Ophthalmology Flashcards
Describe the 3 zones of the retina
- Zone 1: includes the optic nerve and the macula.
- Zone 2: from the edge of zone 1 to the ora serrata (the pigmented border between the retina and ciliary body).
- Zone 3: outside the ora serrata.
Define glaucoma
Optic nerve damage due to raised intraocular pressure caused by a blockage of aqueous humour.
Anterior vs posterior chambers of the eye
- Anterior chamber: between cornea and iris.
- Posterior chamber: between lens and iris.
Describe the normal circulation of aqueous humour
The aqueous humour supplies nutrients to the cornea. It is produced by the ciliary body. It flows through the posterior chamber and around the iris to the anterior chamber. 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 the normal range of intraocular pressure?
10-21 mmHg
Describe the pathophysiology of open-angle glaucoma
- Gradual increase in resistance to flow through the trabecular meshwork, causing pressure to slowly build up.
- Raised intraocular pressure causes cupping of the optic disk —> cup-disk ratio >0.5.
Outline the risk factors for open-angle glaucoma
- Increasing age
- Family history
- Black ethnic origin
- Myopia (nearsightedness)
Describe the typical features of open-angle glaucoma
- Gradual onset of peripheral vision loss (tunnel vision)
- Fluctuating pain
- Headaches
- Blurred vision
- Halos around lights, particularly at night
Name 2 investigations to measure intraocular pressure
- Non-contact tonometry
- Goldmann applanation tonometry (gold standard)
How would you go about diagnosing open-angle glaucoma?
- Goldmann applanation tonometry for the intraocular pressure.
- Slit lamp assessment for the cup-disk ratio and optic nerve health.
- Visual field assessment for peripheral vision loss.
- Gonioscopy to assess the angle between the iris and cornea.
- Central corneal thickness assessment.
Describe the management of open-angle glaucoma
- Treatment started at an intraocular pressure > 24 mmHg.
- 360° selective laser trabeculoplasty (improves drainage of trabecular meshwork) - first line.
- Prostaglandin analogue eye drops (e.g. latanoprost) are the first-line medical treatment after SLT. They increase uveoscleral outflow. Notable side effects are eyelash growth, eyelid pigmentation and iris pigmentation (browning).
- Beta-blockers (e.g. timolol) eye drops, reduce the production of aqueous humour - second line medical.
- Carbonic anhydrase inhibitors (e.g. dorzolamide) eye drops, reduce the production of aqueous humour - second line medical.
- Sympathomimetics (e.g. brimonidine) eye drops reduce the production of aqueous fluid and increase the uveoscleral outflow - second line medical.
- Trabeculectomy surgery may be required where other treatments are ineffective. Creates a new channel from the anterior chamber, through the sclera to under the conjunctiva (bleb).
Describe the pathophysiology of acute angle-closure glaucoma
Iris budges forwards and seals off the trabecular meshwork from the anterior chamber, preventing aqueous humour from draining and leading to an increase in intraocular pressure. The pressure builds in the posterior chamber, pushing the iris forwards and exacerbating the angle closure. It is an ophthalmological emergency.
Outline the risk factors for acute angle-closure glaucoma
- Increasing age.
- Family history.
- Female (four times more likely than males).
- Chinese and East Asian ethnic origin (compared to black people in open-angle).
- Shallow anterior chamber.
- Adrenergic medications (e.g. noradrenaline).
- Anticholinergic medications (e.g. oxybutynin and solifenacin).
- Tricyclic antidepressants (e.g. amitriptyline), which have anticholinergic effects.
What are the symptoms and signs associated with acute angle-closure glaucoma?
Acute onset:
- Severely painful red eye.
- Blurred vision.
- Halos around lights.
- Associated headache, N+V.
Signs:
- Red eye.
- Hazy cornea.
- Decreased visual acuity.
- Fixed dilated pupil.
- Hard eyeball on gentle palpation.
Outline the management of acute angle-closure glaucoma
- Pilocarpine eye drops: muscarinic agonist causing pupil constriction (miotic agent) and ciliary muscle contraction, to open up pathway for the flow of aqueous humour.
- Acetazolamide (oral or IV): carbonic anhydrase inhibitor that reduces the production of aqueous humour.
- Hyperosmotic agents (e.g. IV mannitol): increase the osmotic gradient between the blood and the eye.
- Timolol (beta blocker): reduces the production of aqueous humour.
- Dorzolamide (carbonic anhydrase inhibitor).
- Brimonidine (sympathomimetic): reduces aqueous humour production and increases uveoscleral outflow.
