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Published on: May 26, 2021
Development of refraction and strabismus
Insights
Nighttime light exposure in early childhood may increase myopia risk. Research also explores hyperopia, spectacle interventions, and the complex causes of strabismus and infantile esotropia.
Area of Science:
- Ophthalmology
- Developmental Biology
- Genetics
Background:
- Emmetropization, the eye's coordinated growth to achieve normal vision, is crucial for visual development.
- Disruptions in emmetropization lead to refractive errors like myopia and hyperopia.
- Preterm infants and children with Down syndrome exhibit higher refractive errors, indicating impaired emmetropization.
Purpose of the Study:
- To review recent advancements in understanding eye refraction development and associated disorders.
- To highlight novel findings on environmental influences and genetic factors affecting refractive error.
- To discuss current knowledge and remaining mysteries in strabismus and infantile esotropia.
Main Methods:
- Literature review of recent research on refractive error development.
- Analysis of studies investigating environmental factors (e.g., nighttime illumination) and genetic predispositions.
- Examination of clinical data on refractive error interventions and strabismus etiology.
Main Results:
- Nocturnal ambient light exposure in the first two years of life is linked to increased myopia prevalence.
- Hyperopia development is axial, similar to myopia.
- Spectacle interventions do not appear to worsen myopia in children.
- High AC/A ratios and hyperopia are associated with esotropia and intermittent exotropia.
- Oculomotor anomalies like asymmetric optokinetic nystagmus may precede infantile esotropia, but causal links are unclear.
Conclusions:
- Environmental factors, particularly nighttime light, play a significant role in myopia development.
- The etiology of infantile esotropia remains complex and multifactorial, involving early-onset oculomotor anomalies.
- Further research is needed to fully elucidate the mechanisms underlying refractive error development and strabismus.
Abstract:
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.
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