,1. Which ultrasound artifact most likely explains a false elevation in axial length
during A-scan biometry?
A. Posterior acoustic enhancement
B. Reverberation within the vitreous
C. Refraction artifact at the cornea
D. Beam-width artifact at the macula
Answer: B. Reverberation within the vitreous
Reverberation from strong vitreous interfaces produces multiple equidistant echoes
that can be misinterpreted as the retinal spike, artificially increasing measured axial
length. Posterior enhancement, refraction, and beam-width artifacts do not typically
cause a false elongation of axial length in A-scan biometry.
2. In B-scan evaluation of a choroidal melanoma, which sonographic feature best
differentiates it from a choroidal metastasis?
A. Low internal reflectivity with acoustic hollowing
B. High internal reflectivity with irregular surface
C. Diffuse choroidal thickening with subretinal fluid
D. Bilateral, multifocal, flat lesions
Answer: A. Low internal reflectivity with acoustic hollowing
Choroidal melanoma classically shows low to medium internal reflectivity and acoustic
hollowing (excavation) due to its homogeneous cellular composition. Metastases often
exhibit higher internal reflectivity, irregular surface, and diffuse or bilateral
involvement, making them less likely to show acoustic hollowing.
3. When performing A-scan biometry, which gate setting is most appropriate to
avoid corneal compression?
A. Use a fluid-filled standoff with the probe perpendicular to the cornea
B. Apply the probe directly to the cornea with topical anesthesia
C. Set the gate at the anterior lens capsule
D. Increase the gain to maximum to capture all echoes
Answer: A. Use a fluid-filled standoff with the probe perpendicular to the cornea
A fluid-filled standoff or immersion technique prevents corneal compression, which can
artificially shorten axial length. Direct contact with the cornea risks indentation, and
gate placement or gain adjustments do not address compression.
Page 2
,4. Which Doppler parameter best distinguishes a low-resistance central retinal
artery from a high-resistance ophthalmic artery?
A. Peak systolic velocity
B. Resistive index
C. Pulsatility index
D. End-diastolic velocity
Answer: B. Resistive index
Resistive index (RI) quantifies downstream vascular resistance; the central retinal
artery typically has a lower RI than the ophthalmic artery. While pulsatility index also
reflects resistance, RI is the standard parameter used in ophthalmic Doppler to
differentiate these vessels.
5. Which quality assurance test is essential for verifying the accuracy of an A-scan
biometer's axial length measurements?
A. Daily testing with a tissue-mimicking phantom
B. Monthly calibration with a known-velocity test object
C. Weekly check of probe cable integrity
D. Annual preventive maintenance by the manufacturer
Answer: B. Monthly calibration with a known-velocity test object
A known-velocity test object (e.g., acrylic block) verifies the system's velocity
calibration and measurement accuracy. Phantom testing is more relevant for B-scan
image quality, while cable checks and annual maintenance do not directly validate axial
length accuracy.
6. Which sonographic finding is most consistent with a total retinal detachment on
B-scan?
A. Thick, dome-shaped choroidal mass with low reflectivity
B. Mobile, hyperechoic membrane attached at the optic disc
C. Fixed, hyperechoic membrane with no optic disc attachment
D. Diffuse vitreous opacities with posterior shadowing
Answer: B. Mobile, hyperechoic membrane attached at the optic disc
Total retinal detachment appears as a mobile, hyperechoic membrane that remains
attached at the optic disc and ora serrata, often with a funnel shape. Choroidal masses,
fixed membranes without disc attachment (e.g., vitreous membranes), and vitreous
opacities do not typify retinal detachment.
Page 3
, 7. When calculating IOL power using the SRK/T formula, which parameter most
influences the effective lens position?
A. Axial length
B. Keratometry
C. Anterior chamber depth
D. White-to-white corneal diameter
Answer: A. Axial length
In the SRK/T formula, axial length is a major determinant of the predicted effective
lens position (ELP) through its regression-derived relationship. While keratometry and
anterior chamber depth also affect IOL power, axial length has the strongest influence
on ELP in this formula.
8. Which precaution is critical when performing an ophthalmic ultrasound on a
patient with a suspected open globe injury?
A. Apply gentle pressure with the probe to improve image quality
B. Use a sterile technique and avoid direct contact with the globe
C. Instill a topical anesthetic before probe placement
D. Perform the examination with the patient in the supine position only
Answer: B. Use a sterile technique and avoid direct contact with the globe
In open globe injury, any pressure on the globe can extrude intraocular contents;
therefore, a no-contact or sterile standoff technique is mandatory. Applying pressure,
using topical anesthesia, or positioning alone does not prevent the risk of globe rupture.
9. What is the primary advantage of using a 20 MHz probe compared to a 10 MHz
probe for anterior segment imaging?
A. Increased depth of penetration
B. Improved axial resolution
C. Reduced risk of thermal injury
D. Better visualization of the posterior pole
Answer: B. Improved axial resolution
Higher frequency transducers provide improved axial resolution, which is essential for
detailed anterior segment imaging. However, higher frequencies have decreased depth
of penetration, so they are not suitable for posterior pole evaluation and do not
inherently reduce thermal risk.
