Dyslexia is a language based learning disability and reflects a difficulty in assigning sounds to letters or processing speech sounds. Dyslexia is not a vision problem. When children are first learning to read, it is common for them to reverse letters or read from right to left; for example, “no” becomes “on”.
Dr. Guinevere Eden, a professor at Georgetown University who studies the neurology of dyslexia, explains that the problem is that our “visual system” is designed to be "flexible” (Source). Our visual system recognizes a cat whether it is facing right or left. Unfortunately, when reading the word “tan” it makes a difference in meaning if we read from left to right or right to left. Our brains have to be trained to recognize that “b” and “d” are not the same letters or that lowercase “p”,”q”and “g” are not the same letters and have different sounds. With experience, children develop the habit of reading from left to right and can discriminate between letters that look very similar.
In an attempt to better distinguish some easily confused lower case letters, some students adopt the strategy of capitalizing easily confused letters such as “b” or “d”, even in the middle of a word.
Other corrections to myths:
The International Dyslexia Association is a good source for information about dyslexia.