Ophthalmology · UKMLA & AKT
Optic neuritis
A free high-yield preview for the UKMLA Applied Knowledge Test, covering how to recognise this condition. The full SA Note notes add investigations, management and complications, with practice questions on this topic.
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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