Increasing age is the dominating factor for the onset of cataracts and AMD because of physiological and biochemical changes due to old age. Living (geographic location) and working environment can also cause problems.
PMC Article April 2013
Astaxanthin neutralizes free radicals thereby reducing the ROS (Reactive Oxygen Species) in your body, staving off age related diseases like macular degeneration. It also boosts the functioning of your immune system by increasing the number and activity of T cells and macrophages, two kinds of protective cells that fight infection and cancer. Unlike other antioxidants, astaxanthin is available both inside and outside the cell wall allowing it to fight free radicals that are attacking the cell.