In the web of Steam about Valve Index:
Canted optics
Instead of a mount perpendicular to the user’s eyes, the headset’s displays cant outward by 5 degrees. This improves outer FOV while balancing the inner FOV.
So, canted displays, but how? " / \ " like pimax or " \ / " ?
" / \ " is the regular version, " \ / " is the mutant version 
From the Index steam page:
“Instead of a mount perpendicular to the user’s eyes, the headset’s displays cant outward by 5 degrees. This improves outer FOV while balancing the inner FOV.”
also: “Optics: Double element, canted lens design”
also you can see an image of the displays. They are 4:3 but the do not say the size. they look smaller than pimax’s that’s for sure (might have higher ppd than the pro)
This thread here: https://www.reddit.com/r/virtualreality/comments/b8m2ot/here_are_some_ppd_calculations_for_the_valve_index/em8i1g9/
given same res as vive pro but higher fov yet RGB matrix, it probably levels out to be the same as the vive pro and the vive pro is definitely not as high res as the pimax 5k+ although this is all conjecture as the lens matters very much!
The guy on reddit does not really know what he is talking about. He even mentions doc-ok doc for the FOV, but conveniently omits the other doc-ok doc (The Display Resolution of Head-mounted Displays, Revisited | Doc-Ok.org) which actually measures the PPD for OG Vive and Oculus CV1. If he read it he would see why his assumption was totally wrong.
The assumption that having larger FOV automatically makes the PPD lower (because we need to stretch the same amount of the pixels over the bigger angle) is also wrong.
The total stereo FOV is not an addition of each eye FOV, because there is also a stereo overlap. So for example extending the FOV by rotating the panels does not touch the PPD at all, but will diminish the stereo overlap in the center of the view.
The other option how to extend the FOV is “pulling” the views further apart (again at the expense of the stereo overlap), but without changing the PPD.
In other words, you can change the total (horizontal) FOV, without changing (much) the individual FOVs of each eye thus also ensuring the similar PPD.
My personal opinion is that Index will be on par with Pimax on PPD and have possibly better optics, but lower overall (horizontal) FOV.
The question is whether they are using those display panels in landscape (like P8k/5k) or portrait orientation (like Vive/Rift).
If the former, and if density variance across the view is about the same as previous HMDs, I would speculate about the same PPD as Pimax.
If the latter; A not insignificant bit better (1600 pixels against 1440, over say 120-ish degrees vertical, which should be more predictable than the horizontal per-eye FOV (…and sorry, but I won’t consider the p8k 2160 pixels tall - come back when you can show off the 8kX, which actually takes an incoming 4k image, and even then only fully if it has since ditched the pentile-ish displays of the 8k, for actual 4k ones)), but with a severe downcut of the stereo overlap.
A previously gleaned picture of a developer’s SteamVR settings window seems to show that it may very well be portrait, and with the same 1.4 base render target multiplier as the Vive (suggesting similar lens properties).
Not that we had a choice. Pre order delivery’s already backed up to September!
Yes it appears that same res as vive pro but RGB but bigger FOV will relegate the actual perceived definition to that of the pimax 5k+ if the lenses are no better. Only time will tell though. Imagine those sweet XTAL lenses with native RGB led 4K/eye panels, talk about pretty! Too bad the valve index FOV is basically like the small setting on the pimax though, while an improvement, it would still leave much to be desired!
Either way too much speculation.
Perceived SDE Valve Index should look better. Clarity by description Valve Index should loom better than Vive pro & likely Pimax 5k.
And yet that still small FOV;( I will wait to see if HP brings out something competitive with higher res!
Yes max of 130. But you can move the display&lenses closer to your eyes instead of moving the whole HMD so it lets you really dial in the fov. It’s going to be close to pimaxs normal mode for a lot of people
Embezzelment of the footwear emergencies fund is no laughing matter. 
Ha , I tried that, but when I went to order, it said I needed a U.S. credit card
I even created a new us account but that tripped me up.
How can you get a 130fov headset to gain another 20 degrees? 20 degrees is substantial!
Valve Index not 130 FOV of course, it’s same as Vive without face cover. I see renderer headset mirror and comparing with Vive render - is same FOV about 110. Valve lenses more flat and more people must see all rendered FOV and even display edges.
Just believe it’s not 130 FOV, maximum 110-112 horizontal FOV. Lenses diameter only 48-49 mm on photo and it’s near not Pimax FOV (Pimax Small Fov still more than Valve Index).
But, of course, Valve Index it’s solid HMD in overall - image, comfort, sound, tracking and controllers.
i also have a feeling they’re lying on the increased fov…saying it’s “20 more than than vive!” why not just say it’s 130 then? getting closer to the lenses doesn’t count @valve…
My biggest issue is with Index confirmed by RTVR and tested
Low resolution panels
LCD Black levels
God rays worse than vive pro
Unavailable to steam account holders outside EU and US
Obviously this is a well polished device but artifacts like god rays are the last thing I expected from Valve
This has not been reported by any other hands on and norm from tested said he did not see significant god rays.
https://www.reddit.com/r/ValveIndex/comments/bj5r6z/handson_with_valve_index_and_impressions/em5ohre
Also
“the 5 degree canting didn’t give me eyestrain”
Q:”Index Vs. HP Reverb which is more noticeable upgrade?}
A:”probably Index for FOV and refresh rate. we need more time with both”
Ben Lang from Road to VR absolutely confirmed this with his hands on review
“Valve’s dual-element optics might be focused on a wide field of view and large sweet spot, it seems to have come at the cost of an increase in internal reflections (god rays). Moderately high contrast scenes cause significant glare which unfortunately detracts from the other benefits in clarity”
Well then we have at least 2 different views.
Also No other hands on mention god rays