The mess of prescription optical inserts for VR headsets
Articles
VR headsets are in the news a lot these days (“spatial computing” = VR, at least, for now), and one of the things that I’ve found to be a source of confusion is how to be sure one can focus correctly while in VR. I’ve been lucky enough not to need contact lenses or prescription optical inserts to focus in VR, but over the last year I’ve noticed a little more fatigue as my vision changes (losing close focus ability as I get older).
Understanding how focus works in VR isn’t very straightforward. Consumer VR headsets are fixed focal distance, which means that users are focused at a single distance all the time. When you use a screen in the real world, whether it’s a phone, tablet, TV, or movie theater screen, your eyes are focused at a fixed distance, and it’s no different in today’s VR headsets. VR experiences are presented in stereoscopic 3D, so your eyes are converging all over the place as objects float forward and move back. However, your eyes are focused at a single distance. This is exactly what happens when you watch a 3D movie in a theater: an object comes out from the screen, but while your eyes converge on the object, both eyes are still focused on the screen itself. This phenomenon is called “vergence-accommodation conflict (VAC)“.
Most people can tolerate mild VAC for long periods of time, but when VAC is extreme, it can cause discomfort and nausea. For the purposes of this article, VAC is not super important other than to explain that we’re always focused at a fixed distance in current consumer headsets.
So… in VR headsets, where are we focused? In Meta Quest 2 headsets, the focal distance, per John Carmack, is at 1.3 meters. As a user, this means that if you can focus at 1.3 meters, all content in headset will be sharp regardless of how “far away” objects are in the virtual environment. This can be strange for folks who, for example, can’t see up close without reading glasses in the real world, but find that they can hold objects in VR very close and focus on them just fine. However, folks who can focus fine at distance but not at 1.3 meters will find that everything in headset is blurry.
It is well understood how to make VR headsets multi-focal, and it’s likely that in the future, headsets will focus where users are looking, eliminating VAC and replicating the real world more accurately. These headsets would also likely be able to correct vision based on calibration, introducing VAC selectively in order to allow users to focus on virtual objects close and far.
This is all to say that at the moment, if you can’t focus at the fixed focal distance of your VR headset, you will need corrective optics in the form of glasses, contacts, or prescription optical inserts.
Although I can focus at 1.3 meters comfortably in one eye, that distance is at the close edge of comfort in my other eye. When I’m tired or when I’m looking at darker content in VR, I find that one eye isn’t as sharp as I’d like it to be. As as result, I’ve been looking into prescription optical inserts for my VR headsets so I don’t need to get a special contact lens prescription just for VR use.
This is where things have become messy.
I looked at Zenni’s VR Lenses for Meta Quest 3. They have options for a prescription upload, but also allow users to manually select lens strength per eye. Knowing that I would need optics to make 1.3 meters comfortable in both eyes, I chatted with a Zenni service agent and asked what prescription I should upload. The response? Upload my distance prescription. Unfortunately in my case, this would have resulted in pushing my “good” VR eye out into blurriness and leaving the eye I wanted to correct alone. What I really needed was a prescription that was just a bit pushed out from my computer glasses, which target focus at just under a meter. I confirmed this with a colleague who is an ophthalmologist and ended up placed a manual order at Reloptix instead. If I had listened to the Zenni agent, I would have ended up not being able to focus in my Quest 3.
Apple partners with Zeiss for their Vision Pro optical inserts, and their order flow allowed for the upload of multiple prescriptions. I uploaded my distance prescription (very mild), along with reading and computer prescriptions. I checked the box that asked whether or not I was over 40. The optical inserts flow during setup was easy–I snapped them in (magnetically) and then showed the included QR code to the Vision Pro. Unfortunately, there is no information about the actual power of the delivered lenses, and even after I registered the Zeiss optics in Zeiss Vision Care, my account only shows the prescription information I uploaded. This isn’t surprising for an Apple solution, but it looks like I’m going to have to test the optics myself to see how strong they are. Luckily, the inserts work very well. I can use Vision Pro fine without the inserts, but the experience seems to be less fatiguing with the optics installed. (Update: the Vision Pro itself tells me the lens powers when I snap them in, but it tells me my distance prescription with a note that says that the prescription could have been adjusted–this is NOT useful because as is the point of this article, the distance prescription would yield to failure).
As a side note, on Friday at the Apple Store, the employee who took me through the full Vision Pro demo told me, “most things are far away, but some things are closer,” when I asked him what the fixed focal distance was. I found the product demo to be extremely nauseating due to being seated at a very close table and being taken through a mixed-reality (MR) demo that was mostly about looking at virtual objects that collided in disparity. This seemed like the standard demo, which was pretty shocking. I overheard another person at the table saying that he was feeling sick. Luckily, I didn’t have any of this nausea when I used the product at home (sitting further away from objects in MR).
Coincidentally, I’m going through this process with Bigscreen Beyond at the same time. I pre-ordered the headset in February of 2023 a year ago, and in January 2024, I finally received an email asking me to scan my face and upload prescription information. I sent them an email asking how far away the virtual screen is, and they responded, “the focal distance of Beyond is around 1 meter, and it can vary between 0.8m to 1.2m.” Unfortunately, since diopters are non-linear, this range is pretty big. At 0.8m, my computer prescription would work well, but at 1.2m, I would not be able to focus well in one eye. As in the case with Zenni, if I had blindly given them my distance prescription, I would not be able to focus in either eye.
Given the complexity of this space, I’ve taken things into my own hands and purchased an optometry trial lens set to figure out the appropriate power for corrective VR optical inserts.
Disclaimer: I work for Meta on VR stuff. These opinions are my own.