Ophthalmology · UKMLA & AKT
Optic neuritis
A free high-yield preview for the UKMLA Applied Knowledge Test. Below are the key points to recognise optic neuritis — the full SA Note notes add investigations, management, complications and 10 practice questions.
Key high-yield points
- Painful monocular vision loss - subacute onset over hours to days, ranging from mild blur to near-total loss
- Pain on eye movement - traction on inflamed optic nerve sheath; highly specific feature
- Red desaturation (dyschromatopsia) - red objects appear washed out; colour vision often first deficit to appear
- Central scotoma - most common visual field defect; papillomacular bundle involvement
- Relative afferent pupillary defect (RAPD) - Marcus Gunn pupil on swinging light test; paradoxical dilation when light swung to affected eye
- Uhthoff's phenomenon - temporary worsening with raised body temperature (exercise, hot bath); does NOT represent a new relapse
- Fundoscopy: retrobulbar neuritis (most common) - normal disc acutely; papillitis (anterior) - swollen disc; chronic - disc pallor
Classic teaching: in retrobulbar neuritis 'the patient sees nothing, and neither does the doctor' - normal fundoscopy does NOT exclude optic neuritis.
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