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.
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.
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!