My uncle has swelling of the cornea and vision loss in his right eye. What could cause this. He is awaiting results from a specialist, but I'm curious?

Abnormal cells. This sounds like fuch's dystrophy. Abnormal cells on the inside of the cornea stop doing their job. They stop 'pulling' fluid out of the cornea. It swells, vision gets cloudy, and surgery may be needed to replace the cells.