Light Seal Numbers Decoded

The information below has been pieced together by Reddit User "_Avalanche_", after doing a lot of reading and the use of Apple's Vision Pro Size Help tool).

THE NUMBER PART

• 11, 12, 13, 14

• 21, 22, 23, 24, 25, 26

• 33, 34, 35, 36

The first digit refers to how far forward your forehead and cheeks protrude relative to one another.

• "2" is average/typical.

• "1" means your forehead protrudes further forward (relative to your cheeks) than average.
  This is why if you start with a 23W in the size help tool, and you specify "too much pressure on my forehead," then it's going to recommend that you switch to 13W.

• "3" means your cheeks protrude further forward (relative to your forehead) than average.
  This is why if you start with a 23W in the size help tool, and you specify "too much pressure on either cheek," then it's going to recommend that you switch to 33W.

The second digit refers to how deep the light seal is. (Likely relative to your cheek position, not your forehead. If so, this is causing a lot of confusion, since most photos are taken from above.)

• "1" & "2" are the shallowest, "3" & "4" are moderate in depth, and "5" & "6" are the deepest.

  • This is why 21W is the most common recommendation, as you want your eyes to be as close to the screen as possible in order to increase your FOV (field of view).

  • This is why 25W is the most common fit for those with Zeiss optic inserts, in order to make some room for the inserts, but also to make room for the vertex distance.
    Speculation: If your eyeglass diopter isn't significant, then this big jump may likely be more than necessary, at the greater expense of decreasing your FOV.

  • This is why if you start with a 23W in the size help tool, and you specify "I'm receiving a device alert — Too Close to Displays," then it's going to recommend that you switch to 25W.

  • This is why if you start with a 23W in the size help tool, and you specify "I'm receiving a device alert — Too Far from Displays," then it's going to recommend that you switch to 21W.

  • Dubious speculation: This number may be relative to your cheek position, which might explain why there are no sizes 15, 16, 31, or 32. (If this is confusing, don't worry about it; it's not important, and I may be wrong. However, I'll elaborate in case it interests you...)

    • For 15 & 16, your forehead is further forward (relative to your cheeks) than most, so simply by choosing a size that starts with "1", some depth has already been added for your recessed cheeks. (If any deeper, the bottom of the light seal would be untenably long.)

    • For 31 & 32, your cheeks are further forward (relative to your forehead) than most, so simply by choosing a size that starts with "3", some depth has already been subtracted to make room for your protruding cheeks. (If any shallower, the bottom fo the light seal would be untenably short.)

  • Edit: I'm starting to suspect that odd/even numbers change the shape around the cheek area. This explains why vertical forehead/cheek adjustments either don't change this number, or change it an even number of digits. On the other hand, horizontal nose/temple adjustments change this number an odd number of digits.

    • If you start with a 23W in the size help tool, and you specify "too much pressure close to my nose," then it's going to recommend that you switch to 24W.

    • If you start with a 24W in the size help tool, and you specify "too much pressure close to my temple," then it's going to recommend that you switch to 23N. [sic] (The 23 makes sense to me. The N does not. Something is missing in my understanding.)

      • Do we have an image that compares, say, 21 vs 23/25, or 22 vs 24/26? (Rather than 21 vs 22/24/26, or 22 vs 23/25.) Evidence either supporting or contradicting this hypothesis is appreciated.

W/N refers to wide/narrow faces. (W adds a couple millimeters of width at the temples.)

• This is why if you start with a 23W in the size help tool, and you specify "it feels too loose or light is coming in," then it's going to recommend that you switch to 23N.

• This is why if you start with a 23N in the size help tool, and you specify "it feels tight and it's squeezing my face" or "too much pressure close to my temple," then it's going to recommend that you switch to 23W.

• What I don't understand, is that if you start with 23W in the size help tool, and you specify "too much pressure close to my temple," then it's going to recommend that you switch to a 23N. [sic] Huh, what? (Is this a bug? This directly contradicts the prior bullet point's suggestion.)

W/N vs W+/N+ light seal cushions:

• W+/N+ don't actually add any extra cushioning, only extra depth.

  • "Huh?" For example, try squeezing both a W and W+ with your fingers. The W+ will squeeze about the same amount as the W insert, until you hit something harder embedded inside the W+. Surprise! After realizing this, I stopped using the + cushions, in order to increase my FOV.

The 23 size was used in most of my tests because of how it overlaps with the available 13 and 33 sizes. In cases where there was no equivalent (e.g., 21 has no 31 equivalent, and 25 has no 15 equivalent), then the size help tool will sort of just do its best:

• This is why if you start with a 25W in the size help tool, and you specify "too much pressure on my forehead," then it's going to recommend that you switch to 13W. (Or from 26W to 14W. Why not switch to 14W for both? Because I speculate that odd/even numbers for the second digit separately change the shape around the cheek area in order to provide horizontal adjustments between the nose and temple.)

• This is why if you start with a 21W in the size help tool, and you specify "too much pressure on either cheek," then it's going to recommend that you switch to 33W. (Or from 22W to 34W. Why not switch to 33W for both? Again, because I speculate that odd/even numbers for the second digit separately change the shape around the cheek area in order to provide horizontal adjustments between the nose and temple.)

I'm sure I still have some details/nuances wrong, but I hope we're getting a bit closer to decoding this. In the spirit of Cunningham's Law, tell me where I'm wrong.

I may revise this post in order to incorporate feedback/learnings from comments. (Or I may just disappear and leave you to figure it out from here, haha...)