If someone's wearing a colored contact lens I would expect iris recognition to not work. That's like trying to use a fingerprint reader with gloves on.

Glass eye I'm not sure about either. That seems along the lines of using a fingerprint reader on a prosthetic hand. Sure, you could mold a fingerprint onto one and scan it, but with a sophisticated fingerprint sensor it's going to look like a fake finger. Do we deliberately make everyone's fingerprint scanner weak to allow someone without fingers to use it?

Maybe the answer is to introduce a "weak mode" option where most users could have the scanner verify "yes, this is a real eyeball," and if someone with a glass eye still wanted to use iris scanning in a way that can be copied by a photo, they have the choice to disable the security measures.

If someone with a glass eye is using a smartphone then one would suspect they are seeing their other, real, eye. This can then be scanned as normal.

You'd think so, but iPhones are incredibly useful to blind people.

https://finance.yahoo.com/news/david-pogue-on-iphone-voiceov...

The first time I saw a blind person using an iPhone on the subway (years ago, I think it was an iPhone 4), I was completely blown away at how much he could do with it.

Personally I think apple should allow you to turn the backlight for the screen off entirely for their use. Perfect over the shoulder privacy and better battery life to boot!

It's called "Screen Curtain" and it's been around for a long time.