It's worth noting that with Optotypes, the goal of having clear and unambiguous letters is inverted. The aperture of C, for example is much narrower than the comparable types because the objective is to see if the viewer's eye is able to distinguish the closed-aperture C from O.

I have a personal trainer called Dave, and when talking one day he mentioned that his mum invented a very popular eye chart. I looked into it further, and yeh, his mum, "Jan E Lovie-Kitchin" is the one mentioned here, she co-invented the "Bailey-Lovie Chart" though I don't think it's as commonly used now. Pretty cool contribution though.

I distinctly remember being tested with the Tumbling E chart when I was 6. Public school checked the eyesight of all first-graders, who can't all read proficiently.

Pretty amazing how a typical visit to an optometrist hasn't changed much in decades or even a century: Snellen eye charts from the 1860s, modern phoropters from the 1920s, widely used tonometers from the 1950s. A branch of medicine can afford to stand still if we collectively resign ourselves to buying a new assistive device every year or two.