Several partygoers at a Russian rave lost part of their sight to damage from a laser light show, Reuters reports. Dozens have appeared at Moscow hospitals for treatment of retinal burns. Loss of vision is as high as 80% and "regaining it is impossible," according to one ophthalmologist. The problem was apparently caused when lasers reflected into people's eyes off tents erected as rain shelters. "I immediately had a spot like when you stare into the sun," said one raver.