CDOS Exam Questions with Verified Solutions
PVD - Answers Posterior vitreous detachment
4 positions to evaluate the macula - Answers 1. Horizontal axial
2. Vertical transverse
3. Longitudinal
4. Vertical macula
Vertical Macula Scan - Answers obtained by displaying a vertical axial scan and then directing
the sound beam slightly temporally
Reverse macular scan - Answers performing a longitudinal exam of the nasal meridian with the
patient's gaze forward or slightly nasal with the probe placed so that it is slightly overlapping the
limbus; macular region is located in the lower aspect of the echogram
ultrasound - Answers an acoustic wave that consists of an oscillation of particles within a
medium
angle of sound incidence - Answers the angle at which the sound beam strikes an interface
smooth flat interface - Answers will return almost all of an echo back to its source creating a
specular or mirror-like reflex (retinal surface)
smooth convex interface - Answers some of the echo will be reflected away from its origin
resulting in a weaker echo (dome shaped lesion)
irregular/coarse interface - Answers part of the echo will be scattered resulting in a weaker echo
even if the transducer is perpendicular
reflectivity evaluation - Answers observed spike height of A scan and the brightness of the B
scan
reflectivity categorization - Answers determined by estimating the heights of the spike on A
scan as a percentage in relation to the vitreous baseline and the top of the initial spike
extremely low reflectivity - Answers 0-5%
low reflectivity - Answers 5-40%
medium reflectivity - Answers 40-60%
medium high reflectivity - Answers 60-80%
high reflectivity - Answers 80-100%
, internal structure - Answers refers to degree of variation of histologic architecture in a masslike
lesion and is evaluated by noting differences in the height and length of the A scan spikes and
the differences in echodensity on B scan
regular internal structure - Answers little or no variation in the height and length of spikes on A
scan; uniform appearance on B scan
irregular internal structure - Answers marked differences in echo appearance
sound attenuation - Answers occurs when sound energy is scattered, reflected, or absorbed by
the medium indicated on B scan as a decrease in the brightness of echoes or a reduction in
spike height on A scan
posterior shadowing - Answers absence of echoes posterior to the structure due to sound
attenuation
Quantitative echography type II - Answers method for differentiating a retinal detachment from
a vitreous membrane:
1.Horizontal line is placed in the middle of the screen
2.Probe is placed perpendicular to the membrane
3.Probe is placed perpendicular to the sclera
4.The decibel level is decreased until the spike from these surfaces touches but does not
surpass the horizontal line
5.Difference in decibel setting required to display the membrane and the sclera at the specific
spike level may help differentiate retina from vitreous membranes
*6-15db = retina
*>20db = vitreous membrane
aftermovement - Answers the motion of the lesion echoes before, during, and immediately after
an eye movement
horizontal spike movement - Answers represents lateral motion and can be observed on B scan
vertical spike movement - Answers caused by minimal change in position of the lesion relative
to the sound beam and is usually not appreciable on B scan
vascularity - Answers fast spontaneous motion of echoes representing bloodflow within blood
vessels displayed as low amplitude continuous flickering of the internal lesion spikes on A scan
vascularity assessment - Answers eye is fixated steadily with probe stationary on the eye
PVD - Answers Posterior vitreous detachment
4 positions to evaluate the macula - Answers 1. Horizontal axial
2. Vertical transverse
3. Longitudinal
4. Vertical macula
Vertical Macula Scan - Answers obtained by displaying a vertical axial scan and then directing
the sound beam slightly temporally
Reverse macular scan - Answers performing a longitudinal exam of the nasal meridian with the
patient's gaze forward or slightly nasal with the probe placed so that it is slightly overlapping the
limbus; macular region is located in the lower aspect of the echogram
ultrasound - Answers an acoustic wave that consists of an oscillation of particles within a
medium
angle of sound incidence - Answers the angle at which the sound beam strikes an interface
smooth flat interface - Answers will return almost all of an echo back to its source creating a
specular or mirror-like reflex (retinal surface)
smooth convex interface - Answers some of the echo will be reflected away from its origin
resulting in a weaker echo (dome shaped lesion)
irregular/coarse interface - Answers part of the echo will be scattered resulting in a weaker echo
even if the transducer is perpendicular
reflectivity evaluation - Answers observed spike height of A scan and the brightness of the B
scan
reflectivity categorization - Answers determined by estimating the heights of the spike on A
scan as a percentage in relation to the vitreous baseline and the top of the initial spike
extremely low reflectivity - Answers 0-5%
low reflectivity - Answers 5-40%
medium reflectivity - Answers 40-60%
medium high reflectivity - Answers 60-80%
high reflectivity - Answers 80-100%
, internal structure - Answers refers to degree of variation of histologic architecture in a masslike
lesion and is evaluated by noting differences in the height and length of the A scan spikes and
the differences in echodensity on B scan
regular internal structure - Answers little or no variation in the height and length of spikes on A
scan; uniform appearance on B scan
irregular internal structure - Answers marked differences in echo appearance
sound attenuation - Answers occurs when sound energy is scattered, reflected, or absorbed by
the medium indicated on B scan as a decrease in the brightness of echoes or a reduction in
spike height on A scan
posterior shadowing - Answers absence of echoes posterior to the structure due to sound
attenuation
Quantitative echography type II - Answers method for differentiating a retinal detachment from
a vitreous membrane:
1.Horizontal line is placed in the middle of the screen
2.Probe is placed perpendicular to the membrane
3.Probe is placed perpendicular to the sclera
4.The decibel level is decreased until the spike from these surfaces touches but does not
surpass the horizontal line
5.Difference in decibel setting required to display the membrane and the sclera at the specific
spike level may help differentiate retina from vitreous membranes
*6-15db = retina
*>20db = vitreous membrane
aftermovement - Answers the motion of the lesion echoes before, during, and immediately after
an eye movement
horizontal spike movement - Answers represents lateral motion and can be observed on B scan
vertical spike movement - Answers caused by minimal change in position of the lesion relative
to the sound beam and is usually not appreciable on B scan
vascularity - Answers fast spontaneous motion of echoes representing bloodflow within blood
vessels displayed as low amplitude continuous flickering of the internal lesion spikes on A scan
vascularity assessment - Answers eye is fixated steadily with probe stationary on the eye
