Describe how you would identify the cause of an ophthalmology problem?
- History - Full medical and neurological exam - Blood tests - Imaging (MRI)
Ocular motility defects can be caused by defects in...? (5 answers)
CN III CN IV CN VI Inter-nuclear Supra-Nuclear
Describe CN VI palsy?
Most common cranial nerve palsy Cranial Nerve 6 - Abducens Causes abduction of the lateral rectus If palsy, eye is unable to abduct (remains staring straight ahead while the other eye abducts)
Cause of CN VI palsy?
Microvascular (Micro-stroke) Raised intracranial pressure Tumour Congenital
Describe how raised intracranial pressure cause CN VI palsy?
CN VI has to pass over the petrous tip of the temporal bone Raised ICP can press the nerve against the bone and cause palsy
Describe CN IV palsy?
2nd most common cranial nerve palsy Cranial Nerve 4 = Trochlear Innervates superior oblique to cause abduction, elevation and intorsion In palsy, eye is unable to fully depress when in adduction
Causes of CN IV palsy?
Most commonly congenital Then microvascular Tumour Trauma (if bilateral)
If a patient presents with a BILATERAL CN IV palsy, what would you expect the cause to be?
Blunt Trauma to the head
Patient presents with - Inability to full depress both eyes in abduction - Chin depressed - Extorsion of eyes
CN IV Palsy Due to blunt trauma to head
Patient present with: - Headache - Sudden onset - Inability to abduct one eye?
CN VI Palsy Probably caused by raised ICP
Describe CN III palsy?
Cranial nerve 3 = Oculomotor Innervates all other extra-ocular muscles Least common but important not to miss Eye looks DOWN and OUT Pupil may also be dilated in aneurysm
Patient presents with: - Eye looking down - Eye abducted - Pupil dilated - Painful
CN III palsy Caused by aneurysm = EMERGENCY
Causes of CN III palsy?
Microvascular (most common and benign) Aneurysm (Emergency) Tumour MS Congenital
Difference between microvascular-caused CN III palsy and aneurysm causing CN III palsy?
- Aneurysm is painful - Aneurysm is an emergency - Aneurysm causes dilated pupils
Look at this photo
Appreciate cranial nerves
Describe briefly how the eyes work when you hear a noise to your left?
Eyes work together Both move to left Both move at same time and at same speed
Describe internuclear ophthalmoplegia?
This is a disorder of gaze (where eyes move to same place at the same time) Caused by failure of adduction of one eye Causes horizontal diplopia (double vision)
Most causes of Internuclear ophthalmoplegia?
Caused by dysfunction in the medial longitudinal fasciculus This can be caused by MS (young) or vascular (e.g.: Stroke in elderly)
Describe the optic pathway?
Light hits retina Optic Nerve Optic Chiasma Optic Tract Optic Radiation Visual cortex of the occipital lobe
Give some causes of visual field defects?
Vascular (Strokes) Space Occupying Lesions Demyelination (MS) Trauma (eg: Surgery)
What causes damage to the optic nerve?
Ischaemic Optic Neuropathy (Damage due to lack of blood) Optic Neuritis - Inflammation of optic nerve (Caused by demyelination and inflammatory changes seen in MS) Tumours
Describe the visual field defects from optic nerve?
Can affect entire field of vision Can affect just the superior/inferior parts If vascular cause, commonly just the top or bottom is affected and not both (altitude)
Describe Optic Neuritis?
Inflammation of the optic nerve Often painful Progressive Loss of quality of vision (but most vision is still retained) Will get better over a period of months but some atrophy may have occurred
What can affect the optic chiasma?
Pituitary Tumours (Common) Craniopharyngioma (Seen in children, Rare) Meningioma (Rare)
Describe how visual loss is caused by optic chiasma pathology? What happens after treatment?
Compression causes visual field defects (Eg: Bitemporal hemianopia) After surgery, normal vision is restored
Patient presents with: - Bitemporal Hemianopia?
What can affect the optic tract and radiations?
Tumours Demyelination Vascular Abnormalities
Describe the visual field disturbance from an optic tract/optic radiation pathology?
Homonymous defects No macula sparing Quadrantanopia (Quadrants affected)
What can affect the visual cortex?
Vascular Disease (CVA) Demyelination
Describe the visual field disturbance from a visual cortex pathology?
Homonymous Defect Macular Sparing
When considering a differential, age is important
In someone over 50, most likely cause for ocular disease?
In someone in their 20s?
In someone aged 5 with a head tilt?
Congenital 4th Nerve Palsy