Ophthalmic Imaging 7% Flashcards
What does the corneal topography do?
Makes a colored map of the corneal curvature. Provides a greater detail of the surface of the cornea, including peaks and valleys. Uses color code to indicate the areas of steepness and flatness
Test that uses placido disk that is projected onto the cornea and the computer software creates a series of data points to create a map with colors which represents varied elevations.
Corneal topography
Corneal topography measures 1000’s of points from ___to ___of the K
limbus to limbus
What is the corneal topography information used for?
CL fitting, Diagnosing and managing corneal pathology like KCN, and post corneal refractive sx evaluations
The warm colors(red, orange, yellow) on corneal topography shows the ___areas of the K
steeper
The cool colors(green and blue) on corneal topography represents the ___areas of the K
flatter
On corneal topography ____=steeper K
____=flatter K
Warm colors(red, orange, and yellow)
Cool colors (green, blue)
Corneal topography is ____detailed than the standard keratometer
more
Peaks and valleys of the K are areas that are impacted by ___
CL
The computer on the corneal topography interprets the ____of the placido discs on the K to create a map
reflection
The scale on the corneal topography is adjustable so that if a pt has a very steep or a very flat cornea you can adjust the scale and it will still show…..
the relative areas of flatness or steepness
________makes cross sectional images of different structures in the eye to the sub mircometer
OCT (Optical Coherence Tomography)
What does the term tomography mean?
cross sectional imaging
OCT uses an ____technique similar to contact and emersion Ascan but it uses _____technology not sound.
echo
laser light
What cause a weak signal in the OCT?
dry eye or K scars
What does the OCT image?
AC, Retina, ON
The OCT is much better tolerated and much lower risk than an _____
angiogram
______can prevent you from getting a quality scan with OCT
very dense media
(dense CAT or K opacification)
OCT measures a standard deviation which will tell you the _____
quality of the scan
OCT uses a technology called ____ which is the ability to reproduce precise skin placement in subsequent scan so that they can be realigned to directly compare with the baseline exam.
Registration
Registration technology will lock on to certain _____in the base line exam then in the f/u exams it will look for those same ones and lock onto them. It will pivot subsequent scans to that they align precisely with the baseline exam so that they can do a direct comparison to them.
anatomical features
Nerve fiber analyzers such as HRT and GDX are ____lasers
scanning
Nerve fiber analyzers make multiple sequential scans to create at ____image of different ocular structures and it also uses registration technology to align them with the baseline for comparative purposes.
3D
HRT and GDX starts above the _____, captures ______images at increasing depths
retinal surfaces
parallel
To obtain and accurate scan with HRT and GDX you must….
-correct refractive error including cyl of >1D
-have a good tear film
-may need to dilate pt
HRT and GDX(nerver fiber analyzers) use traffic light signal for quality; ____=good and ____=bad scan
Green
Red
HRT and GDX images…..
ON and macula
HRT and GDX software compares the pts data to …..
population at large
progress analysis
Fluorescein angiography documents……
Retinal circulation
Fluorescein angiography exploits the fact that ….
light has a range of wavelengths
Fluorescein angiography uses ___to filter out certain wavelengths of light that will appear on the film.
different interference filters
The visible spectrum of the human eye is between____
400-700nm
What type of dye is used in the fluorescein angiography?
fluorescein sodum dye injected into the pts arm or hand
____is a property of certain transparent substances.
Fluorescein
When a substance is exposed to light of a shorter wavelength ____is absorbed by it and its molecules become excited which raises electrons to a higher energy level.
energy
As molecules return to their original state the substance emits light of a ____wavelength
longer
Fluorescein Sodium is a ___soluble dye
water
Light absorption peak is _______.
______ filter in FA’s uses wavelength within this range.
465-490nm
Blue exciter
Light emission peak is at a wavelength between _______
520-530nm
What are the different interference filters used in FA’s?
Exciter (Blue) and Barrier (yellow-green)
In FA’s the ________ filter excites the fluorescein molecules to a higher state of activity.
Exciter(Blue)
Exciter (blue) filter emits a ______light of a higher wavelength.
greenish yellow
The______filter is positioned in the light path between the eye and the film or digital image which filters out the ___light and only allows the fluorescence to be recorded on the film
Barrier (yellow-green)
(Also known as “red free”)
Blue light
With infra red phase of FA’s there is such a thing as _____illumination
too much
In FA’s turn up the illumination until ……..
you just see the fundus (even illumination)
_____images are taken as a control prior to injecting the fluorescein dye. This records the pts natural ______
Red free
auto fluorescence
FA performs ___images per minute
60
In order to get quality images in FA you must have
Even illumination (may need to increase when pupil small)
Minimal artifacts
Center of the macula, unless other wise indicated.
Always better to take more images than less.
Take one image per second for the first 1 minute (60 images per minute)
Make sure pt is relaxed and cooperation is key
How do you adjust intensity in FA
by adjusting the sensitivity knob
Describe the path of Fluorescing dye.
