Bhubaneswar (Odisha) [India], March 17: Worldwide estimates put the figure for those with glaucoma at around 80 million. Approximately 50% of them are unaware of it, and this number may be even higher in underdeveloped countries. This is because glaucoma is asymptomatic until a very late stage. If untreated, glaucoma may progress to blindness. Glaucoma, an eye problem associated with increased eye pressure, is called the 'Silent Thief of Vision' because the vision once lost to it cannot be restored.