .25, for venular caliber).

Conclusions

Our study in children found no association between axial length and retinal vascular caliber after correcting for ocular magnification, suggesting that the previously reported association was likely related to differences in ocular magnification.

Section snippets

Study Population

Details of the Singapore Cohort Study of the Risk Factors for Myopia (SCORM) population have been described elsewhere.16, 17 Children with serious medical conditions (e.g., heart disorders, syndrome-associated with myopia) or eye disorders (e.g., cataract) were excluded from the study. In 2001, 851 randomly selected children from the full cohort were offered retinal photography. Retinal photography of at least one eye was obtained in 775 (91%) children.18, 19 Children without complete ocular (n

Results

Participants’ characteristics by myopia status are listed in Table 1. Among all children, 581 (75.7%) were myopic (spherical refraction, ≤ −0.5 diopter [D]). Of the 186 (24.3%) nonmyopic children, 34 were hyperopic (spherical refraction, > 0.5 D). The mean (standard deviation) of spherical equivalent refraction was −1.45 D (spherical refraction, 1.84 D) in the studied population.

Table 2 shows that after adjusting for age, gender, and ethnicity, eyes with longer axial length had narrower retinal

Discussion

In this study of healthy young children, we demonstrate that the association of longer axial length with smaller retinal vessels was largely the result of the effects of ocular magnification and found no association between axial length and retinal vascular caliber in either myopic or nonmyopic children after correction for ocular magnification.

Our findings support the theoretical effect of ocular refraction and optical dimension on the image size of retinal photographs. As shown previously,

Ning Cheung is a research fellow at the Centre for Eye Research Australia, University of Melbourne, Australia. His research interests include retinal image analysis and its use in the prediction of ocular and systemic diseases, and general ophthalmic epidemiology. The authors of this article are a group of researchers currently undertaking studies exploring the associations of traditional and novel retinal vascular changes with ocular and systemic parameters in both adults and children.

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