Optic neuritis (OP) Flashcards
Define optic neuritis.
Inflammation of the optic nerve
What is the most common cause of optic neuritis?
Multiple sclerosis
Who does optic neuritis affect most? (2)
- F>M
- 30-50 years
What is the most common form of optic neuritis?
Idiopathic optic neuritis - primary demyelinating disease occurring in isolation or as part of MS
What are some infectious aetiologies of optic neuritis?
Rare but include Lyme disease and syphilis
What portions of the optic nerve might optic neuritis include?
May involve retrobulbar or intrabulbar portion of the optic nerve, or both:
- retrobulbar –> retrobulbar neuritis
- intrabulbar –> papillitis
How does optic neuritis manifest?
Subacute or acute onset of pain in the eye, and pain with eye movements and loss of vision, typically with central or centrocaecal scotoma (blind spot) that usually reaches its worst at approximately 1-2 weeks
What are the clinical features of optic neuritis? (8)
- vision loss - relatively quick, over hours to days
- decrease in visual acuity over days to weeks with scotoma (foggy)
- peri-orbital/retro-ocular pain exacerbated by eye movements
- colour desaturation (red)/loss of colour vision
- RAPD
- optic disc swelling
- phosphenes (bright interrupted circles)
- MS symptoms
What is relative afferent pupillary defect (optic neuritis)?
- both pupils paradoxically dilate when bright light swung from unaffected eye to affected eye
- this is because, when light shone on unaffected eye both pupils constrict (afferent pathway controlling both eyes working), but when we switch to affected eye, optic nerve (afferent pathway) is injured so both pupils dilate instead of constricting
What two phenomena are seen in optic neuritis?
- Uhtoff’s phenomenon - worsening of visual or other neurological Sx that accompanies an increase in body temperature
- Pulfrich’s phenomenon - illusion, altered perception of moving objects
What are some risk factors for optic neuritis? (4)
- 30-50y
- female sex
- white ethnicity
- HLA-DRB1*1501 genotype
What are the first-line investigations for optic neuritis? (3)
- MRI of optic nerves
- FBC
- ESR & CRP
What scan do we do in optic neuritis and what would we see?
Gadolinium-enhanced MRI of orbit and brain - enlarged and enhanced optic nerve, and helps diagnose MS too (white matter lesions)
How do we check for RAPD in optic neuritis?
Swinging light test - paradoxical dilation of both eyes when light shone on affected eye
What might uric acid be like in optic neuritis?
Low in MS and primary demyelinating optic neuritis
