Red eye & Retinal disorders Flashcards
What kind of tests can we do to inspect the retina? [6]
- Direct Ophthalmoscope
- Optical Coherence Tomography (OCT)
- Fundus Fluorescein Angiography (FFA)
- Electrical Physiology including Electroretinogram (ERG), Electroculogram (EOG) and Visually Evoked Potentials (VEP)
What is Optical Coherence Tomography? [1]
A cross sectional scan of the Fovea Centralis (Macula)
How does a Fundus Fluorescein Angiography work?
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
Name 3 of the 9 retinal layers
Layers 1,2 & 9
1 - Retinal Pigment Layer
2 - Layer of rods and cones
9 = Inner cell fiber layer
What is electrical physiology? [1]
Give 3 examples
Series of investigations recording electrical signals from the eye, optic nerve or brain in response to visual sitmuli [1]
Includes:
- Electroretinogram (ERG)
- Electrooculogram (EOG)
- Visually Evoked Potentials (VEP)
What does an electroretinogram test? [3]
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)
What does an Electrooculogram test?
What does it measure? [2]
Function of retinal pigment epithelium and photoreceptors (Layers 9 & 8). [2]
It measures the Resting Potential in both layers and forms a ratio called the Arden Ratio (1.85 is normal)
What does a Visually Evoked Potentials (VEP) Test measure? [2]
They record optic nerve function [1] by measuring electrical activity in the visual cortex [1] in response to stimuli. (if optic nerve isnt working the visual cortex wont be active)
VEP test: state the clinical significance of each of these pathological signs:
- Reduced amplitude [2]
- Latency in signal [2]
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.
List some retinal disorders
- 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
What retinal disorders cause a gradual visual loss [4] and which a sudden visual loss [4]?
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
What causes Central Retinal Vein Occlusion [4]
What causes Central Retinal Arterial Occlusion [2]
CRVO:
- Hypertension
- Glaucoma
- Hyperviscosity eg polycythemia
- Inflammation eg DM
CRAO:
- Emboli from atheromatous plaque, valve, dental abscess
- Inflammation eg SLE, IVDU
How does the retina appear on Central Retinal Vein [3] /Artery Occlusions?
CRVO: - The retina is darker - Tortuous dilated and engorged veins - Macular & Optic Disc Oedema - Cheesy pizza! Flame shaped hemorrhages All because of the back up of blood
CRAO:
- Pale retina, cherry red spot at macula
- Conspicuously lacking blood
What are the types of Ischaemic Optic Neuropathy? [3]
Arteritic (AION) - Usually caused by giant cell arteritis
Non-Arteritic (NAION) - Unknown cause
AION
- Definition [2]
- GCA presentation [6]
- GCA investigations [2]
- Treatment [2]
Optic nerve damage [1] when posterior ciliary arteries are blocked [1] by inflammation or atheroma GCA presentation - Headache - Scalp Tenderness - Jaw Claudication - Neck Pain - Nausea/Anorexia - Visual Loss/Diplopia
Test for inflammatory markers & a Temporal Artery Biopsy
Carry out ix before steroids
Treatment
- Prednisolone 80mg for 24h PO
- Taper steroids as ESR and symptoms settle, may take >1y
What are the symptoms of optic neuritis [4] and its cause [1]?
- Pain on eye movements
- acute onset Loss of vision (central scotoma)
- Relevant Afferent Pupil Defect
- Swollen Optic Disc
MS!
Define scotoma
Loss of visual acuity [1] in a specific area of vision [1]
What are the risk factors for age related macular degeneration? [3]
ARMD nature of vision loss [3]
What are the types of Age Related Macular Degeneration and explain differences in pattern of vision loss?
Age
Smoking
Poor Diet (B12 def)
Progressive loss of the central vision with distortion (metamorphopsia). Quiet eye.
Wet (20%) - sudden
Dry (80%)- slow onset, gradual
Wet AMD pathogenesis [2]
Dry ARMD description [2]
Fundal signs [4]
Wet AMD occurs when aberrant vessels grow from the choroid into neuro-sensory retina and leak
Dry ARMD- drusen and degenerative changes at the macula
Ophthalmoscope:
- Optic disc edge is made irregular by lumpy, yellow matter
- Optic cup absent
- Vessels show abnormal branching patterns
- Disciform scar - as blood vessels grow subretinally and bleed, blood reabsorbs with subsequent fibrosis and raised sub retinal scar is left
Diabetic retinopathy
What is the main first step in microvascular disease of diabetes in the eye?
