Hacking reading glasses

This is part of the post-cataract adaptation saga.  I had a Technis Symfony toric IOL put in my left eye 4 days ago as the first of 2 cataract surgeries.  While I have concerns, I can certainly see better than without the lens.  This hack is part of exploring my new vision.

The first thing I did was to remove the left lens from my “good” $$$ glasses – 8 month old progressives I wear when I’m out of the house, and always when driving.  That gave me something I could drive with and a sort of monovision so I could read labels etc at the store.  Worked pretty well – certainly much better than with the left lens in.

Then I took a pair of single vision “reading” glasses – maybe +2 or 2.5D from my normal distance prescription – that I use for reading/bench/computer work at maybe 13″ and removed the left lens from those.  That provided a more extreme monovision for around the house that let me read (right eye) and still have some moderate distance vision – with the less-perfect-than-I’d-hoped-for left eye.  I used those at the computer, but got a headache after the first extended session.  I put a loose cardstock patch over the left side of the frame, and that pretty much fixed the headache.  Later, and in shorter sessions, I got away without the patch.

I was a little concerned that I was teaching my brain to ignore the left eye when I used those glasses – which I did a lot.  And since the left eye wasn’t great anyway, that extra training didn’t seem like a good thing.  But in order for the left eye do any work at that distance, it would need a normal reader/magnifier lens.  Off to Walmart.

The donor glasses and measurements

I tried a few readers, and decided +2.0D let the new left eye see about right at 13″.  I chose a $6 pair with largish lenses to give me something to work with.  I popped one lens out (the wrong one, as it turns out) and when I held it over the missing lens of the good old readers, it seemed to do about what I expected.

Of course I’d need to set the PD correctly.  The glasses I’ve gotten from Zenni were ordered with 65mm PD, but since these were for closer work, I expected my eyes to be more converged.  Holding a ruler up to the centers of my eyes and looking into a camera about 13″ away, I took pictures that showed a PD of ~62mm.  Now I have a target.

To find the optical centers of the old and new lenses, I set up a laser diode pointing down at the bench, and marked where the beam hit.  Holding the lens near the laser, I moved it around so the beam hit the same spot on the bench as without the lens, and marked the spot the laser was going thru the lens with a black Sharpie.  As a double check, I moved the lens around and verified that I saw the shadow of the Sharpie mark when the spot was in the undeflected place.  With marks on the right lens of the glasses and the loose +2 lens, I was set for the next step.

Putting the new lens in

In an awkward maneuver requiring more hands than I had, I held the loose lens up to the frame and slid it back and forth so the 2 marked spots were 62mm apart according to the ruler I was holding with my left foot.  With a combination of trying not to let the lens move and a mental snapshot of about where it had been when the PD was set right, I marked the outline of the frame on the lens with a Sharpie in my third hand.  A double check showed the spots still about 62mm apart.  Good.

The lens didn’t completely fill the frame, but looked workable.  So how do I cut the lens down?  One corner just needed to be relieved a mm or so, so I put on safety glasses and took it tentatively to the belt sander.  The acrylic lens sanded away perfectly, and it didn’t feel at all like the lens was about to shatter.  I have no idea why I thought I’d know what that felt like, but I seemed to.  Removing the rest of the lens down to the Sharpie outline (maybe 1/4″ in places) was quick and uneventful.  I started shaping the edges so the front surface of the lens would fit into the concave inside of the frame.  A few cut and try iterations, and it was ready for final fitting with a file.

I rotated the lens a little to let it sit where it wanted in the places not designated for the final fitting.  I think that was a good idea, and probably avoided unpleasant surprises about having removed too much.  Of course since there was no astigmatism to worry about, the exact orientation of the lens didn’t matter.  A couple more iterations with a file, and the lens snapped in, and has been there ever since!

Do they work?

When I put them on, things seemed about in focus for both eyes, but the difference in magnification between the eyes was very evident in “swimming” movement when I’d turn my head.  No surprise, but duly noted.

I could vaguely see the center spots on the lenses, but had trouble matching them up.  Turns out when I was looking straight thru the centers of the lenses, the spots were so closely superimposed that I missed them.  That test passed with surprisingly flying colors.  I cleaned the heavily handled lenses and took a pic showing how the new lens doesn’t fill the frame.  Pretty close, though.

I sat down at the computer to write up these notes (while wearing the new glasses) and the big limitation leaped out:  The only way these are practically useful is when I’m looking right thru the lens centers.  Image fusion suffers a LOT anywhere else.  Interesting.

On the comment about having removed the wrong lens from the OTC readers:  I arbitrarily took the left lens out to fit into the other glasses.  If I’d taken the right lens out, it would have left the option of trying those readers as near-vision monovision, with 13″ for the left eye (new IOL plus the +2 reader lens) and my naked old right eye with its 7″ working distance.  Not a big deal, and fixable for another $6.

Hmmm – just tried it with the new readers upside down.  That worked well enough to let me see how it worked/felt – about as I expected.  Interesting, though not terribly practical.  Done.

It’s not clear whether these will be useful or whether I’ll pop the new lens out and use them one-lensed as they started.  I’ll post an update some time.  But it was an interesting experiment in any event.

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One Response to Hacking reading glasses

  1. Jim Harvey says:

    That’s a great hack! Probably would have worked better if right side wasn’t progressive. I tried progressive once and hated them.

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