Superhuman 'night' vision during the total eclipse? Research offers a biological explanation

September 5, 2017 by Misti Crane, The Ohio State University
Credit: The Ohio State University

If you were fortunate enough to witness the recent total solar eclipse in all its glory, you might have noticed something surprising.

It was dark as night, yet people and objects were easier to see than on a typical moonless night.

Scientists at The Ohio State University have discovered a possible biological explanation - the presence (or absence) of a protein in the retina known as a GABA receptor. GABA, short for gamma-aminobutyric acid, is a chemical messenger responsible for communication between cells, especially those in the brain.

The GABA receptor is in abundance on certain cells in the retina on sunny days, and enhances the ability to see details and edges of objects. At night, it disappears.

But that process is normally gradual. When the took viewers from brightness to darkness in minutes, the GABA receptor would have still been present on those cells in their eyes, giving them super-sharp vision for a brief time, said lead researcher Stuart Mangel, a professor of neuroscience at the Ohio State University College of Medicine.

The study, which was conducted in rabbits, also found that the neurotransmitter dopamine, which increases in the light and decreases in the dark, regulates whether the GABA receptor is working.

"It has been known for decades that there is a mechanism in the retina in the eye that helps us see small objects and detect edges on bright days, and that this mechanism gradually turns off when it is dark. However, what this mechanism is and how it is controlled has been a mystery," said Mangel, a member of Ohio State's Neuroscience Research Institute.

The research appears in the journal Current Biology.

"On bright days, are high and signaling is strong, enhancing the detection of spatial details and edges," Mangel said. "On moonless nights, however, dopamine levels are low and the GABA signal is minimal, decreasing our ability to see those details."

Mangel, who visited Tennessee for the Aug. 21 eclipse, said he and others experienced an unusual clarity of vision during the minutes when the moon shut out the sun's rays.

"During the total eclipse, it was as dark as it usually is at dusk. Several people I was with commented that they could see as well during totality as they could when it had been bright, and that their acuity was much better than it usually is when it is dark at dusk," he said.

He realized at the time that his research offers one explanation.

Normally, when you're outdoors, it takes hours for the background light to decrease from bright to dark as the Earth rotates on its axis. When it finally becomes dark at dusk, a person or animal's ability to see small details is much lower than during the middle of the day.

Visual performance needs change with the ambient light level, Mangel said. We need to see fine spatial details on bright days and to see large dim objects on moonless nights.

"Evolution has made trade-offs so that we can see well on bright days and on moonless nights," he said.

"My findings show that the change in background light triggers a process in the retina that normally takes hours. This process involves assembling and moving the GABA receptor protein to a specific site in the retina when it is bright, and disassembling the same protein and moving it away from the synapse as it becomes dark," Mangel said.

"The reason our acuity stayed high during the total eclipse is that there wasn't enough time for protein disassembly to take place."

Explore further: Study helps explain how zebrafish recover from blinding injuries

More information: Antoine Chaffiol et al. Dopamine Regulation of GABA A Receptors Contributes to Light/Dark Modulation of the ON-Cone Bipolar Cell Receptive Field Surround in the Retina, Current Biology (2017). DOI: 10.1016/j.cub.2017.07.063

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5 / 5 (9) Sep 05, 2017
So... this effect should work when moving from a sunny porch to a dark room inside right? You certainly do not need a total eclipse to change the amount of light in your environment!
5 / 5 (3) Sep 05, 2017
I saw the eclipse near Unity, Oregon. When totality began I expected total darkness but it didn't happen. There was plenty of light left. I could see mountain ranges miles away on either side of the path that were bathed in sunshine. I simply thought that light was being reflected off the sky and landscapes from outside the path. Guess I was wrong.
5 / 5 (3) Sep 05, 2017
"During a total eclipse, the sun's corona is about as bright as a good full moon," reports. "Additionally, the edge of the moon's shadow is, at most, only 35 miles away and considerable light will still come in from nearby areas not in total eclipse. Generally speaking, it will be as dark during a total eclipse as it is about a half hour after sunset, or as dark as mid-twilight."
I take it all back-------------I was right the first time!
5 / 5 (1) Sep 05, 2017
The theory is flawed. Go out from a bright room to dark night, you won't see anything. It takes 30 minutes or more for full dark adaptation. At that point, you see as much as you are going to. Ask any amateur astronomer how it works.
not rated yet Sep 06, 2017
So... this effect should work when moving from a sunny porch to a dark room inside right? You certainly do not need a total eclipse to change the amount of light in your environment!

The article points in that direction but so far, all I've managed to do testing the premise is achieve multiple blind shin-jackings after making the transit from full sun to dark(ish) environs. Even with an accounting for pupillary lag/retinal inuration, I've not found any appreciable acuity variance... so maybe?
not rated yet Sep 06, 2017
Seems that when I walk from bright sunshine, to a dark room I don't see the same effect, and if this research is correct that may very well be the case. There may be a more simple explanation than that. I was in Oregon during the eclipse more or less on the centre line. In every direction I could see the horizon was lit like it is at sunset. So while it is dark overhead, its not dark around the horizon. The darkness was like a deep twilight. Also the light levels dropped over time, not instantaneously except for the final totality. Even then the corona is about as bright as the full moon and is considerably larger so there is another light source that is in view during the eclipse.
not rated yet Sep 11, 2017
I saw this and the description here is completely wrong.
It wasn't as dark as moonless night, that's nonsense!
The sun outer Corona is 50 times brighter than a full moon, so it was relatively bright with no problem to see anything, however since the corona is less spread in the atmosphere, even less than moonlight (which is direct sunlight) there is no problem to see stars, even very close to the sun and its corona.

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