Development of refraction and strabismus.
In the past year, as in recent years, most of the research on the development of refraction has focused on the following: 1) mechanisms whereby the eye can maintain coordinated growth to achieve emmetropia and 2) disruptions of emmetropization resulting in myopia or hyperopia. Preterm children and those with Down syndrome have higher refractive errors than other children, suggesting a failure of emmetropization. One of the most intriguing studies of the past year and one certain to lead to follow-up studies reported that ambient room illumination at night in a child's first two years is associated with a higher prevalence of myopia than sleeping in darkness. Reports on the development of hyperopia showed that it is axial in nature, similar to myopia. The effects of spectacle interventions to correct refractive errors are still being debated, with recent evidence from children suggesting that lenses do not exacerbate myopia. Analyses of risk factors and numerous new screening procedures detect patients with strabismus for referral at a variety of sensitivity and specificity levels. Hyperopia and high AC/A ratios are most clearly associated as causal agents for esotropia and intermittent exotropia. However, the action of even these simple mechanisms is confounded by abnormal binocular fusion mechanisms and the inability of optical correction to align the eyes of many patients. Asymmetric optokinetic nystagmus, latent nystagmus, and dissociated vertical deviation appear to be linked to infantile esotropia from before its onset. But the way the mechanisms underlying these oculomotor anomalies are causally related to the onset of infantile esotropia remains a mystery.