Why does foreign body in the eye cause light sensitivity?

Light Sensitivity is a common presentation of Foreign Body in the Eye. A grain of sand, metal fragment, eyelash or contact-lens debris can rub on the clear front surface of the eye. This surface has many nerve endings. Irritation can lead to tearing, blinking, a gritty feeling, redness and a tendency to keep the eyelid closed in bright places.

The object may remain under the upper eyelid or may already have washed out while leaving a scratch on the cornea. Light sensitivity can have other causes too, so it does not by itself show that something is still in the eye.

Do not rub, press or try to dig an object out with fingers, tweezers or cotton buds. If there was dust or a loose particle, rinse the eye gently with clean water or sterile saline and blink several times. Remove contact lenses and leave them out until the eye is comfortable and a clinician says it is safe to wear them again.

Use sunglasses for comfort and avoid driving if vision is blurred or light is difficult to tolerate. Do not use someone else's eye drops or an eye patch unless a clinician advises it.

Arrange urgent eye assessment if the object was moving at speed, is embedded, came from metalwork or grinding, or the eye was exposed to chemicals. Seek care promptly for reduced vision, increasing pain, marked redness, discharge, an irregular pupil, persistent light sensitivity, or an inability to open the eye. Chemical exposure needs immediate, continuous rinsing while you arrange emergency help.

Ask whether any material remains under the eyelid, whether the cornea has been scratched, when contact lenses can be used again, and which drops or pain relief are suitable. Tell them how the injury happened and whether you were using eye protection.