Ophthalmology question?

I know that the pupil's contracting and dilating is largely reflex, but is it handled by brain or the optic nerve, i.e. is someone who is totally blind due to severe damage or total severing of the optic nerve still going to have pupil reactions to light changes?

The actual processing of the information is handelled in the brain. The passing of the information travlels through the optic nerve. Here are a couple of scenarios

1. One eye has severe nerve damage... the eye reacts to light but not to the same level as the other eye (depends on level of damage as to how much). However, when a light is shone in the other eye the 'damaged' eye competely contracts like normal.

2. The optic nerver is cut through. Because of this no information regarding can be passed to or from this eye. Under no circumstaces will this eye react to light.... nor will it react to light shone into the other eye

A very good question.
We just call that reaction as pupil reflex.
If a patient is unconscious, we just open his or her eyes and use a flash light to see the pupil. If the pupil reflex is negative, we assume the patient is in agony or near death.

If a person is blind in one eye and you shine the light in that eye, nothing should happen, but if you shine the light in the "good" eye then both will have the reflex...

BTW by blind I mean NLP which is No light perception. There are many stages of blindness and if a person can tell there is light at all then there will be the reflex...

Pupil function is a neurologic response to light and accommodation. It is controlled mainly by some of the cranial nerves (2 and 3). If there is severe damage to the optic nerves there will be what we call an afferent pupillary defect (APD), which will result in no/reduced pupillary constriction depending on the amount of damage. In addition, some retinal disorders can also give reduced pupillary function. Basically, anything that would cause a severe drop in vision can cause and APD. Hope this helps.

htey have abnormal pupillary response like an marcus gunn pupil