Technology

Question 1

What is OCT?

Answer 1

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

Question 2

What manufacturers make OCTs?

Answer 2

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

Question 3

What light wavelength does an OCT use?

Answer 3

843 nm (near infrared)

Question 4

How does the OCT work?

Answer 4

interference signal from retina is compared to reference beam via spectrometry

Question 5

What does a spectrometer do?

Answer 5

evaluates changes in wavelength between reference beam and reflected beam

Question 6

What is the size of the Zeiss reference circle?

Answer 6

r=3.64 mm around the center of disk

Question 7

What is Zeiss data compared to?

Answer 7

adult age matched norms 19 yo+, 256 scans

Question 8

What does yellow mean?

Answer 8

1-5% percentile

Question 9

What does red mean?

Answer 9

<1% of normals in this range

Question 10

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

Answer 10

check how close the value is to the next probability level

Question 11

What is the ICD-10?

Answer 11

the diagnosis, linked to the CPT

Question 12

How do you code the OCT of ONH?

Answer 12

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

Question 13

How does CPT reimbursement work?

Answer 13

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

Question 14

What is the ganglion cell complex?

Answer 14

evaluation of ganglion cells, dendrites and axons about the macula

Question 15

Is the GCC preferentially affected in glaucoma?

Answer 15

possibly, 15% of glaucoma pts have early central change

Question 16

What is contained in the GCC?

Answer 16

inner plexiform, ganglion cell layer, retinal nerve fiber layer

Question 17

Where is the GCC densest?

Answer 17

macula

Question 18

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

Answer 18

early in glaucoma, results in isolated paracentral damage

Question 19

What is the floor effect?

Answer 19

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

Question 20

What is the problem with the floor effect?

Answer 20

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

Question 21

T/F GCC loss is always glaucoma

Answer 21

false

Question 22

What does the cirrus ganglion cell analysis measure?

Answer 22

ganglion cell and inner plexiform layers GCIPL

Question 23

What does the optovue ganglion cell complex measure?

Answer 23

IPL, ganglion cells and RNFL

Question 24

What does the spectralis measure in terms of GCC?

Answer 24

measures each layer individually: IPL, GC, NFL

Question 25

Which machine does not have normative data?

Answer 25

spectralis

Question 26

What did Moreno find?

Answer 26

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

Question 27

What did Kim find?

Answer 27

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

Question 28

What did Rolle find?

Answer 28

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

Question 29

What are the most effective GCC parameters of the cirrus?

Answer 29

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

Question 30

What are the most effective GCC parameters of the optovue?

Answer 30

global loss volume, thickiness in inferior quadrant

Question 31

Why is inferior/inferior-temporal macula so important?

Answer 31

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)

Question 32

What is the average disc area?

Answer 32

1.84 mm squared

Question 33

How does disc size impact OCT RNFL thickness measurement?

Answer 33

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

Question 34

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

Answer 34

RNFL will measure thinner, may over diagnose glaucoma

Question 35

What is the panomap feature?

Answer 35

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

Question 36

What should you keep in mind about the panomap?

Answer 36

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

Question 37

How does Zeiss show progression?

Answer 37

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

Question 38

What does the guided progression analysis work?

Answer 38

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

Question 39

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

Answer 39

cup to disc ratio

Question 40

What did JH Na find?

Answer 40

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

Question 41

What is Optovue data compared to?

Answer 41

330 normative database

Question 42

What does the optovue printout contain?

Answer 42

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

Question 43

What is in the optovue RNFL interpretation?

Answer 43

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

Question 44

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

Answer 44

4 mm

Question 45

What does NHM4 protocol mean?

Answer 45

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

Question 46

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

Answer 46

false, the reference circles are different sizes

Question 47

How high above the RPE is the RTVue reference line?

Answer 47

150 microns above RPE

Question 48

What is in the Optovue progression analysis?

Answer 48

RNFL trend analysis and 6 regions of ONH graphed out

Question 49

What are the most effective parameters of the Optovue GCC?

Answer 49

global loss volume, GCC thickness inferiorly

Question 50

What is the Spectralis GMPE?

Answer 50

glaucoma module premium edition-- evaluates RNFL and macula

Question 51

What is the APS?

Answer 51

anatomic positioning system of the spectralis, compensates for head tilts

Question 52

How does the APS work?

Answer 52

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

Question 53

What is the BMO-MRW?

Answer 53

spectralis' bruchs membrane opening minimum rim width

Question 54

What is BMO?

Answer 54

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

Question 55

How is BMO-MRW measured?

Answer 55

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

Question 56

What is the spectralis progression analysis?

Answer 56

event: circumpapillary RNFL; trend: sector RNFL measures