One of the simplest and most cost-effective treatments for a child with visual dysfunction and associated risks to reading fluency is the preschool vision assessment. In Alberta, the basic ‘eye exam’ is covered by the Province and this should be sufficient to rule out amblyopia and extremes in astigmatism and other refractive errors. Note, however, that not all optometrists practice in the same way and you should ask about experience dealing with behavioural/developmental vision issues as they relate to learning.
Here are a few articles to get you going on your own research:
Optical treatment reduces amblyopia in astigmatic children who receive spectacles before kindergarten.
http://www.ncbi.nlm.nih.gov/pubmed/19232733