Reading Problems
When it comes to reading problems, behavioural optometrists tend to look at a wider series of measures of visual performance when compared to conventional optometrists, paediatricians, orthoptists and ophthalmologists.
The British Dyslexia Association recommends that people with possible visual difficulties are assessed via an NHS sight test for binocular accommodation and convergence.
A Behavioural optometry assessment will look at these measures in detail as well as assessing eye movements and further measures of accommodation and fusional ability.
Specifically measures of ‘accommodation’ include ‘amplitude of accommodation’ the ability to maintain focus at one distance, which also relates to ‘accommodative lag’, the ability to accurately focus at a specific distance. For some people maintaining such focus takes much effort and their eyes can tire easily so potentially affecting their ability to read as well as maintain concentration.
Another measure of accommodation is ‘accommodative facility’, the ability to easily alter focus from one distance to another. For some people altering focus can take much effort and after a while their eyes can become tired and slower to focus. This can potentially affect their ability to read as well as copy from the board quickly and accurately.
In order to read, it is important for the eyes to track across the page accurately. It is also important to be able to look accurately to and from the board in order to copy correctly.
If the eyes to do not track accurately (make pursuit eye movements) or jump from one point to another accurately (make saccadic eye movements) this can affect the ability to read.
Eye movement deficits are seen more frequently in children with learning difficulties and such children tend to make more saccadic eye movements and regressions when reading and make significantly longer fixations when looking at words compared to a normal reading population1.
Such children also have issues making ‘anti-saccades’ that is looking in the opposite direction to a given stimulus. Some eye movements are trainable. A study found that daily training of eye movements improved the ability to make anti-saccades which transferred in 80% of cases to an improvement in reading errors by 50% in the experimental group and 20% in the control group. After six weeks of training the group of children with learning problems were no longer statistically different from the control group2. A recent study in Hong Kong found that computerised eye-tracking training improved the saccadic eye movements of children with attention deficit/hyperactivity disorder. The authors felt that this preliminary study supported the use of eye tracking training to improve the saccadic eye movements in children with ADHD3.
Another factor found to relevant to learning is vergence facility, the ability to alter eye coordination from one distance to another rapidly4.
1Bellocchi S, Muneaux M, Bastien-Toniazzo M, Ducrot S. 2013. I can read it in your eyes: what eye movements tell us about visuo-attentional processes in developmental dyslexia. Res Dev Disabil Jan:34(1):452-60
2Fischer B, Hartnegg K. Saccade control in dyslexia: development, deficits, training and transfer to reading. Optometry & Vision Development 2008. Vol 39 Iss 4, p181-190
3Lee TL, Yeung MK, Sze SL, Chan AS. Computerised eye tracking training improves the saccadic eye movements of children with attention deficit/hyperactivity disorder. Brain Sci. 2020 Dec 21;10(12):1016.
4Quaid P, Simpson T. Association between reading speed, cycloplegic refractive error and oculomotor function in reading disabled children versus controls. Graefes Arch Clin Exp Ophthalmol 2008;79:228-34