Ophthalmic Imaging CH13 Flashcards
Match the types of slit-lamp illumination to its definition:
Term:
diffuse
direct
indirect
retroillumination
tangential
Definition:
a) highlighting an area of interest by illuminating the structure behind it
b) illumination source is shined at an oblique angle across the surface of a structure
c) a softer lighting that evenly illuminates the entire subject without highlighting any particular part
d) illumination source is shined on another structure than the one of interest
e) the illumination source is shined directly on the area of interest
C) diffuse
E) diffuse
D) indirect
A) retroillumination
B) tangential
All of the following would be well documented using slit-lamp photography except:
a) pterygium
b) hypertropia
c) corneal scar
d) iris lesion
b) Answers a, c, and d are all entities of the anterior segment that would be ideal to document via slit-lamp photography. If one wished to document hypertropia, an external photograph showing both eyes in relation to each other would be needed.
When performing slit-lamp photography, a photograph of the eye using low magnification and diffuse lighting is recommended to:
a) judge the patient’s tolerance to the flash
b) judge the corneal reflection
c) provide identification
d) provide orientation
d) Before photographing pathology, take a photo of the entire eye using diffused lighting. (The diffuser is a foggy-looking filter that flips up over the slit-lamp’s illumination source.) This helps orient the viewer when photos are examined later, as well as provides documentation of the eye’s general appearance. Keep in mind, it is very difficult to identify a patient from a shot of a single eye!
By convention as well as for ease of use, the illuminator in slit-lamp photography is
usually positioned:
a) nasally
b) temporally
c) temporally for OD and nasally for OS
d) nasally for OD and temporally for OS
b) Illumination for slit-lamp photos is usually directed from the temporal side. This convention helps orient the viewer, for one thing. For another, it avoids the physical limitations of the patient’s nose when positioning the illuminator.
You are taking a slit-lamp photo of an iris lesion that may be melanoma. The illumination technique of choice is:
a) diffuse
b) direct
c) indirect
d) retroillumination
b) Direct illumination is used for opaque entities. (A subject that is more see-through would be better photographed using indirect illumination.)
You are taking a slit-lamp photo of a cortical cataract. The illumination technique of
choice is:
a) diffuse
b) direct
c) indirect
d) retroillumination
d) Using retroillumination, the light reflection from the retina (giving a bright orange/red
background) will show any lens opacities in silhouette.
The technique for taking photographs of the angle structures of the anterior eye is:
a) goniography
b) trabeculography
c) iridography
d) pupillography
a) A goniolens is used to view the angle structures of the eye at the slit lamp; it is placed directly on the anesthetized cornea. Photographs can then be taken of the angle structures.
The method used to take photographs of the endothelial layer of the cornea is:
a) specular photomicrography
b) fluorescein angiography
c) corneal topography
d) retroluminar reflectography
a) Specular photomicrography is a special technique used to capture images of the cornea’s single-layer endothelium. The endothelium does not regenerate and is key in maintaining the cornea’s clarity. The cells can get bumped and damaged during any kind of intraocular surgery, so evaluating the endothelium’s health prior to surgery can be very important (especially if the patient has some type of corneal degeneration/dystrophy). The cells in the
photo are examined for health as well as number (thus the term cell count).
Before taking the fundus photograph, it is important to do all of the following except:
a) check the patient’s record to confirm the requested photographs
b) enter patient information into a log manual or camera imprint system
c) study any previous fundus photos that the patient has had
d) make sure that the patient has had a visual field test
d) A visual field test is not a prerequisite for having fundus photos.
The most important thing to do before using any fundus camera each day should be:
a) confirm the diopter compensator is at the “+” setting
b) ensure all patients are dilated with homatropine
c) check to see that the eye piece is correctly set
d) clean the camera lens whether or not it is dirty
c) Check the eye piece! (That is the first rule when using any piece of focusable eye equip-
ment.) If the lens is not dirty, do not touch it. Homatropine is not necessary for dilation;
usually, weaker drops are used. The dioptric compensator should be set on a patient-by-
patient basis.
