Retinal Disorders Flashcards
What instrument is used to examine the retina?
An ophthalmoscope
Can be direct or indirect
What is the purpose of biometry?
Calculates lens power
What is the purpose of perimetry?
Calculates the visual field
What is a fundus camera used for?
A fundus camera or retinal camera is a specialized low power microscope with an attached camera designed to photograph the interior surface of the eye, including the retina, retinal vasculature, optic disc, macula, and posterior pole (i.e. the fundus).
Which imaging modality allows the production of cross sectional images of the eye?
Optical coherence tomography
What is fluorescin angiography?
Fluorescent dye is injected into the bloodstream. The dye highlights the blood vessels in the back of the eye so they can be photographed.
What are the common conditions fluorescin angiography is used for?
Macular degeneration
Diabetic retinopathy
What are the risks associated with fluorescin angiography?
Nausea
Vomitting
Severe allergic reaction (anaphylaxis)
What are the ocntraindications of fluorescin angiography?
Poor kidney function
Pregnancy
What does electrophysiology determine?
It is a series of investigations recording electrical signals from the eye, optic nerve and brain in response to visual stimuli
What electrophysiology test measures retinal function?
Electroretinogram
How does an electroretinogram work?
Measures the electrical activity generated by neural and non-neuronal cells in the retina in response to a light stimulus
ERGs are obtained using electrodes embedded in a corneal contact lens, which measure a summation of retinal electrical activity at the corneal surface
What electrophysiology test measures RPE and photreceptors?
RPE is called the retinal pigment epithelia
Electro-oculogram
How is the arden ration derived in an electro-oculogram?
During dark adaptation, resting potential decreases slightly and reaches a minimum (“dark trough”) after several minutes. When light is switched on, a substantial increase of the resting potential occurs (“light peak”)
Arden ratio is light peak / dark trough and is usually 1.85
What test is used to record optic nerve function?
Visually evoked potentials
(Used to aid the diagnosis of MS)
How does visually evoked potentials work?
Measures electrical activity in the visual cortex in response to either a flashing light or a checker board pattern
What can visually evoked potentials be used to detect?
A tumor compressing the optic nerve, an ischemic disturbance, or a demyelinating disease
Although VEP is not a specific test so detailed history and MRI may be needed to uncover the aetiology
What are causes of sudden painless loss of vision?
- Central retinal vein occlusion
- Central retinal artery occlusion
- Ischaemic optic neuropathy
- Stroke
- Vitreous haemorrhage - (leakage, of blood into the areas in and around the vitreoushumor of the eye)
- Retinal detachment
- Sudden discovery of pre-exisiting unilateral LoV
What are common causes of central retinal vein occlusion?
Hypertension
Glaucoma
Hyperviscosity
Inflammation
The artery and the vein are in the same bundle – atherosclerosis in the artery causes occlusion in the vein
Lots of blood on fundoscopy means vein occlusion
What are causes of central retinal artery occlusion?
Emboli (from the carotid arteries and heart)
Inflammation
What are the findings of central retinal artery occlusion on fundoscopy?
Pale retina
Central cherry spot
What are the findings of ischaemic optic neuropathy on fundoscopy?
Poor visualisation of the optic disk
What are the two types of ischaemic optic neuropathy?
Arteritic (giant cell arteritis)
Non-arteritic (associated with a better porgnosis)
What are the symptoms of giant cell arteritis?
Headache
Scalp tenderness
Jaw claudication
Neck pain
Nausea/anorexia
Loss of vision
Includes raisedinflammatory markers
Needs a temporal artery biopsy
What are the symptoms and signs of optic neuritis?
Pain on eye movements
Reduced vision
Red desaturation (red colour appears washed out - pink or orange instead of red)
Central scotoma
Relative afferent pupil defect
Swollen optic disc
What are the causes of 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 are the two types of age related macular degeneration and what causes them?
Dry AMD - Dry AMD develops when the cells of the macula become damaged by a build-up of deposits called drusen
Wet AMD - develops when abnormal blood vessels form underneath the macula and damage its cells.
In the wet form, anti-VEGF medication injected into the eye or less commonly laser coagulation or photodynamic therapy may slow worsening
What part of the vision does macular degeneration affect?
AMD or ARMD, is a medical condition which may result in blurred or no vision in the center of the visual field
What are the features of diabetic retinopathy on fundoscopy?
Cotton wool spots
Exudates
What are the features of non-proliferative diabetic retinopathy?
No symptoms
The only way to detect NPDR is by fundus photography, in which microaneurysms (microscopic blood-filled bulges in the artery walls) can be seen. If there is reduced vision, retinal ischaemia can be detected by using fluorescin angiography, this will show narrowing or blocked retinal blood vessels. If the patient experiences blurred vision or darkened or distorted images, this can be as a result of macular oedema in which blood vessels leak their contents into the macular region.
Optical Coherence Tomography can show the areas of retinal thickening (due to fluid accumulation) of macular edema.[6]
What happens during proliferative diabetic retinopathy?
Abnormal new blood vessels orm at the back of the eye as part of proliferative diabetic retinopathy (PDR); these can burst and bleed (vitreous hemorrhage) and blur the vision, because these new blood vessels are fragile.
What is the treatment for diabetic retinopathy?
These three treatments are laser surgery, injection of corticosteroids or anti-VEGF agents into the eye, and vitrectomy
What is the difference between hypertensive retinopathy and diabetic retinopathy?
Hypertensives don’t form new arteries in the retina - diabetic neuropathy does however
What are retinal dystrophies?
Series of inherited conditions affecting photoreceptor function leading to progressive loss of vision
Give an example of a retinal dystrophy
Retinitis pigmentosa
How does retinitis pigmentosa develop?
Retinitis pigmentosa (RP) is an inherited, degenerative eyedisease that causes severe vision impairment due to the progressive degeneration of the rod photoreceptor cells in the retina.
Symptoms manifest regardless of age
Patients in the early stages of RP first notice compromised peripheral and dim light vision due to the decline of the rod photoreceptors.
The progressive rod degeneration is later followed by abnormalities in the adjacent retinal pigment epithelium (RPE) and the deterioration of cone photoreceptor cells.
As peripheral vision becomes increasingly compromised, patients experience progressive “tunnel vision” and eventual blindness.
What is the inheritance pattern of retinitis pigmentosa?
Sporadic (23%)
Dominant (43%)
Recessive (20%)
X-linked recessive (8%)
Unknown (6%)
What drugs can cause retinopathy?
Antimalarials:
- Chloroquine
- Hydroxychloroquine
Phenothiazines
Tamoxifen
Give two examples of photo-receptor retinal dystrophies
Retinitis pigmentosa
Cone dystrophy
Give two examples of retinal pigment epithelium dystrophies
North carolina macular dystrophy
Sorsby macular dystrophy
Give two examples of choiroidal dystrophies
Choroideraemia
Gyrate atrophy
Give two examples of vitreoretinal dystrophies
Stickler syndrome
Congenital retinoschisis
Give three examples of acquired maculopathies
Central serous retinopathy
Epiretinal membrane
Choroidal folds
Idiopathic macular hole
What are the stages of gene therapy
Defective or missing gene
Uses viral vector to insert replacement gene into host DNA
Replacement gene synthesises protein
What is the disease process of choroideraemia?
While the complete mechanism of disease is not fully understood, the lack of a functional protein (RAB escort protein 1 - coded for by the CHM gene) in the retina results in cell death and the gradual deterioration of the choroid, retinal pigment epithelium (RPE), and retinal photoreceptor cells
What is a potential treatment for choroideraemia in the future?
Gene therapy
