Aim Previous studies have described the emmetropisation process as inactive in Down's syndrome (DS). However, these studies investigated only a small age range of children—either young children or teenagers. The present study aims to describe refractive error development and distribution in DS throughout childhood and early teenage years.

Methods Subjects were recruited from the Cardiff University Down's Syndrome Vision Research cohort. Refractive error was measured using Mohindra retinoscopy. Subjects were grouped into 15 yearly age groups to allow a cross-sectional assessment of refractive error distribution (n=182). Longitudinal refractive development was observed in 12 children with DS whose refractive error had been monitored throughout their childhood and teenage years.

Results Children were hypermetropic, on average, at all ages, albeit with a wide variation in refractive errors. Change in power vector components, M, J₀ and J₄₅, and the presence of significant astigmatism (≥1.00 D) was assessed with age. There were no statistically significant difference in M and J₀ across age groups. However, there was a significant difference in J₄₅. Prevalence of significant oblique astigmatism increased with age and was highly prevalent (45%) in teenage years. Longitudinally, no significant change in refractive error was reported with regards to the spherical component.

Conclusion The results provide further evidence of the failure in the emmetropisation process in children with DS. Change in spherical refractive error is minimal throughout childhood and early adulthood. The children show a specific development of oblique astigmatism that may be suggestive of a mechanical induction through eyelids.