Optical development in the zebrafish eye lens

The optics of the eye is the key to a functioning visual system. The exact nature of the
correlation between ocular optics and eye development is not known because of the
paucity of knowledge about the growth of a key optical element, the eye lens. The sophisticated
optics of the lens and its gradient of refractive index provide the superior
optical quality that the eye needs and which, it is thought, has a major influence on
the development of proper visual function. The nature of a gradient refractive index
lens, however, renders accurate measurements of its development difficult to make
and has been the reason why the influence of lens growth on visual function remains
largely unknown. Novel imaging techniques have made it possible to investigate
growth of the eye lens in the zebrafish. This study shows measurements using X-ray
Talbot interferometry of three-dimensional gradient index profiles in eye lenses of
zebrafish from late larval to adult stages. The zebrafish lens shows evidence of a gradient
of refractive index from the earliest stages measured and its growth suggests an
apparent coincidence between periods of rapid increase in refractive index in the lens
nucleus and increased expression of a particular crystallin protein group.