Depth of field

Because of a family history of glaucoma and consistently high pressure in my eyes, my optometrist likes to give me a depth of field test every time we meet. Also, she's probably secretly a masochist.

It's the same every time.

Her assistant brings me into a dark room, slaps a patch over one of my eyes (at which time I always ask for a parrot), positions my bony chin in the plastic cup of a big machine that looks like a puppet theatre, and gets me to stare at a small dot of light on the back wall.

In one hand I have a clicker -- so it feels vaguely like Jeopardy -- in the other, a tissue to catch the tears from the pupil dilation.

When the test starts, I'm supposed to continue staring at the dot while little points of light ping around the circumference of the single point.

Every time I see a ping of light, without actually averting my eyes from the centre point, I'm supposed to hit the clicker.

The thing is....you're never supposed to take your eyes off dot. Not even if you're sure you saw something OVER THERE! There it is....no wait, stare at the dot.

Anyway, you can't imagine how hard it is to stare relentlessly at the dot of light. Particularly when the really interesting stuff is actually happening over to the side, or down there, or maybe behind me. It seems unnatural NOT to look.

And the clicker gives you a vague sense of competition. Like, maybe I could actually win something if I become the best depth of field subject in my doctor's tiny office.

What usually happens is I make it through one eye just fine, but by the time I get to eye number two I'm thinking "oh, what the hell", and I'm following the pretty lights all over the back wall.

This is about the time that the machine, and the increasingly more impatient assistant, sound a warning.

Anwyay, you don't need to be an optometrist -- or a brain surgeon -- to figure out that today's topic is all about focus.