More on this theme: A couple of weeks ago, I discovered that I couldn't focus on the focus screen of a DSLR camera. I was trying to take astro-photos, and focus is key to sharp images. Too close, couldn't focus at all; too far back, and and the frame around the focus screen occluded the view.

As the optometrist warned, my eyes have reached "that certain age." Harumph. Time for reading glasses.