Photophobia is a big word that means being very sensitive to light. You know how sometimes when you walk outside into the bright sun, it hurts your eyes and makes them water? That's kind of what it feels like for someone who has photophobia, but even worse. For them, it's not just the sun that bothers them. It could be any kind of light, even just a little bit of light from a computer or phone screen, or a light bulb in the room.
When someone has photophobia, their eyes don't work the way they should. The light that goes into their eyes makes them feel sick or gives them a headache. Sometimes they even close their eyes or have trouble seeing things clearly because of how much it hurts.
To help with photophobia, people can wear special glasses or sunglasses that block out certain types of light. They can also choose to stay inside or in darker rooms to protect their eyes. It's important for people with photophobia to take care of their eyes so they don't get hurt or feel terrible all the time.