Full eye discoloration

My very old kitty, Ginger, had her entire left iris turn from green to brown last week (I believe that the discoloration actually affected her whole eye, but it was hard to tell for sure over the pupil). The change happened within a day. She did not have any brown spots before, so I am fairly sure that this would not be a melanoma. Also, the discoloration has faded gradually over the past week. Her eye is now a kind of muddy green color.
I am wondering if anyone has had any experience with this happening their kitties before? Ginger is almost 22 years old, and I am at the point where I don't want to subject her to vet visits. She deserves to live out her life in the comfort of her home. BUT, I would kind of like to know what may be going on with her eye! My best guess is that she may have scratched it and possibly infected it and that the brownish color may have actually been blood cells fighting the infection. She does normally have discharge out of that eye and paws at it from time to time, but there hasn't been any change in the amount or color of discharge since the discoloration of the eye.
I was never able to get a great picture of the eye, but I am including the best ones that I have. The first was taken the day that I first noticed the change, and the second is from toda
Thank you for any insight or advice that you may have! [emoji]128512[/emoji]

Uveitis?  Which I've read can be painful. Of course, it could be something completely different than that.

This is definitely something of concern.  Can you at minimum discuss this with your Vet over the phone and send the pictures? 

I understand not wanting to subject her to Vet visits if she HATES them, but what if she is in pain?  That would be worse, wouldn't it?  Not saying she is, but she could be. 

Here is an article about eyes changing colors, if it helps at all:  https://www.vetinfo.com/cat-eye-color-changes.html