DIS - Open Angle Glaucoma I - Week 3 Flashcards
What is the prevalence of glaucoma in Australia? What about elsewhere?
Australia - 1.7-2.4%
Elsewhere - 2.5%
Is glaucoma race or age dependent?
Yes to both
What percentage of all blindness is due to glaucoma?
14%
What was the old definition of glaucoma using IOP? Why is this no longer the definition and what is this called now in place of glaucoma?
Used to be IOP > 21mmHg, but many cases of glaucoma never have IOP >21 (LTG)
Now is called ocular hypertension (OHT)
Is both an IOP of 21mmHg and CDR >0.5 a risk factor for open angle glaucoma?
Yes
Is progression of glaucoma evident at the first visit? What does this mean for diagnosis and what four factors is this based on?
Progression isnt evident at first visit
Open angle glaucoma is often a presumptive diagnosis based on:
-risk factors
-appearance of the RNFL
-appearance of the NNR of the ON
-typical VF loss
What defines the management of glaucoma?
The level of risk for glaucoma
What six things are investigated to diagnose glaucoma?
IOP
Angle
Anterior chmaber
RNFL
ONH (NRR)
Visual field
What is the outcome if there is an absence of all signs?
The patient is a glaucoma suspect (low-high risk)
Define a diagnostic risk factor vs prognostic.
Diagnostic - attributes present in greater frequency in a disease
Prognostic - attributes that predict faster change once the disease is diagnosed
What 5 eye conditions are considered high risk for glaucoma?
Myopia
Retinal vein occlusion
Eye injury
Iris degeneration
Papilloedema
Which gender is at a lower risk of glaucoma?
Female
Is diabetes considered a high risk for glaucoma? What about migraines and sleep apnoea?
All are low risk
What defines ocular hypertension?
In a normal population, IOP gives a bell shaped curve, therefore ocular hypertension is a statistical concept, the cutoff of which is based on this normal distribution
What is the average IOP including standard deviation? What IOP range would 95% of the population fall within?
15.6 ± 2.5 mmHg
95% is within 10-21mmHg
Consider individuals with IOP above 21mmHg. Is this normal? What is this called? Explain (3).
Most people above 21mmHg are normal
ONH, RNFL and VF are normal
Called ocular hypertension
What percentage of Australians have ocular hypertension?
3%
Can open angle glaucoma be IOP independent? Explain (2).
Open angle glaucoma can be IOP independent below 18mmHg - low tension glaucoma
Is high IOP a risk factor for glaucoma? Explain.
Above 18mmHg prevalence of glaucoma increases, so it is a risk factor
What are IOP spikes a good indicator of?
Progression
What is needed in all low tension glaucoma cases and for what purpose?
Need diurnal curve in all low tension glaucoma cases to dismiss spikes
What thickness cornea is a higher risk for open angle glaucoma?
Thin cornea
With tonometry, do thicc corneas tend to return higher or lower IOPs?
Higher
If there are repeated measurements of IOP > 29mmHg, what must be done (2)?
Angle evaluated for closure (gonioscopy or OCT - or both)
CCT measured
If there are repeated measurements of IOP < 5mmHg, what should be considered (2)?
Hypotony
CCT measurement
What aspect of high blood pressure can mean it is a risk for glaucoma?
Aggressive BP lowering
Is steroid use a risk factor for glaucoma?
Yes
What race is a risk factor for open angle glaucoma?
African-American
What race is a risk factor for low tension glaucoma?
Japanese
Above what age is a risk factor for low tension glaucoma?
> 65 years old
What is essential to diagnose primary angle closure glaucoma?
Gonioscopy
For an angle to be considered open, on gonioscopy what structure must the angle be open to and over how many degrees? What else (3)?
Angle must be open to ATM for over 180°
Angle must be unimpeded - no pigment, blood, congenital malformation
What disc features are generally evaluated for glaucoma (4)?
Papillary crescents
NNR thickness
Other signs like haemorrhage
CD ratio
Compare a cupped disc to a saucer disc in terms of disc size and defect.
Cup = large disc + surface defect - steep profile for the edge
Saucer = small disc + deep defect - shallow profile/tenting
Is it more difficult to see the NRR in a cupped or saucer disc?
Saucer
If surface fibres are affected, what distance in the visual field is defected?
Surface fibres = proximal VF defect
If deep fibres are affected, what distance in the visual field is defected?
Deep fibres = distal VF defect
What is the CDR an indirect index of (2)?
NNR and RGC number
What does the CDR vary with? How does this affect its reliability for neuropathy?
Size of the scleral opening
So CDR is confounded by disc size
-it is not a reliable index of neuropathy
Does saucerisation alter CDR? Explain.
No, but makes the cup edge harder to see
What is an abnormal CDR? Include asymmetry.
> 0.7
Asymmetry of >0.2
In what percentage of people does the ISNT rule follow? What about IST?
ISNT - 50%
IST - 87%
Is the ISNT rule a reliable for glaucoma diagnosis?
Yes
Does the NRR show pallow in early open angle glaucoma?
Never shows pallor
In a normal NRR, what section is paler?
T margin
What part of the NRR gets wider?
Towards the poles
Describe how ON size can be estimated with the following thecniques:
Slit lamp
Opthalmoscopy
Slit lamp - adjust the slit size to fit the vertical ON
Ophthalmoscopy - compare vertical ON with medium aperture
-small ON <0.75, large ON >1.25
What percentage of the population have very large discs and what should be expected of the NRR, CDR, and ISNT rule?
Expect thin NNR everywhere
CDR will be large (≥0.7) but will give IST in most cases
With what NNR thickness profile (ISNT) should you do VF with macula (2)?
If T=S, I
Or if thinner than expected
Are small discs usually saucerised or cupped?
Saucer
What should you look for in small discs (2)?
Look for PPA and RNFL (visible due to crowding)
