I've mentioned this before - I was coaching kids after school and got a couple of kids, siblings, with dyslexia due to tracking issues. I developed an exercise for them which I'm happy to share.
It's cheap. It DOES require specialised equipment - you need to buy a ball. Not just any ball - get one of those balls which are actually a second, weighted ball floating in fluid (usually water) inside a clear ball. The look - it's usually looking like an eyeball that always looks up at you. You roll the ball and while the clear outer ball rolls, the inner, coloured and weighted ball, merely floats inside and due to the weight, always stays the same. The ball seems to slide across the table, like Tom Cruise in his socks in "Risky Business".
Now for the exercise - take your "eye" ball and roll it from left to right across the table. Roll from the left, catch it with the right. maintain eye contact with the ball. Then pass the ball back to the left hand, UNDER the table, and roll it again to the right hand.
Repeat.
Do this exercise multiple times a day, at least five to ten times each time.
This needs repetition. The more repetition, the more you succeed in training your eyes to track from left to right. [Note: if you live in a culture which reads from right to left, then roll the ball back the other way instead. But if you DO live with such a language as your first language - then how come are you reading this? But I digress.]
When we read our eyes should track across the text. But the tracking is not smooth, we do it in short steps. If you put electrodes on someone's eye muscles and then give them a book to read, the trace will show the short, jerky movements. These are called saccades. While the eye is actually moving, your vision does not pick up the blur. Your brain actually switches off the input for a split second. But when your eye stops moving, your brain collects a snapshot of the words on the page. Not the whole line, but for most people the brain would collect a couple of words, about a sixth to a quarter of the line depending on the length of the line and the individual. My boss used to wire me up to demonstrate saccades to medical students and it used to rile him when I switched into speed reading mode - then, the saccades are far less obvious and often indetectable. And I also noticed - in speed reading mode, my comprehension also goes down. I can really only speed read if I'm scanning the text for key words, or if the text is very familiar to me. There really is a direct correlation between good saccades and comprehension.
Someone with a tracking problem - their eyes aren't making these jumps (saccades) evenly. Or the snapshot is of too short a sequence. Or too long a sequence with no understanding. Or they're not properly remembering the previous sequence (which is an attention thing affecting memory tracks being laid down). Or maybe their eyes are jumping randomly all over the page, so what sequence the brain picks up is jumbled.
This is why training the eye to track left to right in a single line is what is needed. It could cost you a fortune. Or you could buy one of these balls (a couple of dollars) and practice, practice, practice.
If the problem is eyes not working together properly, get a "Magic Eye" book. Maybe photocopy pages from the book every so often, laminate the copies and use them as placemats at the dinner table. This encourages regular practice. Swap them around as he gets the knack.
The thing with Magic Eye is it encourages you to toe your eyes out slightly, as if you're looking into the distance. But your eyes must work together to make the optical illusion work.
Kids who do a lot of close work such as reading or computer games need to do this exercise to overcome the constant 'toe in' of their eyes.
With Magic Eye, you need to stick with it. Your eyes will seem to have 'got it' but actually, there is probably even more to the image. I've stared at these things, thought, "Is that all?" and been about to turn the page, when it leapt out at me - there was another pattern lurking in there and suddenly I could see more detail, like a wide vista reaching out of a flat page.
Behind the toilet door is another good place for these, if your child needs to practice them.
Again, not expensive. But great for working on eyes working together and also on depth perception.
So there you go - two really good eye exercises, very inexpensive and lots of fun.
Marg