The Ocular Surface Disease Index (OSDI) includes 12 questions grouped by poor symptoms and visual disturbance (light sensitivity, eyes feel gritty, painful or sore eyes, blurred vision or poor vision); visual function/tasks (problems when reading, driving at night, working on a computer or watching TV); and environmental questions (problems in windy conditions, places/ areas with low humidity or areas that are air conditioned). The scores range from 0 to 100. On the basis of the score, the patient's symptoms can be categorized as normal (0-12), mild dry eye (13-22), moderate dry eye (23-32), or severe dry eve (33-100).