Diabetes does its damage quietly, and Matej Sklenář's story shows how far that silence can go. The 33-year-old lived with elevated blood sugar that produced no felt symptoms, a pattern doctors encounter constantly. People can carry the disease for years without knowing it, by which point serious complications have already taken hold. Diabetes sits among the leading causes of blindness in adults, and Sklenář was heading toward exactly that outcome. The article describes his ordeal as life in total darkness. A unique operation at the Ophthalmology Centre of Bory Hospital changed the course of his condition. Surgeons there restored what the disease had been steadily eating away. Cases like his are the argument specialists keep making for regular blood sugar testing, even among people who feel perfectly fine.