A visual processing disorder is any disorder in which the brain does not process visual stimuli in an effective manner. This is currently a poorly defined set of conditions, and may overlap with diagnoses of dyslexia, learning disability, and sensory integration disorder. The most common, and most obvious effects of a visual processing disorder are difficulties reading and writing, attention problems, and clumsiness. Headaches are a common side effect of these disorders. Varieties of visual processing disorders include problems with:

Visual Discrimination: Discriminating subtle differences between shapes, patterns, and even colors. This is most often a problem in reading, as it may make distinguishing between different letters and processing spaces between letters and words difficult.

Visual Figure-Ground Discrimination: Discriminating an image from a busy background, which includes finding and focusing on specific words and sentences within a page of text.

Visual Sequencing: Maintaining the correct order when reading a sequence of letters or numbers. It is common to find people identified as dyslexics who see letters and numbers out of order or perceive the letters on a page as 'dancing' and changing position with successive readings. This sort of disorder is most obvious when looking away from a page and then back, for example, looking from a test to an answer sheet, or when looking back and forth from the audience and a page of written notes.

Visual Motor Processing: Using information from the eyes to guide movement. Difficulties in this area may be evidenced by trouble staying within lines when writing, forming letters correctly, bumping into things, and trouble with sports. There is some evidence that behaviors such as toe walking might be based on visual motor processing issues, as walking so that your toes hit the ground first will give more tactile feedback for those children who cannot reliably judge exactly where the floor is through vision and other senses.

Visual Memory: The ability to recall visual sequences. Academically, this may affect the ability to spell (particularly words with irregular spellings), use a keyboard effectively, do mental math, and remember phone numbers.

Visual Closure: The ability to 'fill in' missing visual information. This may mean that a picture with part missing or covered up is unrecognizable or difficult to process. People with this sort of difficulty will have difficulty doing puzzles, and may have difficulty in completing partially-spelled words, losing track of where in the word they are.

Spatial Relationships: Holding a mental image of where things are in the world. This includes tasks from organizing words on a paper to being able to read a map. People with this disorder may be clumsy, get lost easily, appear to become confused easily, have trouble locating information that they have just read on a page, and be unable to plan how to use space on a page.

Visual processing disorders do not include myopia or hyperopia, and are often present in people with 20/20 vision. There are theories that some visual processing disorders, particularly visual sequencing disorders, may stem from uneven development between the eyeballs or from uneven processing along the optic nerve, but most of these disorders are believed to affect the visual cortex.

This sort of disorder is often diagnosed as dyslexia, although as the science behind these diagnoses develops, it is likely that we will start to distinguish dyslexia as those reading problems that take place in areas of the temporal, frontal, and parietal lobes, and visual processing disorders as those that take place in the visual cortex. At this time dyslexia is also in an ambiguous position, and there is a trend away from diagnosing it specifically, in favor of the more general 'learning disability'.

The popularity of the label of a learning disability reflects the most common philosophy in treating these disorders -- to use effective, but generalized, remedial learning strategies with lots of teacher assistance. Strategies that specifically address visual and phonological difficulties are either used across the board, or are implemented on the level of the classroom depending on the motivation and educational background of individual teachers.

Visual processing disorders are not currently recognized as a specific learning disability in the US, and are rarely diagnosed unless a parent seeks out a diagnosis through a specially licensed ophthalmologist. While it is clear that visual processing disorders are a real problem, therapies to treat them are still under development, and there is little evidence that most therapies are generally effective.

However, there are a number of specific aids and modifications that may help people with visual processing disorders, including prism lenses, colored lenses and overlays, modified text (large font, specific typefaces, color of text and background), changes in lighting, and even some forms of stimming, such as rapid movement in one's peripheral vision. The removal of obnoxious stimuli, such as bright lights, glare, and busy backgrounds may also help, as will the removal of distracting stimuli and stressors not directly related to vision, such as loud peers and time pressure. Unfortunately, determining what will help an individual with a visual processing disorder is currently a matter of trial and error, and is usually only done by the most motivated of teachers, parents, and adult sufferers.

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