A study about the connection between an elder's eyesight and depression was conducted recently at the University of Alabama, Birmingham. The study showed that elders that don't get their eyesight checked regularly, and their glasses updated, showed more signs of depression.
This shouldn't surprise anyone. Many elders don't hear well. They have other health problems. They lose so much outside stimulation, that if their eyesight isn't kept as sharp as possible, they will just decline more. Of course they get depressed.