How we see light

Lighting up the future

We live in exciting times. Already this year we’ve seen virtual reality eye tests and groundbreaking research into how patients view their optician. Well, we’re happy to let you know that we have another groundbreaking piece of research into eyes to let you know about.

For the first time in human history, we have been able to pinpoint individual colour sensing cells in the eyes of living individuals. Not only this, we’ve been able to activate them.

This was published in a report for the journal Science Advances. A team of scientists used flashes of light to stimulate cells at the back of two men’s eyes. These cells are called cone cells and they are used to detect colour, or so we thought. In response to the flashes of light, only some of the cone cells registered colour, others leaving only a sensation of whiteness with the men tested.

This is where the science gets a little bit more complicated. First of all, we need to understand that there are actually two sets of cells at the back of your eyes – cones and rods. Rod cells are adapted to help us see in the dark. They can’t detect colour, because our vision in the dark relies upon detecting tiny amounts of light. In the light rod cells become unresponsive. Cone cells detect bright light. In other words, you see with two different parts of your eye based upon how light it is around you.

Next: there are different types of cones. L-cones are sensitive to red and yellow light. These forms have longer wavelengths than other forms of light. M-cones absorb green light. S-cones detect shorter wavelengths, helping us to see blue light.

The paper in Science Advances, co-authored by Brian P. Schmidt, explains that the experiment reveals that large sections of the M- and L-cones detected white sensations when activated alone, whereas only a small fraction of L- and M-cones detected red or green. It’s important to understand that these results were consistent. Taking place over a number of weeks, tests always produced the same results – right down to the cell.

What this means is twofold. On the one hand, we now know that our eyes divide their labour very efficiently, separating cells into types of “job roles”. We also know that our eyes use different cells to detect colour than those cells used to detect brightness and form. This means that, theoretically, we detect light differently, interpreting an accumulation of data input into different receptors in nanoseconds.

All in all, we have to reach the conclusion that eyes are simply amazing things – complex organisms the study of which will never get old.