What is Vitritis and Anterior Chamber Reaction?
Vitritis is inflammation involving the vitreous body (the gel-filled posterior chamber of the eye), characterized by cellular infiltration that creates haziness and obscures visualization of the posterior segment, while anterior chamber reaction refers to inflammation in the anterior chamber manifested by inflammatory cells (cell) and protein (flare), often with hypopyon, fibrin, or hyphema. 1
Vitritis
Vitritis represents extension of intraocular inflammation into the vitreous cavity, typically occurring as:
- Cellular infiltration of the vitreous body that creates haziness and obscures fundus visualization 2
- Progression from chorioretinitis where infection or inflammation extends from the retinal/choroidal layers into the vitreous 1
- Can present with dense, grayish vitreous bands particularly in the peripheral fundus, depending on etiology 3
Clinical Significance of Vitritis
Vitritis indicates more severe disease with worse visual outcomes compared to isolated chorioretinitis 1. This occurs because:
- Many antifungal and antimicrobial agents cannot achieve adequate concentrations in the avascular vitreous body
- Higher organism burden exists in the posterior chamber
- Fungal or bacterial abscesses may be hidden by vitreal haziness and are inaccessible to systemic agents 1
Grading and Assessment
Vitreous haze is traditionally graded using the Standardization of Uveitis Nomenclature (SUN) classification with six severity grades 4. However, this subjective grading has significant interobserver variability and poor reproducibility, particularly in mild inflammation 5.
Anterior Chamber Reaction
Anterior chamber reaction manifests as inflammation within the space between the cornea and iris, characterized by:
Key Components:
- Cell: White blood cells floating in the aqueous humor
- Flare: Protein leakage creating a "Tyndall effect" (light scatter visible on slit-lamp examination)
- Hypopyon: Layered white blood cells settling inferiorly in the anterior chamber
- Fibrin: Fibrinous exudate
- Hyphema: Blood in the anterior chamber 6
Clinical Context
Anterior chamber reaction is frequently present alongside bacterial keratitis and other infectious/inflammatory conditions 6. The presence and severity help distinguish:
- Infectious causes: Often accompanied by pain, redness, photophobia, and conjunctival injection
- Non-infectious inflammation: May present without pain or significant external signs 7
Important Clinical Pitfall
The hypopyon in bacterial keratitis is usually sterile, and aqueous or vitreous taps should NOT be performed unless there is high suspicion of microbial endophthalmitis (following intraocular surgery, perforating trauma, or sepsis) 6.
Combined Presentation
When both anterior chamber reaction and vitritis occur together, this suggests:
- Endophthalmitis (exogenous or endogenous) 1
- Severe uveitis with pan-ocular inflammation 2, 8
- Drug-related inflammation (e.g., following intravitreal anti-VEGF injections) 7, 3
Management Implications
The extent of ocular infection must be determined by an ophthalmologist to guide treatment decisions 1:
- Isolated chorioretinitis: Systemic therapy may suffice
- Vitritis present: Requires intravitreal injection of antimicrobials PLUS consideration of vitrectomy 1
- Anterior chamber involvement: May require anterior chamber paracentesis for diagnosis 9
Critical principle: Decisions regarding antifungal/antimicrobial treatment and surgical intervention should be made jointly by an ophthalmologist and infectious diseases physician 1.