Has your son had a full eye examination done by a reputable developmental or pediatric optometrist? This would be different than just seeing the eye dr for a regular eye exam.
Reading and Vision
"Reading requires children to accurately use all of their language, decoding, phonetic, and visual skills to successfully recognize words and gather meaning from the written text. Unfortunately, about 20% of school-aged children struggle to read. Some of these children suffer from learning disabilities or dyslexia, the inability of the brain's verbal language or auditory processing centers to accurately decode print or phonetically make the connection between the word's written symbols and their appropriate sounds. However, a large portion of children struggling to read are not dyslexic at all; their phonetic awareness and language processing skills are fine. It's their vision that is interfering with their ability to read."
Some children do have dyslexia, but others instead have vision problems that can benefit from a variety of therapies.
Vision therapy itself is controversial, as some people praise it highly and others feel it of little value. Their praise or lack thereof likely stems from whether or not they felt the therapy useful for their particular situation. So I can't comment on that. However, I do personally know parents who feel it changed their child's life.
So that might be a helpful path to explore.
Additionally, there are theories suggesting that a lack of vitamin D could be a contributing factor to autism and even dyslexia.
[YOUTUBE="http://www.youtube.com/watch?v=--NqqB2nhBE"]Dr. John Cannell on vitamin D[/YOUTUBE]
As an aside, the evidence to support vitamin D supplementation for a variety of health benefits is compelling - this video is long, but snappy, and quite interesting:
[YOUTUBE="http://www.youtube.com/watch?v=Cq1t9WqOD-0"]Vitamin D and Prevention of Chronic Diseases[/YOUTUBE]
Some food for thought - I wish you the best with your son.