retinal disorders

Question 1

Explain FFA

Answer 1

• Fundus Fluorescein angiography

- Injected intravenously 
- Both inner and outer blood-retinal barriers are impermeable to fluorescein
- If there is a lot of leak at the retinal level then there is a pathology
- The dye is excited by blue light but the camera can only photograph green light and so they quickly change the filter from blue to green just before the picture is taken

Question 2

Explain OCT

Answer 2

• Optical coherence tomography (OCT)
- High resolution, cross sectional images of the retina, vitreous, choroid and optic nerve
Short coherence length light

Question 3

Explain EOG

Answer 3

• Electro-oculogram (EOG)

- Measures function of RPE and photoreceptors
- Measures the resting potential difference between the RPE and photoreceptors
- Maximum potential difference in light adapted eye
- Minimum potential difference in dark adapted eye
- Arden ratio 1.85

Question 4

Explain VEP

Answer 4

Visually evoked potentials (VEP)

- Records optic nerve function
- Measures electrical activity in the visual cortex in response to either a flashing light or a checker board pattern
- Reduced amplitude: reduced cell number, ischaemic/ traumatic optic neuropathy
- Latency: reduced call function, optic neuritis (demyelination)

Question 5

What is central retinal vein occlusion?

Answer 5

• The main vein in the retina gets blocked
  
  • Common causes: Hypertension, Glaucoma, Hyperviscosity, Inflammation
    
    • Causes sudden painless loss of vission

Question 6

What is central retinal artery occlusion?

Answer 6

• Common causes: Emboli (carotids/ heart) and inflammation
  
  • In an artery occlusion the retina looks pale and doesn’t have any blood
    
    • Causes sudden painless loss of vission

Question 7

What is ischaemic optic neuropathy?

Answer 7

• Optic nerve doesn’t get a blood supply (posterior ciliary artery)
  
  • This makes the optic disk difficult to see
  • Arteritic (involves the arteries): headache, scalp tenderness, jaw claudication, neck pain, nausea/ anorexia, loss of vision (permanent), raised inflammatory markers, diagnosed with a temporal biopsy and if not treated in time it will cause death
  • Non-arteritic: better outcome as their vision can be returned almost back to normal, we don’t know what causes this

Question 8

What are the causes of sudden painless vision loss?

Answer 8

• Central retinal vein occlusion
  
  • Central retinal artery occlusion
  • Ischaemic optic neuropathy
  • Stroke
  • Vitreous haemorrhage
  • Retinal detachment
  • Sudden discovery of pre-existing unilateral LoV

Question 9

What are the retinal conditions that cause gradual painless vision loss?

Answer 9

• Cataract
	• Refractive error
	• Age related macular degeneration
	• Open angle glaucoma
	• Diabetic retinopathy
	• Hypertensive retinopathy
	• Inherited retinal dystrophies
	• Drug-induced retinopathy
	• Other acquired maculopathies
	- Central serous retinopathy
	- Idiopathic macular hole
	- Epiretinal membrane
	- Cystoid macular oedema
	- Myopic retinopathy
	- Choroidal folds
	- Angioid streaks

Question 10

Explain central retinal vein occlusion

Answer 10

• The main vein in the retina gets blocked

- Common causes: Hypertension, Glaucoma, Hyperviscosity, Inflammation

Question 11

Explain central retinal artery occlusion

Answer 11

• Common causes: Emboli (carotids/ heart) and inflammation

- In an artery occlusion the retina looks pale and doesn’t have any blood

Question 12

Explain ischaemic optic neuropathy

Answer 12

• Optic nerve doesn’t get a blood supply (posterior ciliary artery)
  
  • This makes the optic disk difficult to see
  • Arteritic (involves the arteries): headache, scalp tenderness, jaw claudication, neck pain, nausea/ anorexia, loss of vision (permanent), raised inflammatory markers, diagnosed with a temporal biopsy and if not treated in time it will cause death
  • Non-arteritic: better outcome as their vision can be returned almost back to normal, we don’t know what causes this