Page 4
during A-scan biometry?
A. Posterior acoustic enhancement
B. Reverberation within the vitreous
C. Refraction artifact at the cornea
D. Beam-width artifact at the macula
Answer: B. Reverberation within the vitreous
Reverberation from strong vitreous interfaces produces multiple equidistant echoes
that can be misinterpreted as the retinal spike, artificially increasing measured axial
length. Posterior enhancement, refraction, and beam-width artifacts do not typically
cause a false elongation of axial length in A-scan biometry.
2. In B-scan evaluation of a choroidal melanoma, which sonographic feature best
differentiates it from a choroidal metastasis?
A. Low internal reflectivity with acoustic hollowing
B. High internal reflectivity with irregular surface
C. Diffuse choroidal thickening with subretinal fluid
D. Bilateral, multifocal, flat lesions
Answer: A. Low internal reflectivity with acoustic hollowing
Choroidal melanoma classically shows low to medium internal reflectivity and acoustic
hollowing (excavation) due to its homogeneous cellular composition. Metastases often
exhibit higher internal reflectivity, irregular surface, and diffuse or bilateral
involvement, making them less likely to show acoustic hollowing.
3. When performing A-scan biometry, which gate setting is most appropriate to
avoid corneal compression?
A. Use a fluid-filled standoff with the probe perpendicular to the cornea
B. Apply the probe directly to the cornea with topical anesthesia
C. Set the gate at the anterior lens capsule
D. Increase the gain to maximum to capture all echoes
Answer: A. Use a fluid-filled standoff with the probe perpendicular to the cornea
A fluid-filled standoff or immersion technique prevents corneal compression, which can
artificially shorten axial length. Direct contact with the cornea risks indentation, and
gate placement or gain adjustments do not address compression.
Page 2
,4. Which Doppler parameter best distinguishes a low-resistance central retinal
artery from a high-resistance ophthalmic artery?
A. Peak systolic velocity
B. Resistive index
C. Pulsatility index
D. End-diastolic velocity
Answer: B. Resistive index
Resistive index (RI) quantifies downstream vascular resistance; the central retinal
artery typically has a lower RI than the ophthalmic artery. While pulsatility index also
reflects resistance, RI is the standard parameter used in ophthalmic Doppler to
differentiate these vessels.
5. Which quality assurance test is essential for verifying the accuracy of an A-scan
biometer's axial length measurements?
A. Daily testing with a tissue-mimicking phantom
B. Monthly calibration with a known-velocity test object
C. Weekly check of probe cable integrity
D. Annual preventive maintenance by the manufacturer
Answer: B. Monthly calibration with a known-velocity test object
A known-velocity test object (e.g., acrylic block) verifies the system's velocity
calibration and measurement accuracy. Phantom testing is more relevant for B-scan
image quality, while cable checks and annual maintenance do not directly validate axial
length accuracy.
6. Which sonographic finding is most consistent with a total retinal detachment on
B-scan?
A. Thick, dome-shaped choroidal mass with low reflectivity
B. Mobile, hyperechoic membrane attached at the optic disc
C. Fixed, hyperechoic membrane with no optic disc attachment
D. Diffuse vitreous opacities with posterior shadowing
Answer: B. Mobile, hyperechoic membrane attached at the optic disc
Total retinal detachment appears as a mobile, hyperechoic membrane that remains
attached at the optic disc and ora serrata, often with a funnel shape. Choroidal masses,
fixed membranes without disc attachment (e.g., vitreous membranes), and vitreous
opacities do not typify retinal detachment.
Page 3
, 7. When calculating IOL power using the SRK/T formula, which parameter most
influences the effective lens position?
A. Axial length
B. Keratometry
C. Anterior chamber depth
D. White-to-white corneal diameter
Answer: A. Axial length
In the SRK/T formula, axial length is a major determinant of the predicted effective
lens position (ELP) through its regression-derived relationship. While keratometry and
anterior chamber depth also affect IOL power, axial length has the strongest influence
on ELP in this formula.
8. Which precaution is critical when performing an ophthalmic ultrasound on a
patient with a suspected open globe injury?
A. Apply gentle pressure with the probe to improve image quality
B. Use a sterile technique and avoid direct contact with the globe
C. Instill a topical anesthetic before probe placement
D. Perform the examination with the patient in the supine position only
Answer: B. Use a sterile technique and avoid direct contact with the globe
In open globe injury, any pressure on the globe can extrude intraocular contents;
therefore, a no-contact or sterile standoff technique is mandatory. Applying pressure,
using topical anesthesia, or positioning alone does not prevent the risk of globe rupture.
9. What is the primary advantage of using a 20 MHz probe compared to a 10 MHz
probe for anterior segment imaging?
A. Increased depth of penetration
B. Improved axial resolution
C. Reduced risk of thermal injury
D. Better visualization of the posterior pole
Answer: B. Improved axial resolution
Higher frequency transducers provide improved axial resolution, which is essential for
detailed anterior segment imaging. However, higher frequencies have decreased depth
of penetration, so they are not suitable for posterior pole evaluation and do not
inherently reduce thermal risk.
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