Glaucoma 1 Flashcards
What is glaucoma?
“A disease of the optic nerve with characteristic changes in the optic nerve head (optic disc) and typical defects in the visual field with or without raised intraocular pressure.”
[NICE 2017- National Institute for health and Care Excellence]
What do we mean when we classify glaucoma as primary or secondary?
What are the three types of primary glaucoma?
Define prevalence
Prevalence is the number of all cases in a given population at one point in time
What is the prevalence of glaucoma?
Main take away: It affects the elderly more than the young.
What are the ocular risk factors to Primary Open Angle Glaucoma (POAG)?
High IOP – modifiable risk factor +++
Myopia
Corneal thickness
What are demographic and genetic risk factors for Primary Open Angle Glaucoma?
Age prevalence – over 40yrs: 2%, over 75 years: 10%
Race – African ethnicity - 4x more risk
Gender ? Men more than women
Family history - 6.7%
What systemic diseases are risk factors for Primary Open Angle Glaucoma?
Diabetes (3.3%)
Potential link to Migraines/Vasospasms
How do we detect Primary Open Angle Glaucoma (POAG) and what can make it difficult?
POAG is asymptomatic until end stages of the disease
It may be detected through a triad of tests:
IOPs
Optic Disc
Visual Fields
[Also important to assess angle]
Do all pxs with glaucoma have raised IOP?
No- pxs can still have glaucoma without having a raised IOP, although raised IOP is the most important risk factor for glacuoma it is not a criteria for glaucoma.
[Up to 50% of patients with glaucoma have normal IOP]
What factors affect the value of IOP?
Diurnal variation – i.e. IOP is higher in morning
Central corneal thickness CCT
How does Central Corneal Thickness affect IOP measurements?
A thin CCT will result in an underestimation of IOP Thin =uNder
A thick CCT will cause an overestimation of IOP
When assessing the optic discs in each eye for glaucoma what six things are we looking out for?
What is deemed a suspicious for glaucoma in regards to C/D ratio?
A ratio >0.6 is suspicious or
>0.15 change in C/D ratio over time
In regards to the neuro-retinal rim, what signs of glaucoma do we look out for in a suspected px?
The neuro-retinal rim should follow the ISNT rule i.e. it should be thickest Inferiorly then superiorly then nasally then temporally. [Glaucoma causes vertical thinning of the neuroretinal rim].
We should also be looking out for any thinning - i.e. where the neuroretinal rim gets thinner, and if that is focal (i.e. only affects one side of the rim) or difuse (thins generally all over).
True or False- Larger discs have larger cupping than smaller discs
True
True or False-Optic Disc size varies on average between racial groups - largest in Caucasion population
False- Optic Disc size varies on average between racial groups - largest in Afro-Caribbean population
How do glaucomatous haemorrhages at the disk appear?
What condition can give high IOP readings yet is not glaucoma?
Ocular Hypertension (IOP>21mmHg in the absence of glaucoma) – the prevalence of this is 2.7% - 10%
What does the abbreviation NRR stand for?
Neuro-retinal rim
How would you use a slit lamp to measure the size of the optic disc?
You would adjust the length of the beam until it is equal to the size of the optic disc - you would then read off the length of the slit lamp beam off the scale.
What are we looking for in regards to nerve fibre defects when screening for possible signs of glaucoma?
Any nerve fibre atrophy. This would be a darkened part of the fundus and is best seen with a green filter or red-free photography.
What must you bear in mind when assessing the visual field of a px you suspect to have glaucoma?
There may have been considerable nerve fibre death (up to 50%) before the patient has a definite field defect.
Visual fields are very subjective – variability, need to repeat test to account to fatigue/learning effect
What visual defects are characteristic of glaucoma?
A nasal step - early on
An arcuate scotoma - this start of as small scotomas which join together forming that arc.
A larger than normal blind spot.
[At end stage a px is left with tunnel vision]
How can we diffrentiate between ocular hypertension (OHT) and the symptoms of glaucoma?
Those with Ocular Hypertension will have:
Elevated IOP
IOP >21 mm Hg
Normal optic discs
Normal visual fields
Open anterior chamber angle
Whereas those with glaucoma:
- May or may not have raised IOP
- Abnormal optic disc
- Visual field defects
- Possible closed angle depending on the type of glaucoma
True or False-Between 4% and 10% of individuals with OHT will eventually develop glaucoma
True
What is the difference between open angle and closed angle glaucoma?
What is the prevalence of Ocular Hypertension (OHT)?
Prevalence of OHT in the adult population is between 2.7%- 10%
What is the glaucoma checklist (way of remembering everything to check in a px you suspect of glaucoma)?
