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Glaucoma > Technology > Flashcards

Technology Flashcards

1
Q

What is OCT?

A

optical coherence tomography; uses low coherence laser light to evaluate reflection of laser light off different tissues (the science not the instrument)

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2
Q

What manufacturers make OCTs?

A

Spectralis (Heidelberg), Cirrus (Zeiss), RTVue (Optovue), 3-D OCT 1000 (Topcon), etc

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3
Q

What light wavelength does an OCT use?

A

843 nm (near infrared)

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4
Q

How does the OCT work?

A

interference signal from retina is compared to reference beam via spectrometry

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5
Q

What does a spectrometer do?

A

evaluates changes in wavelength between reference beam and reflected beam

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6
Q

What is the size of the Zeiss reference circle?

A

r=3.64 mm around the center of disk

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7
Q

What is Zeiss data compared to?

A

adult age matched norms 19 yo+, 256 scans

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8
Q

What does yellow mean?

A

1-5% percentile

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9
Q

What does red mean?

A

<1% of normals in this range

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10
Q

What does the triangle on the Zeiss machine allow you to do?

A

check how close the value is to the next probability level

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11
Q

What is the ICD-10?

A

the diagnosis, linked to the CPT

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12
Q

How do you code the OCT of ONH?

A

92133 (OCT of ONH) linked to H40.113_ (glaucoma ICD-10)

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13
Q

How does CPT reimbursement work?

A

paid for the technical and professional components (without interpretation it’s incomplete), CPTs are now bilateral procedures

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14
Q

What is the ganglion cell complex?

A

evaluation of ganglion cells, dendrites and axons about the macula

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15
Q

Is the GCC preferentially affected in glaucoma?

A

possibly, 15% of glaucoma pts have early central change

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16
Q

What is contained in the GCC?

A

inner plexiform, ganglion cell layer, retinal nerve fiber layer

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17
Q

Where is the GCC densest?

A

macula

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18
Q

When does ganglion cell loss occur and what does it cause?

A

early in glaucoma, results in isolated paracentral damage

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19
Q

What is the floor effect?

A

loss of RNFL down to the vessels and other tissues where the machine picks up the connective tissue and vessels

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20
Q

What is the problem with the floor effect?

A

it makes the OCT look stable over time even if the 10-2 field loss is progressing– insurance may not cover the test if floor effect is exhibited

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21
Q

T/F GCC loss is always glaucoma

A

false

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22
Q

What does the cirrus ganglion cell analysis measure?

A

ganglion cell and inner plexiform layers GCIPL

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23
Q

What does the optovue ganglion cell complex measure?

A

IPL, ganglion cells and RNFL

24
Q

What does the spectralis measure in terms of GCC?

A

measures each layer individually: IPL, GC, NFL

25
Q

Which machine does not have normative data?

A

spectralis

26
Q

What did Moreno find?

A

GCC and pRNFL in early GLC– 40% identified GCC only, 33% pRNFL only, 27% identified on both aka use both measurements

27
Q

What did Kim find?

A

early v moderate v severe– inferior GCC detected early and severe glaucoma best, mean GCC was more effective than mean RNFL, global loss volume accurate for GLC

28
Q

What did Rolle find?

A

pre-perimetric glaucoma, GCC and global loss volume comparable to pRNFL, high specificity, lower sensitivity, challenging with early stage

29
Q

What are the most effective GCC parameters of the cirrus?

A

minimum ganglion cell and inner plexiform layer, inferotemporal GCIPL, average GCIPL, comparable to pRNFL

30
Q

What are the most effective GCC parameters of the optovue?

A

global loss volume, thickiness in inferior quadrant

31
Q

Why is inferior/inferior-temporal macula so important?

A

anatomically fibers from the I/IT macula enter ONH at inferior aspect of ONH which is a higher risk area (superior macular is able to enter ONH temporally)

32
Q

What is the average disc area?

A

1.84 mm squared

33
Q

How does disc size impact OCT RNFL thickness measurement?

A

a larger optic nerve will have the RNFL measured closer to the edge and will measure thicker regardless of disease level aka mask glaucoma

34
Q

What happens when the reference ring of the OCT is further from the edge of the ONH like in a small nerve?

A

RNFL will measure thinner, may over diagnose glaucoma

35
Q

What is the panomap feature?

A

On Zeiss the RNFL and GCC maps are on the same printout

36
Q

What should you keep in mind about the panomap?

A

it is not comparing the exact same tissue, one is RNFL and one is ganglion cell + IPL

37
Q

How does Zeiss show progression?

A

guided progression analysis of pRNFL, 2 baseline tests with up to 6 total

38
Q

What does the guided progression analysis work?

A

(zeiss) gives the best-fit slope line of the average RNFL thickness, superior thickness, inferior thickness, and CD ration

39
Q

Which guided progression analysis aspect goes up instead of down with progression?

A

cup to disc ratio

40
Q

What did JH Na find?

A

poor correlation of OCT GPA to progression of expert analysis on ONH and HVF/HVF GPA– this is the point…. software should be better than clinicians

41
Q

What is Optovue data compared to?

A

330 normative database

42
Q

What does the optovue printout contain?

A

ring color codes on the ONH map (difference between normative data), GCC, TSNIT graph, focal loss volume and global loss volume, graph comparing OD to OS

43
Q

What is in the optovue RNFL interpretation?

A

RNFL thickness (warmer color is thicker), probability plots for norms, optic nerve assessment in middle

44
Q

What is the size of the optovue/rtvue reference circle?

A

4 mm

45
Q

What does NHM4 protocol mean?

A

the nerve head map reference circle is 4 mm (difference from Zeiss 3.64 mm)

46
Q

T/F you can compare data optic disk data across instruments

A

false, the reference circles are different sizes

47
Q

How high above the RPE is the RTVue reference line?

A

150 microns above RPE

48
Q

What is in the Optovue progression analysis?

A

RNFL trend analysis and 6 regions of ONH graphed out

49
Q

What are the most effective parameters of the Optovue GCC?

A

global loss volume, GCC thickness inferiorly

50
Q

What is the Spectralis GMPE?

A

glaucoma module premium edition– evaluates RNFL and macula

51
Q

What is the APS?

A

anatomic positioning system of the spectralis, compensates for head tilts

52
Q

How does the APS work?

A

maps macula then nerve then the axis between them and then takes the measurement

53
Q

What is the BMO-MRW?

A

spectralis’ bruchs membrane opening minimum rim width

54
Q

What is BMO?

A

bruch’s membrane opening is set as the anatomical border of the NRR

55
Q

How is BMO-MRW measured?

A

rim tissue is measured from the MBO to the closest appearance of ILM and NRR thickness is measured perpendicular to the path of the axons

56
Q

What is the spectralis progression analysis?

A

event: circumpapillary RNFL; trend: sector RNFL measures

Glaucoma (4 decks)

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