On Pupils and Spasms and Self-Evident Truths

… but sometimes it’s nice to see objective evidence!

And so here is a quick example of SB, an 8 year-old child who is a reasonably good reader, but whose mother observes him to be putting in considerable effort. It’s not that there’s necessarily anything wrong with having to put work in to read. It’s just that the extra effort to focus and keep place often times misallocates effort, attention, and concentration that should be put into fluency and comprehension.

SB’s entering visual acuity was 20/20 unaided through either eye, but he had to work noticeably harder with the left eye to attain clarity at both distance and near. Here are SB’s auto-refractor findings. The one on your right side is his manifest, and the one on your right is his cyclo only 15 minutes after instilling one drop of 1% tropicamide in each eye. You’ll notice from his manifest that he is experiencing accommodative excess, particularly through his left eye. From measurement #1 to #2 to #3 the minus goes from -0.25 to -1.50 to -2.00. That is all pseudo-myopia of course, and it is knocked out quickly with the relatively modest cycloplegic effect of tropicamide.

Complementary to the spasm tendency of the left eye being greater than the right eye are SB’s pupillary responses to the pupillary dilation component of tropicamide. Here are his pupils 10 minutes after installation of the drops and, as you can see, the left eye (on your right) is more tenacious about holding to his pupillary constriction.

Not every parent wants detailed information about their child’s condition, but SB’s mother very much appreciated the explanation. SB responded very well subjectively to +0.50 sph lenses at distance and near before I instilled the drops, and I had made the decision that we would go with the symmetrical lens powers despite the measured asymmetry. These are “bread and butter” cases and, in this instance I would prescribe that power irrespective of what the binocular findings showed. in SB’s case he measured 2^ esophoria at distance and 2^ exophoria at near, with no fixation disparity and good vergence ranges.

There is no doubt in my mind that certain practitioners eschew cycloplegia as “artificial”, and would never put any stock in auto-refractors preferring instead to hang their hats on manual retinoscopy. In fact, either tool (cycloplegia or auto-refraction) is anathema to them. They would likely derive the same +0.50 OU I Rxed through their own self-evident truths. On the other side of the coin are practitioners who would Rx +0.50 sph OU irrespective of what the findings show. They have their own set of self-evident truths, irrespective of the objective evidence.

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4 thoughts on “On Pupils and Spasms and Self-Evident Truths

  1. Possibly he teared and thus diluted the L as he was dropped? Assuming R eye dropped, then L eye dropped? The other factor probably more involved with infants is the working distance of retinoscopy and autorefractors….not surprised sometimes when an infant is scoped at 12″ and is +.75(in visual contact), and at 16″ scopes +3.00 since they haven’t learned space at 16 inches yet….Thanks for sharing this!

    • Sure, Curt. That’s always a possibility. Yes, I did put the drops in the right eye first, but I always put one additional drop in the left just for that very reason. Regarding the second point, it would be a wash, as whatever difference there is in scoping distance is the same for OD vs. OS. As always, thanks for reading and providing input.

  2. Hah, I’m one of those manual retinoscopy die-hards. I’m curious if you did retinoscopy and were able to scope the plus on him before tropicamide? I know he would have fluctuated all over though and it wouldn’t have been the cleanest of rets.

    Now that I’m delving into syntonics, this would be a classic case where people would say to check for the alpha-omega pupil and to check his functional fields. I’d have been curious to see those on him, see if the asymmetry is reflected even in the functional fields.

    • Thanks for commenting, Justin. I still do pick up my retinoscope, though not religiously. My contention is that a good auto-refractor is a very smart retinoscope, and that there is a qualitative as well as quantitative element to the sampling of the three sweeps it conducts (or with some ARs, five). I did not detect any plus on him before tropicamide.

      Syntonics continues to intrigue me, though my bucket list seems to be getting wider while the bucket narrows. For now I’m content to leave that to others.

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