Ocular shape and myopia.

INTRODUCTION: To learn if eye shape might be a useful parameter in refractive research.
MATERIALS AND METHODS: Laboratory research on eye growth mechanisms is summarised. The available clinical literature relating refraction to eye shape and peripheral refraction is critically assessed in the context of the laboratory research on refractive development.
RESULTS: Almost all refraction research assesses optical and length parameters exclusively along the visual axis. Contemporary laboratory research demonstrates a remarkable phylogenic conservation of the neural mechanisms regulating refractive development. On-axis image quality regulates central refractive development in animals and probably, to some extent, in humans. Off-axis image quality at the retina depends on anterior segment geometry and optics, and on the 3-dimensional conformation of the retina. In chicks, eye shape is a predictable parameter linked to the underlying neural mechanisms modulating eye development. Based on the sparse clinical literature in human adults and children, the eye shapes induced in chicks are also seen in human subjects in patterns suggesting that eye shape may be a useful parameter in clinical studies.
CONCLUSION: The diverse findings suggest that incorporating the 3-dimensional conformation of the eye into future clinical studies may help resolve many of the ambiguities in contemporary refractive research.