Ophthalmology Flashcards
most common cause of blindness in the UK
Age-related macular degeneration
Age-related macular degeneration characteristics
Degeneration of the central retina (macula) is the key feature with changes usually bilateral. ARMD is characterised by degeneration of retinal photoreceptors that results in the formation of drusen which can be seen on fundoscopy and retinal photography. It is more common with advancing age and is more common in females.
Age-related macular degeneration risk factors
advancing age (DUH)
smoking
family history
CVD
two forms of macular degeneration?
traditionally -
dry macular degeneration
-90% of cases
-also known as atrophic
-characterised by drusen - yellow round spots in
Bruch’s membrane
wet macular degeneration
- 10% of cases
- also know as exudative or neovascular macular
degeneration
- characterised by choroidal neovascularisation
- leakage of serous fluid and blood can subsequently
result in a rapid loss of vision
- carries worst prognosis
more updated classification:
- early age-related macular degeneration (non-exudative, age-related maculopathy): drusen and alterations to the retinal pigment epithelium (RPE)
- late age-related macular degeneration (neovascularisation, exudative)
Clinical features of age related macular degeneration
Gradual worsening central visual field loss
Reduced visual acuity
Crooked or wavy appearance to straight lines
signs/examinations for ARMD
distortion of line perception using amsler grid test
fundoscopy reveals the presence of drusen/macular scar (in dry ARMD)
reduced acuity using snellen chart
investigations for ARMD
Slit-lamp biomicroscopic fundus examination is the initial investigation of choice.
Optical coherence tomography is a technique used to gain a cross-sectional view of the layers of the retina. It can be used to diagnose wet AMD.
Fluorescein angiography involves giving a fluorescein contrast and photographing the retina to look in detail at the blood supply to the retina. It is useful to show up any oedema and neovascularisation. It is used second line to diagnose wet AMD if optical coherence tomography does not exclude wet AMD.
management of ARMD
refer to ophthalmologist for assessment and management
dry ARMD -
Avoid smoking
Control blood pressure
combination of zinc with anti-oxidant vitamins A,C and E has some evidence in slowing progression
wet ARMD -
anti-VEGF agents (EG ranibizumab and typically need to be started within 3 months of diagnosis)
laser photocoagulation does slow progression of ARMD where there is new vessel formation, although there is a risk of acute visual loss after treatment so anti-vegf preferred
what are the 4 key layers of the macula?
At the bottom, there is the choroid layer, which contains blood vessels that provide the blood supply to the macula. Above that is Bruch’s membrane. Above Bruch’s membrane there is the retinal pigment epithelium and above that are the photoreceptors.
what is glaucoma and types
glaucoma is damage caused to the optic nerve due to raised intraocular pressure. The raised intraocular pressure is caused by a blockage in aqueous humour trying to escape the eye. There are two types of glaucoma: open-angle and closed-angle.
what are the anterior and posterior chambers and what are they filled with?
The anterior chamber between the cornea and the iris and the posterior chamber between the lens and the iris are filled with aqueous humour that supplies nutrients to the cornea.
normal flow of aqueous humour in the eye?
The aqueous humour is produced by the ciliary body. The aqueous humour flows from the ciliary body, around the lens and under the iris, through the anterior chamber, through the trabecular meshwork and into the canal of Schlemm. From the canal of Schlemm it eventually enters the general circulation.
normal intraocular pressure?
The normal intraocular pressure is 10-21 mmHg. This pressure is created by the resistance to flow through the trabecular meshwork into the canal of Schlemm.
pathophys of OAG
In open-angle glaucoma, there is a gradual increase in resistance through the trabecular meshwork. This makes it more difficult for aqueous humour to flow through the meshwork and exit the eye. Therefore the pressure slowly builds within the eye and this gives a slow and chronic onset of glaucoma.
acute angle closure glaucoma pathophys
In acute angle-closure glaucoma, the iris bulges forward and seals off the trabecular meshwork from the anterior chamber preventing aqueous humour from being able to drain away. This leads to a continual build-up of pressure. This is an ophthalmology emergency.
fundoscopy sign of raised intraocular pressure
cupping of optic disk, ie, optic cup size>0.5 of optic disk
risk factors for open angle glaucoma
increasing age
black ethnic origin
family history
myopia
presentation of OAG?
often asymptomatic rise in intraocular pressure and diagnosed on routine screening at optometrist
peripheral vision loss and tunnel vision
halos around lights
blurred vision
gradual onset of fluctuating pain, headaches
ix to measure intraocular pressure?
- non-contact tonometry - less accurate but gives a helpful estimate for general screening purposes
- goldmann applanation tonometry - gold standard
management of OAG
treatment usually started at 24mmHg or above and pts are monitored closely for treatment response.
prostaglandin analogue eyedrops (eg latanoprost) - 1st line. increase uveoscleral outflow.
other meds -
- beta blockers (eg timolol) - reduce aqueous humour production
- carbonic anhydrase inhibitor (eg dorzolamide) - reduce aqueous humour production
- Sympathomimetics (e.g. brimonidine) reduce the production of aqueous fluid and increase uveoscleral outflow
Trabeculectomy surgery may be required where eye drops are ineffective.
side effects of latanoprost eye drops?
pigmentation of of eyelids and iris
eyelash growth
complication of acute angle closure glaucoma
Acute angle-closure glaucoma is an ophthalmology emergency. Emergency treatment is required to prevent permanent loss of vision.
RFs for acute angle closure glaucoma
increasing age female sex family hx Chinese and East Asian ethnic origin. Shallow anterior chamber
certain medications -
Adrenergic medications such as noradrenalin
Anticholinergic medications such as oxybutynin and solifenacin
Tricyclic antidepressants such as amitriptyline, which have anticholinergic effects
presentation of acute angle closure glaucoma
pt generally unwell in themselves short hx of - - severely painful red eye - blurred vision - halos around lights - associated headache, N&V
