> how is focusing in a VR headset

From a practical point of view, at least for me, "it just works like normal".

As I understand the biology of it, there are really two different relevant mechanisms for "focus".

The lens that is your eyeball changes shape to focus on things closer/father away in real life. In VR this doesn't happen, there's a fixed focal plane a few meters away. I know this, but I don't notice it at all. Everything is always in focus and my brain doesn't seem to have any trouble dealing with it.

There is also the problem of "vergence", your eyes point at the thing you are looking at, which means they point "closer to eachother" when looking at something close, and in parallel lines when looking at something at infinite distance. VR headsets implement this reasonably well. If you hold a finger a few inches in front of your nose and focus on something a few meters away you should be able to see two copies of your finger (or at least I do, I'm told that other people have to try to see this). This works in VR as well.

As an aside. Trying to play shooters in VR has been surprisingly hard for me because of the vergence issue. I'm not use to aiming a real weapon, and it turns out I have trouble figuring out which near-field image corresponds to the eye I'm trying to aim with while I focus on the target in the distance. I'm not sure if I'd find it easier in real life.

No idea actually. I haven't noticed any strain or discomfort though so whatever it is is fairly compatible with how your brain works.

To add to your questions - What about old farts with reading glasses, like me? Do they just work with VR, or are they even needed?

I wear glasses and VR is fine for me. I know some people who can't use it with glasses, but I think that's for clearance reasons.

There's prescription lenses for headsets, but they're fairly expensive and IMO only worth it if you use VR a lot.

Also worth noting the foam guard on your headset can be adjusted or replaced for a better/different fit. I have three foam guards I alternate between (because people get sweaty when I have them over for Beat Saber and it's easy to swap in a clean one for the next person) and one of them didn't fit my glasses until I cut out some clearance for them. Now all three work well, and I wear glasses in VR 100% of the time.

thanks. Good to know. I'll be sure to bring my reading glasses when I go try on headsets. Something I would have likely neglected to do otherwise.

I’m pretty sure you never focus on anything up close in VR. It’s all “far away”, as someone who is near sighted I absolutely have to use glasses in VR. I suspect but am not certain some far sighted people might not need correction, as something may seem close up but really it’s just “big and far away”.

Try it!

> It’s all “far away”, as someone who is near sighted I absolutely have to use glasses in VR

Yeah, me too. As far as my eye is concerned, most things are "far away". Interestingly though, I can read things in VR "farther" than I can in real life. I am not exactly sure what the convergence looks like.

The focal plane is typically a few meters (depends on the headset)... so I guess if you don't need glasses at that distance you would be fine.

*IANA optician

That is for presbyopia, right? Unless it is severe (or combined with other conditions like myopia), you may not even need them. Give it a try!