Neuro-ophthalmology Flashcards
Describe optic neuropathy?
-Neuropathy = disease or dysfunction of one or more peripheral nerves
-Damage to the optic nerve due to any cause – encompasses optic atrophy, optic oedema, optic neuritis
-Both swelling and atrophy give signs of optic neuropathy
Describe optic atrophy?
-Type of optic neuropathy
-Atrophy = wasting away
-Generally causes pale coloured nerve
Describe optic oedema?
-Type of optic neuropathy
-Oedema = swelling
Describe optic neuritis?
-Type of optic neuropathy
-‘itis’ = inflammation
-Kanski: inflammation, infection or demyelinating process of the optic nerve
-Retrobulbar neuritis = inflammation of optic nerve just behind the ONH ONH may look normal but something behind it is causing inflammation
-MS is most common cause of optic neuritis –> demyelinating process of optic nerve
List all the possible symptoms a px with a neuro issue may have?
- Decreased vision:
o H&S important to find out if refractive problem or neuro - Pain
- Headache:
o Common symptom of neuro problem - Double vision:
o Common symptom of neuro problem - Ocular motility problems:
o If problem with nerve supply - Nystagmus / spontaneous eye movements
- Pupillary abnormalities
- Eyelid / facial / head abnormalities
- Transient visual loss (short period of time)
- Illusions / hallucinations
- Higher cortical function:
o Dyschromatopsia – colour defects – px experiences loss of intensity or saturation or total loss of colour perception
o Visual agnosia – problem with recognition of visually presented objects
o Micropsia – objects perceived to be smaller than actually are
o Macropsia – objects perceived to be bigger than they are
o Metamorphopsia – if px looks at grid of straight line, lines appear wavy, parts of grid may appear missing - Ataxia (loss of bodily movement), hemiparesis (weakness of one entire side of body) / hemisensory weakness (loss of sensation on one half of body)
Describe history of reduced vision in neuro and the symptoms/time course?
Associated symptoms
* – do they happen at the same time? w/ the reduced vision?
* Unilateral/bilateral:
o Unilateral: lesion anterior to chisam
Some pxs may say if affects RE but they actually mean right side of their vision
Get them to shut each eye to check this
Homonymous hemianopia: pxs often describe as monocular involvement on side of affected hemifield
o Bilateral: either bilateral optic nerve or retinal, chiasmal or retrochiasmal disease
* Time course:
o Rules of thumb:
Minutes: ischaemic retinal event
* Blockage of BV can happen v quickly & reduced vision happening v quick
Hours: most commonly ischaemic, more likely optic nerve
Days-weeks: more frequently inflammation (may reflect ischaemia)
Months-years: compressive
o There could be overlap – not everything follows the above
o Pxs can become suddenly aware of chronic problem when fellow eye covered
Ask px to describe what happened – px may describe that they covered eye
Describe sympathetic innervation of pupil?
- Innervates dilator pupillae muscle
- Info leaves eye, travels along short ciliary nerve, synapsing in ciliary ganglion
o Keeps travelling towards brain via 3rd CN, synapsing at Edinger-Westphal nucleus & then hypothalamus - Sympathetic innervation going back to dilator pupillae, starts at hypothalamus, travels down spinal cord where it synapses, before travelling within spine to level between C8 & T1.
o Travel upwards & synapse in superior cervical ganglion.
o Continue to travel up to level of internal carotid artery (in neck).
o Travel alongside ophthalmic division of trigeminal ganglion.
o Fibres pass through ciliary ganglion w/o synapsing & join the short & posterior ciliary nerves back into eye & back to dilator – causing dilation of pupil in dim light
Describe parasympathetic innervation of pupil?
- Innervates sphincter pupillae muscle – causes pupil constriction
- Afferent pathway – light travels AWAY from eye to brain
o If light shone into left eye (see left image), at optic chiasm it branches & ½ of info goes to R side of brain & ½ goes to L side & ends up in R & L pretectal nuclei - Efferent pathway – light travels from brain to Eye
o Starts at pretectal nuclei, some info crosses over just as leaving pretectal nuclei – info from one pretectal nucleus goes to both eyes, travels to Edinger-Westphal nuclei, then via CN3, synapsing at ciliary ganglion & travelling into eye via short ciliary nerves, moving forward & innervating sphincter pupillae muscle
What are the four steps in investigating pupils?
