Minor problems with convergence and tracking are extremely common and children will overcome them, in many cases, just by practising reading consistently and frequently. But it may be that you can help your child in the following ways:-
Let him or her point at words, when reading, with a pencil or a finger, if he or she wants to.
(If the child is struggling to ‘fixate’, this will take some of the stress out of the process.)
Let the child use a card under the line he or she is reading, to stop him or her jumping or wandering up or down away from it.
Let him or her use a larger typeface if it seems to help.
In other words, don’t try to accelerate the process of growing out of ‘baby’ reading …. some Scandinavian and European countries do not make children start reading until they are about eight, when the eye muscles are fully developed. It might spare children a huge amount of pain and embarrassment if the same policy was adopted in Britain. A web-site called ‘eyecanlearn.com’ is invaluable and offers a variety of tests and simple exercises which you – a concerned parent – can use with your child.
The reference below takes you straight to a test to see how accurately and quickly a child who is already happy and confident about numbers can move his or her eyes across a virtual page: