Page 1 of 136
Certified Diagnostic Ophthalmic Sonographer CDOS
exam ACTUAL QUESTIONS AND DETAILED ANSWERS
WITH RATIONALES LATEST UPDATE THIS YEAR
CDOS EXAM – HIGH-YIELD COVERAGE (SUMMARY)
Ophthalmic Ultrasound Principles
• A-scan vs B-scan vs M-mode applications
• Sound physics in ocular tissue (velocity, attenuation)
• Frequency selection (high-frequency = higher resolution, lower penetration)
• Acoustic impedance and reflection principles
• Gain, TGC, dynamic range control
Ocular Anatomy (Ultrasound Relevance)
• Cornea, anterior chamber, lens capsule
• Vitreous cavity characteristics
• Retina, choroid, sclera layers
• Optic nerve and orbital structures
A-Scan Biometry
• Axial length measurement
• IOL power calculation
• Immersion vs contact technique
• Common errors (corneal compression, poor alignment)
• Sound velocity variations in ocular media
B-Scan Imaging
• Retinal detachment patterns
• Vitreous hemorrhage appearance
• Posterior vitreous detachment
• Tumors (retinoblastoma, melanoma)
• Foreign bodies and calcifications
Orbital & Posterior Segment Pathology
• Endophthalmitis
• Choroidal detachment
• Posterior scleritis (“T-sign”)
• Orbital masses and inflammation
Artifacts & Image Quality
• Shadowing
• Enhancement
• Reverberation
• Motion artifacts
• Gain-related distortion
Safety & Clinical Practice
• Avoid pressure in open globe injury
• Infection control and probe hygiene
• Patient positioning
• Documentation and labeling standards
, Page 2 of 136
1.
Which ultrasound principle explains why high-frequency probes provide better ocular resolution but
reduced penetration depth?
A. Increased acoustic impedance mismatch
B. Higher attenuation of sound waves in tissue
C. Reduced reflection at tissue boundaries
D. Increased Doppler sensitivity
Answer: B
Rationale: Higher frequency ultrasound attenuates more quickly, improving resolution but limiting
depth penetration.
2.
In ophthalmic A-scan biometry, axial length measurement is primarily used for which clinical purpose?
, Page 3 of 136
A. Retinal thickness mapping
B. Intraocular lens power calculation
C. Corneal endothelial evaluation
D. Optic nerve imaging
Answer: B
Rationale: Axial length is essential for calculating IOL power in cataract surgery.
3.
Which structure produces the strongest anterior echogenic reflection in a normal eye ultrasound?
A. Retina
B. Cornea
C. Vitreous
D. Choroid
, Page 4 of 136
Answer: B
Rationale: The cornea-air interface produces a strong reflective echo due to high impedance difference.
4.
Which finding is most consistent with retinal detachment on B-scan ultrasound?
A. Diffuse vitreous haze
B. Mobile echogenic membrane attached at optic disc
C. Completely anechoic globe
D. Thickened lens capsule only
Answer: B
Rationale: Retinal detachment appears as a mobile echogenic membrane tethered posteriorly.
5.
What is the primary purpose of immersion A-scan technique?
Certified Diagnostic Ophthalmic Sonographer CDOS
exam ACTUAL QUESTIONS AND DETAILED ANSWERS
WITH RATIONALES LATEST UPDATE THIS YEAR
CDOS EXAM – HIGH-YIELD COVERAGE (SUMMARY)
Ophthalmic Ultrasound Principles
• A-scan vs B-scan vs M-mode applications
• Sound physics in ocular tissue (velocity, attenuation)
• Frequency selection (high-frequency = higher resolution, lower penetration)
• Acoustic impedance and reflection principles
• Gain, TGC, dynamic range control
Ocular Anatomy (Ultrasound Relevance)
• Cornea, anterior chamber, lens capsule
• Vitreous cavity characteristics
• Retina, choroid, sclera layers
• Optic nerve and orbital structures
A-Scan Biometry
• Axial length measurement
• IOL power calculation
• Immersion vs contact technique
• Common errors (corneal compression, poor alignment)
• Sound velocity variations in ocular media
B-Scan Imaging
• Retinal detachment patterns
• Vitreous hemorrhage appearance
• Posterior vitreous detachment
• Tumors (retinoblastoma, melanoma)
• Foreign bodies and calcifications
Orbital & Posterior Segment Pathology
• Endophthalmitis
• Choroidal detachment
• Posterior scleritis (“T-sign”)
• Orbital masses and inflammation
Artifacts & Image Quality
• Shadowing
• Enhancement
• Reverberation
• Motion artifacts
• Gain-related distortion
Safety & Clinical Practice
• Avoid pressure in open globe injury
• Infection control and probe hygiene
• Patient positioning
• Documentation and labeling standards
, Page 2 of 136
1.
Which ultrasound principle explains why high-frequency probes provide better ocular resolution but
reduced penetration depth?
A. Increased acoustic impedance mismatch
B. Higher attenuation of sound waves in tissue
C. Reduced reflection at tissue boundaries
D. Increased Doppler sensitivity
Answer: B
Rationale: Higher frequency ultrasound attenuates more quickly, improving resolution but limiting
depth penetration.
2.
In ophthalmic A-scan biometry, axial length measurement is primarily used for which clinical purpose?
, Page 3 of 136
A. Retinal thickness mapping
B. Intraocular lens power calculation
C. Corneal endothelial evaluation
D. Optic nerve imaging
Answer: B
Rationale: Axial length is essential for calculating IOL power in cataract surgery.
3.
Which structure produces the strongest anterior echogenic reflection in a normal eye ultrasound?
A. Retina
B. Cornea
C. Vitreous
D. Choroid
, Page 4 of 136
Answer: B
Rationale: The cornea-air interface produces a strong reflective echo due to high impedance difference.
4.
Which finding is most consistent with retinal detachment on B-scan ultrasound?
A. Diffuse vitreous haze
B. Mobile echogenic membrane attached at optic disc
C. Completely anechoic globe
D. Thickened lens capsule only
Answer: B
Rationale: Retinal detachment appears as a mobile echogenic membrane tethered posteriorly.
5.
What is the primary purpose of immersion A-scan technique?
