From an optometric point of view the greatest risk to the healthy development of a child's vision arises from uncorrected hyperopia. Children are born with eyes that anatomically predispose them to being long-sighted (hyperopic) but as if to compensate for this they also have very active accommodative ability (ie their eyes can work much harder than adult eyes to bring things into focus – but this can give rise to problems).
Society increasingly demands that children read easily and speedily, and children's desires to be constantly interacting with modern IT systems makes great demands of their developing visual system, Any weakness or potential weak points in that system will result in normal binocular vision being stressed. Click here for some fun exercises to help your eyes work together.
The Extreme Case (amblyopia and/or squint) usually, but not always, arises when one eye has a different prescription to the other (usually more long sighted or hyperopic), The visual centres in the brain do not like this difference (imagine looking at a 3D image without the right 3D glasses) so it learns to ignore some messages coming from the more long-sighted eye (this eye only learns to see the bigger picture not the smaller details). If this situation persists the eye becomes ' lazy' and usually develops 'a turn' towards the nose (a squinting eye).
- When this condition is picked up early enough then constant wear of spectacles may be all it takes to restore normal vision to both eyes.
- 'A squinting eye' can sometimes be corrected with patching, surgery and/or exercises but if picked up to late the outcome is unlikely to be normal vision.
- If no interventions are made to correct amblyopia then the eye may never learn to see clearly and the child may be left with an eye that persistently turns in.
The Milder Case – in instances when both eyes see more equally (and there is only a small amount of hyperopia) then one eye does not develop 'a turn' but a child may struggle to maintain comfortable binocular vision. In the early stages this may simply make it more difficult for a child to acquire or maintain good reading habits. If it persists for even a few months then vision at near and possibly distance becomes fuzzy. The child may get headaches (from 'squinting' or frowning) and it becomes increasingly difficult to restore comfortable vision.
- If picked up early then simple exercises may be sufficient to restore normal binocular vision although spectacles may be prescribed that must be worn for all near vision tasks (especially reading, and when looking at any screen or playing with toys within an arms length). Bar reading or Beads on a String activites may be useful to restore comfortable vision.
- If left uncorrected then glasses may need to be worn constantly to retrain the visual system and restore normal binocular function.
As the child grows older and the visual system matures glasses may naturally cease to be needed. However if binocular function has not been established then it may always cause problems, reappearing when the eyes are required to spend long periods reading.
Not all reading problems are the result of poor binocular function, but poor binocular function will make it more difficult for a child to cope with reading difficulties.