Since the first eye I keep misjudging kerbs and putting the milk jug down next to the mug. Is depth perception part of this too?

Right eye done, left eye booked for the 12th of August, and I am counting the days for a reason nobody warned me about.

It is not the brightness this time, that has settled. It is that I have stopped being able to judge where things ARE. I put the milk jug down on Sunday about two inches to the left of the mug and poured it straight onto the tablecloth. I have caught my toe on the same kerb outside the post office three times. Coming down our stairs I now do the thing my mother used to do, one hand on the rail, feeling for the next step with my foot like a woman testing bath water. I am 71 and I did not expect to acquire an old lady's staircase walk in the space of a month.

Nobody at the clinic mentioned this at all. They talked about colour, brightness, drops, driving. Not one word about not being able to find my own kitchen table. Is this a known thing between the two eyes, or has something else gone on? And does it go the moment the second one is done, or is there more settling after that?

Known thing. Very known thing. I did the same with a teapot and a worktop and I still maintain the worktop moved.

For me it went almost immediately once the second eye was done, within days. The bit that lingered a fortnight or so was reaching for door handles, I kept grasping air just short of them. Your brain has two eyes sending it wildly different pictures and it is trying to build one world out of them, so it hedges. Once both eyes agree it stops hedging.

Stairs were the worst of it for me too. Two things that actually helped, neither of them clever.

One, I stuck a strip of white tape on the edge of the bottom step, because that is the one that gets you. Two, when I really needed to judge a distance, threading a nut onto a bolt for instance, I just shut the unoperated eye. One eye gives you no stereo depth at all but it does give you a picture the brain isn't arguing with, and it turned out to be better than two eyes disagreeing.

Sixteen days is not long, Betty. Take the stairs like an old lady for a fortnight and don't be proud about it. Falling is the thing to avoid here, not looking daft.

Add pouring tea into a cup that isn't quite where you think to the list. I did that twice in my gap and blamed the cup both times.

Betty, what you are describing is expected, it is well recognised, and it is not a sign that anything has gone wrong with the operated eye.

The direct answer first. Judging distance uses two mechanisms. One is stereopsis, the comparison of two slightly different images from two eyes, and it does the fine work in the near range, roughly arm's length, which is precisely where a milk jug and a mug live. The other is a set of single-eye cues, shadow, relative size, texture, motion, which carry longer distances such as kerbs and stairs. Between operations both mechanisms are disturbed at once. Your two eyes are now sending images that differ not just in clarity but in brightness, contrast and, importantly, in size, because a lens implant magnifies the image slightly differently from the natural lens it replaced. When the two images differ in size, a condition called aniseikonia, the brain cannot fuse them cleanly, so it downgrades stereo depth and leans on the cues from the better eye. That is the two inches to the left of the mug, and it is also why your foot has started asking the stairs for confirmation.

What it depends on, in practical terms: the size of the mismatch between the two eyes drives how strong the effect is, which is why the people who notice it most are those whose two eyes are furthest apart in prescription, and why the eye that has been operated on and the eye still carrying a dense cataract are about as far apart as they will ever be. Timing: for most people it resolves quickly once the second eye is done and the two images match again, though a short period of recalibration afterwards, days rather than months, is normal. Harold's trick of closing one eye is sound reasoning, since one clear image beats two that conflict, and covering the unoperated eye for close work is something people do throughout this gap.

Two things I would separate out from ordinary in-between wobble, because they are not this. Sudden onset double vision, particularly if images sit one above the other rather than side by side, is worth reporting rather than waiting out. So is any new shadow, curtain or shower of floaters in the operated eye, which needs same-day attention. And if the near-misses on those stairs are turning into actual falls before the 12th, tell the clinic now rather than after, because scheduling and the risk of a fall are things they will want to weigh together. The site's account of having the second eye done describes this imbalance from the patient side, but only your own team can tell you whether your gap needs shortening.

Left eye done on the 12th as planned and I am pleased to report the kitchen has stopped moving.

Honestly it took about four days. On the Sunday I reached for the kettle and just picked it up, no hovering, no adjusting, and I stood there feeling ridiculously emotional about a kettle. Stairs are normal again. Kerb outside the post office remains where it always was.

The tape on the bottom step is staying though. Harold is right that it is the one that gets you.