Dry eye treatment. Your description sounds like dry eye. Initial treatment is frequent artificial tears during the day, ointment at night, warm compresses a few times a day, and omega-3 fatty acid supplements. If no improvement, you should see an eye doctor for further evaluation.
Several causes. Many possible causes of what doctors call "photophobia", or excess light sensitivity. Corneal disorders like scarring or inflammation, dry eye, cataract, inflammation inside the eye (iritis) and certain retinal problems all come to mind. A thorough eye examination will help pinpoint the cause. Sometimes, no cause is found and the patient is just labeled "photophobic". Sunglasses will help.