Why testing for 20/20 isn't enough when testing vision after a concussion

I've noticed that a lot of people with symptoms like headaches, light sensitivity, sensitivity to crowds, difficulty with visual focus, eye strain, and so on also haven't seen a neuro optometrist or concussion-experienced optometrist for testing or have seen a regular optometrist who says their vision is fine.

Similarly, no doctors have explained the importance of thorough vision testing.

So, I'm repurposing one of my earlier comments as a post to share my understanding of why 20/20 testing isn't enough after a concussion.

(I'm 11+ years out from my concussion, and have been through vision therapy with an excellent optometrist. I'm not a doctor.)

The norm for ages was that satisfactory vision was measured by how close to 20/20 vision someone had, but what's only slowly becoming known is that there's a lot more to vision than 20/20.

This is my understanding:

Each eye has six muscles that control its movements. The eyes, to focus on objects near and far, need to work together to turn in, turn out, turn to both sides and up and down and so on. There's something like a dozen skills or more. This system of muscles is obviously contained in our heads, so when someone gets a concussion, a lot of the time these muscles get thrown out of whack.

When out of whack, your brain needs to work a lot harder to make sense of visual signals, which can be a factor in concussion-related symptoms like light sensitivity, headaches, brain fog, trouble concentrating, etc.

Testing these skills would require more than just an eye chart or equivalent. It's worth asking what kind of visual testing you got if you're not sure.

One reason these muscles being out of whack is hard to notice for those of us who have them out of whack is because we can force our eyes to focus on these movements with intense effort, for short periods. We experience that in increases in eye strain, problems concentrating, headaches, etc., all things we're already experiencing from them being out of whack all the time. It's not like bigger muscle groups where we can easily say something like, "The back of my right shoulder hurts when I move my arm like this."

Edited to add: Did your doctors explain any of this? Did you get your vision checked? For anything beyond 20/20?

Edit 2: Be sure to see this response: https://www.reddit.com/r/PostConcussion/s/JiDs0JNZC4