Open angle glaucoma Flashcards
What is glaucoma?
Optic nerve damage due to raise intraocular pressure
Raised intraocular pressure is due to blockage to aqueous humour trying to escape the eye
What is the path of aqueous humour?
The aqueous humour is produced by the ciliary body.
The aqueous humour flows from the ciliary body, 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 is normal intraocular pressure?
10-21 mmHg
What is the pathophysiology in open-angle glaucoma?
Gradual increase in resistance through the trabecular meshwork
It is therefore more difficult for aqueous humour to drain out of the eye, increasing intraocular pressure slowly
What is the pathophysiology of acute angle-closure glaucoma?
The iris bulges forward and seals off the trabecular meshwork
Aqueous humour cannot drain out the eye
Leads to continuous build up of pressure
An ophthalmic emergency
What features are seen on fundoscopy?
Optic disc cupping:
-Optic cup becomes larger (>0.5 size of the optic disc is abnormal and suggest glaucoma)
Presentation of open-angle glaucoma
Asymptomatic for a long period of time
Often found during routine optometry screening
Peripheral visual loss until they experience tunnel vision
It can present with gradual onset of fluctuating pain, headaches, blurred vision and halos appearing around lights, particularly at night time.
Investigations in suspected glaucoma
Visual field assessment
Fundoscopy - for cupping and optic nerve health
Non-contact tonometry - estimates IOP - good screening tool:
- Puff of air shot at cornea and response measured
Goldmann applanation tonometry is the gold standard to measure IOP:
- Uses special device attached to slit lamp
- Applies different pressures to the cornea to assess accurate IOP
Diagnosis of open-angle glaucoma is made with
Combination of:
- Goldmann applanation tonometry
- Fundoscopy
- Visual field assessment (looking for peripheral vision loss)
Management of open angle glaucoma
Usually started at IOP of 24 mmHg or higher
Topical latanoprost is first line
Other options:
- Timolol - reduces production of aqueous humour
- Dorzolamide (carbonic anhydrase inhibitor) - reduces production of aqueous humour
- Sympathomimetics (e.g. brimonidine) reduce the production of aqueous fluid and increase uveoscleral outflow
How does Latanoprost work? Side effects?
It is a prostaglandin analogue - increases uveoscleral outflow
Side effects include eyelash growth, eyelid pigmentation and iris pigmentation (browning)
