Unilateral vision loss

Question 1

A 23-year-old woman walks into the Accident and Emergency Department. She complains of blurred and cloudy vision in her right eye. These symptoms have been present for one week. There is also discomfort behind the right eye. She has finally come to hospital because the problems with her vision got much more marked for ten minutes whilst she was having a hot bath. She has felt a little tired and under the weather for the last two weeks but denies any other physical symptoms.
The neurological examination by the admitting SHO in Accident and Emergency reveals a reduced direct light response in the right eye associated with reduced indirect response on the left. Direct and indirect light responses are normal when light is shone into the left eye. Visual acuity is 6/6 in the left eye and 6/60 in the right eye. Visual acuity in the right eye does not improve with pinhole correction. Fundoscopy, eye movement and cranial nerve examination is normal. The examination of the limbs reveals no abnormalities

Answer 1

Multiple sclerosis

Question 2

Direct and indirect light response - outline the pathway

Answer 2

Light detected - sent along optic nerve, optic tract to lateral geniculate (pretectal) nucleus, then to BOTH Edinger-Westphal nuclei (Afferent pathway)
Efferent limb = oculomotor nerves from E-W nuclei go to ciliary ganglia and cause the iris sphincters to contract and constrict the pupils

Question 3

What is a Marcus-Gunn pupil?

Answer 3

AKA:Relative afferent pupillary defect (RAPD)
A Marcus Gunn pupil is a medical sign observed during the swinging-flashlight test whereupon the patient’s affected pupil constricts less (therefore appearing to dilate) when a bright light is swung from the unaffected eye to the affected eye.

Question 4

Vascular causes of unilateral vision loss

Answer 4

Central retinal arterial occlusion (Amaurosis fugax)
Central retinal vein occlusion
Ischaemia of posterior choroidal artery via giant cell arteritis or a non arteritic cause

Question 5

Non vascular causes of unilateral vision loss

Answer 5

Optic neuritis
Retinal detachment
Vitreous haemorrhage
Acute angle closure glaucoma

Question 6

Optic neuritis - causes

Answer 6

inflammation of optic nerve

• multiple sclerosis/clinically isolated syndrome
• infection (lyme, syphilis, HIV)
• B12 deficiency
• arteritis

Question 7

optic neuritis - features/presentation

Answer 7

Reduced visual acuity over a few days
Painful to move eye
Afferent pupillary defect
Loss of colour vision (dyschromatopsia)

Question 8

optic neuritis - management

Answer 8

usually with resolve spontaneously with 6 weeks - but steroids can speed it up

40% 15 year risk of MS though

Question 9

amaurosis fugax - what is it

Answer 9

as if a curtain goes down over the eye

indicative of transient retinal ischaemia - (causes - carotid stenosis, and/or emboli to retinal artery)

Question 10

retinal vein occlusion - overview

Answer 10

common, sudden, painless unilateral loss of vision

via thrombus or compression on vein. macular oedema causes the vision loss

Question 11

retinal detachment

Answer 11

new onset of floaters/flashes
sudden onset progressive visual field loss (periphery to centre)
Relative Afferent Pupillary Defect

see specialist urgently

Question 12

vitreous haemorrhage

Answer 12

sudden painless vision loss, may have a red hue

may follow trauma especially in the young

Question 13

acute angle closure glaucoma

Answer 13

painful eye 
blurred vision - vision loss 
coloured haloes around lights 
nausea and vomiting 
red eye 
hard globe (raised intraoccular pressure)

urgent treatment required