Corneal Reflex (Blink Reflex)

Your corneal blink reflex is when you automatically blink when something touches your cornea. Your cornea is your eyes’ first line of defense against dirt, grit and debris, and germs. It also filters UV light. Your corneal reflex protects your eyes and vision. It’s one of the more important eye reflexes.

How does the corneal reflex work?

Blinking may look easy. But it’s really a complicated process. It involves your trigeminal nerve, your facial nerve and a muscle that pulls your eyelids up and down. Your trigeminal nerve sends signals between your brain and eyes. Your facial nerve manages muscles in your face.

Your cornea is extremely sensitive. It doesn’t take much to trigger your blink reflex. A loose eyelash landing on your cornea or bright light can set the following process in motion:

1. The ophthalmic nerve branch in your trigeminal nerve signals your brainstem. Your brainstem sends messages between your brain and other parts of your body.
2. Your brainstem notifies your facial nerve.
3. Your facial nerve sends the news to your eyelid muscles.
4. They immediately tighten so your eyelids close.
5. Both eyes react even if the bright light or loose eyelash only affects one eye.

All this activity takes place in seconds. If you’re like most people, you blink about 15 to 20 times a minute.

What conditions affect the corneal reflex?

Anything that affects your brainstem, certain nerves or eye muscles can have an impact on your reflex. Some common conditions and issues include:

• Autoimmune diseases, like multiple sclerosis or lupus
• Benign or cancerous tumors
• Inflammation that affects your brainstem or nerves
• Traumatic brain injury or other head injuries

How do doctors check your corneal blink reflex?

Healthcare providers may test this reflex to check your eye health. For example, an ophthalmologist may do a Hirschberg test to see if your eyes line up as they should. Another corneal reflex test checks your trigeminal and facial nerves. In this test, a provider checks whether you blink when they touch your cornea with a cotton swab.

What is the tear reflex?

Blinking is one way your body gets rid of dirt or other stuff in your eyes. The tear (lacrimatory) reflex is when your tear system floods your eyes. Your tears wash away dirt or other things on your cornea.