What does a hypopyon represent on slit-lamp examination?

Layered white blood cells in the anterior chamber Hypopyon is an accumulation of white blood cells forming a visible fluid level inferiorly when the patient is upright; it is a sign, not a disease.

Layered blood in the anterior chamber

Lens material released after capsule rupture

Pigment released from the iris pigment epithelium

Which mechanism produces the layered appearance of a hypopyon?

Neutrophils and fibrin settling inferiorly under gravity Inflammatory cells, mainly neutrophils, migrate from limbal vessels into the anterior chamber and settle inferiorly with fibrin and exudate under gravity.

Osmotic drawing of aqueous into the iris stroma

Blockage of the trabecular meshwork by protein

Reflux of vitreous through a zonular dehiscence

What is the most common infectious cause of hypopyon?

Postoperative endophthalmitis after intraocular surgery Postoperative endophthalmitis, usually after cataract or other intraocular surgery, is the most common infectious cause of hypopyon.

Ocular toxoplasmosis reactivation

Congenital rubella-associated uveitis

Which feature suggests a sterile rather than infectious hypopyon?

Mobile material that shifts with head position Sterile hypopyon, as in Behcet disease, is typically non-adherent to the corneal endothelium and moves freely, while infectious hypopyon is sticky and immobile from fibrin deposition.

Dense fibrin strands crossing the pupil

Marked corneal oedema with a ring infiltrate

Turbid material adherent to the endothelium

Which systemic condition causes a non-infectious hypopyon?

HLA-B27-associated acute anterior uveitis Non-infectious causes include HLA-B27-associated acute anterior uveitis, Behcet disease, Vogt-Koyanagi-Harada syndrome and sympathetic ophthalmia.

Chronic obstructive pulmonary disease

Which investigation is used when hypopyon obscures the fundus view?

B-scan ultrasonography When the posterior segment cannot be examined directly, B-scan ultrasonography detects vitreous echoes that point to endophthalmitis.

Fluorescein angiography of the posterior pole

Gonioscopy of the anterior chamber angle

Which entity most closely mimics a true hypopyon in the anterior chamber?

Pseudohypopyon from tumour cells or lipid material Pseudohypopyon, formed by tumour cells, haemorrhage or lipid, layers like pus and must be distinguished from an inflammatory hypopyon, as must hyphema.

Krukenberg spindle on the endothelium

Posterior synechiae after chronic iritis

Keratic precipitates in a triangular distribution

Which intravitreal regimen is used for hypopyon due to endophthalmitis?

Vancomycin with ceftazidime Immediate broad-spectrum intravitreal vancomycin 1 mg/0.1 ml plus ceftazidime 2.25 mg/0.1 ml is given, with vitrectomy reserved for severe or non-resolving cases.

Amphotericin B with voriconazole

What is the first-line topical treatment for a non-infectious hypopyon?

Prednisolone acetate 1% with a cycloplegic Sterile hypopyon is treated with tapering topical prednisolone acetate 1% plus a cycloplegic such as atropine to ease pain and prevent synechiae.

Fortified tobramycin drops hourly

Topical ganciclovir gel five times daily

Topical mitomycin C for two weeks

How does prognosis differ between infectious and sterile hypopyon?

Infectious is guarded, sterile usually resolves with steroids Infectious hypopyon has a guarded prognosis and delayed treatment risks irreversible loss, whereas sterile hypopyon usually clears with corticosteroids but recurs if systemic disease stays uncontrolled.

Both resolve fully once the cornea clears

Sterile carries the higher risk of permanent blindness

Neither affects final visual acuity if treated late

Hypopyon: When Pus Fills the Eye - Ophthalmology Education

Case Study

A 55-year-old man presented with an acute onset of redness, severe pain, and decreased vision in his left eye for two days. He had undergone cataract surgery one week earlier.

On slit-lamp examination, his visual acuity was counting fingers at 1 meter, with intense conjunctival injection, corneal edema, and a dense layer of white fluid occupying one-third of the anterior chamber inferiorly — a classic hypopyon.

The pupil was poorly reactive, and the view of the posterior segment was obscured. B-scan ultrasonography revealed dense vitreous echoes suggestive of endophthalmitis.

A diagnosis of postoperative infectious endophthalmitis with hypopyon formation was made. The patient was treated urgently with intravitreal antibiotics (vancomycin and ceftazidime) and intensive topical therapy.

