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Comment by abrookewood | Hacker News Reader

Do we know what the effects are likely to be of wearing a VR headset for hours at a time? I don't think our eyes are going to be happy with a fixed focal length for an extended period of time.

At least when I'm working on a laptop/desktop, I'm constantly looking around the room, at my keyboard etc.

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Plenty of people are spending many hours in VR these days. It's not affecting their eyesight. It may not be good for young children when their vision is still developing, but for adults there is no issue. Especially once you're old enough to have presbyopia; then you can't focus your eyes anyway so it's moot. And presbyopia happens to everyone, VR or not.

I understand that this is still a big problem in the air force when training fighter pilots with VR headsets. The fixed focal length means extended use still leaves pilots disoriented even after taking the headsets off. I would imagine this will hamper real world adoption and keep VR pretty niche for the time being. Using light-fields is the obvious solution but that's still a pretty nascent tech.

It's not entirely clear what problem VR is trying to solve in a lot of situations where's it's claimed to apply (like office use). There's obviously some places where it could be quite useful, but light-field fixed screens might offer a lot of similar benefits for a lot of these applications and at this point at least, that tech is a bit further along (and might be more comfortable for users).

I'm not that worried about that since I already spend most of the day staring at a monitor at a fixed distance. But, I would be a lot more worried about the added weight. My posture is not the greatest and having a bulky headset weighing down the head levering the backbone could be problematic if done for long stretches of time.

VR Exercises and posture corrections add-ons

The main thing is that its often troublesome wearing glasses with them. You can get the lenses changed to your prescription and you can wear some headsets with glasses. Sometimes the light shines in the side of the lens making it distracting.

Curious of this too, I don't want to go blind!

There is not a fixed focal distance in VR. The screens are an inch in front of your eye, but the objects you look at can be (virtually) at any distance. It’s like normal vision.

The question of the effect on vision of shining screens into your eyes for hours at a time still stands.

Edit: whoops, guess I was wrong about that!

Over the years ive found it increasingly difficult to find a way it could be harmful: latest nugget that comes to mind is that daylight is 1000s of times more intense than any indoor light

I don't believe this to be true - don't you need a light field for this to be possible? i.e. what magic leap was doing?

It is obviously saliently true just via direct experience. Your eyes focus at different distances when looking at 3d objects in VR. You can feel it!

I am not a physicist by any means, and I am not sure what a "light field" exactly is in terms of engineering, but as a everyday skeptic I am generally rather wary of anything Magic Leap puts out.

Nah, they have fixed focus (I think at infinity, but that might not be true). You use other depth cues in normal VR systems, but not focal depth.

You are confusing optical focus (like a camera lens or the lens in your eye) with stereopsis - the mechanism by which your brain detects depth information through parallax.

The VR headset shows each eye a slightly different image. Objects appear in slightly different locations in each image. When you look at these virtual objects, the relative angle between your eyes changes which creates the illusion of depth. (This is my layman understanding. I am open to correction).

The optical focal distance remains constant, however.

I've followed up and verified that indeed, most all VR displays have a static focal distance. Thank you for taking the time to correct my and others misconception on the topic!

This is inaccurate. Unlike IRL in which objects can appear at varying focal distances, requiring the eye muscles to constantly adjust the focal distance of the eye, the two images in a VR headset (one for each eye) remain at a constant focal distance as determined by the lenses.

The 3D illusion in VR comes from stereoscopy. The objects that appear in VR are actually all at the same focal distance.

So why do you need glasses in VR? Just trying to understand.

Because there are lenses in the headset that focus the two images at a set focal distant (between a couple of meters and infinity focus, depending on the headset).

You need glasses for the same reason one would need glasses to see a flat image several meters aways, or to see the stars as the case may be.

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