Refractive development in children with Down's syndrome: a population based, longitudinal study

Abstract

Aims: To study the refractive development in children with Down's syndrome longitudinally.

Methods: An unselected population of 60 children with Down's syndrome was followed with repeated retinoscopies in cycloplegia for 2 years or more (follow up 55 (SD 23) months). Accommodation was assessed with dynamic retinoscopy.

Results: From longitudinal spherical equivalent values of the right eye, three main categories of refraction were defined: stable hypermetropia (<1.5 D difference between the first and last visit) (n=34), increasing hypermetropia ("hypermetropic shift"; >/=1.5 D difference) (n=11), and decreasing hypermetropia/development of myopia ("myopic shift"; >/=1.5 D difference) (n=9). Patients with anisometropia (n=6) were evaluated separately. In the stable hypermetropia group three sublevels were chosen: low (</=+2.0 D at the last visit), moderate (+2.25 to + 4.0 D), and high (>+4.0 D). An accommodation weakness was found in 55% of the children. Accommodation weakness was significantly less frequent in the stable, low grade hypermetropia group (22%) than in all the other groups (p=0.008). The frequency of astigmatism >/=1.0 D at the last visit was 57%, the direction of axis being predominantly "with the rule." All the eyes with oblique astigmatism had a side specific direction of axis; the right eyes belonging to the 135 degrees axis group and the left eyes to the 45 degrees axis group.

Conclusion: A stable, low grade hypermetropia was significantly correlated with a normal accommodation. Accommodation weakness may be of aetiological importance to the high frequency of refractive errors encountered in patients with Down's syndrome. A striking right-left specificity in the oblique astigmatic eyes suggests that mechanical factors on the cornea from the upward slanting palpebral fissures may be a major aetiological factor in the astigmatism.

Figure 1

Individual curves of spherical equivalent values from children with Down's syndrome and stable, low grade hypermetropia (A), stable, moderate hypermetropia (B), stable, high grade hypermetropia (C), increasing hypermetropia (D), and decreasing hypermetropia or development of myopia (E).

Figure 2

Direction of axis in the left and the right eyes in 12 children with Down's syndrome with oblique astigmatism. The signs in the columns "first" and "last" show the direction of the astigmatism when the astigmatism was first noticed and at the last examination, respectively (patient numbers correspond with Table 2).