Over the next several days, the hypopyon gradually resolved, and pain subsided, but visual recovery remained limited due to retinal involvement.

Disease Overview

Hypopyon refers to the accumulation of white blood cells (pus) in the anterior chamber of the eye, forming a visible fluid level when the patient is upright.

It is a sign of severe intraocular inflammation, usually secondary to infection (such as bacterial or fungal endophthalmitis) or intense sterile inflammation (as in Behçet’s disease or HLA-B27-associated uveitis).

Hypopyon is not a disease by itself but rather a clinical sign indicating a serious underlying ocular or systemic condition that requires prompt diagnosis and management.

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Pathophysiology

Hypopyon develops when inflammatory cells (mainly neutrophils) migrate from the limbal vasculature into the anterior chamber in response to infection or inflammation.

These cells, along with fibrin and exudates, accumulate at the bottom of the anterior chamber due to gravity. The process is mediated by cytokines, chemokines, and increased vascular permeability in the iris and ciliary body.

In infectious causes, bacterial toxins or fungal elements directly stimulate this intense immune response. In non-infectious causes (e.g., autoimmune uveitis), immune complexes or autoantigens trigger the inflammatory cascade without microbial invasion.

The hypopyon may be sterile (non-infectious) or purulent (infectious) depending on the etiology.

Etiology

The causes of hypopyon can be divided broadly into infectious and non-infectious origins:

Infectious Causes:
- Postoperative Endophthalmitis: The most common cause, usually following cataract or intraocular surgery.
- Post-traumatic Endophthalmitis: Following penetrating injuries with contamination.
- Corneal Ulcers (Bacterial, Fungal, or Acanthamoeba): Severe keratitis can lead to spillover inflammation in the anterior chamber.
- Endogenous Endophthalmitis: Secondary to systemic sepsis, such as from Staphylococcus aureus or Candida albicans infections.
Non-Infectious Causes:
- HLA-B27-associated Acute Anterior Uveitis
- Behçet’s Disease
- Vogt-Koyanagi-Harada Syndrome
- Sympathetic Ophthalmia
- Rheumatoid Arthritis-associated Sclerouveitis
- Leukemic Infiltration or Masquerade Syndromes

Clinical Features

Patients with hypopyon typically present with:

Severe ocular pain, photophobia, and redness
Blurring of vision or decreased visual acuity
White or yellow layer in the lower anterior chamber is visible even without magnification
Conjunctival and ciliary injection
Corneal edema (especially in infectious cases)
In sterile hypopyon, the fluid is usually immobile and may shift minimally with head movements
In infectious hypopyon, the material may appear turbid, mobile, and accompanied by fibrin strands

A distinguishing feature of sterile hypopyon (e.g., in Behçet’s disease) is that it is often non-adherent to the corneal endothelium and tends to move freely, whereas in infectious causes (e.g., bacterial keratitis or endophthalmitis), the hypopyon is sticky and immobile due to fibrin deposition.

Diagnostic Evaluation

A comprehensive workup is crucial to determine the underlying cause:

Slit-Lamp Examination: Confirms the presence and extent of hypopyon, corneal ulceration, or keratic precipitates.
Fundus Examination: If possible, to assess posterior segment involvement; if obscured, perform B-scan ultrasonography.
Anterior Chamber Tap or Vitreous Tap: For microbiological culture and sensitivity testing in suspected endophthalmitis.
Corneal Scrapings: In ulcer-related hypopyon, smears and cultures identify causative pathogens.
Blood Tests: ESR, CRP, HLA-B27 typing, autoimmune markers, and infectious serologies (if systemic disease is suspected).
Imaging: Optical Coherence Tomography (OCT) may reveal anterior chamber reaction and retinal involvement in non-infectious cases.

Differential Diagnosis

Pseudohypopyon (from tumor cells, hemorrhage, or lipid material)
Hyphema (blood in the anterior chamber)
Endogenous endophthalmitis
Sterile postoperative inflammation
Inflammatory uveitis without layering

Management

The treatment of hypopyon depends entirely on the underlying etiology:

Infectious Hypopyon (Endophthalmitis or Corneal Ulcer):
- Immediate broad-spectrum intravitreal antibiotics: Vancomycin (1 mg/0.1 ml) + Ceftazidime (2.25 mg/0.1 ml).
- Intensive topical antibiotics: Fortified tobramycin or cefazolin for corneal ulcers.
- Systemic antibiotics or antifungals: Based on culture results.
- Surgical intervention: Pars plana vitrectomy in severe or non-resolving cases.
Non-Infectious Hypopyon (Uveitis):
- Topical corticosteroids: Prednisolone acetate 1% drops, tapered gradually.
- Cycloplegic agents: Atropine or cyclopentolate to relieve pain and prevent synechiae.
- Systemic corticosteroids or immunosuppressive agents: In Behçet’s disease or autoimmune uveitis.
- Biologic therapies: Anti-TNF agents (e.g., infliximab) in refractory cases of Behçet’s or HLA-B27 uveitis.

