What is Glaucoma?
An optic neuropathy characterised by cupping of the optic nerve with corresponding visual field defects due to loss of retinal nerve fibre layer with the main risk factor being raised intra-ocular pressure
NOT raised IOP but an optic neuropathy with a characteristic cupping of optic nerve for which raised IOP is the main risk factor
What is high IOP?
> 21mmHg
What is it if you have normal IOP (10-21mmHg) and normal optic nerve and visual field?
Normal
What is it if you have normal IOP (10-21mmHg) but abnormal optic nerve and visual field?
NTG = Normal Tension Glaucoma
What is it if you have high IOP (>21mmHg) but normal optic nerve and visual field?
OHT = Ocular hypertension (not glaucoma as the optic neuropathy isn’t there)
What is it if you have high IOP (>21mmHg) and abnormal optic nerve and visual field?
Glaucoma
How does high IOP cause optic nerve damage (optic neuropathy)?
- Raised IOP causing mechanical damage to axons?
- Raised IOP reducing blood flow at nerve head and then causing damage to axons?
What are the 2 outflow routes of aqueous humour (for stable and steady IOP?
1) The conventional route: Trabecular meshwork –> Schlemm canal –> Episcleral veins –> Bloodstream
2) The uveoscleral route (4%+): across the ciliary body into suprachoroidal space
What do you need to be able to see to determine closed and open angle when looking into the iridocorneal angle?
I - Iris
Can’t - Ciliary Body
See - Scleral Spur
The - Trabecular Meshwork
Stupid Line - Schwalbe’s Line
What are the grades for anterior chamber angles?
- Grade 0
- Grade 1
- Grade 2
- Grade 3
- Grade 4
What is the Glaucoma Classifcation?
Primary Glaucoma
Open
- POAG = primary open angle glaucoma
- NTG = normal tension glaucoma
Closed
- PACG = Primary angle closure glaucoma
Secondary Glaucoma
Open
- e.g. pigment dispersion syndrome (PDS), uveitis, post-surgical
Closed
- e.g. Rubeosis, Phacomorphic
What are some risk factors of POAG?
- 1% of over 40s
- Increasing to 80% of over 80s
- Males = Females
- Family history
- Black > white
- Myopia
- Diabetes
Often symptomless and picked up at opportunistic screening at the optometrists
What findings on examination do we have for POAG?
- High IOP (typically 22-40mmHg)
- Open angle
- White eye, clear cornea
- No PXF (pseudoexfoliation syndrome), PDS (pigment dispersion syndrome)
- Pathologically cupped optic disc
- Visual field defects
What are some treatments for POAG?
Treatment aimed at lowering IOP to reduce risk of progression
- Medical
- LASER
- Surgery
What VF pattern do we get in glaucoma?
Arcing defect starting often as a nasal step that eventually joins with the blind spot
What drugs can we give to help with POAG?
- Prostaglandins (Inatanoprost; increases outflow through the non-conventional uveal-scleral route)
- Pilocaprine (miotic; tries to increase the angle but well tolerated, better tolerated in closed-angle glaucoma)
- A-agonist, Brimonidine (dual action)
- B-Blockers such as Timolol, carteolol, betaxolol (reduces production fo aqueous)
- CAIs like dorzoloamide (reduces production of aqueous)
Either does:
- Reduces aqueous production
- Increases outflow
- Both of the above
What is Prostaglandin Analogues? Example, Action, Side Effects
Topical Medicine
Example:
Latanaprost, bimataprost, travaprost
Action:
Increase outflow via uveoscleral pathway
Side Effects:
Longer, darker lashes, red conjunctiva, skin pigmentation changes
What is Beta-Blockers? Example, Action, Side Effects
Topical Medicine
Example:
Timolol, Carteolol
Action:
Decrease secretion
Side Effects:
Contraindicated in asthma and heart block. Bradycardia, hypotension
What is an Alpha-2 agonist? Example, Action, Side Effect
Topical Medicine
Example:
Apraolnidine, Brimonidine
Action:
Increase outflow and decrease secretion
Side Effects:
Stinging, red eyes
What is a Carbonic Anhydrase Inhibitor? Example, Action, Side Effects
Topical Medicine
Example:
Dorzolamide, Brinzolamide
Action:
Decrease secretion
Side Effects:
Stinging, unpleasant taste
What is our first line treatment in glaucoma?
Prostaglandins
What is LASER for POAG considered?
Evidence that Selective LASER trabeculoplasty (SLT) may be best for first line treatment and reduce/negate need for drops
What is the name of the surgery in POAG?
Trabeculectomy
What are some complications of Trabeculectomy?
- Hypotony
- Failure (Pressure might be too low or might not come down)
- Scarring causing failure (MMC; conjunctival scars up and the new drainage passageway scars up so might need scarring agents like MMC to stop scar formation)
- Intraocular infection (blebitis; severe complication but not as VA threatening as endophthalmitis)
