Making the transition is easy in Photoshop. The trick is NOT to try to put something there that didn't exist in the first place. If you've ever tried to put a catchlight into an eye you know what I mean. It just winds up looking goofy and way too artificial.
While you're working in the eye, you may also want to remove anything there that isn't the catchlight or the pupil. Often subjects will have bloodshot eyes closest to the nose. Use a very light touch with the Clone or Healing tool to wipe them away.
The whole process took me under five minutes on this image. "Eye" think it was time well spent. (sorry...)