Intervention for Dyslexia - The British Dyslexia Association

presuppose any neurological link between dyslexia and visual stress. However,
recent studies indicate that visual stress is more prevalent in people with dyslexia
than in the rest of the population, which is probably because visual sensitivity is
heightened as a result of the dyslexic’s poor reading strategies, thus
exacerbating visual stress reactions.
5) Visual stress interferes with the ability to read for any reasonable duration.
Children who suffer from this problem tend to avoid reading, to the detriment of
their progress in reading fluency and reading comprehension. The most widely
used, and generally effective, treatment for visual stress is that of coloured tints,
in the form of either acetate overlays or tinted lenses. This is not an appropriate
treatment for dyslexia, but the increased prevalence of visual stress amongst
people with dyslexia indicates that teachers should be especially vigilant for the
signs of visual stress in dyslexic pupils (see also paragraph 30).
6) Few of the studies in this field conform to methods that may be described as
‘gold standard’ (i.e. randomised control trials), but most may be considered as
conforming to a ‘silver standard’ (i.e. well-constructed quasi-experimental
studies). Wherever possible, effect sizes of findings are quoted. Effect size is a
well-established method of reporting the magnitude of a result. Cohen’s d is used
as the standard effect size measure throughout this review. However, it is
important to note that effect size will depend on the type of control group used.
If the control group has also received treatment, effect sizes will be smaller than
if it was untreated. Where it has not been possible to report effect sizes, ratio
gains (i.e. rates of monthly gain) have been reported instead (and sometimes
additionally to effect sizes).
7) Research studies on interventions for dyslexia carried out the UK, and in the USA
and other countries, are considered in separate chapters because of differences
in school systems and approaches to special educational needs.
Studies of secondary intervention (Chapter 2)
8) ‘Secondary intervention’ is a generic term for the provision of more intensive
instruction given individually or in groups to failing readers in the first 3-4 years
of schooling. The term does not refer to intervention given in secondary school.
9) There have been several important reviews and meta-analyses of the impact of
secondary intervention in the USA and other countries. Over 100 studies are
covered by these reviews, the results of which are summarised in this report. In
addition, eight high-quality studies of secondary intervention programmes using
phonological approaches with children with dyslexia or learning disabilities are
considered in more detail.
10) The results of the reviewed studies indicate that such interventions are beneficial
for children with dyslexia, even when instruction is provided by non-teachers,
provided they have received adequate training, and even when instruction is
given to small groups of children (up to 4–5 children per group).
11) The average effect size of gains of intervention groups over controls or
comparison groups for phonic skills was 1.02, for word reading accuracy 0.80
and for reading comprehension 1.86.
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