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N. D. Joachim, E. Rochtchina, A. G. Tan, P. Mitchell, J. J. Wang, Sydney Childhood Eye Study; Inter-Eye Correlation of Retinal Vessel Calibre Measurements in Anisometropic versus Emmetropic Children. Invest. Ophthalmol. Vis. Sci. 2009;50(13):105.
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We previously reported strong inter-eye (right-left) correlations in retinal vessel calibre. Given magnification differences in anisometropia we hypothesised that this should impact inter-eye correlation. Our purpose was then to assess the correlation of retinal vessel calibre between right and left eyes in a sample of children with anisometropia compared to the corresponding correlation of children emmetropic in both eyes.
From participants of the Sydney Childhood Eye Study, we selected 214 children aged 12 years who were emmetropic in both eyes (Group 1, spherical equivalent (SE) between -0.50 and 0.50 dioptres (D) (inclusive) in both eyes, and inter-eye SE difference <0.25D), 35 children with inter-eye SE difference ≥1.00D but <2.00D (Group 2), and 32 children with anisometropia (Group 3, inter-eye SE difference ≥2.00D). Retinal arteriolar and venular calibres were measured from digital retinal images in a zone 0.5 to 1.0 disc diameters from the optic disc margin, using a validated, computer-assisted program. Pearson correlations (r) between the two eyes were calculated and correlations in Groups 2 and 3 were compared with Group 1 using the student’s t-test. Linear regression models, constructed with data from all three groups, were used to assess retinal vessel caliber in relation to refractive error in terms of right-left eye differences.
In Group 1 r between right and left eyes was 0.57 for central retinal arteriolar equivalent (CRAE), and 0.70 for central retinal venular equivalent (CRVE). In Group 2, rcrae = 0.60 and rcrve = 0.82. This was not significantly different from Group 1. However, there was a borderline significant difference between Group 1 and Group 3, where rcrae = 0.36 (p1,3 = 0.08) and rcrve = 0.52 (p1,3 = 0.07) for anisometropic eyes. Inter-eye differences in refractive error were linearly associated with inter-eye retinal vessel calibre differences. For each 1.00D increase in SE difference between right and left eyes, the inter-eye differences for mean CRAE and CRVE increased by 0.84µm (p=0.018) and 1.30µm (p=0.004) , respectively.
Right-left eye correlations in retinal vessel calibre measurements were lower in anisometropic children. It is known that ≥2.00D differences in refraction between two eyes can affect image size, and could contribute to measurement variation in retinal vessel calibre - anisometropia needs to be considered when assessing relationships with these measurements.
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