stressedbutfabulous
The problem regarding dyslexia has been a decade or more of the UK not keeping pace with International research regarding the underlying causes, and an industry which is more concerned with its own funding rather than the problems facing those who have the dyslexic symptom.
Another problem has been fringe parents acquiring a diagnosis for children who does not have dyslexia just to gain some extra help for their child.
Dyslexia is a man made problem, a social construct, about having cognitive problems processing a man made communication system the visual notation of speech, or decoding and recoding the graphic symbols society chooses to represent the sounds of speech. Dyslexia is language dependent, and in societies that do not use the visual notation of speech as a communication system there is no dyslexia.
Nearly all dyslexic children have developmental dyslexia, which has a genetic origin and three cognitive subtypes: auditory, visual, and attentional. Which means that an auditory processing disorder ( listening disability), a visual processing disorder, an attention disorder, or any combination of the three can cause the dyslexic symptom. And each of the different subtypes require different forms of support and remediation. MY list of Key References provides links to the key research papers etc, which can provide more detailed research based information.
Ideally dyslexia should be diagnosed by a multi-discipline (multi - professional) assessment team consisting of an audiologist to identify an auditory processing deficits, an optometrist to identify and visual processing deficits, and a psychiatrist to identify and attention deficits, with further multi discipline assessments for any individual disorder assessment and diagnosis.
The cognitive causes of the dyslexic symptom, all have a clinical / medical origin and diagnosis, so may be your GP could refer your DS for a clinical assessment, preferably at a regional centre, but if not you could always suggest Great Ormond Street Hospital.