The Eyevolution of Cephalopods

Most people have never set eyes upon the mysterious deep sea squid that inhabit our oceans. In fact, our evolutionary cousins could teach us a thing or two about our own vision.

Researchers from the Auckland Myopia Laboratory in New Zealand are looking outside the traditional short-sighted treatments for a more revolutionary approach to myopia. Teaming up with cephalopod expert Dr. Steve O’Shea, they have set their sights on Sepioteuthis australis, a species of squid found around the coast of Australia and New Zealand.

Despite their underwater habitat, squid possess remarkably similar eyes to humans. The last common ancestor of squid and humans existed around 530 million years ago during the Cambrian explosion. Since then, we have independently evolved similar ‘camera-type’ eyes that can adjust focus and brightness to suit the environment.

Optometrist and PhD candidate Philip Turnbull believes that this convergent evolution of the human and cephalopod eye may hint at some fundamental mechanism of eye growth. “Myopia is a disorder where the eye grows to long for the focusing power of the eye,” he explains. “Something has gone wrong with the growth control mechanism.”

Turnbull’s doctoral research has shown that the eye size of S. australis can be manipulated by growing them in different wavelengths of light.

“Because squid have an optically-guided growth mechanism as we do, they may be a good model for myopia,” he explains.

Despite the similar growth mechanisms, the cephalopod eye is relatively simple, with fewer photoreceptor cell layers. This means that squid may provide a simpler model in which to pinpoint where the disrupted growth control mechanism occurs.

“We’re stepping away from the vertebrate model to look at the more fundamental physiological processes,” says Dr. John Phillips, principle investigator of the Auckland Myopia Laboratory.

With up to 90% of the population suffering from myopia in some Asian countries, this is evolutionary research with a future.

But growing squid in captivity is not easily sailing. “There’s a phenomenal amount of work involved in keeping these animals alive,” says Dr. Steve O’Shea, former Director of the Earth and Oceanic Science Research Institute at the Auckland University of Technology, and the first person to grow squid in captivity. 

“Here we’ve got someone who’s conducting some serious research,” he says. “I was amazed how that might benefit humans.”

5-minute Myopia with Dr John Phillips

Eyevolution spoke with Dr John Phillips, principle investigator of the Auckland Myopia Laboratory at the University of Auckland. He cleared our view of short-sightedness.


What is myopia?

Myopia is a condition of the eye in which people can see clearly at near but when they try to look in the distance everything seems to be blurry. We’re not sure why it develops, but it certainly develops in a relatively large number of people, in children particularly.

Who gets myopia?

There are a number of different stages. Some people are born with myopia and they have myopia for the rest of their life. Most children, if they’re going to develop myopia, they develop it at the age of about 8 or 12. In fact, a significant number of people develop myopia when they’re over 30, but predominantly they develop it as a school child.

Why do people develop myopia?

There are actually a very large number of hypotheses! One of course is that some people have a genetic susceptibility to developing myopia, if they’re put in a particular environment. At the moment people think that it’s something to do with too little time spent outdoors and too much time spent studying indoors in relatively low lights levels, and things like that. There are lots of pieces of evidence that suggest it’s the environment, not the genes. This huge increase in the prevalence of myopia has only come about in a couple of generations, so it’s highly unlikely that the gene pool has changed that much, whereas the environment has changed hugely for many people.

Describe the progression of myopia.

Typically an optometrist would see a child at say 8 or 9 or 10 because they’re complaining that they can’t see well enough in class to take part or they can’t recognise their friends across the street or something like that. Initially the severity of their short sight is not terribly bad so they would have rather weak spectacles to correct it. Typically what happens now is that they’d be given a pair of spectacles and they’d be sent away and they’d be seen again in 6 months time, and almost inevitably their myopia would have become worse and have to have more powerful spectacles than they’d had before, or contact lenses. And this would go on until perhaps they’re 18 when they’d stop progressing and the severity of their myopia would even out at a constant degree of myopia. And that may be anything from very mild to quite severe.

Can you predict whether someone will develop myopia?

The straight answer to that is no, but we can guess who is likely to develop myopia and who isn’t. A child who has both parents who are myopic is more likely to develop myopia than someone who doesn’t have parents who are myopic. There’s been some work looking at the shape of the eye as to whether people are more likely to develop myopia depending to the particular eye shape that they have, but that has actually not proved to be a reliable way of predicting whether a child will develop myopia. So at the moment we don’t have anything more than that.

How many people get myopia?

In America and Europe the prevalence is about 30%. In Australia, and therefore presumably new Zealand, the prevalence is less than 20%. But in some Asian centres, some studies have shown that 80% of young people are myopic, so it’s hugely variable. In underdeveloped countries the prevalence is very very low, something like 3% typically.

Do we currently have any treatments for myopia?

Not really, we don’t have treatments. We manage myopia by correcting it so that the blurry vision goes away, and at low levels of myopia that’s actually reasonably successful. Adults can receive laser surgery that can permanently correct their vision, like wearing a permanent contact lens on the front of the eye. But these management schemes—contact lenses, spectacles—they just correct the myopia, they don’t actually treat it at all, because the fundamental problem is that the eye too big, so basically what they do is to correct the refractive error. "For some people it is potentially quite a serious issue, but for society it’s a widespread issue."

How big a problem is myopia for New Zealand in general?

We think that a little less than 20% of children in New Zealand have myopia. Well that’s a pretty high prevalence of any sort of condition, and consequently it’s an expensive burden that’s born by a significant number of people in New Zealand. So just from the social economic point of view, it’s a burden. It limits career choices. You really can’t be a pilot if you don’t have good vision, and we’re talking about low levels of myopia. Significant number of people have high myopia, and high myopia is a medical condition that can lead to sight loss later in life. I should say that even low levels of myopia are associated with increased risk of glaucoma and cataract. "It’s bad news really all round."

The final day of squid research

Today, 2 years of squid husbandry draw to a close for Optometrist and researcher Philip Turnbull.

 The cephalopod charges have served as experimental models for human myopia (short-sightedness). At least, that's what Phil is hoping. Vision research to date has focused on our vertebrate cousins, such as rats and mice, whereas squid have not yet seen the light of short-sighted research.

Despite their underwater dwellings, squid have remarkably similar eyes to humans, making them suspected candidates for vision research. Squid eyes evolved separately to ours, through a process known as 'convergent evolution'. This could make them very interesting indeed...

Today, Phil gave his squid a new life that he could not provide for them. A short car-ride to Kelly Tarlton's Sealife Aquarium, and the squid were transferred to the largest tank they had ever seen with their beautiful myopic eyes. A sense of sadness lay in the air. Despite all the early mornings and late night fishing sessions, rain, hail, or shine, Phil has obviously developed a certain fondness for his cephalopod friends. He peers into their tank and they bob up and down in the water, waving goodbye with their tentacles.

But a lot still lies ahead for Phil, who must now dive into his data and see exactly what his squid did for him. Are squid a good model for human myopia?