It enters through central retinal arteries, then enters the arteries, then the capillaries, then the veins then finally through the central retinal vein.
In FA explain mnemonic CACVC
path of fluorescein:
Centeral retinal arteries
Arteries
Capillaries
Veins
Central retinal veins
The _______phase of FA occurs 8-10 seconds after injection.
Choroidal (pre-arterial)
In the____ phase of FA the choroid is illuminated with fluorescein but non of the fluorescein has filled any of the retinal vessels yet.
choroidal (pre-arterial)
___phase in FA occurs about 10-12 sec after injection (about 1 sec after choroidal phase)
Arterial phase
In the ___phase of FA the dye has entered the central retinal artery and fans out to the superior and inferior arcades. However, the veins have not received any dye yet.
arterial phase
The ____phase of FA occurs about 3 seconds after the choroidal flush
Capillary
Choroidal flush or background fluorescence is int the _____phase
choroidal phase
In the ____phase of FA the fine capillaries around the fovea fill and in the periphery
Capillary
The _____phase of the FA occurs 5 seconds after choroidal filling(flush), evidenced by ____
Eary venous phase
Laminar flow
What is laminar flow in early venous phase of FA?
White stripping of outer walls of veins
Why are the veins striped in laminar flow?
Because the fluorescein dye enters the vein and fills on the periphery first and then gradually fills towards the center of the vein.
___phase in FA is 10 seconds after choroidal filling (flush)
Full Venous Phase
_____phase of FA is where the laminar filling is complete and the dye is filled to the center of the veins.
Full venous phase
Once all the phases of FA is reached you have ____
Complete fill of the arteries and veins
The ____phase of FA occurs 3-5 minutes after injection
Recirculation phase
In ___phase of FA the veins and arteries remain roughly equal in brightness and the intensity of fluorescence diminish slowly during this phase.
Recirculation phase
Early leakage and staining can occur during the ___phase of FA
Recirculation phase
In FA, Photos are typically captured ____minutes after injection
7-15 minutes
Late phase (Elimination Phase) occurs _____minutes after injection
30-60
In FA, _____spaces fill slowly, about 20-30 minutes after the dye has pooled
cystic
____phase demonstrates the gradual elimination dye from retinal and choroidal vasculature
Late phase
FA: Late staining of the optic disc is a ___finding
normal
In FA , in the ____phase and in the normal eye, the dye has mixed with blood to a point where it is almost invisible with the camer
Late phase
____uses a radiating wave of ultrasound to help detect tumors and to image different intraocular and periocular structures.
B Scan
B Scan is a ___dimensional scan
2
An a wave in an A scan travel a ____line, a beam of light (a linear wave)
single straight
A B scan extends below and above the _____and sweeps the contents of the entire globe
horizontal
The “B” in B scan stands for …
brightness
The scan that uses ultrasound..
(A scan or B scan)
B scan
In Bscan the sound waves _____ different tissue of varied densities at varied speeds and are ____by other tissue.
pass through
reflected
The speed that a sound wave travels at through tissue during a B scan depends on …..
the density of the tissue
In B scan the sound waves are converted into images by the ______
Transducer
Why is it useful for the transducer in the Bscan to convert soundwaves to images especially if pt had dense media opacities?
Because sound travels through dense media just fine and light technology does not.
Most setting on B scan are _____
left constant
What can you adjust on
B scan to enhance the view of anatomical structures, tumors, and foreign bodies?
Sound intensity adjustment
What does the marker at then end of the Bscan probe indicate?
top of oscilloscope display
(what’s at the top of your display)
If marker on Bscan probe is pointed up this means….
the top part of the pts eye is at the top of our display
If marker on the Bscan probe is aimed nasally then…
the nasal aspect of they eye is at the top of the display
For vertical scans on B scan you orient the probe ____
for horizontal scans ____
superiorly
nasally
When placing the Bscan probe on the eyelid or eye itself you want to place it _____to the structures that you want to image so that the sound waves travel back to the transducer rather than bouncing off of them in another direction, allows you to get a higher quality image.
perpendicular
Explaing how to perform a Bscan.
First locate the ON (acts as a landmark), typically you’ll place the probe medially, temporally, superiorly, and inferior to limbus.
If you find pathology when performing Bscan, place the probe…..
place the probe opposite to clock hour to where the pathology is.
B scan: You are always imaging the _____clock hour to the eye to where your probe is oriented.
opposite
_____is used to image endothelial cells.
Specular Biomicroscopy
_____photographs K endothelial cells and can be contact or non contact
Specular Biomicroscopy
Endo cells do not _____
regenerate
What caused endothelial cells to diminish?
age, cataract distraction (intraocular sx)
When performing contact endothelial cell count….
-Do not press on K
-Patient must be stabilized with forehead rest
-Topical anesthetic uses
-Take a photo of the endo cells and then place a graph over top rotate grid and count the number of cells in that grid, you then use a formula used to figure endo cell count
-Appropriately clean and disinfect probe
