Why the eye is nature's miracle

Eye of the beholder: The miracle of our sight.

When the body of Dr Yoshiki Sasai, an eminent Japanese biologist, was discovered in August this year, his death was widely mourned across the world of science. Not just for the abrupt end to his glittering career,for which he won several awards including the 2010 Osaka Science Prize, and was appointed the laureate of the 2012 Inoue Prize for Science. Nor because of the tragic manner of his death: the 52-year-old was found hanged in his own laboratory - an apparent suicide, some say, after a scandal over a research paper he'd co-authored in January.

Instead, the scientific world lamented what, perhaps, Dr Sasai was about to achieve. As one of the directors at the RIKEN Centre for Developmental Biologyin Kobe, he was one of the world's leading experts in stem cell technology. His team had pioneered incredible new techniques for creating organ-like structures - making giant strides towards a future where replacements for our failing human organs could be grown in a Petri dish.

Most tragically, the months before his death had heralded Sasai's biggest achievement. His team had already grown partial pituitary glands and even bits of the brain, but now he'd coaxed embryonic stem cells into forming the functioning tissue of arguably the most complex and scrutinised organ in the entire animal kingdom.

An optic cup made from embryonic stem cells. Photo: M. Eiraku and Y.Sasai at RIKEN C

Sasai had grown an eye. And in doing so, he'd also helped resolve a scientific obsession that had lasted centuries.

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In very basic form, the eye is thought to have first developed in animals about 550 million years ago. But such is its perfect design - its infinite adaptability, and irreducible complexity - that many argue it is proof of the divine itself. Even today, Christians and creationists argue that Charles Darwin himself was troubled by its existence - seizing upon an (oft-misquoted) aside in Origin of Species, where Darwin remarked that the whole idea of something so flawless "could have been formed by natural selection, seems, I freely confess, absurd in the highest degree".

The eye has become a focal point for biologists, ophthalmologists, physicists and many other branches of science ever since. So when the Spanish neuroscientist Santiago Ramon y Cajal made the first anatomical diagrams of neurons and the retina in 1900, it stoked a century of attempts by biologists to unlock the eye's secrets.

And there have been several discoveries. Unlike our ears and nose, for example, which never stop growing our entire lives, our eyes remain the same size from birth. Then there's the complicated process of irrigation, lubrication, cleaning and protection that happens every time we blink an average of 4,200,000 times a year.

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Why the eye is nature's miracle