I’d been thinking about writing a post about why I’m wearing glasses full time. I got distracted by thinking about the phrase “blind as a bat” and whether this can be the basis of a scale of measurement. 

That is, if someone is blind as a bat, meaning completely blind, we can say that person scores 1 on the bat scale. 

Thinking further, since two bats don’t see any less than one, we can establish that one is the upper limit of the bat scale. Also, how can someone see less than nothing at all. 

I think that zero would be the other end of the scale, meaning that a person with perfectly normal eyesight would score a zero on the bat scale.

To illustrate this further, before I had lasik eye surgery, I’d score 0.75 on the bat scale. After lasik eye surgery, I score about 0.1 bats. 

I’m aware that some folks have better than normal vision, but I’m not sure how to express this on the bat scale. My first inclination is to use negative numbers. I’m not sure where the lower limit would be. 

Besides, -0.3 bats sounds stupid.