A 32-year-old woman presents with acute onset photophobia, pain, and blurred vision. Slit-lamp examination reveals granulomatous anterior uveitis with posterior synechiae. B-scan ultrasonography shows no posterior segment involvement. Which clinical feature best distinguishes anterior uveitis from posterior uveitis in this patient?

Explanation

## Discriminating Features Between Anterior and Posterior Uveitis ### Key Anatomical Distinction **Key Point:** Keratic precipitates (KPs) and anterior chamber (AC) cells are the most specific clinical signs that **positively identify** anterior uveitis and distinguish it from posterior uveitis, where these findings are characteristically absent. ### Comparative Table | Feature | Anterior Uveitis | Posterior Uveitis | |---------|-----------------|-------------------| | **Keratic precipitates** | Present (granulomatous or non-granulomatous) | Absent | | **Anterior chamber cells/flare** | Prominent | Minimal or absent | | **Vitritis / floaters** | Absent or minimal | Prominent (hallmark) | | **Photophobia / pain** | Marked | Minimal (but can overlap) | | **Posterior synechiae** | Common | Absent | | **Chorioretinal lesions** | Absent | Present | | **Vision loss** | Mild–moderate | Can be severe | ### Why Option B is Correct The question asks which feature **best distinguishes anterior uveitis** in this patient. The gold-standard discriminators are **slit-lamp findings**: keratic precipitates deposited on the corneal endothelium and cells/flare in the anterior chamber. These are **pathognomonic of anterior segment inflammation** and are absent in isolated posterior uveitis (Kanski, Clinical Ophthalmology 9e, Ch 8). - **Option A (Photophobia and pain):** These symptoms occur in anterior uveitis due to ciliary spasm, but they are **non-specific symptoms** that can also occur in other anterior segment conditions and even in severe posterior uveitis with secondary anterior involvement. They are symptoms, not signs, and are less specific as discriminators. - **Option C (Association with systemic granulomatous diseases):** Both anterior AND posterior uveitis can be granulomatous (e.g., sarcoidosis causes both). This does not distinguish between the two. - **Option D (Vitritis and floaters):** These are hallmarks of **posterior uveitis**, not anterior uveitis. The question asks what distinguishes anterior uveitis — vitritis/floaters would be absent in anterior uveitis, making this a feature of the opposite entity. ### Clinical Pearl **Clinical Pearl:** On the slit lamp, KPs (especially mutton-fat KPs in granulomatous disease) and AC cells/flare are the definitive signs of anterior uveitis. Their presence localizes inflammation to the anterior segment; their absence, combined with vitritis, localizes it posteriorly. (Kanski Clinical Ophthalmology 9e; Yanoff & Duker Ophthalmology 5e) ### High-Yield Mnemonic **Mnemonic:** **KP = Keratic Precipitates = Keratouveitis = anterior**; **VF = Vitritis + Floaters = posterior** [cite:Kanski Clinical Ophthalmology 9e Ch 8; Yanoff & Duker Ophthalmology 5e]