In the early 2000s, I was told to read out a set of letters arranged as a triangle on a chart in a health clinic in my local town.
I was told to start at the top with the larger letters: “C, O, H, Z, V,” I said out loud. Then to the next line, with slightly smaller letters: “S, Z, N, D, C.” All good. When I reached the fourth line, I was struggling: “H… O…? K…?”
I was told I had astigmatism, which results in distorted or blurred vision at all distances, together with near-sightedness. Of course, I didn’t know it at the time, but that was my first encounter with the Sloan typeface on a LogMAR eye chart.
Fast forward to early 2018. Working with brand identities, I was boarded onto a new brand identity project for an optometrist, Optician-K. The K stands for Krogh, a Norwegian family of optometrists who created their first optometry business in 1877.
As we usually do when working with new clients, we started doing research. This time, though, it was research on optometry, looking for a way to connect the Optician-K brand and their over 100-year history as optometrists to the craft of optometry.
As a graphic designer who works with type often, the old eye chart from the health clinic came to my mind. Where all clinics using the same typeface? Why does it look the way it does? Who made it originally? Can we use it in the identity?
An eye chart is used to measure visual acuity. And up until the 1800s, each ophthalmologist usually had their own preferred chart. A standardization was needed to allow a patient to go from one eye doctor to another and get the same results.
Dutch ophthalmologist Hermann Snellen did just that in 1862. The chart was developed using characters drawn in a 5x5 grid. That means that the thickness of the strokes is the same as the white space in between the letters. The reason for this is a little more complicated. A standard placement for the chart is 6 meters from the reader. This makes the thickness of the lines and the white space between them subtend one minute of arc. That line (designated 6/6 or 20/20) is the smallest-letter line that a person with healthy visual acuity can read at the corresponding distance of 6 meters.
Based on the Snellen letters, Louise Sloan designed a new set consisting of 10 letters in 1959. These 10 letters are designed to be co mparable to tests using the Landolt broken rings charts, another visual acuity system in which subjects identify the side of a broken ring where the break occurs.
The new Snellen letters were picked up by the National Vision Research Institute of Australia in 1976, when they developed the current standard for testing visual acuity today, the LogMAR chart. The LogMAR chart