What exactly is the significance of the references to "fine eyes"?

Does JA mean "big brown eyes", that some people have? Or even deep dark blue eyes?

Or is this is reference to something like the dilation of the pupils, which is a signal of attraction? And which can cause people to "find eyes attractive".

Presumably Darcy has had the opportunity to look into those eyes.

I'm not sure how the physiology of pupil dilation, and attraction works, but presumably this is caused by hormones inside Elizabeth's mind.

Who actually takes the initiative in attraction? Isn't it always the woman? By some signal, with the eyes, to which the man responds.