This NYT Article outlines a research project by some folks over at Columbia which can take a high-resolution photograph of someone's eyes and determine exactly what they were seeing, and even exactly what they were focusing on:
Dr. Nishino and Dr. Nayar plan to try their corneal imaging system with archival photographs. "It will be fascinating to go back and look at photographs of important people like John Kennedy," Dr. Nayar said. "From a single image of the eye, we may be able to figure out what was around him and what he was looking at."
...How cool is that?!