The viral eye test that has everyone freaking out over their eyesight.

A simple tweet showing two photos of traffic is literally changing people’s lives as they realise they’ve been living with a common eye condition.

The tweet, posted by a Twitter account called Unusual Facts, shows two images side-by-side of cars in traffic at night. On the left, the light from the car brakes appears in streaks, and on the right, it doesn’t.

The difference, according to the poster, who has the condition themselves, is that people with an eye condition called astigmatism see the left, while people with normal eyes see the right.

Astigmatism is when the cornea is slightly curved rather than completely round..

With astigmatism, light focuses on several points of the retina rather just one point. This is what people with Astigmatisms vs without. pic.twitter.com/RXWWayFBRJ

— Unusual Facts (@UnusualFacts6) March 25, 2019

As with colour blindness though, if you’re never told what you’re seeing isn’t normal, then you’re unlikely to realise on your own.

Which is why reading that tweet was an eye-opening experience (yeah, we went there) for many people, who for the first time ever, realised they may have astigmatism.

Wait people can see lights normally? I thought everyone saw those lines-

— Hilda (@HildaBillda) March 25, 2019

Holy shit I thought everyone saw the lines, when I was litttle I would squint to make em longer to entertain myself, thought that was normal

— Mi (@MamaKekkin) March 27, 2019

…my life and seeing is a lie, I thought everyone saw the lines

— Ambient Quetzalcoatl (@AmbientGryph) March 25, 2019

I always thought this was normal wtf

— Aldnox (@aldnox) March 25, 2019

According to Optometry Australia, astigmatism is a condition where, usually due to the cornea being curved differently to in a normal eye, the person suffers blurred vision.

However, unlike short- or long-sightedness, it can be more difficult for those living with the condition to realise because some directions can be more out of focus than others. With short-sightedness, all directions at a far distance are blurry.

Other symptoms of astigmatism include headaches and fatigue because of constant squinting to see clearly.

The good news is that once people realise they have astigmatism they can talk to an optometrist about correcting it with glasses or contact lenses.