Pathogenesis of Glaucoma Flashcards
What is a key feature of glaucoma?
Loss of retinal ganglion and thinning of the retinal nerve fibre layer
Name the five risk factors of glaucoma
1) Black ethnicity
2) Intraocular pressure >26mmHg
3) Myopia
4) Diabetes
5) FH
What are the clinical features of glaucoma?
- Thinning of the NRR
- Disc cupping
- Visual field loss
- Asymmetric between the eyes
- Raised IOPs–> important in screening for the disease
With primary angle closure glaucoma, what is the clinical features?
Close angle- this can be seen with gonioscopy
What is peripheral anterior synechiae?
Points of attachment between the trabecular meshwork and iris
What is iris block?
Pupil margin is attached to the anterior surface of the lens which causes a ballooning forward
What increases the risk of progression of glaucoma of closed angle glaucoma?
Raised IOPs
In open angle glaucoma, what causes raised IOPs?
Increased resistance to outflow
What produces aqueous?
Ciliary epithelium (pars plicata)
What are the two ways that aqueous is excreted?
1) Irido-corneal angle - Canal of Schlemm/ trabecular meshwork (70-90%)
2) Uveoscleral outflow (10-30%)
What is the IOP determined by?
Aqueous production and aqueous drainage
Describe the mechanism of aqueous production
The double epithelium of ciliary epithelium (pigmented layer and non-pigmented layer) work together to produce aqueous, formed by ion-driven transport system. The ions are transported from the ciliary stroma to the pigmented epithelium then by gap junctions to non-pig epithelium. Then is ACTIVELY transported into the posterior anterior chamber
What enzyme plays a huge role in aqueous secretion?
Carbonic anhydrase
What is prostaglandin analogues and give an example of a type.
Drug used to treat open angled glaucoma, an example is latanoprost
Do you know different layers of the trabecular meshwork?
No- go through it
What layer of the trabecular meshwork causes resistance to outflow?
Juxtacanalicular
What two ways which helps to reduce resistance of the outflow from the trabecular meshwork?
1) Drugs
2) Laser therapy
How does laser therapy lower IOPs?
Burns holes to open up spaces for the aqueous to be drained out of
With secondary open-angle glaucoma what causes the IOPs to increase?
Meshwork becomes blocked with materials such as pigment and inflammatory material
What is uveo-scleral outflow?
It enters the ciliary body and is removed via vascular routes
Describe the mechanism of optic nerve damage.
Stress and strain is put on the ONH due to raised IOPs and this compression can result in remodelling the lamina cribosa which leads to axonal disruption then apoptosis and degeneration of retinal ganglion cells.
What is an alternative way the ONH can become damaged? (Hint; it is a vascular mechanism)
Interruption to blood supply- raised IOPs can reduce ocular blood flow which leads to axons being deprived of nutrients (ishaemic mechanism)
What three kinds of drugs inhibit aqueous production?
1) Beta blockers (block beta receptors)
2) Alpha receptor agonist (stimulate alpha receptors)
3) Carbonic anhydrase inhibitors
What is pilocarpine?
Muscarinic agonist - opens up the trabecular meshwork
Contraction of ciliary muscles - widens up the space
What is the first line of drugs used to treat glaucoma?
Prostaglandin agonists
Name three surgery methods to improve drainage
1) Selective laser trabeculoplasty
2) Trabeculectomy
3) Minimally invasive glaucoma surgery
What is selective laser trabeculoplasty?
Punching holes in the TM to open up the pathway
what is Trabeculectomy?
Creates a new aqueous outflow pathway from posterior chamber to ocular surface
What is Minimally invasive glaucoma surgery?
Tubes or stents put in the eye to take aqueous form anterior chamber to be drained into the supra choroidal space
