|Visual impairment (VI) is the loss of vision to such an extent which cannot be corrected by refractive correction or any medication and is caused through a significant limitation of visual capability from either disease, congenital or degenerative conditions or trauma. Eye disorders that lead to visual impairments include many diseases like retinal degeneration, cataract, albinism, muscular problems and glaucoma which causes visual disturbances, corneal disorders, congenital disorders, diabetic retinopathy and other infections. Visual impairment can also be caused due to brain and nerve disorders, in such case it is called cortical visual impairment (CVI).
Visual impairment can be classified into three levels: mild VI, moderate VI and severe VI. In mild VI the person can easily read relatively larger characters and has no difficulty in identifying shapes, colors and brightness contrasts. In mild VI person can tell the shapes and colors of the object and can differentiate between brightness and darkness and can only read characters with larger size. In severe VI a person is able to distinguish only the changes in brightness and darkness and may not see completely. Symptoms of visual impairment include: lack of eye contact, no blinking of eyes, do not visually follow the moving objects in front of the eyes and no imitation of othersâ expressions and actions, jerky movement of the eyeballs, limited facial expression and body language, search for the way using hands and abnormal response to white light.