These are specialized tests, which use the highly differentiated
properties of the nerves and special organs of the eye and
ear to study the site and degree of their dysfunction if
any.
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In the electrical testing of vision,
which is especially useful in the newborn and children,
the mentally retarded and demented or in the malingerers,
the eye is tested from the retina and its pigment epithelium
to the brain along the  visual
pathways. The Electroretinogram (ERG) the Electro-oculaogram
(EOG) and the Visual Evoked Responses (VER) are
highly skilled and useful tests in detecting dysfunction
of the various cells of the retina, the macula, the optic
nerves, the optic pathways and the visual cortex in the
brain.
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Similarly for hearing, special techniques
are used to stimulate the cochlea i.e. The organs of hearing/and
study the integrity of the Auditory pathway right up to
the brain ( Brainstem Auditory Evoked Responses). 
Brainstem Electric Response Audiometry (BERA)
is a useful test to evaluate for hearing loss(deafness)
especially in newborn babies and children who do not cooperate
for audiometry as adults too. It can be performed after
sedating the children with oral medication, which does
not interfere with the results.
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Special auditory stimuli are also
used to evoke cognitive potentials (P—300),
which help in differentiating organic from non-organic
dementias, Schizophrenia etc.
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With the hospital programme
of Cochlear implants, Electrocochelography (Ecoch G) is
carried out with the help of ENT colleagues who insert
the transtympanic electrodes for us.
These electro diagnostic tests are especially
useful in neonates, infants and children, the mentally affected
and the comatose patients who cannot co-operate in their own
evaluation.
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