Ocular changes can be classified into 2
Ocular changes can also be staged into 2
Microvascular disease leads to ocular ischemia and hypoxia, increased VEGF
Ocular changes can be classified into
- Structural changes
- Retinopathy
Stages:
- Non-proliferative diabetic retinopathy
- Proliferative diabetic retinopathy
What are Retinal Dystrophies? [3]
A large number of inherited disorders [1] which affect photoreceptor function [1] leading to Progressive Visual Loss [1]
What are the types of retinal Dystrophies? [4]
Photoreceptor Dystrophies e.g. Retinitis Pigmentosa
RPE-Dystrophies (Retinal Pigment Epithelium) e.g. Stargardt Macular Dystrophy
Choroidal Dystrophies
Vitreoretinal Dystrophies
What is retinitis Pigmentosa [2] and its inheritance [1]
Symptoms [2]
Causes severe degeneration [1] of the Rod photoreceptors [1]
Can be Autosomal dominant, recessive or x-linked. [1]
Night blindness
Tunnel vision loss (loss of peripheral retina)
Name some drugs that cause drug-induced retinopathy? [3]
Pattern of loss of vision in drug-induced retinopathy [1]
Antimalarials
Phenothiazines
Tamoxifen
All can lead to gradual loss of vision
List some modern treatments for retinal diseases? [2]
Gene Therapy
Bionic Eye
How does Gene Therapy work for retinal disorders? [3]
- Disorder due to a defective or missing gene (E.g. Choroideraemia)
- Viral vector inserts replacement gene
- Replacement gene synthesises protein
CRAO
Presentation [2]
Signs [3]
Presentation
- Dramatic visual loss within seconds of occlusion
- Episodes of amaurosis fugax
Signs:
- Afferent pupil defect + cherry red spot (fovea)
- retina appears pale
- may see emboli inside arteries
CRVO
Compare pattern of visual loss to CRAO and explain this difference [2]
State 2 types of CRVO
Pattern of visual loss
- Sudden painless visual loss
- Less sudden than CRAO why?
- Mechanism of visual loss due to development of ischemia and macular edema
Non-ischemic, ischemic CRVO
CRVO Investigation What is the treatment given and why [2] Prognosis [2] What should you aim to prevent long term [1] and how [4]
Fundus fluorescein angiogram
- Determines degree of ischemia
Treatment
- Pan-retinal photocoagulation [1] prevents and treats neovascularisation [1]
- Aim to prevent rubeotic glaucoma and painful eye
- Give beracizumab for macular edema
- dexamethasone intravitreal implants
Prognosis - visual prognosis is poor [1] even if macular edema resolves anatomically [1]
BRVO
- presentation [1]
- explain difference [2]
Presentation
- Asymptomatic if macula not affected
- Unilateral visual loss
- Visual field defect corresponds to affected area
Only a portion of retina is affected as opposed to the whole retina in central retinal a/v occlusion
But otherwise same predisposing factors as CRVO
Explain how retinal ischemia can cause macular edema [4]
- Retinal ischemia leads to release of VEGF [1]
- neovascularisation [1]
- fragile and leaky blood vessels [1]
- prone to hemorrhage [1]
- macular edema
Explain how drusen is formed in pathogenesis of dry ARMD [4]
Drusen signify optic nerve head axonal degenration [1]
Abnormal axonal metabolism leads to intracellular mitochondrial calcification [1]
Some axons rupture and mitochondria are extruded [1] into extra-cellular space
Calcium is deposited here and drusen form [1]
This causes the optic disc head to become irregular and lumpy and the optic cup to become absent with abnormal branching vessels
AMD risk factors [4]
Symptoms [5]
Signs [3]
RF:
- increasing age, smoking, CV RFs, FHx
Sy:
- initially no deterioration in visual acuity but difficulty making out images
- difficulty reading and making out faces
- difficulty with night vision and changing light conditions (specifically changes in Amsler grid self-evaluation and trouble with reading)
- visual fluctuation, metamorphsia (distortion of central vision)
- central vision loss
Si:
- poor visual acuity (especially near vision early in disease)
- full peripheral field
- quiet eye
Diabetic retinopathy Classification Mild NPDR Moderate NPDR [5] Severe NPDR [3] Proliferative diabetic retinopathy features
Structural changes
- Age-related cataracts (AGE)
- Ocular ischemia causing neovasculargenesis (rubeosis)
- Glaucoma
Mild NPDR
- 1 or more microaneurysm
Moderate NPDR
- microaneurysms
- blot haemorrhages
- hard exudates
- cotton wool spots, venous beading/looping
- intraretinal microvascular abnormalities (IRMA) less severe than in severe NPDR
Severe NPDR:
- blot haemorrhages and microaneurysms in 4 quadrants
- venous beading in at least 2 quadrants
- IRMA in at least 1 quadrant
Stage 1: hyperglycemia damages pericytes but eye exam normal
Proliferative:
- hypoxia causes increased VEGF > neovascularisation
- fragile leaky capillaries are prone to bleeding
- Vitreous hemorrhage > increased risk of RD due to fibrosis causing traction
- Maculopathy - leakage from vessels near macula cause edema
