Ophthalmology Flashcards
What is glaucoma ?
Refers to the optic nerve damage caused by a rise in intraocular pressure.
Raised intraocular pressure is caused by a blockage in aqueous humour trying to escape the eye.
What are the types of glaucoma ?
Open angle glaucoma
Acute angle-closure glaucoma
What is the vitreous chamber filled with ?
Vitreous humour
What is the anterior and posterior chamber filled with ?
Aqueous humour
Where is the anterior chamber ?
Between the cornea and iris
Where is the posterior chamber ?
Between the lens and iris
What produces aqueous humour ?
Ciliary body
How does aqueous humour drain into the circulation ?
It drains through the trabecular meshwork to the canal of schlemm at the angle between the cornea and the iris. From the canal of schlemm it eventually enters the general circulation.
What is normal intraocular pressure ?
10-21 mmHg
How does open angle glaucoma occur ?
There is a gradual increase in resistance to flow through the trabecular meshwork. The pressure slowly builds in the eye.
What occurs in acute angle closure glaucoma ?
The iris bulges forward and seals off the trabecular meshwork from the anterior chamber preventing aqueous humour from draining.
There is a continual build up of pressure and an acute onset of symptoms.
What does raised intraocular pressure cause ?
It causes cupping of the optic disc.
The optic cup becomes wider and deeper.
A cup-disk ratio greater than 0.5 is abnormal.
Where is the optic cup ?
In the centre of the optic disc
What are some risk factors of open angle glaucoma ?
Increasing age
Family history
Black ethnic origin
Myopia ( nearsightedness )
How does glaucoma initially present ?
It affects the peripheral vision first resulting in tunnel vision.
How can glaucoma present ?
Fluctuating pain
Headaches
Blurred vision
Halos around lights ( particularly at night )
How can intraocular pressure be measured ?
Non-contact tonometry
Goldmann applanation tonometry
How does non-contact tonometry work ?
It involves shooting a puff of air at the cornea and measuring the corneal response.
( general screening purpose ).
What is Goldmann applanation tonometry ?
Gold standard way to measure intraocular pressure.
It involves a device mounted on a slip lamp that makes contact with the cornea and applies various pressures.
How can the cup-disk ratio be measured ?
Slit lamp
How can the angle between the iris and cornea be measured ?
Gonioscopy
At what value of intraocular pressure is treatment started ?
24 mmHg
What is the management of glaucoma ?
360 degree laser trabeculoplasty
Prostaglandin analogue eye drops
Trabeculectomy
How does 360 degree selective laser trabeculoplasty ?
During the procedure, a laser is directed at the trabecular meshwork improving drainage. It may delay or prevent the need for eye drops.
What are some side effects of prostaglandin analogue eye drops ?
Eyelash growth
Eyelid pigmentation
Iris pigmentation
What happens in a trabeculectomy ?
It involves creating a new channel from the anterior chamber through the sclera to a location under the conjunctiva causing a bleb on the conjunctiva. From here it is reabsorbed into the general circulation.
Why is acute angle closure glaucoma important to not miss ?
It is an ophthalmological emergency requiring rapid treatment to prevent permanent vision loss.
What are some risk factors of angle closure glaucoma ?
Increasing age
Family history
Female
Shallow anterior chamber
What medications can precipitate acute angle closure glaucoma ?
Adrenergic medications ( noradrenaline )
Anticholinergic medications ( oxybutynin )
Tricyclic antidepressants ( amitriptyline )
How does acute angle closure glaucoma present ?
Severely painful red eye
Blurred vision
Halos around lights
Headache, nausea and vomiting
On examination what are some signs of acute angle closure glaucoma ?
Red eye
Hazy cornea
Decreased visual acuity
Mid dilated with a fixed size pupil
What are some measures to take for acute angle closure glaucoma before an ambulance turns up ?
Lying the patient on their back without a pillow
Pilocarpine eye drops
Acetazolamide
Analgesia
How does pilocarpine work ?
It acts on the Muscarinic receptors in the sphincter muscles in the iris and causes pupil constriction. It also causes ciliary muscle contraction. This help open up the pathway for the flow of aqueous humour.
How does acetazolamide work ?
It is a carbonic anhydrase inhibitor that reduces the production of aqueous humour.
What is the definitive treatment of acute angle closure glaucoma ?
Laser iridotomy
What does laser iridotomy work in the management of acute angle closure glaucoma ?
It involves making a hold in the iris using a laser which allows the aqueous humour to flow directly from the posterior chamber to the anterior chamber. This relieves the pressure pushing the iris forward against the cornea and opens the pathway for the aqueous humour to drain.
What are the 2 types of age related macular degeneration ?
Wet - neovascular
Dry - non-neovascular
What are the 4 layers of the macula ( base to surface ) ?
Choroid layer
Bruch’s membrane
Retinal pigment epithelium
Photoreceptors
What is Drusen ?
