A 28-year-old woman presents with sudden-onset visual loss in the left eye over 24 hours, accompanied by pain on eye movement. Fundoscopy reveals hyperaemia of the optic disc with blurred margins, and visual evoked potentials show delayed latency. All of the following are features of papillitis EXCEPT:

Explanation

## Distinguishing Papillitis from Papilloedema ### Definition and Core Pathology **Papillitis** is inflammation of the optic nerve head (anterior optic neuritis), whereas **papilloedema** is passive swelling of the optic disc due to raised intracranial pressure (ICP). ### Key Differentiating Features | Feature | Papillitis | Papilloedema | |---------|-----------|---------------| | **Onset** | Acute (hours to days) | Gradual (days to weeks) | | **Pain on eye movement** | Present (90%) | Absent | | **Visual acuity** | Severely reduced early | Normal until late stages | | **RAPD** | Present | Absent (unless bilateral or severe) | | **Disc appearance** | Hyperaemic, blurred margins | Hyperaemic, blurred margins | | **Associated symptoms** | Colour vision defects, scotoma | Headache, vomiting, diplopia | | **Aetiology** | Demyelination, infection, inflammation | Raised ICP | ### High-Yield Distinguishing Points **Key Point:** Papillitis = **inflammation** (painful, vision loss early); Papilloedema = **mechanical** (painless, vision preserved until late). **Clinical Pearl:** The presence of **pain on eye movement** is virtually pathognomonic for papillitis and rules out papilloedema. This is a cardinal feature tested frequently in NEET PG. **High-Yield:** RAPD is present in papillitis because there is direct damage to axons at the optic nerve head. In papilloedema, RAPD is absent unless the swelling is severe and bilateral, or there is underlying optic atrophy. **Mnemonic — PAPILLITIS features:** **PAIN** (Pain on movement, Acute onset, Inflammation, No ICP elevation) ### Why Option 4 is Incorrect Option 4 states "**Bilateral optic disc swelling with normal visual acuity is the hallmark finding**" — this is a **hallmark of papilloedema**, NOT papillitis. In papillitis: - Swelling is typically **unilateral** (though bilateral cases occur in demyelinating disease) - Visual acuity is **severely compromised** from the outset - The patient presents with acute vision loss, not preserved vision This is the classic trap: confusing the clinical presentation of the two entities. ### Clinical Context The stem describes a young woman with: - Sudden vision loss (papillitis) - Pain on eye movement (papillitis) - Delayed VEP latency (demyelination, suggesting optic neuritis/papillitis) - Hyperaemic disc with blurred margins (both can show this) All findings point to **papillitis**, making option 4 the incorrect statement about papillitis features. [cite:Harrison 21e Ch 379]