Glaucoma Flashcards
(36 cards)
What produces the aqueous fluid?
Where is it secreted to?
Ciliary bodies
Posterior chamber
Where are the anterior chambers and posterior chambers respectively?
Anterior chamber: between the cornea and iris
Posterior chamber: between the iris and the lens
How does the aqueous fluid drain?
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 is glaucoma?
Glaucoma refers to the optic nerve damage that is caused by a significant rise in intraocular pressure. The raised intraocular pressure is caused by a blockage in aqueous humour trying to escape the eye
The normal intraocular pressure is 10-21 mmHg. This pressure is created by the resistance to flow through the trabecular meshwork into the canal of Schlemm.
Risk factors for POAG
raised IOP Family history Myopia Black race diabetes
Describe the pathophysiology of POAG
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 - slow and gradual onset
What is the presentation of progressive open angle glaucoma
visual field defect in peripheral vision, closing in to eventual tunnel vision
blindness
It can present with gradual onset of fluctuating pain, headaches, blurred vision and halos appearing around lights, particularly at night time.
OR:
ASYMPTOMATIC: does not present until a patient is almost blind - picked up on routine screening
How can we prevent progressive open angle glaucoma?
Screening
Regular assessments: IOP readings, visual field analysis and optic disc examination
What are the signs of POAG?
OPITIC DISC CUPPING (increased cup disc ratio)
optic disc atrophy (blurring or borders
Cup to disc ratio largest Inferiorly, Superiorly, Nasal, temporally
ISNT)
What is acute angle closure glaucoma?
Acute angle-closure glaucoma occurs when the iris bulges forward and seals off the trabecular meshwork from the anterior chamber preventing aqueous humour from being able to drain away.
This leads to a continual build-up of pressure in the eye. The pressure builds up particularly in the posterior chamber, which causes pressure behind the iris and worsens the closure of the angle.
What are the risk factors of AACG?
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
long sightedness (small eyes)
Certain drugs can precipitate:
Adrenergic medications such as noradrenalin
Anticholinergic medications such as oxybutynin and solifenacin
Tricyclic antidepressants such as amitriptyline, which have anticholinergic effects
What is the presentation of AACG?
Severely painful red eye
Blurred vision
Halos around lights
Associated headache, nausea and vomiting
What signs will you see on examination of AACG?
Headache and vomiting Red-eye Teary Hazy cornea Decreased visual acuity Dilatation of the affected pupil Fixed pupil size Firm eyeball on palpation
What is the emergency treatment of AACG?
Emergency! Same day assessment by ophthalmology
Lie patient on their back without a pillow
Give pilocarpine eye drops (2% for blue, 4% for brown eyes)
Give acetazolamide 500 mg orally
Given analgesia and an antiemetic if required
What is the secondary care management of acute angle closure glaucoma?
Pilocarpine Acetazolamide (oral or IV) Hyperosmotic agents such as glycerol or mannitol increase the osmotic gradient between the blood and the fluid in the eye Timolol Dorzolamide Brimonidine (sympathomimetic)
Laser iridotomy is usually required as a definitive treatment. This involves using a laser to make a hole in the iris to allow the aqueous humour to flow from the posterior chamber into the anterior chamber. The relieves pressure that was pushing the iris against the cornea and allows the humour the drain.
What is the cause of rubeotic glaucoma??
What are the signs and symptoms of rubeotic glaucoma?
Rubeotic glaucoma follows central retinal vein occlusion or diabetic retinopathy – new vessels form and occlude the angle – although this is rarer now
red eye
corneal oeema
rubeosis
pupil distortion
What would IOP of 21-25 signify?
Blindness in 15 years
What would IOP of 25-30 signify?
blindness in 6 years
What would IOP of >30 signify?
blind in 3 years
How can visual field testing be done?
Goldmann perimetry - hollow white spherical bowl positioned a set distance in front of the patient.
Test light of variable size and intensity
test range of peripheral vision
Describe how automated perimetry works
mobile stimulus moved by a perimetry machine
Patient sits in front of a concave dome in small machine with a target in teh centre
Computer shines a light on inside dome and patient clicks the button whenever a light is seen
Maps and calculates visual field
What is the aim of treatment for glaucoma?
lower IOP
What is the medical treatment for progressive open angle glaucoma?
MYABC:
Miotic - pilocarpine: increases outflow
SurgerY (trabeculoplasty) – bleb
Analogue prostaglandin - latanoprost (first line)
Beta blockers - timolol (slows down aqueous production)
Carbonic anhydrase inhibitors: (dorzolamide) - slows down aqueous production
first line: latanoprost
second line: beta-blocker, carbonic anhydrase inhibitor, or sympathomimetic eyedrop
What is the laser treatment for glaucoma?
Argon/selective laser trabeculoplast - 50-100 shots delivered around trabecular meshwork to try to increase drainage
