Ophthalmology Flashcards
What is glaucoma
optic nerve damage caused by a significant rise inintraocular pressure
What is the normal range of intraocular pressure
10-21 mmHg
Describe the flow of aqueous humour
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.
What creates intraocular pressure
the resistance to flow through the trabecular meshwork into the canal of Schlemm
Pathophysiology of open-angle glaucoma
gradual increase in resistance through the trabecular meshwork -> more difficult for aqueous humour to flow through the meshwork -> pressure slowly builds within the eye and this gives a slow and chronic onset of glaucoma
Effect of raised intraocular pressure on optic disk
Increased pressure in the eye causes cupping of the optic disc (indent becomes wider and deeper)
Risk factors of open-angle glaucoma
Increasing age
Family history
Black ethnic origin
Nearsightedness (myopia)
Presentation of open-angle glaucoma
The rise in pressure is often asymptomatic
As glaucoma worsens the peripheral vision gradually closes in (tunnel vision)
Can present with gradual onset of fluctuating pain, headaches, blurred vision and halos appearing around lights, particularly at night time
How is intraocular pressure measured
Non-contact tonometry commonly used
Goldmann applanation tonometry is the gold standard
Investigations to diagnose glaucoma
Goldmann applanation tonometry/ non-contact tonometry can be used to check the intraocular pressure
Fundoscopy assessment to check for optic disc cupping and optic nerve health.
Visual field assessment to check for peripheral vision loss.
Management of open-angle glaucoma
1st line: Prostaglandin analogue eye drops (e.g. 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 uveoscleral outflow
If medical mx fails: trabeculectomy surgery
Pathophysiology of acute closed-angle glaucoma
the iris bulges forward and seals off the trabecular meshwork from the anterior chamber preventing aqueous humour from being able to drain away -> continual build-up of pressure in the eye -> pressure builds up particularly in the posterior chamber, which causes pressure behind the iris and worsens the closure of the angle
Risk factors of closed-angle glaucoma
Increasing age
Females are affected around 4 times more often than males
Family history
Chinese and East Asian ethnic origin. Unlike open-angle glaucoma, it is rare in people of black ethnic origin.
Shallow anterior chamber
Medications that precipitate closed-angle glaucoma
Adrenergic medications such as noradrenalin
Anticholinergic medications such as oxybutynin and solifenacin
Tricyclic antidepressants such as amitriptyline, which have anticholinergic effects
Closed-angle glaucoma: presentation
Short history of:
Feeling unwell in themselves
Severely painful red eye
Blurred vision
Halos around lights
Associated headache, nausea and vomiting
