What are the causes of sudden light sensitivity, preceded & accompanied by itchy / watery eyes?

Scratch or iritis. A sudden corneal scratch can cause this. If your eyes get very dry or you rub them, you might get a small scratch which hurts, makes your eyes water and become sensitive to sunlight. Alternative, you may have an iritis (swelling inside the eye). If it stays for a several hours, get checked.

Related Questions

What are the common causes of sudden light sensitivity and itchy/watery eyes?

Allergy. The key symptoms of allergy are itching and sensitivity and the key signs are redness and watering. If you feel you have an eye allergy, antihistamine drops can help alleviate the symptoms. If they persist, please see your ophthalmologist.
Many. Tearing and photophobia can be related to a corneal problem, infection, foreign body, lashes, contact overwear, allergy, irritation, congenital glaucoma, inflammation inside the eye such as iritis, some type of mass stimulating lacrimal gland, etc.