The problem does not need to necessarily be an eye issue. It can be a processing issue. When we read, we rarely read the entire word. Our brain does not need to see and define every letter to understand what the word is in normal situations. It tries to take short cuts as we read. For some of us, those short cuts fail. As the brain see 'cha' or even 'cha ge' it attempts to fill in the rest based on words indexed in memory and the context of the word. Occasionally, especially for those of us with mTBI, it messes up.

Stress tends to make this problem worse. Fatigue does too.

I have this problem. Have for over a decade.

Google 'jumbled words' and you will find a lot about how the brain takes short cuts in this way.

In my experience, this symptom parallels word finding struggles. It happens at times when I am also having word finding troubles. It could be that the brain, as it reads the word, is struggling to recognize and index the correct word and instead, substitutes the wrong word.

I just had to learn to live with it.