You've just been reading the wrong sort of "everything".
You can dilate your pupils permanently with eye drops designed to do that, but if a bright light shines in your eye, you'll be blind as a bat for a couple of minutes under the night sky, dilated pupils notwithstanding. It's intuitively kind of evident from everyday experience, e.g., persistent after-images from bright lightsources.
The way rhodopsin works is quite fascinating. It's an integral cell membrane protein: a molecular machine that is triggered by a single photon. The photon causes the molecule to pull one proton (hydrogen ion) through it's tubular interior from one side of the membrane to the other. During this process it changes conformation (shape) and needs to reset itself before it's ready for another photon. This requires some biochemistry (and energy) and takes some time.
http://www.nature.com/nature/journal.../406653a0.html