A 32-year-old man presents with acute anterior uveitis. All of the following are characteristic features of anterior uveitis EXCEPT:

Explanation

## Anterior vs. Posterior Uveitis: Key Distinction **Key Point:** Anterior uveitis is inflammation of the iris and ciliary body; posterior uveitis involves the choroid, retina, and vitreous. The clinical presentation differs fundamentally between the two. ### Characteristic Features of Anterior Uveitis | Feature | Anterior Uveitis | Posterior Uveitis | |---------|------------------|-------------------| | **Primary site of inflammation** | Iris, ciliary body | Choroid, retina, vitreous | | **Keratic precipitates** | Present (on corneal endothelium) | Absent or minimal | | **Posterior synechiae** | Common (iris-lens adhesions) | Not applicable | | **Ciliary injection** | Prominent | Minimal or absent | | **Photophobia** | Marked | Absent | | **Vitritis** | Minimal or absent | Prominent (snowball opacities, snowbanking) | | **Floaters** | Absent | Prominent | **High-Yield:** Snowball opacities and snowbanking are pathognomonic for **posterior uveitis**, not anterior uveitis. These represent vitreous inflammation and are the primary finding in conditions like pars planitis, toxoplasmosis, and acute retinal necrosis. ### Why the Distractors Are Correct Features of Anterior Uveitis 1. **Keratic precipitates** — Collections of inflammatory cells (lymphocytes, plasma cells, epithelioid cells) on the corneal endothelium; hallmark of anterior uveitis. 2. **Posterior synechiae** — Iris-lens adhesions that form when fibrin and inflammatory exudate cause the iris to stick to the lens; occur in chronic anterior uveitis and can lead to pupillary membrane formation and iris bombé. 3. **Ciliary injection and photophobia** — Ciliary body inflammation causes circumcorneal injection ("ciliary flush"); photophobia results from iris irritation and ciliary spasm. **Clinical Pearl:** A patient with anterior uveitis presents with a red eye, photophobia, and pain; vision is often relatively preserved initially. In contrast, posterior uveitis presents with floaters, photopsia, and visual field defects, but minimal eye redness or photophobia. **Warning:** Do not confuse the clinical presentation. Snowball opacities = posterior uveitis. Keratic precipitates + ciliary injection = anterior uveitis.