A Scratch on the Surface of the Eye? What a "Corneal Staining Test" Can Reveal

~Finding invisible damage with blue or yellow staining~

If you think you have something in your eye, but the discomfort or pain persists even after a while.

In such cases, a "corneal staining test" is often performed at an ophthalmology clinic.

I personally learned that "staining makes scratches visible" when I had this test done after scratching my cornea. In this article, I have summarized what this test is and why it is necessary, as clearly as possible.

■ Where is the cornea?

The cornea is the transparent membrane on the very surface of the iris (the colored part of the eye).
It is exactly where a contact lens sits.
As the entrance for light, it is a very important place for vision.

However, this cornea is actually very delicate.
It can be scratched by small irritants such as blinking, dryness, eyelashes, or dust.

■ How do you check if there is a scratch?

Often, you cannot tell if there is a scratch on the surface of the eye just by looking at it.
That is when a "staining test" is performed.
This is a method of "visualizing" the condition of the eye's surface by putting a special dye into the eye.

■ What is the staining liquid? How does it look?

Two main types of dyes are used:

① Fluorescein staining (glows yellow to green)

• Method: Apply yellow dye via eye drops or by touching a soaked paper strip to the eye.

• Features: When blue light is shone on the eye, the scratched areas appear to glow green.

• Usage: Used to check for small corneal scratches or dry eye.

② Rose Bengal staining (pink)

• Method: Apply reddish dye via eye drops.

• Features: It stains dead cells or areas not protected by tears.

• Usage: Used to distinguish diseases such as herpetic keratitis.

■ Is the test painful? Does it take a long time?

Only a tiny amount of dye is used, and it feels just like using eye drops.
There is almost no pain, and it is finished in a few minutes.

However, rose bengal may sting a little for some people.
Also, the area around the eyes may temporarily look stained after the test, but it will fade naturally over time.

■ Why is this test important?

Even small scratches on the cornea can affect your vision.
They can also be caused by infections or other underlying conditions.

By accurately identifying the presence, extent, and type of abnormality through a staining test,
the treatment plan can change significantly.

■ Summary

• Since corneal scratches are difficult to see, they are confirmed by staining.

• There are dyes such as fluorescein (which glows green) and rose bengal (which stains pink).

• It is a quick, low-pain test.

• It leads to correct treatment by allowing the exact location and extent of the scratch to be understood.

If you have persistent discomfort or pain in your eyes, do not judge it yourself and see a doctor early.
Having 'invisible scratches' discovered through a staining test is the first step toward faster healing.

Please see here for detailed articles on corneal symptoms.