1) Currently a lot of other services ask people to take "x" number of footsteps away from the screen to approximate "y" feet from the monitor. Using this context, I'd argue that the variation in arm length isn't as dramatic as variation in foot size. Ultimately though, when we're using near vision as a proxy for distance vision, the natural variation in arm length isn't crucial. But! Once we roll out our distance vision check, we won't be relying on arm length.
2) Will leave this to Kristine.
3) Interesting. Hadn't thought about this one. My guess is no because the most important ratio is optotype size:testing distance. (Optotype = the numbers/letters on the screen that a patient is reading)
4) It's possible and we'll need to pressure test this against gold standard in-person maneuvers.
5) Same as #4. Also this is a particularly interesting point because a similar problem exists in person. As an extreme example, I've had patients come in who've memorized the letters in the 20/20 line because they were very motivated by one thing or another (e.g getting their driver's licenses renewed.)
6) Is this the "which is better, 1-or-2" question? All I'll say is that there are a number of interesting ways we could try to simulate these.
Hope this answers some of the q's! Thank you for all the thought that went into them.