When most people hear the word vision, they automatically think of acuity. Acuity describes the keenness or “sharpness” of vision. The ability to perceive small details. The acuity is measured by the letter chart, but this is just one aspect of vision.
To be successful in handwriting, visual perceptual skills. Visual perceptual skills help students organize visual information from the environment and interpret what they see. To form letters properly they need form constancy. The form constancy is the ability to identify a form in different sizes and orientation.
The ability to process information is a visual cognitive skill. Visual cognitive skills allows students to process and interpret meaning from the visual information, we gain information through our eyes. Visual perceptions plays a central role in spelling, mathematics and reading.
For instance spelling is often thought as a memorization of the sequence of letters and use auditory reinforcement (spelling out loud). Others use visualization, reaching for a pen to write the word to see it. Visualization is more effective especially for phonetically irregular words. You know the length of the word and how it is shaped. This is why you can pick the correct word from a list.
Having a detailed understanding of the challenges that a person faces due to their disability helps us to better match the kinds of accommodations that might be appropriate.