Background/Aims: Both eyes of one individual share the same environment and genes. Weexamined interocular differences in biometry to determine the potential role of other factors inrefractive development.Methods: 362 subjects (6-7 years) from the Northern Ireland Childhood Errors of Refraction(NICER) study were studied. Cycloplegic autorefraction was measured with a Shin-Nipponopen-field autorefractor. Axial length and corneal curvature were measured with a ZeissIOLmaster.Results: 257 subjects had an interocular difference of < 0.50D (ISO group) and 105 (29%) adifference of ≥ 0.50D (ANISO group). Twenty-five subjects (6.9%) had anisometropia ≥ 1.00Dand 9 (2.5%) had anisometropia ≥ 1.50D. The two groups, ISO and ANISO, showed differentrefractive distributions (Kolmogorov-Smirnov test, P = 0.001) with the ISO group showing anearly Gaussian distribution and the ANISO group showing positive skew, a hyperopic shiftand a bi-Gaussian distribution. A marker of emmetropisation is the poor correlation betweenrefraction and corneal curvature seen in older children. There was no significant correlationbetween refraction and corneal curvature of each eye in the ISO group (r = 0.09, P = 0.19,Spearman's rank correlation) but these parameters were significantly correlated in the ANISOgroup (r = 0.28, P = 0.004).Conclusion: In young children, small degrees of anisometropia (≥ 0.5D) are associated withimpaired emmetropisation. This suggests that anisometropia is a marker for poorly regulatedeye growth, indicating that, in addition to environmental and genetic influences on eye growth,stochastic processes contribute to refractive outcomes.
- eye growth
- refractive error