Setting the fundus camera eye piece should be done:
a) with one eye shut, in dim light or darkness
b) with both eyes open, in dim light or darkness
c) with both eyes open in a normally lit room
d) with one eye shut in a normally lit room
b) The eye piece should be set in dim light (or in the dark) with both eyes open. On the
fundus camera, this means that one eye is looking through the eye piece and the other eye is not. This is difficult to do, perhaps, but is the best method.
When setting the ocular of the fundus camera system, one must:
a) remove one’s own correction
b) turn the ocular to the maximum plus position, then rotate down
c) turn the ocular to the maximum plus position, then rotate up
d) turn the ocular to the maximum minus position, then rotate up
b) The fundus camera ocular is set like any other eye piece. Turn it all the way to maximum plus. Looking through the eye piece, turn slowly toward the minus. Stop when the image is clear. Do not pass the clear spot in search of more clarity. It is not necessary to remove your correction. But, if you wear your glasses sometimes, and other times do not, you will have to reset the ocular.
If you continue to turn the fundus camera ocular past the first point of clarity:
a) the reticle will become sharper yet
b) you can compensate for the patient’s refractive error
c) you may induce your own accommodation
d) the resulting photograph will be sharper
c) Going past the first point of image clarity adds minus to the ocular, which forces your
eye to add plus (accommodate) to compensate. The resulting photographs will not be clear. You are not compensating for the patient’s refractive error, but your own. During photography, if the image seems to go in and out of focus, yet the camera and patient are stationary, this probably is due to the accommodation of the photographer. Have the patient sit back, and check the focus of your ocular(s) again.
Proper pupil dilation to facilitate fundus photography requires:
a) any dilation is acceptable
b) dilation is not necessary
c) a minimum pupil size of 4 to 5 mm
d) a minimum pupil size of 8 mm
c) Four to 5-mm dilation would be the minimum size for fundus photos (8 mm would be best, of course, but it is not the minimum). (Note: There are now “nonmydriatic” fundus cameras available that require 3.3 mm as the minimum size.)
Inadequate dilation results in photographs with:
a) half of the frame unexposed
b) a general blur
c) a gray, fuzzy quadrant
d) a grainy appearance
b) In addition to causing pupil cuts (not listed), inadequate dilation can cause a general blur
on the photographs.
In fundus photography, high corneal astigmatism can be compensated for by:
a) use of the correction device in the fundus camera
b) placing the dioptric correction dial on “+” for plus cylinder
c) placing the dioptric correction dial on “–” for minus cylinder
d) having the patient wear a toric contact lens during photography
a) Some fundus cameras have an astigmatic correction device that is used much like the
dioptric compensation setting. The dioptric compensation device is for spherical refractive errors, not cylindrical.
In order to image eyes with high refractive errors, it is best to:
a) place a contact lens on the patient’s eye to compensate
b) reset the eye piece reticle to compensate
c) set the diopter compensation device built into the camera
d) remember that eyes with high refractive errors cannot be photographed
c) If the patient is highly hyperopic or myopic beyond the normal focusing ability of the
camera, the diopter compensation device is used.
To take a photo of the external eye with the fundus camera (eg, to document corneal
edema that interferes with a clear view of the fundus):
a) change the diopter setting to “–”
b) change the diopter setting to “+”
c) have the patient sit back from the camera
d) a slit-lamp camera must be used
b) If you set the dioptric compensation device to “+,” it is possible to take a photo of the
external eye using the fundus camera.
Gross focusing with the fundus camera is generally accomplished by:
a) turning the eye piece until the subject is clear
b) moving the joystick
c) having the patient lean forward or back
d) changing the magnification setting
b) Gross focusing can be accomplished by moving the joystick. On some fundus cameras, fine focusing is accomplished by turning a focusing knob on the camera. The subject is never focused by turning the oculars or by asking the patient to move. Changing the magnification setting will make the image larger, but not more focused.
