Maybe. There are different types of drusen. Soft drusen are thought to be the biggest risk for vision loss. They can lead to large areas of retinal loss with "dry" macular degeneration, or for reasons that have yet to be fully understood, lead to a break in the foundation layer of the retina and allow blood vessels to grow and destroy the retina-termed "wet" macualr degeneration.
VA loss in AMD. Drusen are features of dry ARMD but no one knows fully if they cause blindness or more likely, if drusen are part of the constellation of findings that progresses to wet ARMD in some eyes and geographic atrophy (GA) in others or neither in yet others.
No. Drusen do not themselves cause vision loss. In advanced amd, vision is loss because: in 'dry' amd, the light sensitive cells are lost (the photoreceptors) in 'wet' amd, scarring of the retinal occurs at the end stage of the process.
Drusen. Drusen if present in the macula can be associated with macular degeneration.