does pupillary reaction present in blind people?

Answer 1

If blindness is central- that is, is caused by a lesion in the visual cortex of the brain and not in the eye, then there may be some sparing of pupillary constriction. This has been shown by the presence of photoreceptors in the eye different from standard rods and cones. This non-rod/cone system conducts to the brain in a pathway distinct from the classical visual pathway to the cortex. In short, if you take away all rods and cones, or all classical visual afferents, or all visual cortex, there remains a light-sensitive pathway which shows some (weak) pupillary contriction in response to light. This non-cortical visual pathway was discovered in 2003.

http://www.scienceblog.com/community/older/2003/A/20037731.html

HOWEVER, in most blind PERSONS, the pupillary reflex to light is diminished or absent. This is often due to damage to efferents or to all retinal receptors, e.g. by retinal disease like toxoplasmosis.

Answer 2

Pupillary Reaction

Answer 3

It depends on the type of blindness.
Pupillary reaction is controlled by the muscles which are innervated by nerves. As long as there is no damage to the nerve or the muscle, the pupil will still contract or dilate

Answer 4

Totally blind have no pupillary reaction.

Answer 5

Light is transmitted by the optic nerve. This activates the ipsilateral (same side) pretectal region of the brain stem. The ipsilateral pretectal region then activates the oculomotor nerve (CN III) of both eyes. The oculomotor nerve causes the pupil to contract, not the optic nerve. In blindness, the optic nerve is deficient, not the oculomotor nerve.

Section of one optic nerve will result in the complete loss of the direct pupillary light reflex but not the consensual reflex of the blinded eye. That is, if the left optic nerve is sectioned, light directed on the left (blind) eye will not elicit a pupillary response in the left eye (direct reflex) or the right eye (consensual response). However, light directed in the right eye will elicit pupillary responses in the right eye and the left (blind) eye. The effect of sectioning one optic nerve is to remove the afferent input for the direct reflex of the blinded eye and the afferent input for the consensual reflex of the normal eye. Section of one optic tract will not eliminate the direct or consensual reflex of either eye as the surviving optic tract contains optic nerve fibers from both eyes. However, the responses to light in both eyes may be weaker because of the reduced afferent input to the ipsilesional pretectal area.