My mother is 81 year old she has Parkinson's and before 10

Hi
My mother is 81 year old she has Parkinson's and before 10 days she has an Urinary infection with fever .now she is good and the Urinary infection finish but with same day she has also eye problems with one eye only it red and has pain in it and can not open and too much water coming for it .the doctor gave her some drops and become good and we stop the drops
Today the same problem come back to her and an eye doctor make for here home viisit and gave her drops and tell me the surface of the eye has infection
But he tell me also that in this eye the pupil is not responding for the lights.. it size not chang by the lights and this problem is only in one eye which has infection and he will make more test after 5 days and now I am very afraid
My questions
1- is this dangerous ?is this mean she may have a problem in brain?this is the most important question to me
2-if not where it may be the problem will be?
3-what the cause of it?
4-is this mean she may to be not able to see in this eye in future .. now she can see good for her age
Thanks