Dyslexic features and asperger's syndrome?

My son was recently evaluated for dyslexia he is 8. He has carried a PDD.NOS, ADD.NOS, dysgraphia dx for some time. The evaluator an optometrist said that my son has features of dyslexia, dyslexia being a specific reading disability and though my son has features of it with a severely impaired encoding problem, and poor working memory, and eye focusing/teaming problems, that he doesn't fit the dx because his decoding is low, but not that impaired (though psych eval revealed that decoding was very impaired) and because his IQ is below average. The conclusion is that my son needs vision therapy, and was given dx of asperger's, dysgraphia, and a reading disability. Interestingly the optometrist told me that a person can't be dyslexic and asperger's, yet I've been dx both of these by the same person many times over. Does anybody have or know of a person dx with both dyslexia and asperger's syndrome? Can anybody cleary explain why these can't go together? I asked the optometrist and he talked in circles, honestly he was sounding more asperger than myself at that moment. Where do we fit? Just NOS of all dx's?