Ophthalmology - Open-Angle Glaucoma Flashcards
What does glaucoma refer to?
Optic nerve damage caused by a rise in intraocular pressure
What causes raised intraocular pressure in glaucoma?
A blockage in aqueous humour trying to escape the eye
Name the types of glaucoma
- Open-angle glaucoma
- Acute angle-closure glaucoma
- Normal-tension glaucoma (rare- caused by hypoperfusion)
What is the vitreous chamber of the eye filled with?
Vitreous humour
What are the two chambers filled with aqueous humour?
- Anterior chamber (between the cornea and iris)
- Posterior chamber (between the lens and iris)
What is the function of aqueous humour?
Supplies nutrients to the cornea
What produces aqueous humour?
Ciliary body
Where does aqueous humour flow?
Through posterior chamber
Around iris to anterior chamber
Then drains through the trabecular meshwork to the canal of Schlemm
Aqueous veins (part of the episcleral venous system)
What is the normal range for intraocular pressure?
10-21 mmHg
Created by resistance to flow through the trabecular meshwork
Label the diagrams
What causes the gradual open-angle glaucoma?
Gradual increase in resistance to flow through the trabecular meshwork
Pressure slowly builds up within eye
What happens in acute angle-closure glaucoma?
The iris bulges forward, sealing off the trabecular meshwork, preventing drainage
Continual build-up of pressure and acute symptom onset
Ophthalmological emergency
What does raised intraocular pressure lead to?
Cupping of the optic disc
In the centre of the optic disc there is an indent - optic cup
What causes cupping in glaucoma?
Pressure on optic nerve causing thinning of the outer nerve
What is the cup-disk ratio considered abnormal?
Greater than 0.5.
List risk factors for open-angle glaucoma
- Increasing age
- Family history
- Black
- Myopia (nearsightedness)
How does glaucoma present?
Gradual onset of peripheral vision loss (tunnel vision) (due to gradual onset of outer nerve atrophy)
- Fluctuating pain
- Headaches
- Blurred vision
- Halos around lights, particularly at night
What causes halos around lights in glaucoma?
Acute closed angle glaucoma
Spike in intraocular pressure leads to intracorneal oedema
Corneal endothelial cells pump aqueous humour out of the cornea and become unable to compete with the high pressure pushing the fluid into cornea
Cornea fills with AqH, leading to temporary loss of visual acuity, halos form around sources of light due to increased dispersion of light
Open angle glaucoma
Night-time
Iris moves as the pupils dilate to allow more light in at night, further reducing ability of AqH to drain (also during raised adrenalin activities)
Causes increases dispersion of light
How is intraocular pressure measured?
Non-contact tonometry
Puff of air shot at cornea and corneal response measured
What is the gold-standard method for measuring intraocular pressure?
Goldmann applanation tonometry
Slit lamp makes contact with cornea and applies pressure
What are the key components of glaucoma diagnosis?
- Goldmann applanation tonometry for intraocular pressure
- Slit lamp assessment for cup-disk ratio and optic nerve health
- Visual field assessment for peripheral vision loss
- Gonioscopy to assess the angle between the iris and cornea
- Central corneal thickness assessment
At what intraocular pressure is treatment typically started?
24 mmHg or above.
What is 360° selective laser trabeculoplasty used for?
Improving drainage of aqueous humour
Laser is directed at trabecular meshwork, can delay or prevent need for eye drops
Used for all patients
What are the first-line medical treatment eye drops for glaucoma?
Prostaglandin analogue eye drops (e.g., latanoprost)
Increases uveoscleral outflow
