Opthalmology Flashcards
glaucoma definition
optic nerve damage by increased intraocular pressure
caused by blockage in aqueous humour drainage
2 types of glaucoma
open-angle
acute angle-closure
chamber of eye filled with
vitreous humour
where anterior chamber
between cornea and iris
where posterior chamber
between lens and iris
between anterior and posterior chamber filled
aqueous humour
passage of aqueous humour
aqueous humour produced by ciliary body, supplies nutrients to cornea. flows through posterior chamber and around iris to anterior chamber. drains through trabecular meshwork to canal of schlemm at angle between cornea and iris. then enters circulation
intraocular pressure
- normal
- created by
10-21 mmHg
created by resistance to flow through trabecular meshwork
pathophysiology of open angle glaucoma
there is a gradual increase in resistance to flow through the trabecular meshwork. The pressure slowly builds within the eye.
patho 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
how serious acute angle closure glaucoma
opthalmological emergency
fundoscopy glaucoma
cupping of optic disc
optic cup in centre of optic disc….this becomes wider and deeper - cupping
cup-disk ratio >0.5 = bad
risk fx for open angle glaucoma
Increasing age
Family history
Black ethnic origin
Myopia (nearsightedness)
clinical fx glaucoma
asx - detected by routine eye test
gradual onset tunnel vision (peripheral vision affected)
fluctuating pain
headaches
dipolopia
halos around lights, worse at night
how measure intraocular pressure
non contact tonometry - puff of air at cornea and measure corneal response
goldmann applanation tonometry (gold standard) - device makes contact and applies pressure to cornea
diagnosis based on 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
glaucoma when tx
> 24mmHg
mx options of glaucoma
360 degrees selective laser trabeculoplasty - improve drainage
prostaglandin analogue eye drops (latanoprost) - increase uveoscleral outflow
Beta-blockers (e.g., timolol) reduce the production of aqueous humour
Carbonic anhydrase inhibitors (e.g., dorzolamide) reduce the production of aqueous humour
Sympathomimetics (e.g., brimonidine) reduce the production of aqueous fluid and increase the uveoscleral outflow
surgery tx of glaucoma
trabeculectomy - 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.
s/e of prostaglandin eye drops
eyelash growth, eyelid pigmentation and iris pigmentation (browning)
risk fx for acute angle closure glaucoma
Increasing age
Family history
Female (four times more likely than males)
Chinese and East Asian ethnic origin
Shallow anterior chamber
marked difference in risk fx of glaucoma
Open-angle glaucoma is more common in black people, while angle-closure glaucoma is rare in this group
certain meds precipitate acute angle closure glaucoma
Adrenergic medications (e.g., noradrenaline)
Anticholinergic medications (e.g., oxybutynin and solifenacin)
Tricyclic antidepressants (e.g., amitriptyline), which have anticholinergic effects
clinical fx acute angle closure glaucoma
Severely painful red eye
Blurred vision
Halos around lights
Associated headache, nausea and vomiting
examination acute angle closure glaucoma
Red eye
Hazy cornea
Decreased visual acuity
Mid-dilated pupil
Fixed-size pupil
Hard eyeball on gentle palpation
acute angle closure glaucoma mx
emergency admission
Lying the patient on their back without a pillow
Pilocarpine eye drops (2% for blue and 4% for brown eyes)
Acetazolamide 500 mg orally
Analgesia and an antiemetic, if required
MOA pilocarpine
muscarinic recepors in sphincter muscles in iris and causes pupil constriction (miotic agent)…ciliary muscle contraction…open up pathway for flow of aqueous humour from ciliary body and into trabecular meshwork
acetozolamide moa
carbonic anhydrase inhibitor that reduces the production of aqueous humour
secondary care mx of acute angle closure glaucoma
Pilocarpine eye drops
Acetazolamide (oral or intravenous)
Hyperosmotic agents (e.g., intravenous mannitol) increase the osmotic gradient between the blood and the eye
Timolol is a beta blocker that reduces the production of aqueous humour
Dorzolamide is a carbonic anhydrase inhibitor that reduces the production of aqueous humour
Brimonidine is a sympathomimetics that reduces aqueous humour production and increases uveoscleral outflow
definitive tx of acute angle closure glaucoma
Laser iridotomy ….allows aqueous humour to flow from posterior to anterior chamber
age related macular degeneration definition
a progressive condition affecting the macula
2 types of AMD
Wet (also called neovascular), accounting for 10% of cases
Dry (also called non-neovascular), accounting for 90% of cases
macula where found
centre of retina
macula role
high definition colour vision in central visual field
macula layers
4 layers -
Choroid layer (at the base), which contains the blood vessels that supply the macula
Bruch’s membrane
Retinal pigment epithelium
Photoreceptors (towards the surface)
AMD fundoscopy
Drusen - yellowish deposits of proteins and lipids between retinal pigment epithelium and Bruch’s membrane…frequent and larger amounts
Atrophy of the retinal pigment epithelium
Degeneration of the photoreceptors
pathophysiology wet AMD
new vessels develop (VEGF) from the choroid layer and grow into the retina (neovascularisation). These vessels can leak fluid or blood, causing oedema and faster vision loss
risk fx AMD
Older age
Smoking
Family history
Cardiovascular disease (e.g., hypertension)
Obesity
Poor diet (low in vitamins and high in fat)
AMD clinical fx
unilateral
Gradual loss of central vision and ability to read small text
Reduced visual acuity
Crooked or wavy appearance to straight lines (metamorphopsia)
WET AMD v DRY AMD
wet - more acutely within days, and progress to complete vision loss within 2-3 yrs and progress to b/l
glaucoma v AMD
Glaucoma is associated with peripheral vision loss and halos around lights. AMD is associated with central vision loss and a wavy appearance to straight lines. This helps you tell them apart in exams.
