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Summer Final: Glaucoma > Toolbox In Glaucoma > Flashcards

Toolbox In Glaucoma Flashcards

1
Q

Where do you need to obtain data with pachymetry

A

As central as possible

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2
Q

What should you do for pachymetry to increase your reproducibility of data in pachymetry

A

Greater number of measurements

Always use the lowest data

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3
Q

Why always use the lowest data in pachymetry

A

Perpendicular measurements are lowest or smallest in value

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4
Q

What does pachymetry measure

A

CCT

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5
Q

Why do we not use the average data for pachymetry?

A

Lowest is the most accurate and helps decrease error

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6
Q

Do all pachymeters give us the same measurements?

A

No
Values vary basis of
-velocity of ultrasound used in algorithm
-MHz of probe

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7
Q

Ultrasound velocity for pachymetry

A

Usually 1620 or 1640 MHz

20MHz +/- 3um accuracy

50MHz +/-1um accuracy

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8
Q

Which is more accurate, 20MHz or 50MHz pachymetry

A

50

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9
Q

Anterior segment OCT

A

Can get pachymetry this way but its not billable

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10
Q

Difference between OCT and optical techniques and ultrasound pachymetry

A

OCT will measure about 20um lower

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11
Q

How to sue CCT data in glaucoma management

A
  • error in IOP measurements
  • OHTN patients
  • thinner cornea at greater risk of developing glaucoma
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12
Q

Thicker cornea and IOP

A

False high IOP

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13
Q

Thin cornea and IOP

A

False low IOP

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14
Q

The STAR calculator

A
  • OHTS and EGPS data
  • intended for use only in untreated OHT patients
  • age (30-80)
  • IOP 20-32 mmHg
  • CCT 475 to 650 microns
  • PSD 0.50 to 3.00 dB
  • C/S ratio vertical o.oo to o.8

Probability of conversion in 5 years
<55=% observe and monitor
5-15% consider treatment
>15% treat

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15
Q

Ultrasound biomicroscope

A
  • uses 35MHz probe

- can work well through opaque media-OCT does not work well

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16
Q

Thin or thick cornea has higher risk of glaucoma

A

Thinner

17
Q

Pneumotonometer

A
  • IOP:200/sec
  • up to 20 seconds
  • measures 7 pulses and selects 5 best to calculate IOP and POBF
  • also gives pulse amplitude and calculates pulse volume
18
Q

Pulsatile ocular blood flow

A
  • a calculated value
  • suggested that could be indicative of a disease
  • large range of normality and is derived making numerous assumptions
19
Q

Good for seeing plateau iris syndrome or pupillary block

A

Ultrasound biomicroscope

20
Q

Problem with POBF

A

Different systems of pneumotonometry give different values

21
Q

Ethnicity and POBF

A

Someone living in a hot environment, the choroid is pumping blood more and increasing the flow so they will have a higher number

22
Q

Pascal tonometer

A
  • similar yo poneumotonometry
  • 100/sec
  • doesn’t calculate the blood flow but gives the amplitude (diff between min aand max)
23
Q

OPA

A

Difference between systole and diastole

24
Q

OHT and OPA

A

Higher

-better blood flow, could be protective

25
Q

NTG and OPA

A

Lower

-decreased blood flow, enhanced damage even though normal pressure

26
Q

Positive predictive value and OPA

A

Less than 2mmHg increases chance of NTG

27
Q

Lower OPA increase chance of

A

Glaucoma

28
Q

Conclusion on OPA

A

Reduced in normal tension and POAG patients compared with healthy controls. OPA is influences by IOP but not by corneal thickness

29
Q

Cannon laser blood flowmeter

A

Uses two lasers

  • one measures blood velocity
  • second laser measures vessel diamter

Unit is a fundus camera
Large artery or vein is selected
Unit measured at a specific site

Blood flow is calculated

30
Q

Principles of cannon laser blood flowmeter

A
  • based on Doppler principles
  • blood vessels gives back some frequency because it is stationary-not Doppler shifted
  • moving blood is Doppler shifted
  • light from these two reflective sources-interference pattern is produced
  • this interference pattern moves
  • thus blood flow is calculated
31
Q

Heidelberg retinal flowmeter

A

-combines confocal scanning laser technology and Doppler principles

32
Q

Summary of measuring blood flow to eye

A
  • no gold clinical standard where ocular blood flow measurement is concerned
  • expensive
  • noise in measurement is high thus making it difficult to obtain data consistently
33
Q

How does angiovue work

A
  • uses motion contrast to detect blood flow
  • rapidly acquire multiple cross-sectional images from a single location on the retina
  • flow is the diffenve between two sequential scenes
  • flow=frame #1-frame #2
34
Q

Info you can get from angiography

A

Stureucre and function of optic nerve and retina

35
Q

Plus side of angiography

A
  • non invasive, dye free and fast
  • no injection, no NaFL
  • order test as needed to more closely monitor disease progression and treatment repsosne
  • image acquisition in less than 3 seconds
  • total time in room appx 10 minutes
36
Q

Motion correction technology

A

Minimizes saccadic motion to enhance image intensity

37
Q

Angiomontage

A

Provides a wider field of view

38
Q

Angiodisc

A

Gives you a calculation for amount of capillaries that have dropped out (i think that’s what he said)

How many caps are working in that region

Can see how changing treatment can change the caps

39
Q

SWEPT source

A

Calculates 100,000 scans per second and very cleat from top to bottoms

  • fast
  • multimodal imaging
  • signal to noise roll off characteristics in tissue
  • scanning light Is not visible to the patients to decrease eye movements during scan
  • uniform image quality over depth
  • vitreous can be seen much better
  • invisible OCT scanning light and high imaging speed of 100,000 A scans/sec reduce effect of eye movements and allows more data to be collected per scan

Summer Final: Glaucoma (15 decks)

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