Macular Degeneration does not always affect both eyes at once, and sometimes the worst affected eye can interfere with reading with the better eye.
One solution is known as a blanking patch, and these are available from any optometrist.
Many people come up with their own inventive ways of achieving the same thing, by using a folded cloth or tissue, as seen in the picture above. Sometimes a grandchild’s toy box is ransacked for a pirate’s patch!