ROUB CORE EXAM MANUAL UPDATED QUESTIONS AND
ANSWERS GRADED A+
✔✔What is the term for the "markers" or "cursors" displayed on the screen of a biometry
instrument that provide electronic measurements of distance between two or more
acoustic interfaces? - ✔✔Gates
✔✔What is the term for the capacity of an ultrasound instrument to display two or more
interfaces that are very anatomically close to one another as separate echoes? -
✔✔Resolution
✔✔How does increasing the gain setting on the biometer affect the display echo? -
✔✔It increases the amount of amplification of the echo
✔✔What is the range of ophthalmic biometry frequencies? - ✔✔8-12 MHz
✔✔How is the resolution affected when the gain is set at maximum? - ✔✔The resolution
is less
✔✔A non-focused sound beam is always utilized by which type of scan? -
✔✔Diagnostic A-scan
✔✔What scan is used to obtain a two-dimensional image of the globe? - ✔✔Diagnostic
B-scan
✔✔What is the term for a one-dimensional amplitude scan? - ✔✔A-scan
✔✔The strength of an echo is dependent on what three factors? - ✔✔Gain, difference in
density, and proper alignment
✔✔What type of scan uses Prager or scleral shells? - ✔✔Immersion A-scan
✔✔How often should the filter of a biometry instrument be vacuumed? - ✔✔Once a
month
✔✔Measurement of axial length of the eye, thickness of an extraocular muscle, and
tumor height are all within the definition of what term? - ✔✔Biometry
✔✔What is the leading cause of an unplanned, post-operative refractive error? - ✔✔An
error in the measurement of axial length
✔✔An error of 0.1 mm in the axial length measurement can result in a post-operative
refraction error of how many diopters? - ✔✔0.25D
, ✔✔If multiple axial length readings are taken from a single eye, each measurement
should be within how many millimeters? - ✔✔0.2 mm
✔✔The difference in axial length between two eyes should measure within how many
millimeters? - ✔✔0.3 mm
✔✔What are the two technique for measuring axial length? - ✔✔Contact and immersion
✔✔When performing contact biometry, steps should be taken to minimize what factors?
- ✔✔Corneal compression and corneal abrasions
✔✔What are possible causes of a short measurement in biometry? - ✔✔Gain is set too
high; corneal compression; air bubble adherent to the transducer; corneal gate to the
right of the corneal spike; lens measured too thin; misalignment of the sound beam; and
low sound velocity
✔✔What are possible causes of a long measurement in biometry? - ✔✔Air bubble in
fluid bath (immersion); fluid bridge (contact); gain set too low; retinal gate to the right of
the retinal spike; lens measured too thick; misalignment of the sound beam; and sound
velocity too fast
✔✔How is corneal compression determined? - ✔✔AC depth and/or distance between
initial spike and anterior lens spike
✔✔What is more likely to occur during contact method biometry? - ✔✔Corneal
depression
✔✔What are three advantages of A-scan immersion technique? - ✔✔Proper sound
beam alignment, no corneal compression, corneal and crystalline lens thickness
measured
✔✔What generally causes short axial length measurements? - ✔✔An air bubble in the
water of the probe
✔✔What is the correction factor for the normal cornea when measuring axial length? -
✔✔0.04 mm
✔✔A long measurement is generally caused by what issue? - ✔✔Air bubbles in the fluid
bath (immersion)
✔✔What is the axial length measurement of an eye containing silicone oil as compared
to a normal eye? - ✔✔The eye with the silicone oil will measure longer than the normal
eye
ANSWERS GRADED A+
✔✔What is the term for the "markers" or "cursors" displayed on the screen of a biometry
instrument that provide electronic measurements of distance between two or more
acoustic interfaces? - ✔✔Gates
✔✔What is the term for the capacity of an ultrasound instrument to display two or more
interfaces that are very anatomically close to one another as separate echoes? -
✔✔Resolution
✔✔How does increasing the gain setting on the biometer affect the display echo? -
✔✔It increases the amount of amplification of the echo
✔✔What is the range of ophthalmic biometry frequencies? - ✔✔8-12 MHz
✔✔How is the resolution affected when the gain is set at maximum? - ✔✔The resolution
is less
✔✔A non-focused sound beam is always utilized by which type of scan? -
✔✔Diagnostic A-scan
✔✔What scan is used to obtain a two-dimensional image of the globe? - ✔✔Diagnostic
B-scan
✔✔What is the term for a one-dimensional amplitude scan? - ✔✔A-scan
✔✔The strength of an echo is dependent on what three factors? - ✔✔Gain, difference in
density, and proper alignment
✔✔What type of scan uses Prager or scleral shells? - ✔✔Immersion A-scan
✔✔How often should the filter of a biometry instrument be vacuumed? - ✔✔Once a
month
✔✔Measurement of axial length of the eye, thickness of an extraocular muscle, and
tumor height are all within the definition of what term? - ✔✔Biometry
✔✔What is the leading cause of an unplanned, post-operative refractive error? - ✔✔An
error in the measurement of axial length
✔✔An error of 0.1 mm in the axial length measurement can result in a post-operative
refraction error of how many diopters? - ✔✔0.25D
, ✔✔If multiple axial length readings are taken from a single eye, each measurement
should be within how many millimeters? - ✔✔0.2 mm
✔✔The difference in axial length between two eyes should measure within how many
millimeters? - ✔✔0.3 mm
✔✔What are the two technique for measuring axial length? - ✔✔Contact and immersion
✔✔When performing contact biometry, steps should be taken to minimize what factors?
- ✔✔Corneal compression and corneal abrasions
✔✔What are possible causes of a short measurement in biometry? - ✔✔Gain is set too
high; corneal compression; air bubble adherent to the transducer; corneal gate to the
right of the corneal spike; lens measured too thin; misalignment of the sound beam; and
low sound velocity
✔✔What are possible causes of a long measurement in biometry? - ✔✔Air bubble in
fluid bath (immersion); fluid bridge (contact); gain set too low; retinal gate to the right of
the retinal spike; lens measured too thick; misalignment of the sound beam; and sound
velocity too fast
✔✔How is corneal compression determined? - ✔✔AC depth and/or distance between
initial spike and anterior lens spike
✔✔What is more likely to occur during contact method biometry? - ✔✔Corneal
depression
✔✔What are three advantages of A-scan immersion technique? - ✔✔Proper sound
beam alignment, no corneal compression, corneal and crystalline lens thickness
measured
✔✔What generally causes short axial length measurements? - ✔✔An air bubble in the
water of the probe
✔✔What is the correction factor for the normal cornea when measuring axial length? -
✔✔0.04 mm
✔✔A long measurement is generally caused by what issue? - ✔✔Air bubbles in the fluid
bath (immersion)
✔✔What is the axial length measurement of an eye containing silicone oil as compared
to a normal eye? - ✔✔The eye with the silicone oil will measure longer than the normal
eye