Focusing the fundus camera can be simplified by:
a) starting with the camera all the way back, then moving it forward
b) starting with the camera all the way forward, then moving it back
c) focusing the donut on the patient’s closed lid before composing the photograph
d) positioning the fixation light directly in front of the camera lens
c) Have the patient close both eyes while you align and focus the “donut” on the closed lid.
This will put you very close to being in focus when the patient opens his or her eye. It is
also more comfortable for the patient and allows you to avoid fumbling around with the
camera, looking for the eye. If the fixation light is in front of the camera, it will get in the
way of the photograph.
To allow scanning of the patient’s retina without moving the base of the camera
mount:
a) move the fixation light and ask the patient to follow it
b) use the joystick
c) adjust the chin cup
d) swing the camera on its pivot
d) To scan the patient’s retina, swing the camera on its pivot. If you move the joystick, you are moving the camera base. If the patient follows the fixation light or moves his or her chin, you are going to lose your field of view.
When correctly positioned, the orange-yellow background of the fundus should be:
a) at an even color saturation across the viewing field
b) darker in the periphery of the viewing field
c) lighter in the periphery of the viewing field
d) unevenly saturated across the viewing field
a) The orange-yellow background color of the fundus should be even across the viewing
field.
Once the fundal image is correctly positioned and focused:
a) fire the camera
b) ask the patient to blink, then fire the camera
c) have the patient sit back and rest a moment
d) take repeated photographs quickly, warning the patient not to blink
b) Ask the patient to blink just before you fire the camera. This clears the tear film and
increases the chances of the lids being open widely when you snap the picture.
You are attempting to take fundus photographs and see a blue-gray halo around the subject. To correct this, you should:
a) move the camera closer
b) move the camera further back
c) reduce illumination
d) increase illumination
a) A blue-gray halo around the subject indicates that you are too far back. Move the camera closer. If you are too close, you will see a whitish haze in the center of the subject.
You are attempting to take fundus photographs and notice a whitish haze in the center of the subject. This may mean that:
a) the patient is highly myopic
b) the patient is highly hyperopic
c) the patient has his or her eye closed
d) the camera has drifted to one side
d) See answer 24. The whitish central haze means you are too close.
ANSWER 24: A blue-gray halo around the subject indicates that you are too far back. Move the camera closer. If you are too close, you will see a whitish haze in the center of the subject.
You are centering on the macula when a light yellow crescent appears in the upper left
of the viewing field. This is caused by:
a) the illumination being set too high
b) a reflection off of a cataract
c) the pathology in the fundus
d) a reflection off of the edge of the pupil
d) The little yellow crescent is caused by a “pupil cut.”
In the scenario above, you should:
a) reduce illumination
b) move the camera slightly down and to the right
c) move the camera slightly up and to the left
d) use the dioptric compensation device
b) To compensate for a pupil cut, move the camera directly opposite from the crescent.
Periodic photographs to monitor the progress of a disease might be needed in all of the following except:
a) hypertensive retinopathy
b) aphakia
c) diabetic retinopathy
d) glaucoma
b) Fundus photography is used in all of the listed situations except aphakia. Aphakia is a
condition, not a disease, and does not require photographic monitoring.
The primary area of interest in the fundus photo of a glaucoma patient is:
a) the optic disc
b) the macula
c) the retinal vessels
d) the choroid
a) The optic disc is the primary object of interest in monitoring glaucoma patients.
Label the parts of an A-scan echo (Figure 13): peak, width, baseline, descending limb or falling edge, ascending limb or leading edge
C) peak
E) width
B) ascending limb or leading edge
A) baseline
D) descending limb or falling edge
Label the following structures on the A-scan pictured below (Figure 13-2):
posterior lens, orbital fat, cornea, retina anterior lens, sclera
D) posterior lens
G) orbital fat
B) cornea a),
E) retina
C) anterior lens
F) sclera
