Brain shrinkage? You joking? Not trying to undermine your suffering by any means, but what you're saying just isn't physically possible. I will say that based on my own experience your eyes can look more sunken in after severe and quick weight loss, and can take some time to look normal again even after you've gained your weight back. A couple other possibilities- hypothyroidism can make the skin around your eyes puffy, making them look sunken in; there is also the factor of collagen loss in AF which can also make the eyes look more sunken in due to the thinning of the skin around the eyes, leaving many of us with those lovely "dark circles" under our eyes.
You can try to put cold compresses over your eyes to counteract the puffiness, or you can get yourself a good concealer to put on the skin. Guarantee they won't look as sunken in. That is of course if this post is serious and not a joke!