Active emmetropization--evidence for its existence and ramifications for clinical practice

Area of Science:

• Ophthalmology and Vision Science
• Developmental Biology
• Animal Models of Refractive Development

Background:

• Refractive errors are a significant global health concern.
• The concept of emmetropization, the eye's ability to self-correct refractive errors during development, is increasingly supported by animal research.
• Understanding emmetropization mechanisms has critical implications for clinical management strategies.

Purpose of the Study:

• To review recent research on refractive development and emmetropization in key animal models.
• To discuss the clinical ramifications of active emmetropization findings.
• To highlight the evidence for compensatory eye growth in response to induced refractive errors.

Main Methods:

• Review of studies utilizing chick, tree shrew, and monkey models.
• Analysis of compensatory eye growth responses to imposed focusing errors (e.g., lenses).
• Examination of recovery from induced refractive errors like form-deprivation myopia.

Main Results:

• Chicks demonstrate robust emmetropization, compensating for lens powers from +15 D to -10 D via choroidal and scleral mechanisms.
• Tree shrews and monkeys exhibit narrower ranges of compensatory responses, with more complex patterns.
• Evidence strongly supports active emmetropization, indicating refractive plasticity during development.

Conclusions:

• Active emmetropization is a well-supported phenomenon in animal models.
• Early intervention with prescription lenses in neonates may inhibit natural emmetropization.
• Correction of myopia in young individuals could potentially accelerate progression, warranting careful consideration in clinical practice.