AMD examination
Reduced visual acuity using a Snellen chart
Scotoma (an enlarged central area of vision loss)
Amsler grid test can be used to assess for the distortion of straight lines seen in AMD
Drusen may be seen during fundoscopy
Slit lamp exam
Optical coherence tomography
Flurescein angiography
AMD mx
specialist opthalmological review
dry - no tx, monitor, avoid smoking and control BP, vitamin supplement
wet - anti-VEGF meds((e.g., ranibizumab, aflibercept and bevacizum) - intravitreal, once/mth
pathophysiology diabetic retinopathy
hyperglycaemia…damages retinal small vessels and endothelial cells
increased vascular permeability, leaky blood vessels, blot haemorrhages, hard exudates (lipids and proteins)
and microaneurysms and venous beading
damage to nerve fibres…cotton wool spots on retina
Intraretinal microvascular abnormalities form - dilated and tortous capillaries act as shunt between arterial and venous vessels
Neurovascularisation - release of growth factors
characteristic fx of diabetic retinopathy on fundoscopy
cotton wool spots
microaneurysms
neovascularisation
blot haemorrhages
hard exudates
diabetic retinopathy grading fundus
Background – microaneurysms, retinal haemorrhages, hard exudates and cotton wool spots
Pre-proliferative – venous beading, multiple blot haemorrhages and intraretinal microvascular abnormality (IMRA)
Proliferative – neovascularisation and vitreous haemorrhage
key fx of proliferative diabetic retinopathy
neovascularisation
diabetic maculopathy fx
Exudates within the macula
Macular oedema
complications 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
diabetic retinopathy mx
non proliferative - diabetic control and monitor
proliferative - Pan-retinal photocoagulation - laser tx (little spots on background of fundus), anti-VEGF, vitrectomy
macular oedema - dex
two causes of hypertensive retinopathy
slowly with chronic hypertension or develop quickly in response to malignant hypertension
clinical fx on fundus hypertensive retinopathy
silver/copper wiring - walls of arterioles thinkened and sclerosed
AV nipping - compression of veins from arterioles
cotton wool spots - ischaemia of retina
hard exudates - damaged vessels leaking lipids onto retina
retinal haemorrhages - damaged vessels rupturing
papilloedema - ischaemia to optic nerve
classification hypertensive retinopathy
Keith-Wagener Classification
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
hypertensive retinopathy mx
control BP
manage risk fx
role of lens
focus light on retina
lens location
held in place by suspensory ligaments attached to ciliary body
lens size change
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.
how lens nourised
aqueous humour
congenital cataracts screen
red reflex tested during neonatal exam
risk fx for cataracts
Increasing age
Smoking
Alcohol
Diabetes
Steroids
Hypocalcaemia
cataracts defin
opaque eye lens…reduce visual acuity
presentation cataracts
usually asymmetrical
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 red reflex
cataracts mx
Cataract surgery involves drilling and breaking the lens to pieces, removing the pieces and implanting an artificial lens. It can be performed as a day case under local anaesthetic
cataracts after tx monitor for
continued reduced visual acuity…
macular degeneration
diabetic retinopathy
endopthalmitis define
inflammation of inner corners of eye…usually caused by infections
rare but serious confplication of cataract surgery….lead to vision loss
tx with intravitreal abx
causes of abnormal pupil shape
trauma to sphincter muscles in iris
anterior uveitis resulting in adhesions
acute angle closure glaucoma (vertical oval)
rubeosis iridis (associated with poorly controlled DM)
coloboma (congenital malformation)
tadpole pupil (muscle spasm in part of dilator muscle or iris, also present with migraines and horners syndrome)
causes of mydriasis
Congenital
Stimulants (e.g., cocaine)
Anticholinergics (e.g., oxybutynin)
Trauma
Third nerve palsy
Holmes-Adie syndrome
Raised intracranial pressure
Acute angle-closure glaucoma
causes of miosis
Horner syndrome
Cluster headaches
Argyll-Robertson pupil (neurosyphilis)
Opiates
Nicotine
Pilocarpine
third nerve palsy clinical fx
Ptosis (drooping upper eyelid)
Dilated non-reactive pupil
Divergent strabismus (squint) in the affected eye, with a “down and out” position
causes of third nerve palsies
can be idiopathic
not affect pupil - microvascular cause as parasympathetic fibres spared…due to DM, HTN, ischaemia
if fully affected..compression of parasympathetic fibres….due to trauma, tumour, cavernous sinus thrombosis, posterior communicating artery aneurysm, raised ICP
oculomotor nerve pathway
The oculomotor nerve travels directly from the brainstem to the eye in a straight line. It travels through the cavernous sinus and close to the posterior communicating artery.
horners syndrome triad
Ptosis
Miosis
Anhidrosis (loss of sweating)
may have exopthalmus
patho of horners syndrome
by damage to the sympathetic nervous system supplying the face.
The sympathetic nerves arise from the spinal cord in the chest. These are pre-ganglionic nerves. They enter the sympathetic ganglion at the base of the neck and exit as post-ganglionic nerves. The post-ganglionic nerves travel to the head alongside the internal carotid artery.