Mini-Stories: Volume 2

The Snellen Chart by Avery Trufelman

Producer Avery Trufelman is tempted to claim that this is the most iconic poster ever designed, but that would, of course, but hard to quantify. Still, it’s safe to say we have all, at some point, been forced to look at a vision chart. She was originally working on a longer piece about the chart, then, after setting it aside for a while, resurrected it as a shorter piece for this mini-stories episode.

snellen-chart
Snellen Chart by Jeff Dahl (CC BY-SA 3.0)

Everyone knows that pyramid arrangement of black letters on a white background, usually starting with a big E at the top (each line below getting progressively smaller). This is the Snellen chart, named after the Dutch ophthalmologist Herman Snellen, who invented it in 1862.

The cool thing about this piece of graphic design is that it’s actually a tool for testing vision. Patients read off the series of letters on each line. If one gets the majority of the line correct, they move to the next line. Ophthalmologists generally memorize the chart so they can evaluate a patient’s vision without squinting at the chart themselves.

There are various versions of the chart. Most start with E, but some begin with T or A. There are also versions that only feature E but in various configurations (spun or flipped in different directions). These can be helpful for non-English speakers who can just point to indicate the direction the letter faces. Some even have symbols or pictures, designed for children who don’t know their letters yet.

But the Snellen Chart has an obvious problem. When Herman Snellen invented the chart, he knew he wanted big letters at the top and smaller letters at the bottom, but there’s no standard to how many letters are on each line. And because each line has a different number of letters in it, passing each series becomes increasingly difficult. Small differences add up, too. For example: if you get 3 out of 5 right on the 20/20 row, you have 20/20 vision, but 2 out of 5 and you have 20/25.

Visual Acuity chart by the National Eye Institute (CC BY 2.0)
Visual Acuity chart by the National Eye Institute (CC BY 2.0)

One alternative is a chart developed in the 1970s that features exactly five letters on each line. The result looks like an upside-down pyramid, the big letters taking up more space at the top. Correspondingly, the chart has to be much wider and takes up more space, which doesn’t work for every office. Also, this more elaborate chart is harder for doctors to memorize, which could lead to administrative error.

Vision charts present an interesting question about what really makes a design good. On the one hand, you have charts like this newer one, which are standardized and precise but a little harder to use. On the other hand, you have the classic Snellen Chart. It is a less precise a tool, but it is way easier to memorize, which make it a more efficient test for doctors and saves time. Plus: it fits more conveniently on a wall. It is memorable, quick, easy, imprecise, and totally iconic.

Today, you see both versions of vision charts around. Check it out the next time you have your eyes tested: which design has your doctor opted for? If you get a chance, you might ask them why as well!

Comments (28)

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  1. Olivia

    Very excited that you’re talking about my hometown but… it’s Newcastle, not New Castle!

    1. glen

      If you mean the Carl Orff piece at the end of the bit about the Byker Wall, it’s called “Carmina Burana”. The section they played which most people recognise is called “Oh Fortuna”

  2. Aaron

    I’ve loved these mini-story episodes soooo much, partly because of the topics and partly because I get to hear from all of the other (normally) silent members of the 99pi team. Great work, y’all!

  3. Carolyn

    Hi–I started listening to your show a couple years ago after I gave a short talk in Northern England about a landscape park I’d restored–when I finished the organiser’s comment was ‘you sound like Roman Mars’! I thought I’d write with two things about the mini-stories–first, I worked for four years in Newcastle, and discovered among other things that the Geordies love their infrastructure almost as much as their beer and brass bands:

    https://www.youtube.com/watch?v=V80Isj9JK1s

    (Byker is even mentioned a couple of times–there’s a station there.)

    Second, cities or developers nowadays may randomly name streets, roads, avenues, boulevards, etc. but each of these terms once had a very specific meaning. I recently read an article tracing the word ‘way’, indicating that its original meaning suggested a steep street–something useful for waggoners to know before they chose their routes.

  4. Rob

    The city where Byker is located is Newcastle (upon Tyne), not New Castle.

    Surely the bigger problem with having a standardised chart for testing eyesight is that the person being tested may become familiar with the sequence of letters? Sometimes in these tests, I have been not sure whether I can really read the bottom row of letters, or whether I am just remembering what they are.

  5. Brian

    The eye chart story is better than the majority of topics you cover – would love to hear the full version.

    1. Michaƫl

      Totally agree, I normally listen trough a podcast app, this was one of the few times I just had to google something because I wanted to know how it looked.

  6. Jeff Loonin

    The copyright trap is given a sci-fi explanation as well as a practical one in the Doctor Who episode “Face The Raven”. It’s cool when a writer mixes a little bit of truth in with their fiction, no?

