Dyslexia is a learning disability that could be considered "word blindness." However it is not a visual problem, the structure of the eyes is normal and eye exams may reveal normal vision. It also is not affected by intelligence levels - often times people with dylexia are considered more creative.
Dyslexia occurs as difficulty with reading and spelling. Like apraxia it is also a neurological disorder. The area in the brain that processes written language is affected. The cause is unknown.
75% of children with apraxia also show signs of reading difficulty. While this site is mainly focused on apraxia, many of the suggestions I give also help with dyslexia, such as sound therapy and fish oil supplements. If your child is having difficulty learning to read, discuss it with your child's teacher.