Glaucoma Flashcards
What’s glaucoma?
eye of eye diseases where there is progressive damage to the optic nerve –> leads to pattersn of visual field loss
How is aqueous humour produced and drained?
Produced by ciliary bodies.
Two modes of drainage:
- trabecular outflow (90%)
- uveoscleral outflow (10%)
We generally produce less aqueous humour at night (by 50%) but pressure usually goes up because we’re lying down.
What are the two types of glaucomas?
- primary open angle gluacoma (POAG)
most common (70%)
decreased aqueous drainage - primary closed angle glaucoma
chronic: gradual closureof anterior
chamber
Risk factors for POAG and angle closure?
- extremely high: > 80
- high > 50, family history, african-american
IOP > 24 mmHg - moderate: diabetes, myopia (short-sightedness), rural location
IOP 21-24 mmHg - low: smoking
cup: disc ratio
angle closure:
Hypermetropia / Hyperopia (long-sighted)
* Family history of angle closure
* Advancing age
* Female
* Asian/Inuit descent
* Shallow anterior chamber
Clinical signs and symptoms of glaucoma
patients will report a tunnel vision - initially losing their peripheral vision but this doesnt occur until they’ve lost at least 30% axons.
Acute angle closure crisis symptoms
Sudden onset of severely painful red eye
* Blurred Vision
* Coloured rings around lights
* Frontal headache
* Palpitations and abdominal pains
* Nausea and vomiting
* IOP: usually ~ 50-80mmHg
Glaucoma diagnosis
Based on
1. Patient history
2. Eye structure
* Thinning retinal nerve fiber layer
* Angle of anterior chamber
* Optic Disc
3. Eye Function
* Visual field assessment
4. Intraocular Pressure (IOP)
* Normally <21mmHG
* Above are normal but IOP>21mmHG = ocular hypertension
* Above abnormal but IOP<21mmHG = normal tension glaucoma
* Still benefits from ↓ IOP
How do eye drops bypass FPM?
- Trans-conjunctival absorption
- Naso-lacrimal duct drainage with trans-nasal mucosal absorption
What are the drug classes use for glaucoma and how do they work?
increases uveoscleral outflow (prostaglandin analogues)
- so increase outflow
Prostamide analogues: increases trabecular outflow AND increases uveoscleral outflow
decrease aq humour production (beta blockers, carbonic anhydrase inhibitors)
- or decrease inflow
alpha 2 agonists: increase uveoscleral outflow AND decrease aq humour production.
Prostaglin analogues
All ↓ 25-30% IOP
Prostamide?
* Bimatoprost – Allergan
Prostaglandin analogues
* Latanoprost (XalatanTM) – Pfizer
* Travoprost – Alcon
XalatanTM patent covered latanoprost and prostaglandin derivatives
Prostaglandin analogues- counselling
PGF2α agonists
↑ Matrix Metalloproteinases1
* → degrade collagen and ciliary muscle extracelluar matrix
* → ↓ hydraulic resistance to uveoscleral outflow
Only need to use once a day
* Optimal effect at night but unsure why
* Uveoscleral outflow independent of IOP
* Due to bulk flow not diffusion.
But poorer adherence at night2
* Can use in morning if adherence is a problem
Common ADRs of eye drops for glaucoma
Hyperemia (usually 2-6 months)
* Use at night
Irreversible ↑ iris pigmentation
~6 months to occur (Uniocular trial safe)
Occurs more in those with mixed colour
* Blue-brown
* Green-brown
* Yellow-brown
Reversible lengthening and thickening of eyelashes
* “Luscious Lashes”
Preservative-free products for glaucoma
Tafluprost
Bimatoprost (Lumigan PF) - discard immediately after use
Beta-blockers for glaucoma
Timolol – Non-selective β-blocker
– ↓ 25% IOP
* Usually used BD
* XE – once a day
Betaxolol – β1-selective
ADRs
* Common: Stinging, bradycardia
* Infrequent:
* hypotension (more frequent in elderly → falls)
* Confusion, hallucinations
* bronchospasm (less with β 1 selective)
Interactions
* Can cause heart block with Verapamil
* Simultaneous oral and topical β-blocker use ↓ IOP reduction benefit
Carbonic anhydrase inhibitors
Brinzolamide
Dorzolamide
Low pH (5.6) - Stinging
* 1 drop bd – tds (usually tds if used alone or bd when used as adjunct)
both ↓ 15-20% IOP
Precaution: Sulphonamide allergy
