Any question answered...

A question to do with Optics:

As the iris of the eye gets larger to adjust to low light levels. Why does this not create a very shallow depth of field for our vision (or does it?).

And for animals who can really adjust their iris's from pin point small to very big (like cats) do they get a change in focal lengths?

it doesn't give shallow depth of field visually, but as the iris becomes larger then the more peripheral rays focus infront of or 'behind' the retina confusing the image more noticeably than during the day with a small iris. Some people (generally with small uncorrected rx) can find their vision becomes noticeably poorer in bad light due to this.

And magnets.