- Laser iridotomy (definitive treatment): making a hole in the iris, allowing aqueous humour to flow from posterior chamber to anterior chamber, relieving the pressure.
Myopia vs. Hyperopia
- Myopia: nearsightedness.
- Hyperopia: farsightedness.
What is the most common cause of blindness in the UK?
Age-related macular degeneration (AMD)
What is AMD?
Progressive unilateral (sometimes bilateral) condition affected the macula of the eye. It causes atrophy of the retinal pigment epithelium and degeneration of the photoreceptors.
What is the function of the macula?
Found in the centre of the retina and generates high-definition colour vision in the central visual field.
Describe the 2 types of AMD
- Wet (neovascular), accounting for 10% of cases: new blood vessels develop from the choroid layer and grow into retina. These vessels leak fluid/blood causing oedema and faster vision loss. VEGF stimulates this neovascularisation.
- Dry (non-neovascular), accounting for 90% of cases.
Outline the risk factors for AMD
- Older age
- Smoking
- Family history
- CVD (e.g. hypertension)
- Obesity
- Poor diet (low in vitamins and high in fat)
Describe the symptoms associated with AMD
Unilateral visual changes:
- Gradual loss of central vision.
- Reduced visual acuity.
- Crooked or wavy appearance to straight lines (metamorphopsia).
- Gradually worsening ability to read small text.
Glaucoma vs. AMD symptoms
- Glaucoma: peripheral vision loss and halos around lights.
- AMD: central vision loss and a wavy appearance to straight lines.
Describe the key examination findings associated with AMD
- Reduced visual acuity (Snellen chart).
- Scotoma (an enlarged central area of vision loss).
- Amsler grid test: used to assess for the distortion of straight lines.
- Drusen (yellowish deposits of proteins and lipids under the retina) may be seen during fundoscopy.
Name 3 tests used to help diagnose AMD
- Slit lamp examination gives a detailed view of the retina and macula.
- Optical coherence tomography gives a cross-sectional view of the layers of the retina and is used for diagnosing and monitoring AMD.
- Fluorescein angiography involves giving a fluorescein contrast and photographing the retina to assess the blood supply, showing oedema and neovascularisation in wet AMD.
Outline the management for AMD
- No specific treatment for dry AMD. Management involves monitoring and reducing the risk of progression by: avoiding smoking, controlling BP and vitamin supplementation.
- Wet AMD: anti-VEGF medications (e.g. ranibizumab, aflibercept and bevacizumab) block VEGF and slow the development of new vessels. They are injected directly into the vitreous chamber of the eye (intravitreal), usually about once a month.
Define diabetic retinopathy
Damage to retinal blood vessels due to prolonged hyperglycaemia.
Outline the changes seen on fundoscopy for diabetic retinopathy
- Blot haemorrhages (due to increased vascular permeability).
- Hard exudates (yellow-white deposits of lipid and proteins due to increased vascular permeability).
- Microaneurysms and venous beading (due to vessel wall damage).
- Cotton wool spots (due to damage to retinal nerve fibres).
- Intraretinal microvascular abnormalities (IRMA): dilated and tortuous capillaries in the retina, acting as a shunt between the arterial and venous vessels.
- Neovascularisation (only seen in proliferative diabetic retinopathy).
Name the complications associated with diabetic retinopathy
- Vision loss.
- Retinal detachment.
- Vitreous haemorrhage (bleeding into the vitreous humour).
- Rubeosis iridis (new blood vessel formation in the iris) – this can lead to neovascular glaucoma.
- Optic neuropathy.
- Cataracts.
Describe the management of diabetic retinopathy
Non-proliferative diabetic retinopathy requires close monitoring and careful diabetic control.
Treatment options for proliferative diabetic retinopathy are:
- Pan-retinal photocoagulation (PRP): extensive laser treatment across the retina to suppress new vessels.
- Anti-VEGF medications by intravitreal injection.
- Surgery (e.g. vitrectomy) may be required in severe disease.
An intravitreal implant containing dexamethasone is an option for macular oedema.
Describe the features associated with hypertensive retinopathy
- Silver wiring or copper wiring: walls of the arterioles become thickened and sclerosed and reflect more light on examination.
- AV nipping: arterioles cause compression of the veins where they cross due to sclerosis and hardening of the arterioles.
- Cotton wool spots: damage to nerve fibres.
- Hard exudates: damaged vessels leaking lipids onto the retina.
