Retinal Disorders

Question 1

What retinal diseases can lead to sudden painless loss of vision?

Answer 1

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

Question 2

What retinal conditions cause gradual painless loss of vision?

Answer 2

Cataracts
Refractive error
Age-related macular degeneration
Open angle glaucoma
Diabetic retinopathy
Hypertensive retinopathy
Inherited retinal dystrophies
Drug-induced retinopathy

Question 3

How does the retina appear in central artery/vein occlusion?

Answer 3

Artery occlusion

• Pale retina
• Cherry red macula
• Vessel attenuation
• Cattle-tracking

Vein occlusion

• Tortuous dilated veins
• Optic disc swelling
• Might have cotton wool spots
• Widespread haemorrhage

Question 4

How do optic neuritis and ischaemic optic neuropathies develop?

Answer 4

Ischaemic Optic neuropathies

• Arteritic (AION) - Giant-cell arteritis
• Non-arteritic (NAION) - optic disc shape and CV risk factors

Optic neuritis

• infections
• toxins
• neurological disorders

Question 5

Signs/symptoms of optic neuritis?

Answer 5

Pain on eye movements
Reduced vision
Red desaturation
Central scotoma
Relative afferent pupil defect
Swollen optic disc

Question 6

Signs/symptoms of ischaemic optic neuropathies

Answer 6

Sudden, painless loss of vision
Giant cell arteritis symptoms
- headache
- scalp tenderness
- jaw claudication
- neck pain
- nausea/anorexia
- raised inflammatory markers
- temporal artery biopsy

Question 7

What is age-related macular degeneration and what are the risk factors?

Answer 7

Progressive loss of central vision
Dry type (80-90%) and wet type (blood, fluid)

Age
Smoking
Poor Diet

Question 8

What is a retinal dystrophy?

Answer 8

Series of inherited conditions affecting photoreceptor function leading to progressive loss of vision
E.g. retinitis pigmentosa
Can be photoreceptor or retinal pigment epithelium (RPE)

Question 9

What is retinitis pigmentosa?

Answer 9

Photoreceptor dystrophy
1:4000 inheritance
Predominantly rod-related
20% Sporadic
40% Dominant
20% Recessive

Question 10

How would photoreceptor dystrophies compare to retinal pigment epithelium (RPE)-dystrophies in terms of investigation results?

Answer 10

Photoreceptor dystrophies have reduced Electroretinogram

RPE dystrophies have reduced Electrooculogram

Question 11

What investigations are used in retinal disorders?

Answer 11

Acuity, fields, colour vision, relative afference pupillary defect
Fundoscopy
Fluorescein angiography
Optical coherence tomography
Electroretinogram (ERG)
Electrooculogram (EOG)
Visually-evoked potentials (VEP)

Question 12

How does each electrophysiology retinal test work?

Answer 12

Electroretinogram

• measures retinal function via action potentials
• a-waves from photoreceptors, b-waves from Muller’s cells

Electrooculogam

• measures function of retinal pigment epithelium and photoreceptors via resting potential difference between the RPE and photoreceptors
• max potential difference in light adapted eye
• minimum potential difference in dark adapted eye
• Arden ratio 1.85

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 cell function > optic neuritis (demyelination)

Question 13

How can newer therapies be used to treat retinal pathology?

Answer 13

Choroideraemia - (choroidal dystrophy) - x-linked recessive

• gene therapy
• viral vector to insert replacement gene

Bionic eye
- Retinal implant of 60 electrodes connected to camera