An article about vision anomalies claims that the increased sensitivity to UV light in aphakia sufferers has been put to use to detect UV signal lamps from German submarines in World War II.
However, aphakic patients report that the process has an unusual side effect: they can see ultraviolet light. It is not normally visible because the lens blocks it. Some artificial lenses are also transparent to UV with the same effect. The receptors in the eye for blue light can actually see ultraviolet better than blue. Military intelligence is said to have used this talent in the second world war, recruiting aphakic observers to watch the coastline for German U-boats signalling to agents on the shore with UV lamps.
I have not been able to find any evidence of the German (or any) navy using UV lamps for signalling from submarines. If this technique had indeed been employed, it seems likely that the "agents on the shore" would have had some technical means of detecting the UV signals (short of having to be aphakia sufferers), so the "military intelligence" would presumably have been able to use the same technology for watch for submarines (without relying on finding people with a particular eye condition).
Did the German navy use UV lamps for communication from submarines in World War II?