Week 2.06 Gluacoma Flashcards
Definition of glaucoma
Group of eye diseases that damage the optic nerve
Progressive optic neuropathies - degeneration of retinal ganglion cells
Open angle glaucoma
Primary - absence of an identifiable cause
High IOP (POAG)
Normal IOP (normal tension glaucoma NTG)
Secondary - occurs as a side effect to another underlying condition/treatment - damage to trabecular mesh work - steroid use
Closed angle glaucoma
Primary - in absence of identifiable cause (except for size of angle) - hyperopes have smaller angles
Secondary - glaucoma that occurs as a side effect to another underlying condition - trabecular mesh work, advanced cataract - as the IOL is thickening that can cause ant chamber angle to narrow
When would we suspect glaucoma
When we see signs of damage at the optic nerve and or visual field damage
What is ocular hypertension
Consistently or recurrently elevated IOP (greater than 21mmHg) with no clinical evidence of optic nerve damage or visual field defect
(As soon as there is any change to optic disc suspect glaucoma)
Is OHT a risk for developing COAG
Yes
Chronic open angle glaucoma can also be called
Primary open angle glaucoma
Who is certified as severely sight impaired
Group 1: ppl who have VA worse than 3/60 snellen
Group 2: ppl who are 3/60 snellen or better but worse than 6/60 snellen who also have contraction of their visual field
Group 3: 6/60 snellen or better who have significant contracted field of vision which is functionally impairing the person
What are the two main theories of glaucoma
Mechanical
Vasogenic - good vessels and circulation
Mechanical theory of glaucoma
Increased resistance to aqueous outflow through trabecular mesh work leads to increased IOP
Connective tissues of ONH constantly subject to IOP related stress
Mechanical failure of
- laminated cribrosa
- scleras canal wall
- peripapillary sclera
Vasogenic theory of glaucoma
- damage caused by compromise of tiny blood vessels at ONH
- reduction in blood pressure at ONH similar effect to increased IOP
What happens to the prevalence of glaucoma with age
- Prevalence increases with age
- > 60yrs SIX times more likely than <60
Are men or women more likely to have glaucoma
Men more likely to have POAG
What does myopia have to do with glaucoma
o Low myopia (-1.00D to -3.00D) – 2x risk
o Moderate-high myopia (>-3.00D) – 3x risk
o Possible bias as increased visit frequency – due to increase in rx, broken glasses etc
FH and glaucoma
o Definite genetic link
o 13-50% POAG are familial
Biggest risk is if siblings have glaucoma
GH and glaucoma
o Diabetes
- 1.5x risk for POAG
- Increased susceptibility of the optic nerve fibres
- Common risk factors
What are the NICE guidelines for the tests before referring glaucoma
Need to offer all the tests:
1. VF full/supra-threshold
2. Optic nerve assessment and fundus examination using stereoscopic slit lamp and OCT
3. IOP using Goldman-type tonometry
4. Peripheral ant chamber and depth assessment using gonioscopy
What are the guidelines for referring glaucoma then
Optic nerve head damage on stereoscopic slit lamp bimicroscopy
Visual field defect consistent with glaucoma
IOP is 24mmHg or more using Goldman-type tonometry
Why measure CCT
Thicker CCT provides greater resistant to GAT thus ELAVATING IOP measurement to more than actual
Thinner CCT provides less resistance to GAT thus REDUCING IOP measurement
Which corneas thick or thin are more risk of underestimating
So thinner corneas more at risk as ur underestimating the pressure. The pressure is actually higher than the measurement
How to measure CCT
Ultrasound - small transducer contact cornea, good resolution and precision
Optical - attachment to SL, observer dependent
What do we mean by optic nerve head damage
Increase in C/D ratio
Increase in cup depth
Asymmetry of C/D ratio
Loss of NNR (notching)
Bayoneting
What are the typical visual field defects for glaucoma
Paracentral scotomas
Actuate scotomas
Nasal steps
Temporal wedges
On a VF test how can u tell left or right eye
Blind spot is usually nasal in real life
On VF chart it is inverted so is on the temporal side
What does paracentral scotoma look like
Near the centre of the visual field there will be darker areas
What does arcuate defect look like
Connects to blind spot looks like half the bottom has gone black
What are the two main types if management for glaucoma
Surgical - SLT
Medical
What does the management of glaucoma try to do
Reduce IOP
Prevent optic nerve damage
Preserve vision
Selective laser trabeculoplasty
YAG laser
Targets melanin rich cells in trabecular mesh work
Surrounding tissue left intact and unharmed
Cell activity increased to improve drainage of fluid in the eye
Prostaglandin analogues
Latanoprost 1x at night
Increase uveoscleral outflow
More potent than b blockers
Beta blockers
Timolol 2x day
Reduce IOP by reducing aqueous secretion
Dry eye
Carbonic anhydrase inhibitors
Dorzolamide 3 x
Reduce aqueous secretion
Why would anyone use a miotic
Pilocarpine 4x day
Improve trabecular outflow
What trabeculectomy
Produce a fistula to allow aqueous to drain into subconjucntival space
Seen as a ‘filtration bleb’
Iridotomy
helps for narrow angle, iris bulging forward making narrow angle so if you punch a hole in the iris it stops the pressure of the iris pushing forward
What’s the definition of primary angle closure glaucoma
Condition in which elevation of IOP occurs as a result of obstruction of aqueous outflow by partial or compete closure of the angle by the peripheral iris
What is the risk of getting primary closed angle glaucoma
60yrs old
F-M 4:1
Acute closed angle glaucoma
Angle is closed
Intense eye pain
Corneal oedema, blurred vision, haloes
IOP significantly raised
Circumlimbal redness
Headache
Nausea and vomiting
Chronic closed angle glaucoma
Angles are narrow and capable of closure
Symptoms are vague and often intermittent
Occur when angle is narrower - pupil is larger low light
Haloes
Headache
Redness
Blurred vision
Ache in eye
