Visual loss (general)

Question 1

How do you characterise visual loss?

Answer 1

Gradual:
Days, weeks, months
Often degenerative, neuropathic and vascular aetiology
Opticians are valuable sources of advice

Sudden:
Seconds, minutes, hours
Often inflammatory, vascular occlusions or bleeding aetiology

Can also be acute on chronic OR gradual loss that has only just been noticed (and thus mistaken for sudden onset)

Question 2

What things are important in a history and examination of visual loss?

Answer 2

Hx:

• Onset - duration, time course
• Distortion i.e. straight lines are kinked (RED FLAG e.g. retinal detachment, macular degeneration)
• Pain (RED FLAG e.g. GCA, acute glaucoma)
• PMHx - e.g. inflammatory illnesses
• FHx

Examination:

• Assess vision - ask, simple rating of mild-moderate-profound, characterise by loss of daily activities, objective look using Snellen’s
• Check pupils - for relative afferent pupil defect (RAPD)
• Test field - for central scotoma (e.g. “can you see my face clearly?”) and hemianopia (which can sometimes be misinterpreted as a total loss of vision in one eye so if claiming this but score well on acuity this might be the cause)
• Ask about colour vision - can also test directly (compare L+R)

Question 3

What are some common causes of gradual loss?

Answer 3

Presbyopia (age related visual loss)
Cataracts 
Chronic glaucoma 
Macular degeneration 
Optic nerve compression 

May also just need a glasses test

Question 4

What are some causes of sudden + subacute onset sight loss?

Answer 4

Sudden onset:
Ischaemic optic retinopathy 
Retinal detachment 
Vitreous haemorrhage 
Vascular occlusions 
Acute glaucoma 

Subacute/other serious:
Optic/retrobulbar neuritis
Visual field defects (homonomous and bilateral hemianopias from vascular or neoplastic causes)
Transient visual loss (papilloedema, GCA, emboli, from TIA

All need accurate identification and timely referral to stop further serious damage occurring

Question 5

How does ischaemic optic neuropathy present?

Answer 5

Abrupt and profound sight loss

Symptoms of PMR/GCA

RAPD

Question 6

How does retinal detachment present?

Answer 6

3 F’s:

Flashes

Floaters

Field loss

Visual distortion (kinked straight lines)

Question 7

How do vitreous haemorrhages present?

Answer 7

Abrupt (minutes), variable sight loss

Often NO RAPD

Question 8

How do vascular occlusions present?

Answer 8

Abrupt and variable sight loss

Can be arterial or venous

May have RAPD

Central vs branch retinal vein occlusion:

• venous occlusion leads to haemorrhage from capillary beds
• central vein is large so haemorrhage is large, possibly whole eye
• branch veins are smaller so haemorrhage is smaller/localised

Question 9

How does acute glaucoma present?

Answer 9

Abrupt sight loss

Eye PAIN

Unresponsive pupil? (RAPD?)

Conjunctival injection

Elderly

Question 10

How does optic neuritis present?

Answer 10

Usually progressive over days

Painful visual loss, central scotoma

RAPD

Colour desaturation

Other symptoms of demyelination

Neurology advice/referral required

Question 11

What are the DVLA minimum sight requirements?

Answer 11

Car drivers:

• In good daylight, be able to read a modern vehicle number plate at the distance of 20 metres
• Visual acuity must be at least Snellen 6/12 with both eyes open

Lorry drivers:
- Visual acuity needs to be at least Snellen 6/7.5 in better eye and 6/60 in poorer

Both:

• Field of vision = 120 degrees horizontal
• Some scotomas are acceptable - may need to check with ophthalmology etc

If fail to meet - DVLA can revoke license

Question 12

How do you interpret a Snellen’s chart?

Answer 12

Patient to stand 20ft/6m away from chart

• Ask if they normally wear glasses (will want to wear for test)
• Read the lowest line, with each eye then with both eyes

Which line the person can successfully read to is denoted by a fraction e.g. 6/6 = normal vision at 6m, 6/12 = you need to be at 6m to read what a person could normally read from 12m away