Open angle glaucoma Flashcards
Glaucoma
Group of conditions with characteristic optic nerve head changes associated with visual field defects with or without raised intraocular pressure
Pathophysiology of open angle glaucoma
Gradual increase in resistance through the trabecular meshwork
More difficult for aqueous humour to flow through the meshwork and exit the eye via the canal of Schlemm.
Pressure builds within the eye
Speed of onset of open angle glaucoma
Gives a slow and chronic onset of glaucoma
Effect on optic disc
Increased pressure in the eye causes cupping of the optic disc
- indent becomes larger as the pressure in the eye puts pressure on that indent making it wider and deeper > 0.5
Optic cup
Small indent in the centre of the optic disc.
It is usually less than half the size of the optic disc.
Risk factors for glaucoma
- Increasing age
- Family history
- Black ethnic origin
- Near sightedness (myopia)
Presentation of Open-Angle Glaucoma
Often asymptomatic for a long period of time.
Glaucoma affects peripheral vision first - closes in until they experience tunnel vision
It can present with gradual onset:
- fluctuating pain
- headaches
- blurred vision
- halos appearing around lights, particularly at night time
How to measure intraocular pressure
Non-contact tonometry
Goldmann applanation tonometry - gold standard
Non-contact tonometry
Shooting a “puff of air” at the cornea and measuring the corneal response to that air.
Less accurate but gives a helpful estimate for general screening purposes
Goldmann applanation tonometry
Special device mounted on a slip lamp that makes contact with the cornea and applies different pressures to the front of the cornea to get an accurate measurement of what the intraocular pressure is
Investigations for open angle glaucoma
Goldmann applanation tonometry - intraocular pressure.
Fundoscopy assessment - optic disc cupping and optic nerve health.
Visual field assessment -peripheral vision loss.
Management of Open-Angle Glaucoma
Reduce the intraocular pressure if > 24 mmHg
Follow up to assess the response to treatment
1st line:
- Prostaglandin analogue eye drops (e.g. latanoprost)
Other options:
- Beta-blockers (e.g. timolol)
- Carbonic anhydrase inhibitors (e.g. dorzolamide)
- Sympathomimetics (e.g. brimonidine)
Laser trabeculoplasty
Trabeculectomy surgery
Prostaglandin analogue eye drops
These increase uveoscleral outflow
Side effects of prostaglandin analogue eye drops
Eyelash growth
Eyelid pigmentation
Iris pigmentation (browning)
Beta-blockers
Reduce the production of aqueous humour
Carbonic anhydrase inhibitors
Reduce the production of aqueous humour
Sympathomimetics
Reduce the production of aqueous fluid and increase uveoscleral outflow
When is trabeculectomy surgery performed?
When eye drops are ineffective
Trabeculectomy
Involves creating a new channel from the anterior chamber, through the sclera to a location under the conjunctiva.
It causes a “bleb” under the conjunctiva where the aqueous humour drains. It is then reabsorbed from this bleb into the general circulation
Low pressure glaucoma
Caused by poor blood supply to the optic nerve
Normal intra ocular pressure
10 - 21 mmHg
Side effects of latanoprost
Change eye colour from blue to brown
Changes eye lashes - thicker/ longer
