THE PROOF OF MY INNOCENCE (JONATHAN COE) AND OPTICAL DEFECTS

     Phyl is having a good wander around and occasionally lifting up my glasses so that she can get a better look at everything. Adam notices this and says:

Are you long-sighted, or short-sighted, Phyl?

She laughs nervously.

Long, short and everything in between! she says, and then zooms in on a glass cabinet at the centre of one of the walls.

 

That Phyl, in order to pass herself off as a bibliophile, has put on someone else’s glasses, which is why she has to lift them up to be able to see properly. Adam’s suspicions are well founded: it is not possible for the same eye to suffer from both myopia and hyperopia simultaneously, as they are opposite optical defects. In myopia, the eyeball is usually too long and the image forms in front of the retina; that is why it is corrected with diverging lenses. In hyperopia, the opposite is true: the eyeball is usually too short and the rays would come together behind the retina, so it is corrected with converging lenses. I am severely short-sighted and my wife is an incorrigible farsighted person, and so far our offspring have managed to escape both conditions: they must have taken the average of our eyeballs, so to speak.