Glaucoma Flashcards
Where is aqueous produced and secreted into?
Produced in the ciliary body and secreted into the posterior chamber.
How does aqueous drain from the eye?
It drains from the anterior chamber via the trabecular meshwork into the canals of Schlemm.
Then to the collecting channels
Finally into the venous system.
What is the average intra-ocular pressure (IOP)?
15.5mmHg
At what value is IOP dangerously high?
21 mmHg, however damage can occur at lower values.
What is the 1st and 2nd commonest cause of treatable blindness in the developed world?
1st –> cataracts
2nd –> Progressive open angled glaucoma
What % of 40 y/o’s and 75 y/o’s are affected by progressive open angled glaucoma?
1% of over 40’s
5% of over 75’s
What are the risk factors for primary open angled glaucoma?
IOP family history (most important) myopia (short sightedness) black race diabetes
Explain the pathology of progressive open angle glaucoma.
Raised IOP +/- vascular factors damage the retinal nerve fibres leading to their atrophy. This cause optic disk excavation (pathological cupping).
How does the death of optic nerve fibres in glaucoma manifest itself in the patients vision?
Visual field defects, then
Tunnel vision, then
Blindness
At what point does glaucoma present and why?
Late until the patient is almost blind. As they are asymptomatic for a long time.
Is glaucoma generally equal in both eyes?
No one eye generally leads the way
What regular investigations should be done for glaucoma patients?
fundoscopy
visual fields
check IOP
What should you see on fundoscopy in an eye with glaucoma?
Pathological cupping (gets worse in the order inferiorly then superiorly, then nasal then temporal. ISNT) Blurring of cup edges
What are the symptoms of acute angle closure glaucoma?
pain due to high pressure
blurred vision
vomiting
What are the three main types of glaucoma?
primary open angled glaucoma
acute angle closure glaucoma
Rubeotic glaucoma
What signs would you see with acute angle closure glaucoma?
Corneal oedema
Red eye
Fixed mid-dilated pupil (as the iris is stuck to the lens)
What are the risk factors for developing acute angle closure glaucoma?
Hypermetropia (long-sighted)
Family history
What is the treatment for progressive open angle glaucoma?
pilocarpine (parasympathomimetic) or acetazolamide (carbonic anhydrase inhibitor) or prostaglandin analogues or beta blockers or alpha agonists
laser iridotomy or surgical trabeculectomy
Explain the pathology of acute angle closure glaucoma.
Lens grows bigger with age
Pushes iris closer to trabecular meshwork
pressure builds as aqueous still produced but cannot drain.
What can help stave off acute angle closure for a while?
going to bed as this causes pupil constiction and thus the pupil pulls away from the trabecular meshwork allowing drainage
What is the treatment for acute angle closure glaucoma?
pilocarpine (parasympathomimetic) +
acetazolamide (carbonic anhydrase inhibitor)
laser iridotomy or surgical trabeculectomy
Explain the pathology of rubeotic glaucoma.
New vessels form and occlude the angle due to diabetic retinopathy or central retinal vein occlusion.
How common is rubeotic glaucoma?
It is rare
What are the symptoms of rubeotic glaucoma?
pain
reduced vision
What are the signs of rubeotic glaucoma?
red eye
corneal oedema
rubeosis
pupil distortion
How do prostaglandin analogues lower IOP? (give an example drug)
Enhance uveoscleral outflow and may also have some effect on the trabecular meshwork. (latanoprost)
How do beta-blockers lower IOP? (give an example drug)
slows down aqueous production from the ciliary body (timolol)
How do carbonic anhydrase inhibitors lower IOP? (give an example drug)
slows down aqueous production. (dorzolamide)
How do alpha agonists lower IOP? (give an example drug)
Decreasing aqueous humor production and increasing uveoscleral outflow (brimonidine)
How does pilocarpine lower IOP?
Increases outflow by causing contraction of the sphincter pupilae thus opening the angle. (it is a sympathomimetic)
Most forms of treatment for glaucoma are eye drops but what can be taken orally?
carbonic anhydrase inhibitors can be taken orally or via drops
What are the two types of laser used to lower IOP?
laser iridotomy (argon laser) or selective laser trabeculoplasty.
What are the side-effects for beta-blocker eye drops?
cardiac and respiratory effects
What are the side-effects for alpha-agonist eye drops?
dizziness
syncope
allergy
What are the side-effects for prostaglandin analogue eye drops?
eye lash growth
iris pigmentation
What are the side-effects for pilocarpine eye drops?
eye ache
poor vision in low light
What are the side-effects for carbonic anhydrase inhibitor eye drops?
acidosis
taste problems
Describe laser trabeculoplasty
where 50-100 shots are delivered around the trabecular meshwork to try to increase drainage.
For whom is laser trabeculoplasty used for?
used in most age groups and even as a primary treatment. This requires an open angle.
Describe trabeculectomy.
creates a controlled fistula where aqueous leaks out under the conjunctiva.
The surgery results in a drainage bleb
What are the potential complications with trabeculectomy?
1) The surgery results in a drainage bleb and creates a open pathway for infection to get into the internal aspect of the eye.
This is a risk for the rest of the patient’s life and is an ophthalmic emergency.
2) Failure of the treatment where the conjunctiva heals and forms scar tissue.`
Explain the prognosis of open-angled glaucoma with regards to IOP.
IOP 21-25 – blind in 15 years
IOP 25-30 – blind in 6 years
IOP >30 – blind in 3 years
