Retinal Disorders

Question 1

What kind of tests can we do to inspect the retina?

Answer 1

• Direct Ophthalmoscope
• Optical Coherence Tomography
• Fundus Fluorescein Angiography (FFA)
• Electrical Physiology including Electroretinogram (ERG), Electroculogram (EOG) and Visually Evoked Potentials (VEP)

Question 2

What is Optical Coherence Tomography?

Answer 2

A cross sectional scan of the Fovea Centralis (Macula)

Question 3

How does a Fundus Fluorescein Angiography work?

Answer 3

Fluorescein dye injected

• > Binds to blood proteins
• > Blue light shone in and excites the fluorescein
• > Light returns and the yellow-green light is isolated with a filter
• > Yellow-green light shows shines on a film
• > Fluorescein filled vessels appear white

This will help you spot any blockages or bleeds from an optical artery

Question 4

What are the important layers of the retina for us measly 2nd yrs?

Answer 4

Layers 1,2 & 9
1 - Retinal Pigment Layer
2 - Layer of rods and cones
9 = Inner cell fiber layer

Question 5

What is electrical physiology?

Answer 5

Series of investigations recording electrical signals from the eye, optic nerve or brain in response to visual sitmuli

Includes:

• Electroretinogram (ERG)
• Electrooculogram (EOG)
• Visually Evoked Potentials (VEP)

Question 6

What does an electroretinogram test?

Answer 6

Action Potentials in the retina in order to measure retinal function

An A wave ERG tests photoreceptors
A B wave ERG tests Muller’s Cells (Retinal Glial cells)

Question 7

What does an Electrooculogram test?

Answer 7

Function of retinal pigment epithelium and photoreceptors (Layers 9 & 8).

It measures the Resting Potential in both layers and forms a ratio called the Arden Ratio (1.85 is normal)

Question 8

What does a Visually Evoked Potentials (VEP) Test measure?

Answer 8

They record optic nerve function by measurin electical activity in the visual cortex in response stimuli. (You know cos if optic nerve isnt working the visual cortex wont be active)

Question 9

What are the pathological signs on a VEP test?

Answer 9

A reduced amplitude in the signals means theres a reduced cell number. Most often due to Ischaemic or Traumatic Optic Neuropathy.

Latency in the signal means the cell function is reduced. Most often due to Optic Neuritis causing demyelination.

Question 10

List some retinal disorders

Answer 10

• Central Retinal Vein Occlusion
• Central Retinal Artery Occlusion
• Ischaemic Optic Neuropathy
• Optic Neuritis
• Retinal Detachment
• Age Related Macular Degeneration
• Diabetic Retinopathy
• Hypertensive Retinopathy
• Inherited Retinal Dystrophies
• Drug Induced Retinopathy

Question 11

What retinal disorders cause a gradual visual loss and which a sudden visual loss?

Answer 11

Gradual:

• Age-related Macular Degeneration
• Diabetic Retinopathy
• Inherited Retinal Dystrophies
• Drug Induced Retinopathy

Sudden:

• Retinal Detachment
• Optic Neuritis
• Ischaemic Optic Neuropathy
• Central Retinal Artery or Vein Occlusion

Question 12

What causes Central Retinal Vein or arterial occlusions?

Answer 12

CRVO:

• Hypertension
• Glaucoma
• Hyperviscosity
• Inflammation

CRAO:

• Emboli
• Inflammation

Question 13

How does the retina appear on Central Retinal Vein/Artery Occlusions?

Answer 13

CRVO:
- The retina is darker
- Tortuous dilated veins
- Macular & Optic Disc Oedema
All because of the back up of blood

CRAO:

• Pale
• Conspicuously lacking blood

Question 14

What are the types of Ischaemic Optic Neuropathy?

Answer 14

Arteritic (AION) - Usually caused by giant cell arteritis

Non-Arteritic (NAION) - Unknown cause

Question 15

What is Giant cell arteritis, its symptoms and tests?

Answer 15

The most common form of vasculitis.

• Headache
• Scalp Tenderness
• Jaw Claudication
• Neck Pain
• Nausea/Anorexia
• Visual Loss/Diplopia

Test for inflammatory markers & a Temporal Artery Biopsy

Question 16

What are the symptoms of optic neuritis and its cause?

Answer 16

Most commonly cause is MS

• Pain on eye movements + acute onset Loss of vision
• Relevant Afferent Pupil Defect
• Swollen Optic Disc
• Central Scotoma

Question 17

Define scotoma

Answer 17

Loss of visual acuity in a specific area of vision

Question 18

What are the risk factors for age related macular degeneration?

Answer 18

Age
Smoking
Poor Diet

ITs a progressive loss of the central vision

Question 19

What are the types of Age Related Macular Degeneration?

Answer 19

Dry - 80% of cases - Due to Retinal Atrophy - Slow Onset

Wet - 20% - Blood & fluid in the retina - Sudden onset

Question 20

How does diabetic retinopathy occur?

Answer 20

Microvascular disease leads to:

• Capillary Non-perfusion
• Micro aneurysms
• Capillary Fallout

All of which cause the retina to become ischaemic

Question 21

What are Retinal Dystrophies?

Answer 21

A large number of inherited disorders which affect photoreceptor function leading to Progressiv e Visual Loss

Question 22

What are the types of retinal Dystrophies?

Answer 22

Photoreceptor Dystrophies e.g. Retinitis Pigmentosa
RPE-Dystrophies (Retinal Pigment Epithelium) e.g. Stargardt Macular Dystrophy
Choroidal Dystrophies
Vitreoretinal Dystrophies

Question 23

How do the different types of retinal dystrophies show up on electrical physiology testing?

Answer 23

Photoreceptor Dystrophies have a reduced ERG

RPE-Dystrophies have a reduced EOG

Question 24

What is retinitis Pigmentosa and its inheritance?

Answer 24

Inherited dystrophy causing severe degeneration of the Rod photoreceptors

Can be Autosomal dominant, recessive or sporadic.
Approximately 1 in 4000

Question 25

Name some drugs that cause drug-induced retinopathy?

Answer 25

Antimalarials
Phenothiazines
Tamoxifen

All can lead to gradual loss of vision

Question 26

List some modern treatments for retinal diseases?

Answer 26

Gene Therapy

Bionic Eye

Question 27

How does Gene Therapy work for retinal disorders?

Answer 27

• Disorder due to a defective or missing gene (E.g. Choroideraemia)
• Viral vector inserts replacement gene
• Replacement gene synthesises protein