Prognosis

The prognosis of hypopyon depends on the speed of diagnosis and the underlying cause.

Infectious hypopyon has a guarded prognosis; delayed treatment often results in irreversible vision loss due to retinal damage or scarring.
Sterile hypopyon usually resolves completely with corticosteroid therapy, but recurrence is common if the underlying systemic disease remains uncontrolled.

Early intervention, appropriate antimicrobial or anti-inflammatory therapy, and careful follow-up are key to preserving vision and preventing complications such as secondary glaucoma or corneal decompensation.

Prevention

Use protective eyewear during high-risk activities to prevent ocular trauma.
Maintain sterile surgical techniques to minimize postoperative infections.
Monitor systemic inflammatory diseases closely to prevent recurrent uveitis episodes.

References

Taban M, Behrens A, Newcomb RL, Nobe MY, Saedi G, Sweet PM, McDonnell PJ. Acute endophthalmitis: incidence, presentation, management, and visual outcome. Ophthalmology. 2005;112(7):1180–1186.
Nussenblatt RB, Whitcup SM. Uveitis: Fundamentals and Clinical Practice. 5th ed. Elsevier; 2021.
Okada AA, Johnson MW, Liles WC. Endophthalmitis: update on causative organisms, diagnosis, and management. Curr Opin Ophthalmol. 2020;31(3):207–213.
Sakai J, Fukushima A. Immune mechanisms of hypopyon formation in autoimmune uveitis. Front Immunol. 2022;13:868345.

Test yourself

A few questions straight from this article.

1 / 10 0 correct

What does a hypopyon represent on slit-lamp examination?
Hypopyon is an accumulation of white blood cells forming a visible fluid level inferiorly when the patient is upright; it is a sign, not a disease.
Which mechanism produces the layered appearance of a hypopyon?
Inflammatory cells, mainly neutrophils, migrate from limbal vessels into the anterior chamber and settle inferiorly with fibrin and exudate under gravity.
What is the most common infectious cause of hypopyon?
Postoperative endophthalmitis, usually after cataract or other intraocular surgery, is the most common infectious cause of hypopyon.
Which feature suggests a sterile rather than infectious hypopyon?
Sterile hypopyon, as in Behcet disease, is typically non-adherent to the corneal endothelium and moves freely, while infectious hypopyon is sticky and immobile from fibrin deposition.
Which systemic condition causes a non-infectious hypopyon?
Non-infectious causes include HLA-B27-associated acute anterior uveitis, Behcet disease, Vogt-Koyanagi-Harada syndrome and sympathetic ophthalmia.
Which investigation is used when hypopyon obscures the fundus view?
When the posterior segment cannot be examined directly, B-scan ultrasonography detects vitreous echoes that point to endophthalmitis.
Which entity most closely mimics a true hypopyon in the anterior chamber?
Pseudohypopyon, formed by tumour cells, haemorrhage or lipid, layers like pus and must be distinguished from an inflammatory hypopyon, as must hyphema.
Which intravitreal regimen is used for hypopyon due to endophthalmitis?
Immediate broad-spectrum intravitreal vancomycin 1 mg/0.1 ml plus ceftazidime 2.25 mg/0.1 ml is given, with vitrectomy reserved for severe or non-resolving cases.
What is the first-line topical treatment for a non-infectious hypopyon?
Sterile hypopyon is treated with tapering topical prednisolone acetate 1% plus a cycloplegic such as atropine to ease pain and prevent synechiae.
How does prognosis differ between infectious and sterile hypopyon?
Infectious hypopyon has a guarded prognosis and delayed treatment risks irreversible loss, whereas sterile hypopyon usually clears with corticosteroids but recurs if systemic disease stays uncontrolled.

Hypopyon: When Pus Fills the Eye