Gas station without pumps

2016 January 18

Reading glasses

Filed under: Uncategorized — gasstationwithoutpumps @ 18:12
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At my last eye examination, my ophthalmologist told me that my astigmatism had gone away—I now needed a simple –4 circular correction in my right eye (my left eye is difficult to measure correction for, as I have essentially no central vision in that eye).

I have almost no accommodation left in my eyes—my focus range without glasses is about 22cm–26.5cm (3.75–4.5 diopters—a diopter is the reciprocal of the focal distance in meters).  With –4 diopter glasses, my focus range should be 2m—∞, which seems about right for my distance glasses (I don’t remember their prescription).  I just bought a new set of computer glasses with –2 diopters, giving me a focus of 36–52cm, which would be 1.9–2.8 diopters after correction, or 3.9–4.8 diopters before correction, slightly further away than I measured directly).

For bicycling, my distance glasses are fine; for screen work, my computer glasses are fine; and for reading paperbacks I can go without glasses. For really close work like soldering, I want reading glasses—even weak ones would let me get close to the soldering iron without having an exposed eyeball that could easily be damaged. Reading glasses would also be a good substitute for a jeweler’s loupe when looking at the markings on tiny capacitors or integrated circuits

So today I went to the discount store about 1/4 mile from my house and bought 3 pairs of reading glasses at $2 each: +1.5, +2.5, and +3.5.

Three pairs of reading glasses at $2 each.

Three pairs of reading glasses at $2 each.

I tried measuring my focus distance (approximately) for each of the glasses:

glasses min focus max focus diopter range imputed eye range (diopters)
 distance (–4?)  1.5m?  ∞
 computer (–2)  35.5cm  51.5cm 1.94—2.82 3.94–4.82
 none (+0)  21.5cm  26cm 3.85–4.65 3.85–4.65
 +1.5  16cm  18.5cm 5.41–6.25 3.91–4.75
 +2.5  13.5cm  16.5cm 6.06–7.41 3.56–3.91
 +3.5  13cm  14.5cm 6.90—7.69 3.40–4.19

None of the focus measurements are very exact—I was using a ruler held against my face for all but the distance measurement, which was guesstimated—but they are consistent enough to be a useful guideline for me.  I expect that I’ll use the +1.5 reading glasses for soldering work for now, and the others I’ll keep in my toolbox for closer work

Note that even with changing glasses, I have a lot of distances that I can’t focus at—and I expect those gaps to get wider as I age and my eyes become more single-focus.

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