Here's a nice recent review on Visual Perception and Autism (from Neuron). A wide array of visual perceptual difficulties have been found in subjects diagnosed with autism, and it's clear, we're only at the beginning of our understanding how visual information is being conveyed differently.
One example given is how the Ebbinghaus illusion may not work for some subjects with autism because it requires seeing objects in visual context (the illusion is that the center spheres appear different sizes because of the different sizes of surrounding speres).
From our point-of-view, the remarkable thing is how rarely children or adults diagnosed with autism are assessed for perceptual disturbances such as this. Autism is currently a behavioral checklist diagnosis. This may have been because autism was initially a psychiatric, not a neurologic diagnosis.
If you know what you're dealing with, visual or auditory confusion can be reduced by making adjustments in how information is presented or in some cases, by perceptual training or strategic instruction.
Visual Perception and Autism