ROUB Study Guide Actual Questions and Answers 100%
Verified 2023/2024
If your biometry instrument has one pseudophakic eye-type setting, what is the
only IOL material that can accurately be measured?
Polymethyl methacrylate (PMMA)
If a gain setting is increased in order to obtain a 100% tall retina and sclera echo,
what type of cataract is being evaluated?
A dense cataract
What transducer frequency is generally used for a biometry A-scan probe?
10 MHz
What is the velocity of a biometer that only uses an average velocity to measure
the entire axial length?
1550 m/sec
What is one of the most important features of a biometer?
Display screen
What are the velocity settings for a phakic eye?
1532 m/sec for the aqueous; 1641 m/sec for the lens; and, 1532 m/sec for the vitreous
cavity
What should the examiner do to reduce the presence of a reverberation echo
created by a dense cataract?
Reduce the gain
What is the term for the electronic calipers that measure the distance between
two or more anatomic interfaces?
Gates
Of the following settings on the biometer (gain, gates, A-scan probe frequency,
eye type, and screen brightness), which cannot be changed by the examiner?
A-scan probe frequency
What is the proper sound velocity used to measure the distance between the
anterior and posterior lens interfaces in a phakic eye?
1641 m/sec
When performing immersion biometry, which gate in relation to the initial spike
represents the cornea?
Corneal gate is to the right of the initial spike
What is the possible cause for a biometry instrument to indicate an unusually
short measurement of a pseudophakic eye with a PMMA implant?
Multiple signal of the echo with improper identification of the retina
What biometer setting changes the degree of echo amplification?
Gain
What is the term for the relative strength or amplitude of an echo displayed on a
biometer?
Reflectivity
When measuring an eye that has no crystalline lens, the instrument should be set
on which eye type?
Aphakic
, 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?
Verified 2023/2024
If your biometry instrument has one pseudophakic eye-type setting, what is the
only IOL material that can accurately be measured?
Polymethyl methacrylate (PMMA)
If a gain setting is increased in order to obtain a 100% tall retina and sclera echo,
what type of cataract is being evaluated?
A dense cataract
What transducer frequency is generally used for a biometry A-scan probe?
10 MHz
What is the velocity of a biometer that only uses an average velocity to measure
the entire axial length?
1550 m/sec
What is one of the most important features of a biometer?
Display screen
What are the velocity settings for a phakic eye?
1532 m/sec for the aqueous; 1641 m/sec for the lens; and, 1532 m/sec for the vitreous
cavity
What should the examiner do to reduce the presence of a reverberation echo
created by a dense cataract?
Reduce the gain
What is the term for the electronic calipers that measure the distance between
two or more anatomic interfaces?
Gates
Of the following settings on the biometer (gain, gates, A-scan probe frequency,
eye type, and screen brightness), which cannot be changed by the examiner?
A-scan probe frequency
What is the proper sound velocity used to measure the distance between the
anterior and posterior lens interfaces in a phakic eye?
1641 m/sec
When performing immersion biometry, which gate in relation to the initial spike
represents the cornea?
Corneal gate is to the right of the initial spike
What is the possible cause for a biometry instrument to indicate an unusually
short measurement of a pseudophakic eye with a PMMA implant?
Multiple signal of the echo with improper identification of the retina
What biometer setting changes the degree of echo amplification?
Gain
What is the term for the relative strength or amplitude of an echo displayed on a
biometer?
Reflectivity
When measuring an eye that has no crystalline lens, the instrument should be set
on which eye type?
Aphakic
, 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?
