Disorders of the Retina Flashcards
What does a slit lamp examine?
Anterior of the eye
-everything is reversed
What does an ophthalmoscope examine?
Posterior of the eye
- Everything right way up and round
- Bit like looking through a keyhole through
What does biometry do?
Measures shape and size of eye.
Commonly used to calculate power of the intraocular lens implants for cataract and refractive surgery
What does perimetry do?
Systematic measurement of visual field
What does a fundus camera do?
Takes a photo of the back of the eye (retina).
Like a large ophthalmoscope with a camera attached
What is optical coherence tomography?
Optical Coherence Tomography, or ‘OCT’, is a technique for obtaining sub-surface images of translucent or opaque materials at a resolution equivalent to a low-power microscope. It is effectively ‘optical ultrasound’, imaging reflections from within tissue to provide cross-sectional images.
Allows you to look at the fovea as a cross section
What is Fluorescein Angiography?
Medical procedure where a fluorescent dye is injected into the bloodstream. The dye highlights blood vessels in the back of the eye so that they can be photographed.
Describe Fleurescin and its reaction with the Blood-Retinal barrier
85% bound to serum proteins
15% unbound “free”
Inner + Outer Blood-retinal barrer
(retinal capillaries + zonula occludens respectively)
-Impermeable to fleuroscein
Choriocapillaris
-Permeable only to “free” fluorescein
What light do you shine on the eye in Fluorescein angiography and what shines back?
Shine blue at the eye and green light given off
How do cones and rods differ?
Just cones at fovea
Cones more to do with central vision and colour
Rods more black and white and periphery of visual field
What does electrophysiology do?
Series of investigations recording electrical signals from the eye, optic nerve and brain in response to visual stimuli
What is an electroretinogram (ERG)?
Measures retinal function
Records action potentials within the retina.
Different waves measure different cells.
Can test both rods and cones
What is an electro-oculogram (EOG)?
Measures function of RPE and photoreceptors
Measures resting potential difference between the RPE and photoreceptors
- Max PD in light adapted eye
- Max PD in dark adapted eye
What is 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
What does reduced amplitude and latency in VEP indicate?
Reduced amplitude:
- Reduced cell number
- Ischaemic/traumatic optic neuropathy
Latency:
- Reduced cell function
- Optic neuritis (demyelination)
What methods can you use to detect retinal pathology?
Visual acuity, visual fields, colour vision, RAPD
Fundoscopy
Fleorescein angiography
Optical coherence tomography (OCT)
Electrophysiology
What is RAPD?
Relative Afferent Pupillary Defect
In optic nerve pathology what is usually the first aspect of eyesight to go?
Colour vision
before visual acuity and visual fields
What causes sudden painless loss of vision?
- Central retinal vein occlusion
- Central retinal artery occlusion
- Ischaemic optic neuropathy
- Stroke
- Vitreous haemorrhage
- Retinal detachment
- Sudden discovery of pre-existing unilateral LoV
What can cause Central Retinal Vein Occlusion (CVAO)?
Hypertension
Glaucoma
Hyperviscosity
Inflammation
What can cause Central Artery Occlusion (CRAO)?
Emboli (carotids/heart)
Inflammation
What are the two types of Ischaemic Optic Neuropathy?
Arteritic (AION)
Non-Arteritic (NAION)
What are the symptoms of Giant cell arteritis?
Headache Scalp tenderness Jaw claudication Neck pain Nausea/anorexia Loss of vision
What is the cardinal feature of giant cell arteritis?
Raised inflammatory markers
What is the gold standard in diagnosis of giant cell arteritis?
Temporal artery biopsy
What are the symptoms and signs of optic neuritis?
-Pain on eye movements (nerve becomes inflamed) -Reduced vision -Red desaturation (loss of colour first, esp red) -Central scotoma -Relative afferent pupil defect -Swollen optic disc
What conditions cause gradual painless loss of vision?
- Cataract
- Refractive error
- Age-related macular degeneration
- Open angle glaucoma
- Diabetic retinopathy
- Hypertensive retinopathy
- Inherited retinal dystrophies
- Drug-induced retinopathy
What is age-related macular degeneration?
Common:
- 10% >65
- 30% >75
Progressve loss of central vision
Risk factors:
- Age
- Smoking
- Poor diet
What are the two types of age-related macular degeneration?
Dry type (80-90%)
- Slow onset
- Atrophy
Wet type (10-20%)
- More aggressive
- Neurovascular membrane (blood and fluid)
Briefly describe diabetic retinopathy
Diabeted damages pericytes which make up the capillary walls.
Contents of blood vessels leak out. This can be fluid or lipids
Outpouching of capillaries (microaneurysms) along with lipid deposits may be seen
What are pericytes?
Pericytes are contractile cells that wrap around the endothelial cells of capillaries and venules throughout the body.
What is VEGF?
Vascular Endothelial Growth Factor
Causes angiogenesis
Released during ischaemia
What vascular abnormalities may VEGF cause
Angiogenesis forms vessels that grow into vitreous and very commonly bleed
Can occur with diabetic retinopathy
How do you treat vascular abnormalities (commonly caused by VEGF)?
Laser treatment
- Destroys 80% of retina at periphery
- VGEF production reduced and vessels shrink
- Field of vision effected a bit but patient will be still able to see and may even drive
Injections in the eye every 6 months
What may advanced diabetic retinopathy cause?
Scarring and possible retinal detachment
What are retinal dystrophies?
Series of inherited conditions affecting photoreceptor function leading to progressive loss of vision
What retinal dystrophies may you get?
- Photoreceptor dystrophies (ERG reduced)
- RPE dystrophies (EOG reduced)
Give some examples of photoreceptor dystrophies
Retinitis pigmentosa
Cone dystrophy
Leber’s congenital amaurosis
Give some examples of RPE- dystrophies
Best’s vitelliform macular dystrophy
Stargardt macular dystrophy
Sorby macular dystrophy
North Carolina macular dystrophy
Give some examples of Choroidal dystrophies
Choroideraemia
Gyrate atrophy
Give some examples of Vitreoretinal dystrophies
Stickler syndrome
Congenital retinoschisis
What is Retinitis Pigmentosa?
Inheritence 1:4000
Predominantly rod
Tunnel vision as rods start to die off to the cones in the centre
Dead and dying RPE forming pigmentation
What is cone dystrophy?
Photopic ERG rediced (tested in light = cones effected)
Scotopic normal (tested in dark and rods not damaged)
What is the inheritance of Best’s Vitelliform Macular Dystrophy?
Dominant
What is the inheritance of stargart macular dystrophy?
Recessive (90%)
What is the inheritance of sorby macular dystrophy?
Dominant
What is the inheritance of north carolina macular dystrophy?
Dominant
What is choroideraemia?
Inheritance = x-linked recessive
-Incidence 1:50,000
Choroid is damaged and so develops this pale appearance
What is the inheritance of gyrate atrophy?
Inheritance = recessive
What drugs cause drug indiced retinopathy?
Antimalarials
- Chloroquine
- Hydroxycholoroquine
Phenothiazines
Tamoxifen
How do you treat an idiopathic macular hole?
Surgery
What is myopic retinopathy?
Short sightedness
Retina is streched as eye is abnormally large. Retina may tear.
Rare
What condition can you consider gene therapy as a treatment?
Choroideraemia
