In this column, I have discussed the benefits of wearing glasses to correct long or short-sight. This time, I am going to describe cases in which glasses don't work.
I am not talking about the challenge of finding frames to fit a child with a tiny nose or unusual features - that's never insurmountable. I am not talking about a child who hates anything in contact with her head or face; that problem, too, can be overcome, and I will raise that issue next time. I am talking about occasions when glasses are actually counter-productive for vision.
Young children
Very young children only have an interest in objects near to them - we all know how difficult it is to attract the attention of baby from a distance. As a child develops, she becomes more interested in things further away and therefore need good distance vision. But while she is young, it is allowing her to see close things well that is really important.
Short-sightedness
If a child is short-sighted, her eyes have a natural focus for close objects, where it matters. Far objects are out of focus. Therefore, we don't need to worry about getting her into glasses (to make far objects clear) until she reaches the developmental stage of paying attention to distance. And indeed, many little children will reject glasses for short-sight when they are young, or simply look over the top of them.
Nystagmus - and the null point
Some children with nystagmus have a null point (the position in which the eye wobble is least) with their eyes in an extreme right, left, up or down position. So if such a child puts glasses on, either the null position means that she is not looking through the lenses, or the glasses prevent her from adopting the null position, and vision is worse. Again, the child will probably reject the glasses.
Restricted eye movements
Some children have conditions which restrict their eye movements, and as a result, may adopt a head turn or tilt to place their eyes where they want to look. As for children with a null point, the glasses may get in the way of the child's preferred position.
Case study
My decision to write on this topic was prompted by a little girl who came to my clinic a couple of weeks ago. She is short-sighted, has a nystagmus null-point and restricted eye movements. Guess what? She rejects glasses!
Advice for parents
If your child is struggling to accept glasses and you are feeling frustrated by her refusal to wear them, sit down and consider what the glasses are doing for her. It may be that the glasses are making vision worse - your child may be the sensible one. Talk it over with your eye care professional.
Maggie Woodhouse is a Senior Lecturer in special needs optometry at Cardiff University