These genes were thought to lead to blindness 100% of the time. They don't.

Genetic variants previously believed to cause blindness in nearly everyone who carries them actually lead to vision loss in less than 30% of cases, according to new research analyzing data from over 800,000 people in major biobanks. The study challenges the traditional understanding of Mendelian diseases, which were thought to have predictable outcomes based on single genetic mutations. This discovery opens new treatment possibilities by identifying protective genes that prevent disease development despite carrying harmful variants.