Why are so many watches so hard to read?
Even if you have perfect 20/20 vision, this is a problem.
Above is me wearing the most popular wristwatch in the world, the Casio F-91W. I've been wearing this along with my A158 (also seen) a lot lately.
I wear this watch often because it is, without question, the most legible digital watch. I've owned many digital watches, and the F-91W is always the most readable. Why? Three reasons. Uncluttered display, excellent contrast, and readable at almost any angle.
Casio G-SHOCK digitals all have what I call LCD wash. Tilt the watch back just a little and all you see is a bunch of 8's on the display. And even for non-G models, LCD wash happens routinely.
On the analog watch side of things, the three that are most legible are Timex Easy Reader, any model by Mondaine and the Casio MW240.
Uncluttered display and great contrast are the reasons you can read these so well. White dial with solid black hands, or black dial with solid white hands. No shiny crap at all anywhere on the dial.
Field and dive watches aren't the answer
You would think that all field watches would have the highest level of readability. They don't. The majority of what you see is dials with unnecessary clutter on them.
Dive watches are supposed to be absolute best for readability, but they also fall short. Most of them have unnecessary shiny crap on the dial, a cluttered display, and a crystal that has no anti-reflective coating at all. Ever wear one while driving during the day? Not a good idea. Reflections happen that hit you right in the face. And then when you go to read the time, more often than not the crystal will smack a reflection right in your face again.
Simple, uncluttered and not shiny is the answer
There are only two things that reflect on the Casio F-91W at a very minimal level. The buttons and the crystal. That's it.
On the Casio MW240, it's the same situation. Only the crystal and crown reflect, again at a very minimal level.
Contrast on both is as good as it gets for maximum legibility. Dial design on both is also simple and efficient.
A few models that mostly hit the mark for great legibility
When I say "mostly", I mean that there is still something about the watch that sometimes has annoying reflections, but at least it has superior legibility.
Casio MDV106 - Analog diver that has a super-clean dial. This is, as far as I can tell, the most clutter-free dial you can get on a watch like this.
Citizen BI1045-13E - Analog diver that is also super-clean and amazingly even more legible than the Casio I just mentioned - if you don't mind hands of differing colors.
Timex Modern Easy Reader - This is the newer version. Only get the dark dial version of this because the light dial is awful.
Bulova Gemini 63B173 - This is a Swiss automatic with a clean dial and excellent contrast - a rare thing these days. Black hands and black indices on silver dial. Sounds like it wouldn't work but it totally does. The hands cut through pretty much any glare the crystal would give off. Very nice looker.