(CDOS)
Certified Diagnostic Ophthalmic
Sonographer Practice Exam Questions And Correct
Answers (Verified Answers) Plus Explanation 2026
Q&A | Instant Download Pdf.
Certification Certified Diagnostic Ophthalmic Sonographer (CDOS)
Offering
International Joint Commission on Allied Health Personnel in Ophthalmology (IJCAHPO)
Body
Content Ocular Anatomy & Physiology, Ultrasound Physics & Instrumentation, Scanning Techniq
Areas Pathology Recognition, Biometry, Patient Care & Ethics
1. Which ocular layer contains the choroidal vasculature that supplies the outer retina?
A) Sclera
B) Iris
C) Uvea
D) Retina
Correct Answer: C
Explanation: The uvea comprises the iris, ciliary body, and choroid; the choroid provides
the main blood supply to the outer retina. The sclera is the outer fibrous layer; the retina is
the innermost neural layer .
2. The average axial length of an adult human eye is closest to:
,A) 16 mm
B) 22 mm
C) 24 mm
D) 28 mm
Correct Answer: C
Explanation: Normal adult axial length ranges from 22–24 mm; 24 mm is often cited as
the average. Axial lengths >26.5 mm are associated with myopia and staphyloma
formation .
3. What is the term for the normal posterior bulge or outpouching of the sclera seen in
high myopia?
A) Posterior staphyloma
B) Scleral ectasia
C) Optic disc drusen
D) Choroidal detachment
Correct Answer: A
*Explanation: A staphyloma is described as an outpouching of the posterior aspect of
the globe on B-scan. It is commonly associated with high myopia with axial lengths
>26.5 mm .*
4. Which of the following are components of the uveal tract? (Select all that apply)
☐ A) Iris
☐ B) Ciliary body
☐ C) Choroid
☐ D) Sclera
☐ E) Retina
Correct Answer: A, B, C
,Explanation: The uveal tract (vascular layer) consists of the iris (anterior), ciliary body
(middle), and choroid (posterior). The sclera is the fibrous outer layer, and the retina is the
neural layer .
5. The retina is divided into which two primary layers?
A) Neurosensory retina and retinal pigment epithelium (RPE)
B) Inner retina and outer retina
C) Macula and periphery
D) Rod layer and cone layer
Correct Answer: A
Explanation: The retina consists of the neurosensory retina (neural tissue) and the retinal
pigment epithelium (RPE), which supports photoreceptor function .
6. The optic nerve sheath diameter (ONSD) is measured to assess:
A) Glaucoma severity
B) Elevated intracranial pressure (papilledema)
C) Corneal thickness
D) Lens density
Correct Answer: B
Explanation: ONSD measurement is used to assess elevated intracranial pressure. The
optic nerve sheath distends when intracranial pressure increases. A reduction in ONSD by
>20% from primary to 30° gaze suggests redistribution of fluid in the optic nerve sheath .
7. What is the normal depth of the anterior chamber in an adult?
A) 0.5 - 1.0 mm
B) 1.0 - 2.0 mm
, C) 2.5 - 3.5 mm
D) 4.0 - 5.0 mm
Correct Answer: C
*Explanation: The normal adult anterior chamber depth ranges from 2.5–3.5 mm.
Shallow anterior chamber (<2.5 mm) increases the risk of angle-closure glaucoma .*
8. The macula is responsible for:
A) Peripheral vision
B) High-acuity central vision
C) Color vision only
D) Night vision
Correct Answer: B
Explanation: The macula is responsible for high-acuity central vision, including color vision
and fine detail perception .
9. The fovea centralis is characterized by:
A) High concentration of rods
B) High concentration of cones with no overlying retinal blood vessels
C) Thick retinal layers
D) Presence of optic nerve fibers
Correct Answer: B
Explanation: The fovea centralis has the highest concentration of cone photoreceptors and
no overlying retinal blood vessels, allowing maximum visual acuity .