- Observe size, shape & (a)symmetry of pupils
- Check for direct & consensual reflexes
- Swinging flashlight test (check for RAPD)
- Check for near reflex
Describe the first step in testing pupils - 1. observe size, shape & (a)symmetry of pupils
- A distant, non-accommodative target (spot light) in dim light
- Evaluate if px’s pupil are round, symmetrical, regular
- Anisocoria:
o Difference of >0.4mm between 2 eyes
o 25% of normal have this in dim light, 10% in room light
o If anisocoria is present, measure pupil sizes in dim & bright light
o If difference remains constant in all light levels: likely to be normal
o If difference largest in dim light: could be normal or possibly problem with dilation of smaller pupil
o If difference largest in bright light: possibly problem with constriction of larger pupil
Describe the second step in testing pupils - 2. check for direct & consensual reflexes
- Shine pen torch onto RE, observe R pupil reaction, remove
o R direct - Shine pen torch onto RE, observe L pupil reaction, remove
o L consensual - Shine pen torch onto LE, observe L pupil reaction, remove
o L direct - Shine pen torch onto LE, observe R pupil reaction, remove
o R consensual - Can get no response, or sluggish responses (or normal)
o E.g. LE Direct no response - Magnitude of response correlated to degree of damage (not necessarily acuity)
- Direct reflex affected: problem anywhere in nerve pathway
- Direct reflex reduced but not absent: could be problem anywhere in nerve pathway
- No direct reflex in one eye & no consensual reflex in other eye: likely to be problem inside eye/affecting nerve of eye where direct response affected
- Direct but no consensual: problem with efferent (brain –> eye) of consensual eye
Describe the third step in testing pupils - 3. swinging flashlight test (check for RAPD)?
- Shine light into one eye, observe direct and consensual response
- After 2-3 seconds, QUICKLY swap the light to the other eye, looking for any change in pupil size of this eye
- After 2-3 seconds, QUICKLY swap the light to the first eye, looking for any change in pupil size of this eye
- RAPD:
o Gross retinal abnormality (VA 6/60 or worse), in one eye or asymmetric
o Impaired optic nerve function – unilateral – before optic chiasm
o Asymmetric chiasmal compression – affecting optic chiasm but location affecting one eye more than other
o Everything from optic chiasm backwards NOT likely to get RAPD because nerve fibres have crossed over - 3 types of response:
o Pupil stays constricted (normal) = no RAPD
o Pupils dilate fully = total RAPD
o Pupils dilate a little bit and slowly; sluggish response = partial RAPD
o Magnitude correlated to degree of damage to nerve (not necessarily acuity)
o Partial Left RAPD = LE has dilated a little when moved light onto it - RAPD: extra tips:
o May be detected even if pupillary response in 1 eye cannot be evaluated – trauma, pharmacologic
o RAPD does not result in anisocoria – RAPD & anisocoria are independent findings
o Which 2 pathways are affected in a L RAPD? The afferent pathway from LE to left side of brain and the afferent pathway from LE to right side of brain
Describe the fourth step in testing pupils - 4. near reflex
o No condition where near reflex is solely affected – so in general, this is only needed if one of above 3 steps is abnormal narrows down where problem is
o Look at distant, non-accommodative target – in dim light illumination
o Look at near, accommodative target - ~30cm – budge stick – look from spotlight to letter on stick – binocularly – should be constriction at near & dilation at distance
Which tests should be involved in fundus examination of neuro cases?
- Volk lens to get 3D view
- OCT
- Pictures
Plus: colour vision, contrast sensitivity, visual fields
Describe Visual Field Testing and lesions/what would you expect to see (neuro)?
- Supplements acuity in assessing visual loss
- Helps localise lesion along afferent visual pathway
- Quantifies defect and assesses change over time – do it repeatedly on different visits
- Choice of field testing
o Degree of detail required
o Patient’s ability to co-operate - Confrontational, Amsler, Perimetry
- Post-chiasmal defects affect both eyes & respect vertical midline
o Further back the defects are more congruous (similar between the two eyes)
o Keep going back, defects are more homonymous (same part of VF in both eyes)
o Further back in optic radiations towards cortex, macula is interpreted in different place to peripheral fibres so get macular sparing or just macula affected - Lesion at Retina:
o If lesion affect RNFL, in general it would follow the RNFL pattern & respects horizontal midline due to anatomy of RNFL
o Affects one eye only or would be difference/asymmetry between the 2 eyes - Lesion affecting Optic Nerve:
o Large defect/lesion affecting optic nerve no visual field in that eye but other eye unaffected - Lesion affecting nasal part of left optic nerve:
o Produces temporal visual field defect in LE one eye only - Lesion affecting centre of optic chiasm (where fibres cross):
o Likely to cause bitemporal hemianopia
o At optic chiasm –> macular fibres go through centre, inferior fibres cross anteriorly looping into contralateral optic radiations, superior fibres cross posteriorly looping into ipsilateral optic radiations before crossing over
o Lesion on one side of optic chiasm just pressing –> nasal part of one eye affected
o Lesion on one side of optic chiasm but pressing hard & compressing fibres on other side too –> binasal hemianopia - Lesion affecting optic radiations:
o Both eyes affected – inferior right VFs - Lesion affecting further back in optic radiations:
o Affects right VFs of both eyes with macular sparing - Lesion affecting primary visual cortex:
o Affects right side of macula in both eyes
