My PCS brain dyslexia erred from what I meant to say. I edited to correct my comment.

Often, the subtle neck issues do not show up in any diagnostic procedure. But, avoiding bad neck posture during sleep will help with improvements. Much of the healing with PCS is due to us changing our behavior so our body can heal. A chiro can only treat momentarily. It is up to us to not strain our neck during sleep or activities.

For me, I put two and two together when I realized that I had my worst days when I slept crooked and often would have stressful dreams. My wife could predict my day by how I was sleeping early in the morning when she got up. If I was sleeping with a straight head and neck, I would have a peaceful look on my face and breathing quietly and smoothly. If I was not in a good position, I would have a strained look on my face and be breathing unevenly.

Not every symptoms has a direct connection to a cause. Your eyes could be strained because you are not sleeping good leaving your brain easily fatigued because you are not sleeping with good posture. Nobody can say exactly.

Some keep a journal of daily activities and symptoms to see if they can find a correlation between them.

More later, pollen from mowing the lawn is killing my eyes.
Made some more edits. My brain is thinking backwards today.