As a severe myopic, it is no wonder I have always had a certain interest in ophthalmology. And just the other day I had reason to ponder the peculiar Dutch dominance in the history of optics and ophthalmology.
When I was a nearsighted young school boy in Sweden, my mother brought me on the bus into town every fall to see the eye doctor. He must have been in his eighties, a tall man with a bow tie and a long white lab coat. His office was adjacent to his apartment in a white stucco building from the early 1900’s. It was a dimly lit space with dark, angular furniture. The doctor said very little as he made me read the letters on the Snellen eye chart while placing varying lenses in front of each of my eyes in an antique looking device, and while he peered into my eyes while holding a thick magnifying lens that focused a piercing light into my tearing eyes one by one. I could smell his skin and his hair as he leaned into me.
After each of my annual exams, he always sighed and wrote out a stronger eyeglass prescription with an old black fountain pen. He carefully blotted the prescription paper and always said to my mother “don’t let him read too much in bed.”
As my glasses got stronger, I became aware that if I looked at road signs or traffic lights out of the corner of my eye, the colors didn’t line up. The red outer circle of the Swedish no-parking signs would overlap one end of the inner blue circle, and there would be a space between the two colors on the opposite side. In the same way, the red, yellow and green traffic lights wouldn’t be straight on top of each other, but at an angle. I learned in school that red light passes straighter than blue or green light through a prism, like the outer edges of my old-fashioned glass lenses.
As I approached my teens, working with an old viewfinder camera and black and white darkroom equipment, I understood why it was harder to read in dim light: a dilated pupil, just like a wide aperture, creates a shallower depth of field than a smaller one, and the ultimate small aperture, a pinhole, can replace the lens in a simple camera or even your high powered eyeglasses in a pinch.
In medical school, I learned to do a neurologic exam, and the bedside test for visual fields. Donders’ confrontation, as we called it. I figured Donders was a Dutch name, but never gave it much thought.
The other night, wondering why my EMR incorrectly defines visual acuity by “Snelling” rather than Snellen, it struck me that Snellen was probably a Dutch name, just like Donders. A few minutes with my iPad and Dr. Google made me rediscover how much I enjoy medical history.
It turns out Donders built an eye clinic and hired Snellen to run it. They invited their friend Einthoven, who would later invent the EKG, to help in their research. Einthoven studied chromostereopsis, the phenomenon whereby red objects seem closer than blue objects. Donders, Snellen, and their wives were the subjects, and Einthoven’s paper became his doctoral thesis. It seems that chromostereopsis has something to do with the fact that red light travels straighter and that our eyeballs are angled inward when we look at objects up close, which makes blue objects seem ever so slightly blurry.
So, anyway, my little exploration reaffirmed that if I ever cut back my clinic hours, I’ll read more about the history of medicine.
“A Country Doctor” is a family physician who blogs at A Country Doctor Writes:.
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