Red Reflex (Fundus Reflex)

What is the red reflex?

The red reflex is the normal reddish coloration of the pupils that’s visible when light shined into your pupil reflects off the inside surface of your eye. Pediatricians and other healthcare providers caring for infants, toddlers and younger children commonly look for it during regular well-child care and developmental milestone visits. And it’s a commonly visible feature in flash photography.

Despite its name, a healthy red reflex might not always look red. Because of that, some experts recommend calling it the “fundus reflex” instead (which is how this article will mainly refer to it). That name comes from the medical term “fundus,” which is the back of your eye.

What causes the red reflex?

The fundus reflex happens when light enters your eye and bounces off the tissue of the fundus, the back of your eye. When it does, the reflection of that light becomes visible in the pupils of your eyes.

Why is it called the red reflex if it isn’t always red?

A key factor that influences the color of the fundus reflex is skin color, and darker skin means you might have darker tissue at the back of your eye, which can affect the color of the reflection.

That means a healthy fundus reflex may have different colors, such as:

• For people with lighter-pigmented skin: Red to orange.
• For people of Asian descent or with moderately pigmented skin: Orange to yellow.
• For Black people or those with darker skin: Darker color that may even appear green or blue.

How can I see the fundus reflex?

Today, one of the easiest ways to see the fundus reflex is by taking a photo in dim surroundings and using flash illumination to make the scene brighter. Your pupils should be wider in a dimmer room to help you see better. The sudden flash for the picture will reflect off the back of your eye faster than your pupils can narrow.

When it happens in a picture, photographers call this effect “red eye.” It’s something professional photographers generally want to avoid, and many smartphone photo apps and computer programs have special options that can remove the red effect.

When should the red reflex be a cause for concern?

The fundus reflex is an important part of well-child check-ups very early in life. That’s because it can indicate vision problems or certain eye conditions, some of them serious.

There are a few main ways that fundus reflex might appear when there’s an issue:

• Leukocoria: This means “white pupil,” and it causes the fundus reflex to appear pale-colored, yellow or white. It has this different color because something inside of your eye reflects the light instead of the fundus itself. In rare cases, it’s a sign of an eye cancer called retinoblastoma. It can affect one or both eyes, and happens in about 1 in 15,000 to 1 in 20,000 newborns.
• Weaker reflex on one side: The fundus reflex should be even and look about the same on both sides. It might be less obvious on one side, depending on the angle or the lighting. But it shouldn’t consistently look different. 
• No reflex on one side: If one eye has a fundus reflex and the other doesn’t, that could also indicate an issue.

One thing to remember is that the fundus reflex is something trained professionals look for using special tools, like an ophthalmoscope. You can often see the fundus reflex in photos, but you shouldn’t panic if you see a difference in a single picture.

There are a few reasons for that:

• Eye structure: The cornea at the front of your eye reflects light, too, and the reflection can look pale-colored. But in reality, that light isn’t reflecting from inside of your eye, so it’s not the fundus reflex you’re seeing.
• Angles: The fundus reflex looks different depending on the angle. A difference in the fundus reflex’s appearance, like leukocoria, shouldn’t be concerning unless it’s consistent and you notice it in multiple pictures.
• Distance: Healthcare providers and eye specialists look for the fundus reflex from a distance of 1.5 feet to 3 feet (0.45 meters to 0.9 meters). If you’re farther away than that, the fundus reflex is harder or impossible to see. A glow seen from greater distances is usually the reflection off the front of the eye.

What should I do if I see something that seems unusual in my child’s red reflex?

If you see something about your child’s fundus reflex (or in a child you care for) that seems unusual, you might feel anxious, worried or afraid. But remember, a single photo isn’t cause for panic. There are many reasons why a picture might show an unusual difference in the fundus reflex.

If you see the same effect repeatedly in photos, you can call your child’s healthcare provider, tell them what you’ve seen and ask them for an appointment. Your child’s provider can test your child’s fundus reflex and determine if there’s cause for concern.

This kind of test takes only minutes, usually doesn’t require eye dilation and is painless. And if your child’s provider does see something that needs further attention, they can refer you to an eye care specialist who can take a closer look.

Are there smartphone apps that can check the red reflex or detect leukocoria?

Yes and no. There were apps previously available for this purpose, but they were mostly for research purposes. You might still be able to find one, but none have approval from any government authorities for medical use. And while new apps are coming out all the time, you shouldn’t rely on them alone.

If you ever have a question about your child’s eye health, talk to their pediatrician or other care provider. While apps might help spot causes of concern, you should never use them as a substitute for seeing a trained, qualified medical professional.