I would think it'd be more helpful to me to figure out exactly what my CYA level should look like in the sight glass. Of course, once I know it for 100% certain, it doesn't matter that much as it should stay the same.
There is a shadow and reflection effect inside the vial once you have an opaque amount of solution in there that looks exactly the same as still being able to see the eyeball. It's difficult for me to determine when I've transitioned from seeing the eyeball to not being able to see it any more, but now see the shadow and glare that somehow still looks like a dark circle in the center with a bright area around it.