Ophthalmology Flashcards
What is Glaucoma?
Optic nerve damage from rise in intraocular pressure
What causes increased intraocular pressure?
Blockage in aqueous humour trying to escape the eye
What parts of the eye have aqueous humour in them?
Anterior and posterior chamber (from lens to cornea)
NOT the vitreous chamber
Where is aqueous humour produced?
Ciliary body
What is the normal flow of aqueous humour in the eye?
From the ciliary body, around the lens and under the iris, through the anterior cancer, through the trabecular meshwork in to the canal of Schlemm, where it eventually enters the general circulation
What is normal intraocular pressure?
10-21 mmHg
What creates intraocular pressure normally?
Resistance to flow through the trabecular meshwork
What happens in open-angle glaucoma?
Gradual increase in resistance through the trabecular meshwork
What happens in acute angle-closure glaucoma?
Iris bulges forward and seals off the trabecular meshwork from the anterior chamber, preventing any drainage
Ophthalmology emergency
What effect does increased pressure have on the optic disc?
Cupping of the optic disc (cup of more than 0.5 the size of the optic disc is abnormal)
What are risk factors for open angle glaucoma?
Increasing age
Family history
Black ethnic origin
Near sightedness (myopia)
How does open angle glaucoma present?
Asymptomatic
Peripheral vision first -> tunnel vision
Fluctuating pain, headaches, blurred vision, halos around lights, particularly at night time
How do you measure intraocular pressure?
Non-contact tonometry (puff of air to the cornea and measure the corneal response)
Gold standard is Goldmann application tonometry
What is the management of open-angle glaucoma?
Treat if pressure is above 24 mmHg
Prostaglandin analogue eye drops (e.g. latanoprost) - these increase uveoscleral outflow
Also: beta-blockers/carbonic anhydrase inhibitors/Sympathomimetics to reduce production of aqueous humour
What surgery may be required in open-angle glaucoma?
Trabeculectomy - creates a new channel from the anterior chamber, through the sclera to a location under the conjunctiva. Causes a bleb under the conjunctiva where the aqueous humour drains
What are the risk factors for acute angle-closure glaucoma?
Increasing age
Females affected 4 times more
Family history
Chinese and East Asian ethnic origin
Shallow anterior chamber
Medications: adrenergic medications, anticholinergic medications, TCAs
What is the presentation of acute angle-closure glaucoma?
Generally unwell
Severely painful red eye
Blurred vision
Halos around lights
Associated headache, nausea and vomiting
What do you see on examination of acute angle-closure glaucoma?
Red-eye
Teary
Hazy cornea
Decreased visual acuity
Dilatation of the affected pupil
Fixed pupil size
Firm eyeball on palpation
What is the management for acute angle-closure glaucoma?
Same day assessment by an ophthalmologist
Lie patient on back without a pillow
Pilocarpine eye drops (2% for blue, 4% for brown eyes)
Acetazolamide 500 mg orally
Analgesia and antiemetic if required.
How does pilocarpine eye drops work?
Acts on the muscarinic receptors in the sphincter muscles in the iris. Constricts the pupil and contracts the ciliary muscle.
How does acetozolamide work?
Carbonic anhydrase inhibitor - reduces the production of aqueous humour
What is the definitive treatment for acute angle-closure glaucoma?
Laser iridotomy - makes a hole in the iris for the aqueous humour to flow from the posterior chamber into the anterior chamber
What are the two types of macular degeneration?
90% dry
10% wet - worse prognosis
What are the four layers of the macula?
Bottom - choroid layer, providing blood supply
Next - Bruch’s membrane
Next - Retinal pigment epithelium
Top - photoreceptors
What are drusen?
Yellow deposits of proteins and lipids that appear between the retinal pigment epithelium and Bruch’s membrane (normal to have some small ones)
What is the pathophysiology of wet AMD?
New vessels growing from the choroid layer into the retina - these leak and cause oedema and rapid loss of vision. Key chemical is vascular endothelial growth factor - target of medications
What is the macula of the eye?
Part of the retina at the back of the eye
5mm of pigmented retina, responsible for our central vision, much of our colour vision, and fine detail. Lots of photoreceptors
What are risk factors for AMD?
Age
Smoking
White or Chinese ethnic origin
Family history
Cardiovascular disease
What are key visual changes that are key for spotting AMD?
Gradual worsening central visual field loss
Reduced visual acuity
Crooked or wavy appearance to straight lines
What is used to diagnose AMD?
Snellen chart, Scotia, Amsler grid test, fudoscopy
Slit-lamp biomicroscopic fundus examination by a specialist
Optical coherence tomography to diagnose wet AMD (or fluorescein angiography)
What is used to treat dry AMD
Lifestyle measures that slow progression:
Stop smoking
Control BP
Vitamin supplementation
What is used to treat wet AMD?
Anti-VEGF medications - e.g. ranibizumab, bevacizumab, pegaptanib. Injected directly into the vitreous chamber once a month. Need to be started within 3 months
What is the pathophysiology of diabetic retinopathy?
Hyperglycaemia damages retinal small vessels and endothelial cells
Increased vascular permeability - leakage, blot haemorrhages, hard exudate deposits
Microaneurysms
Venous beading
Damage to nerve fibres - cotton wool spots
Intraretinal microvascular abnormalities - dilated and tortuous capillaries in the retina
Neovascularisation
What are the two categories of diabetic retinopathy?
Non-proliferative - more microaneurysms, blot haemorrhages, venous beading
Proliferative - neovascularisation, vitreous haemorrhage
What happens in diabetic maculopathy?
Macular oedema
Ischaemic maculopathy
What are some complications of diabetic retinopathy?
Retinal detachment
Vitreous haemorrhage
Rebeosis iridis (new blood vessel formation in the iris)
Optic neuropathy
Cataracts
What is the management of diabetic retinopathy?
Laser photocoagulation
Anti-VEGF medications
Vitreoretinal surgery
What are some features of hypertensive retinopathy?
Silver wiring (arterioles sclerosed causing increased reflection of the light)
Arteriovenous nipping - due to sclerosis, compress veins that they cross
Cotton wool spots (ischaemia and infarction of nerve fibres)
Hard exudates
Retinal haemorrhages
Papilloedema
What is the classification of hypertensive retinopathy?
Keith-Wagener
Stage 1: Mild narrowing of the arterioles
Stage 2: Focal constriction of blood vessels and AV nicking
Stage 3: Cotton wool patches, exudates and haemorrhages
Stage 4: Papilloedema
What is the job of the lens in the eye?
To focus light onto the retina
What is the lens held in place by?
Suspensory ligaments which are attached to the ciliary body (contracts and relaxes to focus the lens)
When the ciliary body contracts - tension is released, when it relaxes tension is increased.
No blood supply - nourished by the surrounding fluid
What are risk factors for cataracts?
Increasing age
Smoking
Alcohol
Diabetes
Steroids
Hypocalcaemia
How do cataracts present?
Asymmetrical
Very slow reduction in vision
Progressive blurring of vision
Change of colour of vision - become more brown or yellow
Starbursts can appear around lights, particularly at night time
KEY: loss of red reflex
What causes pupil constriction?
Circular muscles in the iris
Parasympathetic nervous system
Acetylcholine as the neurotransmitter
Oculomotor nerve