  7. Nathan Cross

    I totally love these mini story episodes. They are just so dang fun! I welcome the idea of doing more mini story episodes a few times a year. What about perhaps doing a dedicated short-format podcast devoted to single ministories? Something along the lines of Scientific American’s 60-Second science? Just a thought.

  8. Craig Stevens

    Love these short stories. A couple of points that occurred to me about the eye chart. First, if the Snellen chart is easy for the optometrist to memorize, isn’t another down side that it’s easy for the user to memorize. Kind of self defeating for the user, but it could even inadvertently create inaccurate results over time.

    Second, isn’t another interesting aspect of this chart, the design issues related to the creation of the system for measuring eyesight (e.g. 20/20). Weren’t there other systems that were absolute rather than relative?

    Thanks,

    Craig

  9. Frank

    As a Canadian high school student, we studied the Snellen ratio in (accelerated) physics as part of the study of light, and used patterns of parallel lines (like a spatial frequency chart from old TV). I recall my lab partner (a provincially ranked baseball pitcher) had something like a 9/6 for his dominant eye.

  10. So I have a way to get Katie’s eyechart into a full episode, cover a few different things that we use all the time that are hard to use like the qwerty keyboard.

  11. Emily

    I’m with Avery! The design of charts and equipment for measuring vision and what it actually means to test 20/20 on a vision chart sounds like a fascinating concept to cover. I would be interested in hearing more about it. A majority of people wear vision correcting lenses and interact with optometrists, so it strikes me as something with a wide appeal as well.

  12. Brian

    I found it strange that you felt the need to repeat Beatrix Campbell’s lines, not once but twice. I understand that it’s radio, and that the majority of the audience might not be overly familiar with the Geordie accent, but hers wasn’t particularly strong. You’ve had people from all over the world on the show before, without resorting to this, so to do it with a native English speaker is kind of jarring. I liked the episode, and I think that the mini stories concept is great, but I was really distracted by that choice.

  13. John Sanders

    I used to live near Byker and I agree that it is special. It is often cited as the start of community architecture in Britain. I dont know if that is the case – and neither do i know if two other stories about it are true – that the community consultees did not want tradition but pushed the designers to more inventive design once they saw what was being built in the first phase and what is possible. Newcastle has (or had recently) more architects per head of population than any other city in Britain. I sometimes wonder if this is because the architects who came to work on Byker with Ralph Erskine stayed there. The point is that its a place that is sufficiently interesting for people to make myths and poetic comments about. I admit that Bea Campbell’s attempts at architectural criticism are embarrassing but how good to have people who are not designers talking so generously about recent architecture in this way. If you want to know more there is a very good conservation plan written by Jules Brown at the North East Civic Trust.

  14. Mike

    Loved the section on the Byker Wall. Apparently it was originally intended for a main road to run much closer to it, matching the curve of the Wall, but the road was scrapped. The Wall was built in that shape anyway, then the idea of a road was resurrected, following the design that it has now (i.e. alongside the Wall, but much straighter).
    Also, the streets that you were describing “like Billy Elliot” are known as terraced streets (often shortened to “terraces”) :-)

  15. Nikki Reese

    I was the firefighter who emailed you about the knox box. I had completely forgotten about it! Thanks for the awesome mini story.

  16. The modern Byker Wall is kind of horrendous. The old 1970s (and before) Byker estate version seemed to waste a lot of space but seemed more like a neighborhood and community.

    Urban planning is certainly challenging, I wouldn’t want to be in architect Ralph Erskine shoes.

  17. I loved the story about the Snellen chart, and I think it would be interesting to look at visual acuity charts used in other countries, especially those where the written language doesn’t involve our roman alphabet.

    I’ve lived in Taiwan for a couple of years and had to undergo a complete medical check-up for my student visa, which included an eyesight test. I was surprised to see that the chart used was different from our own; instead of letters, it featured a shape resembling a capital E, but oriented in four different ways. To pass the test, I had to name the direction that the three ‘legs’ of the E were facing, either left, right, top, or bottom. Simple enough, can be applied in all languages, but maybe not as easy to memorize as the Snellen. Anyway, I thought it might interest you – I think there are a few images online.

  18. miss pooslie

    my eye dr does the chart digitally (in a dim room with a projector) she also switches up the letters for when she is fine-tuning your prescription.
    i feel like the chart is a jumping off point, giving you the range of vision, not 100% precise. (or maybe that is my darkroom experience talking–doing 5 second increments on a negative then fine tuning from there)
    also, i never knew that you could just get a majority right! i sit there and struggle with c/g e/f etc on the lower lines. glad to know i can just guess and if its wrong, i can still “pass” that level!

  19. Shay

    There’s gotta be a ministory to be told about Begich Towers and The Town Under One Roof!

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