Types Of dyslexia

In addition to varying definitions of dyslexia, educators and clinicians have also developed varying subtypes or classifications of dyslexia based on differing patterns of underlying symptoms. Such categories are useful in choosing among remediation strategies, and also for purposes of defining population groups for purposes of research. Large-scale data from comparative studies of reading patterns in dyslexic and normal readers supports a finding of at least two prevalent and distinct varieties of developmental dyslexia. One common approach has been to differentiate a speech discrimination deficit from a visual perception impairment.Distinct patterns of neuropsychological organization have been reported in the following three varieties of dyslexia.
Dysphonetic or Auditory Dyslexia
The most predominant form of dyslexia identified by researchers is the dysphonetic or auditory subtype, which is associated with difficulty connecting sounds to symbols, and attendant difficulty with sounding out words The American physician Elena Boder, who developed the Boder Test of Reading-Spelling Patterns (1973), reported this pattern among approximately 60% of the children she surveyed
Dyseidetic or visual dyslexia
The dyseidetic (visual or surface) subtype is associated with inability to develop a sight word vocabulary, slow and laborious reading as familiar words must be repeatedly deciphered, and unconventional but highly phonetic spelling. Boder reported that approximately 10% of her subjects exhibited this pattern, with an additional 22% showing a "mixed" type with elements of both the dyseidetic and dysphonetic forms
Rapid automatic naming or Double Deficit
Other researchers have identified a deficit related to "naming speed", which relates to the ability of students to rapidly verbalize the names of symbols such as letters and numbers when tested. A deficit in "rapid automatic naming" is seen as related to an impaired mental timing system.When such difficulties exist in conjunction with a phonological deficit, it is characterized as double deficit dyslexia.