Retinal Disorders Flashcards
What examinations of the eyes can be carried out?
- Direct ophthalmoscope
- Indirect ophthalmoscope
- Fundoscopy
- Biometry
- Perimetry
- Optical coherence tomography
- Fluorescein angiography
What is the inner blood-retinal barrier (retinal capillaries) impermeable to?
Fluorescein
What is the outer blood-retinal barrier (zonula occludens) impermeable to?
Fluorescein
What is the choriocapillaries permeable to?
Free fluorescein
In fluorescein angiography how does the fluorescein bind?
- 85% bound to serum proteins
- 15% unbound free fluorescein
What type of light excites fluorescein in the blood vessels?
Blue light
What type of light emerges from the eye during fluorescein angiography?
Yellow-green and blue light
What type of cells are more prevalent in the fovea?
Cone cells
What is the blind spot?
The area where there is no photoreceptors
Electrophysiology
A series of investigations recording electrical signals from the eye, optic nerve and brain in response to visual stimuli
Electroretinogram
-Measures retinal function
Records action potentials within the retina (a waves from photoreceptors and b waves from Muller’s cells)
Electro-oculogram
- Measures function of RPE and photoreceptors
- Measures resting potential difference between the RPE and photoreceptors
- Maximum potential difference in light adapted eye
- Minimum potential difference in dark adapted eye
- Arden ration 1.85
Visually Evoked Potentials
- Records optic nerve function
- Measures electrical activity in the visual cortex in response to either a flashing light or a checker board pattern
What can visually evoked potentials reveal?
Reduced amplitude -Reduced cell number -Ischaemic/traumatic optic neuropathy Latency -Reduced cell function -Optic neuritis
What investigations should be carried out to diagnose a retinal pathology?
- Visual acuity, visual fields, colour vision, RAPD
- Fundoscopy
- Fluorescein angiography
- Optical coherence tomography
- Electrophysiology
What can cause 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 are the common causes of central retinal vein occlusion?
Hypertension
- Glaucoma
- Hyper viscosity
- Inflammation
What are the common causes of central retinal artery occlusion?
- Emboli (carotids/heart)
- Inflammation
What are the 2 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 investigative result may indicate giant cell arteritis?
- Raised inflammatory markers
- Positive temporal artery biopsy
What are the signs and symptoms of optic neuritis?
- Pain on eye movements
- Reduced vision
- Red desaturation
- Central scotoma
- Relative afferent pupil defect
- Swollen optic disc
What can cause gradual painless loss of vision?
- Cataract
- Refractive error
- Age-related macular degeneration
- Open-angle glaucoma
- Diabetic retinopathy
- Hypertensive dystrophies
- Inherited retinal dystrophies
- Drug-induced retinopathy
What does age-related macular degeneration present with?
Progressive loss of central vision
What is the prevalence of age-related macular degeneration?
Common
- 10% >65
- 30% >75
What are the risk factors for age-related macular degeneration?
- Age
- Smoking
- Poor diet
What are the 2 types of age-related macular degeneration?
- Dry type
- Wet type
How does dry type age-related macular degeneration present?
- Atrophy
- Drusen
What does diabetic retinopathy present with?
- Cotton wool spots
- Exudates
- Vascular anomalies
- Maculopathy
Retinal dystrophies
Series of inherited conditions affecting photoreceptor function leading to progressive loss of vision
Give examples of photoreceptor dystrophies (ERG reduced)
- Retinitis pigmentosa
- Cone dystrophy
- Leber’s congenital amaurosis
Give examples of RPE-dystrophies (EOG reduced)
- Best’s vitelliform macular dystrophy
- Stargardt macular dystrophy
- Sorsby macular dystrophy
- North Carolina macular dystrophy
Give examples of choroidal dystrophies.
- Choroideraemia
- Gyrate atrophy
Give examples of vitreoretinal dystrophie.
- Stickler syndrome
- Congenital retinoschisis
What does retinitis pigmentosa predominantly affect?
Rod cells
What are the different paths of inheritance of retinitis pigmentosa?
- Sporadic
- Dominant
- Recessive
- X linked recessive
- Unknown
What are the different paths of inheritance for cone dystrophy?
- Sporadic
- Dominant
- X-linked recessive
How does photopic ERG present in cone dystrophy?
Reduced
What is the scotopic of cone dystrophy?
Normal
What is the inheritance of Best’s vitelliform macular dystrophy?
Dominant
What is the inheritance of Stargardt macular dystrophy?
Recessive
What is the inheritance of Sorsby macular dystrophy?
Dominant
What is the inheritance of North Carolina macular dystrophy?
Dominant
What is the inheritance of Choroideraemia?
X-linked recessive
What is the inheritance of gyrate atrophy?
Recessive
Give examples of drugs that can induce retinopathy?
- Antimalarials
- Phenothiazines
- Tamoxifen
Give examples of other acquired maculopathies?
- Central serous retinopathy
- Idiopathic macular hole
- Epiretinal membrane
- Cystoid macular oedema
- Myopic maculopathy
- Choroidal folds
- Angioid streaks
How does gene therapy work?
- Defective or missing gene
- Uses viral vector to insert replacement gene into host DNA
- Replacement gene synthesises protein
