List I - Act Core Conditions Flashcards
1
Q
What is glaucoma?
A
- Group of eye diseases that cause progressive optic neuropathy and in which IOP is a key modifiable factor
- Glaucoma is commonly associated with raised IOP and is characterised by:
- Visual field defects
- Changes to the optic nerve such as pathological cupping or as a late sign, pallor of the optic disc
- Ocular hypertension is where there is consistently or recurrently elevated IOP (greater than 21 mmHg) but with no signs of glaucoma
2
Q
What is the anterior chamber?
A
- Fluid filled space between the iris and the cornea
- Anterior chamber angle is the angle between the iris and the cornea where they join the sclera towards the outside of the eye
- Trabecular meshwork is situated in the apex of the anterior chamber angle and is the main outflow route for the aqueous humour
3
Q
What is the aqueous humour?
A
- Fluid produced from plasma by the ciliary epithelium of the ciliary body (the circular structure just behind the iris) - carbonic anhydrase plays a key role in its production
- Aqueous humour is secreted into the posterior chamber between the lens and the iris, it then flows through the pupil into the trabecular meshwork, a small amount drains out via the venous circulation of the iris, ciliary body, choroid, and sclera
- Secretion of the aqueous humour is increased by stimulation of beta-2 receptors and decreased by stimulation of alpha-2 receptors of the sympathetic nervous system that are located on cells of the ciliary body
4
Q
What is the role of intra ocular pressure in the eye?
A
- IOP keeps the eye in the shape of a globe and is maintained by the balance between production and outflow of aqueous humour
- Raised IOP is the main risk factor for developing glaucoma as the raised IOP may damage nerve fibres of the optic nerve or blood vessels supplying these nerve fibres
- A pressure of between 11-21 mmHg is considered normal - some develop glaucoma at pressures below 21 mmHg and some have pressures well above this without showing signs of glaucoma
- Drugs used to treat glaucoma aim to reduce IOP and work by either reducing the production of aqueous humour or increasing its outflow
5
Q
What is glaucoma classified according to?
A
- Age of onset - congenital, infantile, juvenile or adult
- Cause - primary (no known cause) or secondary with a known underlying cause
- Rate of onset - acute, subacute or chronic
- The anterior chamber angle between the iris and cornea - either open or closed
6
Q
What are the features of open angle glaucoma?
A
- Angle between the iris and the cornea is normal
- Primary open angle glaucoma is by far the most common type of glaucoma
- Mainly affects people over the age of 40
- Usually insidious onset and follows a chronic course
- Usually affects both eyes but one may be more affected than the other
- Is typically associated with raised IOP
- Normal tension (pressure) glaucoma occurs in a significant minority of people with POAG where glaucoma develops with normal IOP
- Suspect POAG is when the appearance of the optic nerve head is suggestive of glaucoma but the visual fields appear normal, or conversely, where a visual field defect exists yet the optic nerve appears healthy
7
Q
What are the features of closed angle glaucoma?
A
- Angle between the iris and the cornea is at least partially closed
- Primary angle closure glaucoma (PACG) is the most common type of angle closure glaucoma
- Onset may be acute, subacute or chronic
- Mainly affects older people occurring in about 0.4% of people in the UK over 40 years
8
Q
In which people should acute angle closure (which may progress to glaucoma) be suspected?
A
In a person with an acute painful red eye and in particular who:
- Is female, Asian, long sighted or of older age
- Has a history of episodes of blurred vision, headaches or eye pain associated with nausea and seeing halos around lights; these symptoms typically occur in the evening and are relieved by sleeping
- May also have headache, nausea, vomiting, lights are seen around halos - caused by an oedematous cornea, semi-dilated and fixed pupil, tender, hard eye, impaired visual acuity
9
Q
If acute angle glaucoma is suspected, what is the action?
A
- Admit the person for ophthalmology assessment
- If not possible, emergency treatment should start in primary care
- Lie the person flat with their face up and head not supported by pillows
- If available, pilocarpine drops should be administered - one drop of 2% in blue eyes or 4% in brown eyes, acetazolamide 500 mg given orally (if no contraindications) and analgesia and an anti-emetic provided if required
- If chronic glaucoma is suspected the person should be referred to an optometrist or ophthalmologist
10
Q
What is the main complication of untreated glaucoma?
A
- Irreversible loss of vision (partial or complete)
- Appropriate treatment reduces the risk of progression of the disease
- Treatment of all types of glaucoma and of ocular hypertension when indicated is normally initiated and monitored by specialists
- Mainstay of treatment is to reduce IOP
- Usually done with eye drops but sometimes laser or surgical treatments are required
11
Q
What is the initial presentation of primary open angle glaucoma?
A
- May present insidiously and for this reason is often detected during routine optometry appointments
- Features include:
- Peripheral visual field loss - nasal scotomas progressing to tunnel vision
- Decreased visual acuity
- Optic disc cupping
12
Q
What are the signs on fundoscopy of primary open angle glaucoma?
A
- Optic disc cupping - cup-to-disc ratio >0.7 (normal = 0.4-0.7), occurs as loss of disc substance makes optic cup widen and deepen
- Optic disc pallor - indicating optic atrophy
- Bayonetting of vessels - vessels have breaks as they disappear into the deep cup and re-appear at the base
- Additional features - Cup notching (usually inferior where vessels enter disc), Disc haemorrhages
13
Q
How is diagnosis of POAG made?
A
- Case finding and provisional diagnosis is done by an optometrist
- Optic nerve head damage visible under the slit lamp
- Visual field defect
- IOP > 24 mmHg as measured by Goldmann-type applanation tonometry
- Referral to the ophthalmologist is done via the GP
- Final diagnosis is done by investigations as below
14
Q
What investigations are done for diagnosing POAG?
A
- Automated perimetry to assess visual field
- Slit lamp examination with pupil dilatation to assess optic neve and fundus for a baseline
- Applanation tonometry to measure IOP
- Central corneal thickness measurement
- Gonioscopy to assess peripheral anterior chamber configuration and depth
- Assess risk of future visual impairment, using risk factors such as IOP, central corneal thickness (CCT), family history, life expectancy
15
Q
What is the NICE guidance for managing primary open angle glaucoma?
A
- First line: prostaglandin analogue (PGA) eye drop
- Second line: beta blocker, carbonic anhydrase inhibitor or sympathomimetic eyedrop
- More advanced surgery or laser treatment can be tried
Reassessment
- Important to exclude progression and visual field loss
- Needs to be done more frequently if IOP uncontrolled, the patient is high risk, or there is progression