10. Which extraocular muscle is responsible for elevating the eye?
Certified Diagnostic Ophthalmic
Sonographer Practice Exam Questions And Correct
Answers (Verified Answers) Plus Explanation 2026
Q&A | Instant Download Pdf.
Certification Certified Diagnostic Ophthalmic Sonographer (CDOS)
Offering
International Joint Commission on Allied Health Personnel in Ophthalmology (IJCAHPO)
Body
Content Ocular Anatomy & Physiology, Ultrasound Physics & Instrumentation, Scanning Techniq
Areas Pathology Recognition, Biometry, Patient Care & Ethics
1. Which ocular layer contains the choroidal vasculature that supplies the outer retina?
A) Sclera
B) Iris
C) Uvea
D) Retina
Correct Answer: C
Explanation: The uvea comprises the iris, ciliary body, and choroid; the choroid provides
the main blood supply to the outer retina. The sclera is the outer fibrous layer; the retina is
the innermost neural layer .
2. The average axial length of an adult human eye is closest to:
,A) 16 mm
B) 22 mm
C) 24 mm
D) 28 mm
Correct Answer: C
Explanation: Normal adult axial length ranges from 22–24 mm; 24 mm is often cited as
the average. Axial lengths >26.5 mm are associated with myopia and staphyloma
formation .
3. What is the term for the normal posterior bulge or outpouching of the sclera seen in
high myopia?
A) Posterior staphyloma
B) Scleral ectasia
C) Optic disc drusen
D) Choroidal detachment
Correct Answer: A
*Explanation: A staphyloma is described as an outpouching of the posterior aspect of
the globe on B-scan. It is commonly associated with high myopia with axial lengths
>26.5 mm .*
4. Which of the following are components of the uveal tract? (Select all that apply)
☐ A) Iris
☐ B) Ciliary body
☐ C) Choroid
☐ D) Sclera
☐ E) Retina
Correct Answer: A, B, C
,Explanation: The uveal tract (vascular layer) consists of the iris (anterior), ciliary body
(middle), and choroid (posterior). The sclera is the fibrous outer layer, and the retina is the
neural layer .
5. The retina is divided into which two primary layers?
A) Neurosensory retina and retinal pigment epithelium (RPE)
B) Inner retina and outer retina
C) Macula and periphery
D) Rod layer and cone layer
Correct Answer: A
Explanation: The retina consists of the neurosensory retina (neural tissue) and the retinal
pigment epithelium (RPE), which supports photoreceptor function .
6. The optic nerve sheath diameter (ONSD) is measured to assess:
A) Glaucoma severity
B) Elevated intracranial pressure (papilledema)
C) Corneal thickness
D) Lens density
Correct Answer: B
Explanation: ONSD measurement is used to assess elevated intracranial pressure. The
optic nerve sheath distends when intracranial pressure increases. A reduction in ONSD by
>20% from primary to 30° gaze suggests redistribution of fluid in the optic nerve sheath .
7. What is the normal depth of the anterior chamber in an adult?
A) 0.5 - 1.0 mm
B) 1.0 - 2.0 mm
, C) 2.5 - 3.5 mm
D) 4.0 - 5.0 mm
Correct Answer: C
*Explanation: The normal adult anterior chamber depth ranges from 2.5–3.5 mm.
Shallow anterior chamber (<2.5 mm) increases the risk of angle-closure glaucoma .*
8. The macula is responsible for:
A) Peripheral vision
B) High-acuity central vision
C) Color vision only
D) Night vision
Correct Answer: B
Explanation: The macula is responsible for high-acuity central vision, including color vision
and fine detail perception .
9. The fovea centralis is characterized by:
A) High concentration of rods
B) High concentration of cones with no overlying retinal blood vessels
C) Thick retinal layers
D) Presence of optic nerve fibers
Correct Answer: B
Explanation: The fovea centralis has the highest concentration of cone photoreceptors and
no overlying retinal blood vessels, allowing maximum visual acuity .
10. Which extraocular muscle is responsible for elevating the eye?
