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A hypopyon is a collection of white blood cells that forms in the front part of the eye, called the anterior chamber. Because of gravity, these cells settle at the bottom of the chamber, creating a visible white or yellowish layer. A hypopyon is not a disease itself. Instead, it is a serious sign of a major infection or inflammation inside the eye.
read more about hypopyon ...A hypopyon appears as a milky white or yellow fluid level in the lower part of the colored iris. It is often seen with a very red and painful eye. The line it creates is typically flat and horizontal. The size can vary from a very thin layer to one that fills a large portion of the front of the eye.
A hypopyon is caused by a condition that triggers a strong inflammatory response in the eye. A common cause is a severe infection, such as a corneal ulcer or an infection inside the eyeball called endophthalmitis, which can happen after surgery or an injury. It can also be caused by severe, non-infectious inflammation, known as uveitis.
Seeing a hypopyon is always a sign of a serious eye problem that can threaten your sight. The conditions that cause it, especially infections like endophthalmitis, can lead to permanent vision loss or even the loss of the entire eye if not treated immediately. It is a medical emergency.
While a hypopyon looks like pus, it is not always caused by bacteria. It is a collection of white blood cells (leukocytes).
Infectious Hypopyon - Caused by bacteria, fungi, or viruses replicating in the eye (e.g., after surgery or trauma). This is an emergency.
Sterile Hypopyon - Caused by the body's immune system overreacting to toxins or systemic autoimmune diseases (like Behcet’s disease) without active bacteria present. Both require urgent treatment, but the medications used are different.
You might notice that the white line of a hypopyon is always perfectly level and at the bottom of the iris. This is due to gravity. The white blood cells are heavier than the aqueous fluid filling the eye. When you stand or sit upright, they sink and create a sediment layer. If you were to lie on your side for a long period, the line would actually shift to the side of the eye.
Yes. The underlying problems that cause a hypopyon, like a severe infection or inflammation, are usually very painful. Other symptoms often include redness, extreme light sensitivity, and blurry vision.
No. The hypopyon itself will only go away when the underlying cause is treated with medicine. You must see an eye doctor to treat the serious condition that is causing it.
No, they are very different. A hypopyon is a collection of cells in the fluid space in front of the iris. A cataract is a clouding of the lens, which is located behind the iris.
You must go to an eye doctor or an emergency room immediately if you see a white or yellow layer forming in your eye. Do not wait. This is an urgent situation that requires immediate medical care to find the cause and begin treatment to protect your vision.
1. Hypopyon: What It Is, Causes & Treatment. Cleveland Clinic. https://my.clevelandclinic.org/health/symptoms/hypopyon. November 25, 2024.
2. Overview of Uveitis. Merck Manual Professional Edition. https://www.merckmanuals.com/professional/eye-disorders/uveitis-and-related-disorders/overview-of-uveitis. Accessed March 30, 2026.
3. Endophthalmitis. Sriram Simakurthy and Koushik Tripathy. https://www.ncbi.nlm.nih.gov/books/NBK559079/. August 25, 2023.
4. Bacterial Keratitis. EyeWiki. https://eyewiki.org/Bacterial_Keratitis. March 10, 2026. Toxic Anterior Segment Syndrome. EyeWiki. https://eyewiki.org/Toxic_Anterior_Segment_Syndrome. December 29, 2025.
5. Toxic Anterior Segment Syndrome. EyeWiki. https://eyewiki.org/Toxic_Anterior_Segment_Syndrome. December 29, 2025.