Dyslexia is a term used to refer to a number of complex specific learning difficulties that may include problems with reading and spelling.
Dyslexia is really about information processing: dyslexic people may have difficulty processing and remembering information they see and hear. This can affect learning and the acquisition of literacy skills. British Dyslexia Association
Visual Stress is not Dyslexia, but can run concurrently with Dyslexia. It’s believed there may be a greater propensity amongst the Dyslexic population to suffer from Visual Stress.