As per your requirement of limiting dyslexia to phonological problems it is neither a proven theory or hypothesis.
The common flaw exposed is the underlying premise that dyslexia has a single cause and when evaluated dyslexia fails the test.
All the pieces of dyslexia fall together if considered as a syndrome with major required criteria ( poor reading skills below what would be considered .................................)
And a list of minor criteria that may or may not exist in any particular individual dyslexic.
Phonological problems are not a requirement or major aspect that is needed to diagnose dyslexia. It is a minor criteria that may or may not exist in the individual.
Phonological problems are probably the most common minor symptom associated with dyslexia as evidenced by response to phonological intervention.
My niche is removing the visual difficulties associated with visual dyslexia.Visual problems are minor criteria that exist alone in about 10 % of dyslexics without phonological problems and a less well defined % in more dyslexics.
I have seen at least 1 study done in France that investigated visual aspects in dyslexics without phonological problems.
It seems the tendency in psychology is to determine what is most common for a condition and then define the condition by that for everyone.
Most common does not mean all in a syndrome.
If you look at all the dyslexia fMRI studies of different areas of the brain none have been able to be used to define an individual as being dyslexic or not. Not all dyslexics have fMRI results in areas of the brain associated with phonological problems that indicate dyslexia in those areas.
I contend that the value of all the dyslexia fMRI studies is that they prove dyslexia is a syndrome with as yet no area of the brain showing positive results in all dyslexics.
Embarking on a path to prove phonological problems are required for a diagnosis of dyslexia is doomed to failure as proven exceptions abound.
On the other hand, as phonological problems are probably the most common minor criteria for the syndrome of dyslexia taking that path would be much easier.
You might like to visit my website , www.dyslexiaglasses.com ,about visual dyslexia symptoms which may or may not be present in an individual dyslexic or my blog http://hayesatlbch-visualdyslexiasolution.blogspot.com/ where I discuss the multiple deficit theory of dyslexia.