- Retinal haemorrhages: damaged vessels rupturing and releasing blood in the retina. Dot and blot haemorrhages occur deeper, in the inner nuclear layer or outer plexiform layer. Flame haemorrhages occur in the nerve fiber layer.
- Papilloedema: ischaemia to the optic nerve, resulting in optic nerve swelling.
What is the management for hypertensive retinopathy?
- Control BP.
- Managing risk factors e.g. smoking and lipids.
Describe the function of the eye lens
The role of the lens is to focus light on the retina. It is held in place by suspensory ligaments attached to the ciliary body. The ciliary body contracts and relaxes to change the shape of the lens. When the ciliary body contracts, it releases tension on the suspensory ligaments, and the lens thickens. When the ciliary body relaxes, the suspensory ligaments tension, and the lens narrows. The lens has no blood supply and is nourished by the aqueous humour.
What is cataracts?
Progressive opacification of the eye lens, which reduces the light entering the eye and visual acuity.
Outline the risk factors for cataracts
- Increasing age
- Smoking
- Alcohol
- Diabetes
- Steroids
- Hypocalcaemia
Describe the features of cataracts
Symptoms are usually asymmetrical, as both eyes are affected separately. It presents with:
- Slow reduction in visual acuity.
- Progressive blurring of the vision.
- Colours becoming more faded, brown or yellow.
- Starbursts can appear around lights, particularly at night.
- Loss of the red reflex on examination.
- White/grey pupil.
How can cataracts be managed?
- No intervention may be necessary if the symptoms are manageable.
- Cataract surgery: involves drilling and breaking the lens to pieces, removing the pieces and implanting an artificial lens.
- Cataracts can prevent the detection of other pathology, such as macular degeneration or diabetic retinopathy, which can become apparent after surgery. Therefore, they may still have reduced visual acuity after the cataract is treated.
Name one complication of cataracts surgery
Endophthalmitis - inflammation and infection of the inner contents of the eye (intra-ocular fluid, vitreous/aqueous). It can lead to vision loss. Treated with intravitreal antibiotics injected directly into the eye.
Describe how the lens plays a role in refraction and accommodation
- Refraction: refers to the change in direction of light when it passes from one medium to another. Helps to converge light onto the retina.
- Accommodation: refers to the ability to maintain focus on an image as distance varies. The lens achieves this by altering its shape through contraction or relaxation of the ciliary bodies.
What is the hallmark feature of cataracts?
Painless loss of vision.
Explain the physiology of pupil size
- Pupil constriction stimulated by parasympathetic NS along the oculomotor nerve.
- Pupil dilation stimulated by sympathetic NS.
Outline some causes of abnormal pupil shape
- Trauma to sphincter muscles.
- Anterior uveitis causing adhesions.
- Acute angle-closure glaucoma - vertical oval.
- Rubeosis iridis (neovascularisation in iris) in diabetic retinopathy.
- Coloboma (congenital malformation).
- Tadpole pupil - associated with migraines and Horner syndrome.
Causes of mydriasis (dilated pupil)
- Congenital
- Stimulants (e.g. cocaine)
- Anticholinergics (e.g. oxybutynin)
- Trauma
- Third nerve palsy
- Holmes-Adie syndrome (Holmes-Adie pupil with absent ankle and knee reflexes)
- Raised intracranial pressure
- Acute angle-closure glaucoma
Causes of mitosis (constricted pupil)
- Horner syndrome
- Cluster headaches
- Argyll-Robertson pupil (neurosyphilis)
- Opiates
- Nicotine
- Pilocarpine
Explain the 3 features of a third cranial nerve (oculomotor nerve) palsy
- Ptosis - due to palsy of levator palpebrae superioris.
- Dilated non-reactive pupil - due to palsy of parasympathetic fibres.
- Divergent strabismus (squint) in the affected eye, with a ‘down and out’ position of the affected eye - due to palsy of extraocular muscles, but sparing of lateral rectus and superior oblique.
What is the cause of a third nerve palsy with pupil sparing?
Microvascular cause e.g. diabetes, hypertension, ischaemia.
What causes a full third nerve palsy?
Compression of nerve (including parasympathetic fibres) due to: tumour, trauma, cavernous sinus thrombosis, posterior communicating artery aneurysm, raised ICP.
Outline the triad of features in Horner Syndrome
MAP:
- Miosis
- Anhidrosis
- Ptosis
Are light and accommodation reflexes affected in Horner Syndrome?
No - because these are controlled by parasympathetic NS.
What causes Horner Syndrome?
Damage to sympathetic NS supplying the face.
