Glaucoma 1 - introduction Flashcards by Anisha Dhamrait

What is glaucoma’s?

Group of ocular conditions that produces a characteristic of optic neuropathy

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What are two way glaucoma is classified?

Primary - not associated with any other ocular disorders
Secondary- the increased IOPs are due to another condition

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What percentage of glaucoma’s are primary?

95%

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What is an example of secondary glaucoma?

Steroid induced glaucoma

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What are the three classifications of primary glaucoma?

Open angle, closed angle, congential

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What % of primary glaucoma is open?

85%

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Which is easier to detect POAG or PCAG?

PCAG

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What is the mechanism for open angle glaucoma?

Mechanism is unknown
possibility include:
Chronic injury to axons of the retinal ganglion cells and other optic nerve tissues mainly at the OD and lamina cribrosa causes IOPs to raise above average levels

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What is the mechanical pathogenesis of the glaucomatous optic disc?

Axon damage within the optic nerve is caused by pressure induced deformation of the lamina cribrosa causing retinal ganglion cell death

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What is the vasogenic pathogenesis of the glaucomatous optic disc?

The quality of blood supply to the optic nerve head is impaired which leads to hypoxia and reduced nutrient to the ONH —> retinal ganglion cell death.

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What is meant by characteristic but not diagnostic visual field defects?

The typical VF defect is a arcuate shape, which take the path of the retinal ganglion cells. There is a nasal step as well
*glaucoma is not only disease that causes this- NOT DIAGNOISTIC

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Why is central 20-30 so important, for early open angle glaucoma?

Because Glaucoma will first effect the 20 -30 degrees on the VF at tis earliest stage

And the px will not be able to notice, as no symptoms

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What are the important risk factors for OAG?

1.Age
2.IOP (huge RF)
3.Race
4.FH
5.Myopia
6.Genetics

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What increases with the prevalence of OAG?

Increased IOPs, increased VF loss

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If IOPs are reduced with someone with OAG, what happens?

Optic nerve head damage risk reduced (IOPs should be reduced to the target pressure)

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According to NICE guidelines what is the prevalence of OAG in over 40s?

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According to NICE guidelines what is the prevalence of OAG in over 75s?

10%

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What is normal tension glaucoma (three situations where this is apparent)?

A glaucomatous optic neuropathy but IOP never exceeds 21mmHG
A glaucomatous optic neuropathy with mean IOP over a 24hr period of <21mmHg & peak pressure of <24mmHG
chronic OAG where IOP is rarely above 21mmHg (NICE Definition)

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What does the Bedford glaucoma study show?

21mmHG comes from the mean IOP of 16mmHG +2 standard deviation
IOP is NOT normally distributed

SD is 2.5. 2 SD = 5. 16+5 = 21 21mmHg.

The value of 21 is more statistical not clinical

Is normal tension glaucoma rare?

What percentage of pxs will have IOPs in the normal range at the time of diagnosis?

40-50%

What is high tension glaucoma?

A glaucomatous optic neuropathy with IOP outside statically Normal range

What are the three types of primary angle CLOSURE glaucoma ?

Acute, subacute and chronic
(Makes up 15% of primary glaucomas)

Is the prevalence of PCAG and POAG similar everywhere around the world?

No- it is more prevalent in some places more than others for example in china PCAG is more prevalent than POAG

What percentage of congential glaucomas make up primary glaucomas?

<0.5%

What % of child blindness is caused by Priamry congenital glaucoma ?

2.5-10%

What causes congenital glaucoma?

Mal-development of the anterior chamber angle and as a result incomplete development of the TM

What is shown in severe cases of congenital glaucoma + what would treatment be?

Buphthalmos - visible enlargement of the eyeball due to controlled glaucoma Treatment= surgical to open up drainage angle

Are we involved in the diagnosis of congenital glaucoma?

No- normally the paediatrician

Do people with ocular hypertension (OHT) have glaucoma?

What signs do people with OHT have?

-IOP>21mmHg CONSISTENTLY - Normal discs - Normal VF - Open anterior chamber angle

According to the Norfolk Eye study, what is the prevalence of the population having OHT?

10%

Why is the Norfolk Eye Study good?

Because it is fairly recent but also a study in the UK

According to NICE (2009) what percent of those over 40 have OHT?

3-5%

What are people with OHT at risk of?

Developing POAG

If one identical twin developed OAG what is the chance that the other one gets it too?

98%

Why is it important to ask for a family history of glaucoma?

There is a distinct genetic link, 10-50% of OAG report FH of glaucoma (but lots of people under report so it’s probably a higher %)

If we are able to identify specific gene defects then what should this lead to? (There are 3 points)

- Better understanding of mechanism - Better conventional treatments - Wide spread screening for disease esp those at risk which could reduce risk of visual loss

Do we screen for glaucoma as optometrists?

No- we do opportunistic surveillance or case finding

Why is OAG difficult to detect?

Px nly get symptoms until late stages of the disease

What are the three main tests we do to detect glaucoma?

Measure IOPs Assessment of VF Examination of the optic disc

Are the screening tests for glaucoma perfect?

No- there’s many factors affecting accuracy for each of the tests e.g thick cornea affects IOPs, DISC assessment is subjective , FP & FN on VF

What does sensitivity mean?

The proportion of all diseased pxs who are correctly classified as diseased by the test (should be 100%)

What does specificity mean?

The proportion of all normal pxs who correctly classified as normal by the test (this should be 100%)

What are the 3 stages / types of Congenital Glaucoma?

1.) Neonatal or newborn onset (0-1m) 2.) infantile onset (>1m until 24m) 3.) late onset or late recognised (>2yrs to puberty ) FYI for Anisha specifically: m stands for month x

What could identification of specific gene defects lead to? (3)

1.) better understanding of mechanisms of disease esp as largely unknown in glauc 2.) better conventional treatments 3.) widespread screening for disease, esp in affected families- early risk identification could mean family members have reduced risk of Visual loss in life