List III - Core clinical problems for the student and new doctor Flashcards
What are the most common causes of sudden painless loss of vision?
- Ischaemic/vascular (e.g. thrombosis, embolism, temporal arteritis, etc) - includes recognised syndromes e.g. occlusion of central retinal vein and occlusion of central retinal artery
- Vitreous haemorrhage
- Retinal detachment
- Retinal migraine
When is loss of vision considered sudden?
- If it develops within a few minutes to a couple of days
* May affect one or both eye and all or part of a field of vision loss
What are the mechanisms leading to loss of vision/visual failure?
- Light cannot reach the retina
- Light rays do not focus on the retina clearly
- Retina cannot sense light rays normally
- Nerve impulses from the retina are not transmitted to the brain normally
- Brain cannot interpret information sent by the eye
Which conditions mean that light cannot reach the retina?
- Damage to the cornea by infections such as herpes keratoconjunctivitis or an infection that follows contact lens overwearing
- Damage to the cornea by vitamin A deficiency (keratomalacia) causes dry eyes and results in an opaque corneal scar
- Damage to the cornea caused by a severe injury that results in an opaque scar
- Cataract resulting in loss of clarity to the lens
Which conditions mean that light rays do not focus on the retina clearly?
- Certain types of cataracts mean that light rays cannot focus on the retina very well
Which conditions mean that light rays do not focus on the retina clearly?
- Detached retina
- Diabetes mellitus
- Macular degeneration
- Retinitis pigmentosa
- Inadequate blood supply to the retina - usually block of the retinal artery or vein which may be caused by inflammation of the blood vessel wall (such as that caused by GCA) or due to a blood clot that travels to the eye from somewhere else such as from the carotid artery in the neck
- Infection of the retina (such as toxoplasma or fungi)
Which conditions mean that nerve impulses from the retina are not transmitted to the brain normally?
- Disorders affecting the optic nerve or its pathways inside the brain, such as brain tumours, strokes, infections and multiple sclerosis
- Glaucoma
- Inflammation of the optic nerve (optic neuritis)
Which conditions mean that the brain cannot interpret information sent by the eye?
- Disorders that affect the areas of the brain that interpret visual impulses (visual cortex) such as strokes and tumours
What are the features of an ischaemic/vascular cause of sudden vision loss?
- Often referred to as amaurosis fugax
- Wide differential including large artery disease (artherothrombosis, embolus, dissection), small artery occlusive disease (anterior ischaemic optic neuropathy, vasculitis e.g. temporal arteritis) venous disease and hypoperfusion
- May present as a form of TIA - therefore should be treated similarly with 300 mg aspirin being given
- Altitudinal field defects are often seen - curtain coming down
- Ischaemic optic neuropathy is due to occlusion of the short posterior ciliary arterties causing damage to the optic nerve
What are the features of a central retinal vein occlusion cause of sudden vision loss?
- Incidence increased with age, more common than arterial occlusion
- Causes include: glaucoma, polycythamia, hypertension
- Severe retinal haemorrhages are usually seen on fundoscopy
What are the features of a central retinal artery occlusion cause of sudden vision loss?
- Due to thromboembolism (from artherosclerosis) or arteritis (e.g. temporal arteritis)
- Features incude afferent pupillary defect cherry red spot on pale retina
What are the features of a vitreous haemorrhage cause of sudden vision loss?
- Diabetes, bleeding disorders, anti-coagulants
* Features may include sudden visual loss, dark spots
What are the features of retinal detachment causing sudden vision loss?
- Features include vitreous detachment which may precede retinal detachment, including flashes or light or floaters
What are the clinical features of a posterior vitreous detachment?
- Flashes of light (photopsia) - in the peripheral field of vision
- Floaters, often on the temporal side of the central vision
What are the clinical features of retinal detachment?
- Dense shadow that starts peripherally progresses towards the central vision
- Veil or curtain over the field of vision
- Straight lines appear curved
- Central visual loss
