The convergence is the ability of our visual system to move the eyes synchronously inwards and is activated when confronted with a visual stimulus at close range.
Convergence insufficiency is a binocular vision disorder characterised by an insufficient ability to bring both visual axes of the eyes to a fixation point in space and the difficulty of maintaining binocular near vision.
This disorder is estimated to affect from 4% to 17% of school-age children and is associated with a range of symptoms that appear when reading closely or doing homework.
Children with convergence insufficiency often report symptoms related to the visual discomfort, such as double vision, tired eyes, eye discomfort and headachesor have problems when reading, such as loss of marking, re-reading, loss of concentration, slow reading and difficulty remembering what has been read. Parents of children with symptomatic convergence insufficiency state that their children are more likely than children with normal binocular function to be distracted while reading and to have difficulty completing homework.
Randomised clinical studies have shown that 'office-based' (i.e. carried out on a non-patient basis) vergence/accomodation therapies are effective for symptomatic convergence impairment in children, leading to improvements in clinical and symptom severity as well as in associated behavioural problems. Although some authors have hypothesised that these improvements may have a positive influence on reading, either directly (improved text comprehension and/or reading fluency) or indirectly (increased attention and motivation, improved reading time), different results emerged from a recent study.
The results of a trial called Convergence Insufficiency Treatment Trial - Attention & Reading Trial (CITT-ART)a randomised clinical trial conducted to determine the effect of vergence/accomodation therapy on reading and attention of children aged between 9 and 14 years with symptomatic convergence insufficiency.
The study was supported by the National Eye Institute of National Institutes of Health.
The multi-centre clinical trial enrolled 310 children between 9 and 14 years old with symptomatic convergence failure, divided into two groups (in a 2:1 ratio), the first of which was subjected to vergence/accomodation therapy for 16 weeks, while the second performed for the same weeks placebo therapy. The groups were evaluated, after 16 weeks of therapy or placebo, mainly for the change in reading comprehension, measured by means of a special test (WIAT-III).
The study showed that for children aged between 9 and 14 years with symptomatic convergence insufficiency office-based vergence/accomodation therapy conducted for 16 weeks, not is more effective than placebo in improving performance on standardised reading tests.
Based on these results, clinicians providing the vergence/accomodation treatment should not suggest that this pathway, on average, would lead to improvements in standardised assessments of reading performance.
Further studies could evaluate the effectiveness of combining convergence/accomodation therapy with the use of reading tutorials. The impact of reading instruction interventions may, in fact, be enhanced if potential barriers to improvement, such as the strain and fatigue associated with convergence failure, are removed.
There is already clinical evidence for the hypothesis that combining literacy with treatments aimed at improving the conditions underlying reading difficulties can enhance final reading performance.
Source:
CITT-ART Investigator Group. Effect of Vergence/Accommodative Therapy on Reading in Children with Convergence Insufficiency: A Randomized Clinical Trial. Optom Vis Sci. 2019.
Dr. Carmelo Chines
Direttore responsabile
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