No convicts died, although there were reported cases of dysentery, diarrhoea and nyctalopia. This may also cause concomitant nyctalopia. A peculiar outbreak of Nyctalopia or night-blindness affected many of the prisoners in 1806. It usually starts with decreased vision at night, or nyctalopia. Nyctalopia is the earliest ocular sign of VAD. Nyctalopia (night blindness) is one of the first signs of VAD.