Going down stairs, there is a half-second where your foot is already committed and your eye has not yet confirmed where the step is. Most of the time this passes unnoticed, thousands of times a year.
Then one afternoon the foot arrives and the step is an inch lower than it was supposed to be, and your whole body knows about it before you do.
If that has happened to you, the first explanation offered will probably be about balance. Or about being tired, or rushing, or the light.
There is another explanation, and it is sitting on your nose.
The lens you look at the floor through
Progressive lenses — varifocals, bifocals, whatever your optometrist calls them — put the reading prescription at the bottom of the lens. That is the sensible place for it. It is where your eyes go when you look down at a book.
It is also where your eyes go when you look down at the floor.
So the part of your vision aimed at the next step is being magnified for a book that is not there. Edges lose their crispness. Dept…