Block 16 > Contacts: Tomography > Flashcards

Contacts: Tomography Flashcards

(83 cards)

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1
Q

Keratometry evaluates the central ___mm

A

3

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2
Q

Topography evaluates ______mm of the corneal

A

6-9mm

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3
Q

Tomography which is proffered evaluates around ___mm of the cornea

A

12mm

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4
Q

What instrument can be used to evaluate the corneoscleral profile?

A

Profilometry

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5
Q

What early handheld instrument projected rings onto T the cornea?

A

Placido disc

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6
Q

What instrument involved using a photograph of a placido disc reflections?

A

Reynolds camera

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7
Q

What instrumentation captures placido disc data on a video and is the most commonly and affordable option for evaluating the corneal shape?

A

Topography

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8
Q

Small cone size instrumentation is more difficult to use in what patients?

A

Deep set eyes
Small orbits
Prominent brow

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9
Q

Larger cone size instrumentation is easier to acquire and manipulate but may be _______

A

Less accurate

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10
Q

5 true topographers

A

Medmont
Keratograph
Atlas
ReeSeeVit
Keratron

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11
Q

Which two topographers utilize small cones?

A

Medmont
Keratron

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12
Q

Cassini is very accurate in determining what?

A

Corneal astigmatism
Identifying KC

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13
Q

Tomography is an ________based assessment

A

Elevation

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14
Q

What surfaces does tomography look at?

A

Anterior and posterior

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15
Q

OCT had to be adapted for the cornea and needed longer wavelengths such as ______ for AS and _____ for PS

A

1310 for AS

830 for PS

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16
Q

OCT can scan the _______,______, ______, and ________

A

Cornea, iris, sclera, and limbus

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17
Q

Scheimpflug resolution in comparison to traditional OCT

A

Scheimpflug worse at 18u compared to 6u of OCT

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18
Q

Tomography looks at and evaluates what 4 things?

A

Anterior cornea
Posterior cornea
Thickeners
Elevation

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19
Q

What is the gold standard for monitoring keratoconus and corneal ectasia?

A

Tomography

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20
Q

3 methods of tomography capture

A
  1. Scanning slit with placido disc
  2. Scheimpflug with rotating slit
  3. True anterior OCT combine with placido disc
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21
Q

Axial or sagittal map is based on what shape?

A

Perfect shape

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22
Q

Axial or sagittal map is helpful for things like what?

A

Refractive surgery
OrthoK

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23
Q

Red/whites on axial and sagittal map mean what

A

Steeper and more curved

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24
Q

Blues/purples on axial and sagittal maps mean what?

A

Flatter or less curved

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25
Tangential map is a _____ map
True curve map
26
Tangential map is helpful for what?
-Look at progression of KC over time -change in treatment zone for orthoK
27
Refractive power map is helpful in what?
Helpful over multifocal lenses to see where Powers are in relation to the visual axis
28
Elevation or float map shows how ______ or _____ a best fitting sphere is to the cornea
How high or how low below
29
Hot colors on elevation map relate to what?
Taller/deeper sagittal depth
30
Cool colors on elevation or flat map relate to what?
Shallower/lower sagittal depth
31
What information is provided by these instruments?
SimKs Meriodional readings Thickness (tomography) Kmax HVID Sagittal and AC depth
32
What are additional software options that can be added to these instruments?
Aberrometry Myopia management packages Corneal scleral profilometry Glaucoma packages Cataract packages
33
Holladay report contains what 6 maps?
Axial Tangential Pachymetry (actual and refractive) Anterior elevation Posterior elevation
34
Berlin/ambrosio enhanced display provides what information?
Elevation maps Thickness profiles Apical thickness Pachy min Progression stats Q value
35
What does Q value tell us?
How prolate or oblate the cornea is
36
What does a positive Q value mean?
That the cornea is oblate
37
What does a negative Q value mean?
That the cornea is prolate
38
Aberrometry profile is helpful for what specifically?
Patient education
39
I-S (inferior-superior )indicie + valvues indicate a ___________ cornea and when they are > _____ they suggest _______
Steeper inferior, >1.2 suggests KC
40
What is the SRI (Surface regulatory index) of a normal cornea?
1.0
41
What measurement looks at elevation of height compared to a normal cornea?
CIM (corneal irregularity measurement)
42
The higher the ICM the more_______
Irregular
43
Normal CIM values
0.03-0.68
44
Borderline CIM values
0.69-1.0 irregular CIM value 1.1 and up
45
What does q value asses?
Shape and how oblate/prolate the cornea is
46
What does a Q value if 0 mean?
The cornea is spherical
47
What is the ideal Q value?
-0.26, prolate
48
In what cases may a positive Q value exist?
Post-surgical, orthoK, pellucid
49
E-value asses what?
The eccentricity
50
Normal E-values
0.4-0.57
51
What does a higher E value mean?
Highly prolate
52
KC E-values are_____
Very high
53
Low E value may indicate what?
A slow rate of corneal flattening
54
RBF/RBFE/BFE are the sphere or ellipse curves, what do they provide?
The best overall fit to the corneal shape
55
RBF/RBFE/BFE are helpful in selection of what when fitting a GP?
Selection of the base curve
56
Higher shape factor values are indicative of what?
Asphericity, and therefore a more irregular cornea
57
Belin grading scale for KC
A. Anterior curvature B. Posterior curvature C. Pachymetry D. Distance vision
58
Mild CLEK KC grading steepK
Mild < 45D
59
Moderate CLEK KC grading SteepK
45-52D moderate
60
Severe CLEK KC grading of SteepK
> 52 D
61
Profilometry evaluates the shape of what?
The shape of the sclera
62
What do T and N equal when evaluating scleral shape? T=____ N=____
T = steep N = flat
63
When is profilometry clinically significant?
When lens diameter is > 15 mm and if the scleral toricity exceeds 1D between quadrants
64
Fluorescence based strutted light topographer
sMAP3D
65
How can corneal sag height be evaluated?
Direct observation OCT Topographic maps Eaglet eye
66
SMAP allows us to visualize what properties of the sclera?
Asymmetry and toricity of the sclera
67
What solution is based to used for fluorescein based scans such as eaglet and sMAP?
HA based PF tear saturated with fluorescein and thinned as needed with sterile PF saline
68
Where should drops be instilled when taking images on fluorescein based scans?
Upgaze and down gaze to ensure the fluorescein is across the entire ocular surface
69
SMAP takes 3 images, what are they?
Primary Up Down
70
Is fluorescein required in Pentacam CSP?
No
71
Pentacam CSP takes how many images?
5 images in 5 fields of gaze
72
How many images does the Pentacam CSP Pro take?
One single image (requires lid retraction to at least 15mm)
73
What imaging technique gives you curvature data?
Topography
74
The central ____ is imaged with topography, anything beyond that is _______
6-9mm, calculated
75
Tomography gives you what two data points?
Elevation and thickness
76
Up to about ___mm is images with tomography
12mm
77
What is considered the best way to evaluate the cornea for earliest disease/ectasia detection?
Tomography
78
SIF number mist be well over ____ to be considered KC
1
79
If you take an image and the map looks irregular and incorrect, what can be a quick fix to get a better image?
Add a thin AT for patient and retake the image
80
If the cornea appears flat centrally and steeper in the periphery, what might this indicate?
Post-surgical cornea
81
Pellucid presentation of maps
Kissing doves or crab claw
82
How will WTR astig present in the curvature maps?
Hour glass
83
How will ATR astigmatism present in the curvature maps?
Bow-tie
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