Abstract
Purpose: :
To examine the relationship between colour vision anomalies and refractive errors, using Ishihara and City University colour vision tests, in Australian school children.
Methods: :
1740 6-year old children from 34 randomly selected primary schools and 2353 12-year old children from 21 secondary schools were examined using both the Ishihara and City University colour vision tests, as part of the Sydney Childhood Eye Study. Test distances were 40cm (Ishihara) and 33cm (City University), and both tests were presented binocularly and with spectacles, if worn.
Results: :
Among children aged either 6 or 12 years, Ishihara testing detected 23 and 56 children, respectively, with colour vision defects, while City University testing detected 10 and 28 children, respectively. There was poor symmetry between tests for both cohorts of children (a significant difference, p=0.0013 & <0.0001, respectively), though there appeared to be moderate agreement between measures (kappa, Κ =0.56 & 0.52, respectively). Of children with colour vision defects, males accounted for 95.2% of the total (using the Ishihara test) and 92.7% (using the City University test). There were no ethnic differences in the prevalence of colour vision defects (p=0.23). Ocular biometry was performed in all children, and data from right eyes are used. Significantly longer axial length (SD) was found for children with colour vision defects (defined by Ishihara), than for children with normal colour vision (22.97±0.73mm vs 22.60±0.69mm, p=0.006 for the 6-year old sample and 23.75±0.84mm vs 23.38±0.85mm, p=0.001, for the 12-year old sample). This difference was also evident for children aged 12 years, using the City University test (23.85±0.94mm vs 23.38±0.85mm, p=0.004). The relationship between colour vision and axial length persisted, even after adjusting for height and ethnicity, but was not reflected by any statistically significant difference in spherical equivalent refraction (SER).
Conclusions: :
Despite poor symmetry between Ishihara and City University tests, no difference was demonstrated in SER between children with and without colour vision defects. The presence of colour vision defects was associated with longer mean axial length in both age groups and in both tests. Further studies are warranted to explore these findings.
Keywords: color vision • myopia • clinical (human) or epidemiologic studies: prevalence/incidence