Even though I’m the wrong side of 50 and pay taxes and sometimes watch Newsnight, I still can’t stop myself from taking the default position of a child of six in certain situations.

And here we are in one of them– a medical examination.

This is one of the easiest you can undergo, truth be told, for it’s just an annual eye check up and an excuse to spend a week’s salary on some fragile reading glasses lovingly crafted by a French designer, universally available ever since the free and forgiving NHS bottle top ones disappeared years ago off the opticians’ shelves.

But no need to get my credit card out yet. First we have a full half hour of a very capable lady wrestling with a stack of lenses, a contraption fixed around my head and pointing towards the far wall, and me.

Tell me whether the circles on the red patch or the green patch look clearer, she says, pointing towards the wall. Green, I say. Off comes a lens and on goes another. Red or green? She asks. Red, I say. So far, so easy to dispose of a couple of hundred quid.

But then it starts getting trickier. Read the letters on the bottom line, she says. A few seconds later, she adds: Out loud, please. Oh, right.

But then it happens. My heart starts beating faster. I feel a line of sweat chilling on my forehead. Yes, here it comes. The slight feeling of nausea, the drying of the mouth, the vague wish that I’d gone for a wee before she called me in. That trusty old friend hypochondria has turned up on cue once again. As the letters get smaller, and she says something innocuous like try again or hmm, okay, the part of my brain that isn’t screwing itself up to differentiate an F from a P is in overdrive. This could be serious.

I could have cataracts, which would surely mean an operation with me awake with my eyes open and a knife or a laser beam.

Put your chin on this machine and stare straight ahead while I blow a little puff of air into your eye, she instructs me. The chin wobbles. The eyelid wobbles even more. I need your eye to be open for this, she explains. I’m checking the pressure. Pressure? My eyes have pressure? I’ve obviously said this out loud, in a six-year-old voice, for she pats my shoulder reassuringly. Just checking for glaucoma, she says. It’s fine.

Next, I have to look to the right of her shoulder, then above her head, and eventually complete a circle of observation while she shines a thin bright light into each eye. I can see what looks like the surface of a dry orange planet with a lot of rivers running across it. Either that or a moon has got lost and has just plunged through a high street optician’s roof. I’m very glad when that bit is over. I’m guessing that I’ve just had a glimpse of the veins in my eyeball, though I’m too nervous to ask. Anyway, I don’t like seeing what’s going on in my head.

Would I like her to take a photo of each eye, she asks? Why not, I think. In for new lenses and frames, in for a £15 digital image of two clearly atrophying organs. In fact, I’m rather glad I have once I’ve seen them on screen. They are not unlike a particularly good sunset over the Med, though without the sea and sand and stuff, obviously. I bet the rest of my organs don’t look that good.

Well, she says, smiling (which I can’t help but interpret as a precursor to the delivery of bad news).

A bit of wear and tear, but there’s no need for new long-distance glasses yet. However, you do need new reading glasses. I stand up and head for the sign that says Police. And Dolce and Gabbana.

I breathe out. Blimey. All that searching for nasty diseases and I’ve just got a bit of wear and tear. The relief. I have to stop being so neurotic. It was only a standard eye test, I tell myself. But I can hardly get a word in edgeways.

Wear and tear, says a voice between my ears.

How on earth has that happened, then?