Describe the location of the sympathetic nerves supplying the head and neck
- Pre-ganglionic nerves arise from the spinal cord in the chest and enter the sympathetic ganglion at the base of the neck.
- Post-ganglionic nerves travel to the head alongside the internal carotid artery.
How can the location of the Horner Syndrome lesion be determined?
- Central lesions (occurring before the nerves exit the spinal cord) cause anhidrosis of the arm, trunk and face e.g. stroke, syringomyelia, MS, tumour, encephalitis.
- Pre-ganglionic lesions cause anhidrosis of the face e.g. pancoast tumour, cervical rib, thyroidectomy, trauma.
- Post-ganglionic lesions don’t cause anhidrosis e.g. carotid artery, cluster headache.
List the causes of Horner Syndrome central lesions, pre-ganglionic lesions and post-ganglionic lesions
Central lesions (Sentral):
- S – Stroke
- S – Multiple Sclerosis
- S – Swelling (tumours)
- S – Syringomyelia (cyst in the spinal cord)
Pre-ganglionic lesions (Torso):
- T – Tumour (Pancoast tumour)
- T – Trauma
- T – Thyroidectomy
- T – Top rib (a cervical rib growing above the first rib and clavicle)
Post-ganglionic lesions (cervical):
- C – Carotid aneurysm
- C – Carotid artery dissection
- C – Cavernous sinus thrombosis
- C – Cluster headache
How can you test for Horner syndrome?
- Cocaine eye drops acts on the eye to stop NA re-uptake at the NMJ. This causes a normal eye to dilate as NA stimulates the dilator muscles of the iris. In Horner syndrome, the nerves are not releasing NA, so blocking re-uptake makes no difference, and there is no pupil reaction.
- Alternatively, low-dose adrenaline eye drops (0.1%) will dilate the pupil in Horner syndrome but not a normal pupil.
What causes a Holmes-Adie pupil?
Damage to the post-ganglionic parasympathetic fibres.
Describe the findings seen with an Argyll-Robertson pupil
- A constricted pupil that accommodates when focusing on a near object but does not react to light.
- ‘Prostitute’s pupil’ due to its relation to neurosyphilis and because ‘it accommodates but does not react’.
Define blepharitis and it’s cause
Inflammation of the eyelid margins associated with dysfunction of the Meibomian glands (responsible for secreting meibum/oil onto eye surface). It can lead to styles and chalazions.
What are the common presenting symptoms for blepharitis?
Gritty or burning sensation in both eyes, crusted eyelashes, red eyes, and swollen or greasy eyelids.
What is a common complication of blepharitis?
Dry eye disease
Management of blepharitis?
Warm compresses and gentle cleaning of the eyelid margins to remove debris (e.g., using a cotton bud and baby shampoo).
Types of stye
- Hordeolum externum: infection of the glands of Zeis or glands of Moll. The glands of Moll are sweat glands at the base of the eyelashes. The glands of Zeis are sebaceous glands at the base of the eyelashes. A stye causes a tender red lump along the eyelid that may contain pus.
- Hordeolum internum: infection of the Meibomian glands. They are deeper, tend to be more painful and may point inwards towards the eyeball underneath the eyelid.
Treatment of styes
- Hot compresses and analgesia.
- Topical antibiotics (e.g. chloramphenicol) may be considered if it is associated with conjunctivitis or if symptoms are persistent.
Define a chalazion
When a Meibomian gland becomes blocked and swells (Meibomian cyst). It presents with a swelling in the eyelid that is typically not tender.
What’s the name for the condition where the eyelid turns inwards with the lashes pressed against the eye?
Entropion
Name two complications of entropion
Corneal damage and ulceration.
Management of entropion?
- Taping down eyelid to prevent it turning inwards (with lubricating eye drops).
- Surgery is definitive management.
- Same day referral to ophthalmology if there’s a risk to sight.
What is eyelid ectropion?
When the eyelid turns outwards, exposing the inner aspect.
What are the complications of eyelid ectropion?
Exposure keratopathy (the eyeball is exposed and not adequately lubricated and protected).
When should a same day referral to ophthalmology be made?
When there is a risk to sight
What is the term for the inward growth of the eyelashes?
Trichiasis
Define periorbital cellulitis
An infection of the eyelid and skin in front of the orbital septum, causing swollen, red and hot skin around the eyelid and eye.
Investigations for periorbital cellulitis
- Urgent referral to ophthalmology to rule out orbital cellulitis (sight and life-threatening).
- CT scan.