Yellowish deposits of proteins and lipids between the retinal pigment epithelium and bruch’s membrane.
How does wet age related macular degeneration cause oedema ?
New vessels develop from the choroid layer and grow into the retina. This is due to the chemical vascular endothelial growth factor. These vessels can leak fluid or blood causing oedema.
What are some risk factors of age related macular degeneration ?
Older age
Smoking
Family history
CVD
Obesity
Poor diet
How does age related macular degeneration present ?
Tends to be unilateral
Gradual loss of central vision
Reduced visual acuity
Crooked or wavy appearance to straight lines ( metamorphopsia )
What is used to assess distortion of straight lines seen in age related macular degeneration ?
Amsler grid test
How can Drusen be seen ?
Fundoscopy
What is used for diagnosing and monitoring age related macular degeneration ?
Optical coherence tomography
How can dry age related macular degeneration be managed ?
Avoid smoking
Controlling blood pressure
Vitamin supplementation - slows progression
What is used to treat wet age related macular degeneration ?
Anti-VEGF medications - ranibizumab
It blocks VEGF and slow the development of new vessels. Injected directly into the vitreous chamber of the eye once a month.
What is diabetic retinopathy ?
Involves damage to the retinal blood vessels due to prolonged high blood sugar levels.
What is the pathophysiology of diabetic retinopathy ?
Hyperglycaemia damages the retinal small vessels and endothelial cells.
Increases vascular permeability leads to leaking blood vessels, blot haemorrhages and hard exudates.
In diabetic retinopathy what can damage to the blood vessel walls lead to ?
Microaneurysm - small bulges
Venous bleeding
In diabetic retinopathy what can damage to the nerve fibres in the retina lead to ?
Causes fluffy white patches called cotton wool spots
What are some complications of diabetic retinopathy ?
Vision loss
Retinal detachment
Vitreous haemorrhage
Optic neuropathy
Cataracts
What is the management of diabetic retinopathy ?
Close monitoring - non-proliferative
Proliferative -
Pan-retinal photocoagulation ( PRP )
Anti-VEGF
Surgery
What is hypertensive retinopathy ?
Damage to the small blood vessels in the retina relating to hypertension
What are some features of hypertensive retinopathy ?
Silver wiring or copper wiring
AV nipping
Cotton wool spots
Hard exudates
Retinal haemorrhages
Papilloedema
What are some silver wiring or copper wiring ?
Where the walls of the arterioles become thickened and sclerosed and reflect more light on examination.
What is AV nipping ?
Where the arterioles cause compression of the veins where they cross due to sclerosis and hardening of the arterioles.
What is the management of hypertensive retinopathy ?
Controlling blood pressure
Managing risk factors ( smoking and blood lipids )
What is cataracts ?
Describes a progressively opaque eye lens which reduces the light entering the eye and visual acuity.
What is a risk factor for cataracts ?
Increasing age
Smoking
Alcohol
DM
Steroids
Hypocalcaemia
How does cataracts present ?
Asymmetrical
Slow reduction in visual acuity
Progressive blurring of the vision
Colours become more faded
Starbursts
Loss of red reflex
What is the management of cataracts ?
No intervention may be necessary
Cataract surgery
What is involved in cataract surgery ?
Involves drilling and breaking the lens to pieces, removing the pieces and implanting an artificial lens.
What is responsible for pupil constriction ?
The circular muscles in the iris are responsible for pupil constriction. They are stimulated by the parasympathetic nervous system using acetylcholine as a neurotransmitter.
What is responsible for pupil dilation ?
The dilator muscles in the iris are responsible for pupil dilation. They are stimulated by the sympathetic nervous system using adrenaline as a neurotransmitter.
What are some causes of abnormal pupil shape ?
Trauma to sphincter muscles
Anterior uveitis ( causes adhesions )
Acute angle closure glaucoma
Rubeosis iridis
Coloboma
What is mydriasis ?
Dilated pupils
What are some causes of mydriasis ?
Congenital
Stimulants such as cocaine
Anticholinergics such as oxybutynin
Trauma
Third nerve palsy
Acute angle closure glaucoma
What is Miosis ?
Constricted pupils
What are some causes of Miosis ?
Horner syndrome
Cluster headaches
Opiates
Nicotine
Pilocarpine
What does a third nerve palsy cause ?
Ptosis
Dilated non-reactive pupils
Divergent strabismus ( down and out gaze )
Which intra-ocular muscles are supplied by the oculomotor nerve ?
Superior rectus
Medial rectus
Inferior rectus
Inferior oblique
What may cause a full third nerve palsy ?
Tumour
Trauma
Cavernous sinus thrombosis
Posterior communicating artery aneurysm
Raised ICP
What is the triad of Horner syndrome ?
Ptosis
Miosis
Anhidrosis