If there has been a little itching and redness that has become progressively worse over a period of days or weeks then you likely have a condition called Blepharitis which is treated with hot compresses and massage.
My mother is highly diabetic and is not able to see very clearly. Could it be the onset of glaucoma?
If there is no pain associated with the sensitivity it may be due to dysfunctional year syndrome. If there is pain it may be iritis, an eye disease that requires the attention of an ophthalmologist. Some people are just sensitive to the light and require sunglasses outdoors others may have a retina problem that causes the sensitivity, albinism for example. It is possible but not likely that the tearing is the result of chronic allergy but this would typically be associated with red itchy eyes.