Abstract
Purpose: :
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.
Methods: :
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.
Results: :
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.
Conclusions: :
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.
Keywords: clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • refraction • retina