Opthalmology Flashcards
What is glaucoma?
A group of optic neuropathies associated with raised intraocular pressure that cause optic nerve damage
What is the pathology of glaucoma?
The drainage system for the aqueous humour in the eye is blocked = intraocular hypertension.
What are the types of glaucoma?
Open angle
Closed angle
Normal tension
What is open angle glaucoma?
Chronic glaucoma
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 gives a gradual chronic onset of glaucoma.
What is closed angle glaucoma?
Acute ophthalmological emergency.
The iris bulges forwards and seals off the trabecular network from the anterior chamber, preventing aqueous humour from being able to drain away. This leads to a build up of pressure in the eye particularly in the posterior chamber – which is behind the iris so makes the closure of the angle worse.
Risk factors for closed angle glaucoma
- Increasing age
- Females (4:1)
- FH
- Chinese and east Asian ethnicity
- Shallow anterior chamber
Drugs:
- Adrenergic medications e.g., noradrenaline
- Anticholinergic medications e.g., oxybutynin and solifenacin
- Tricyclic antidepressants e.g., amitriptyline (anticholinergic side effects)
Symptoms of acute closed angle glaucoma
- Unwell patient
- Severely painful red eye
- Blurred vision
- Halos around lights
- Associated headache, nausea and vomiting
- Red eye
- Teary
- Hazy cornea
- Decreased visual acuity
- Dilation of affected pupil
- Fixed pupil size
- Firm eyeball on palpation
Acute management of closed angle glaucoma
- Refer for same day ophthalmology assessment
- If there’s a delay to this:
a. Lay patient on their back without a pillow
b. Give pilocarpine eye drops
c. Give acetazolamide 500mg orally
d. Give analgesia & antiemetic
Secondary care management of closed angle glaucoma
- Pilocarpine (muscarinic receptor agonist) – constriction of the pupil and ciliary muscle contraction to open up trabecular meshwork.
- Acetazolamide (carbonic anhydrase inhibitor) -
- Hyperosmotic agents e.g., glycerol or mannitol – increase the osmotic gradient between the blood and fluid in the eye
- Timolol (beta blocker) – reduces production of aqueous humour
- Dorzolamide (carbonic anhydrase inhibitor) – reduces production of aqueous humour
- Brimonidine (sympathomimetic) – reduces production of aqueous humour and increases uveoscleral outflow
- Laser iridotomy – definitive treatment – laser hole in the iris to allow the aqueous humour to flow from the posterior to anterior chamber.
Risk factors for open angle glaucoma
- Increasing age
- Black ethnicity
- FH
- Intra-ocular pressure >23 mmHg (normal pressure is 10-21)
- Nearsighted (myopia)
Symptoms of open angle glaucoma
- Asymptomatic, found on screening
- Affects peripheral vision first (tunnel vision)
- Gradual onset of fluctuating pain, headaches, blurred vision and halos
Ix for open angle glaucoma
- Tonometry –
a. Non-contact tonometry: shoot a puff of air at cornea and measure the corneal response to the air.
b. Goldmann applanation tonometry: gold standard. Device mounted on a slip lamp that contacts the cornea and applies different pressures to the front of the cornea to get an accurate measurement of IOP. - Fundoscopy: optic disc cupping & check optic nerve health
a. Optic nerve cupping = increased pressure in the eye causes cupping of the optic disc. Abnormal = optic cup >0.5 the size of the optic disc. - Visual field assessment: peripheral vision loss
Mx for open angle glaucoma
- Started when IOP >24 mmHg
- 1st line = latanoprost eye drops (prostaglandin analogue eye drops)
o Increases uveoscleral outflow
o SEs: eyelash growth, eyelid pigmentation, iris browning - Other options:
o Timolol (beta-blocker) – reduces production of aqueous humour
o Dorzolamide (carbonic anhydrase inhibitor) – reduces the production of aqueous humour
o Brimonidine (sympathomimetics) – reduce the production of aqueous fluid and increase uveoscleral outflow - Trabeculectomy surgery – new channel created from the anterior chamber, through the sclera to a location under the conjunctiva. Causes a bleb under the conjunctiva where the aqueous humour drains which gets reabsorbed into the general circulation.
Latanoprost
Prostaglandin analogue - first line for open angle glaucoma.
Increases uveoscleral outflow
SEs: brown pigmentation of iris, increased eyelash length
Why are beta blockers (e.g. timolol) used in glaucoma?
Reduces aqueous production
Just avoid in asthmatics and heart block
