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performance after the hypermetropia is corrected, since the effects of his/her learning disability could have been
amplified by their poor vision. However, the learning disability will certainly persist because it is more neurological
than sensory in nature.

Children with uncorrected myopia exhibit a diminished far-vision acuity and therefore may have difficulty seeing
the blackboard in class. However, these children generally do not have difficulty with their near-vision, especially
if myopia is mild or moderate. Despite their visual condition, there is no correlation between low myopia and aca-
demic achievement. Optical correction, if required, must be determined based on the child’s age-specific visual
25
needs. In addition, studies have shown that the under-correction previously used to decrease myopia progression
25
is unfounded. Similarly, the hypothesis that the addition of bifocals might reduce the progression of myopia has
25
also been shown to be clinically unfounded. 4,20,25,32,33
In school-aged children, astigmatism levels of less than 1.50 D produce only minimal vision impairment and do not
cause amblyopia if symmetrical. 24-26 Oblique astigmatisms, however, are more disruptive to vision. Generally, it is
recommended that astigmatisms of between 1.00 D and 1.50 D in school children should be corrected. However, as
with hypermetropia, the decision to not correct an astigmatism would not cause a learning disability.
4,25
Amblyopia is functionally characterized by reduced visual acuity that cannot be improved by optical correction.
This weakness in vision also creates difficulty in distinguishing letters that are close to each other. Children with
bilateral amblyopia may exhibit a slower advancement of their reading level, but do not have a higher likelihood of
dyslexia than other children. In addition, children with nystagmus, bilateral cataracts or eye health abnormalities
4
may have a variable decrease in their visual acuity. However, children with moderate to severe vision impairment
4
can learn to read with appropriate optical corrections and visual aids specific to low vision. Generally, eye disease
does not affect a child’s ability to learn to read correctly.
In summary, there is no correlation between reading performance and modest uncorrected refraction anomalies.
Based on evidence-based medicine, it is not only unnecessary but actually inappropriate to prescribe a weak correc-
tion to promote the treatment of dyslexia and learning disabilities. 4,6,20 However, it is essential to perform a complete
visual examination including an examination of the refractive condition under cycloplegia in all children with a di-
agnosed or suspected learning disability to detect any refraction error requiring an optical correction in accordance
with the standards generally accepted in the profession.

SACCADES AND FIXATIONS
Saccades are quick, brief eye movements between two areas used to decode the environment. When engaged during
reading, they can be followed by a corrective saccade in the event of ambiguity, for example, when a word or group
of words has been misunderstood. Contrary to certain beliefs, there is no difference in measurements of saccades be-
tween control adults and patients with dyslexia. 4,11,17,18,34-38 The relationships between saccades and fixations in children
with learning disabilities and those in children of the same age are unclear, and no causal link has been clearly estab-
lished. Recent studies have shown that the saccades and fixations of dyslexic readers are similar to those of matched
control readers based on a similar level of reading ability rather than expectations for their age. 9,13,39,40
To date, a phonological deficit is the most widely accepted explanation for dyslexia. 3,4,6-9 Phonemic-based training
should therefore improve visual functions by improving the reading level. Consequently, visual impairments caused by
a lack of reading experience would be the consequence and not the cause of dyslexia. 9-12,40 Children with dyslexia will
often lose their place when reading, confuse sounds and have difficulty reading more uncommon or elaborate words.
Reading is slow, especially since the level required is higher than the capacity. These difficulties require a considerable
investment in energy for reading and comprehension, and therefore lead to anomalies in visual pursuit and saccades.
Improved reading levels would improve saccades and fixations, but there is insufficient scientific evidence to confirm
that saccade and visual pursuit exercises could help dyslexic readers develop a better reading level. 2,4,10,23,35,40,41

Finally, most individuals with a disorder, with regard to either ocular motility or eye movement, have normal levels
of reading skill and reading comprehension. In fact, many children born with significant strabismus, nystagmus or
an eye disease that affects eye movements excel in terms of academic performance and reading level. 3,23,42,43 Thus,
dyslexia is not the result of an eye deficit, but rather the result of a disorder in central information processing that
causes difficulties in decoding and comprehension. As a result, there are longer fixations and more correction sac-
cades when the required reading level is greater than the reader’s ability.

CANADIAN JOURNAL of OPTOMETRY | REVUE CANADIENNE D’OPTOMÉTRIE VOL. 80 NO. 3 65

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