NATIONAL BOARD OF EXAMINERS IN OPTOMETRY
EXAMINATION (NBEO) EXAM PRACTICE QUESTIONS
AND CORRECT ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALE 2026 Q&A| INSTANT DOWNLOAD PDF
1. Which layer of the cornea is primarily responsible for the
majority of its refractive power?
A. Epithelium
B. Bowman’s layer
C. Stroma
D. Endothelium
Correct answer: C. Stroma
The corneal stroma accounts for most of the cornea’s
thickness and is the primary contributor to its refractive
power due to its organized collagen fibrils and uniform
hydration. The epithelium and endothelium play important
protective and fluid-regulating roles but contribute
minimally to refraction.
2. Which cranial nerve controls pupillary constriction?
A. CN II
B. CN III
C. CN IV
D. CN VI
Correct answer: B. CN III
The oculomotor nerve (CN III) carries parasympathetic
fibers to the sphincter pupillae muscle, causing pupillary
constriction. CN II is sensory (vision), while CN IV and VI
control extraocular muscles.
3. The most common cause of painless vision loss in older
adults is:
, A. Cataract
B. Acute glaucoma
C. Retinal detachment
D. Optic neuritis
Correct answer: A. Cataract
Cataracts cause gradual, painless vision loss due to lens
opacification and are the leading cause of reversible vision
impairment worldwide in older adults.
4. Which structure is responsible for aqueous humor
production?
A. Trabecular meshwork
B. Ciliary body
C. Iris
D. Schlemm’s canal
Correct answer: B. Ciliary body
The ciliary processes of the ciliary body actively produce
aqueous humor, which maintains intraocular pressure and
nourishes avascular ocular structures.
5. Which visual field defect is most associated with pituitary
adenoma?
A. Right homonymous hemianopia
B. Bitemporal hemianopia
C. Central scotoma
D. Altitudinal defect
Correct answer: B. Bitemporal hemianopia
Pituitary adenomas compress the optic chiasm, affecting
crossing nasal retinal fibers and resulting in loss of
temporal visual fields in both eyes.
, 6. The primary function of the retina’s rods is:
A. Color vision
B. High-acuity vision
C. Low-light vision
D. Depth perception
Correct answer: C. Low-light vision
Rods are highly sensitive photoreceptors responsible for
scotopic (dim light) vision but do not detect color or
provide high spatial resolution.
7. Which condition is characterized by increased intraocular
pressure and optic nerve damage?
A. Cataract
B. Glaucoma
C. Macular degeneration
D. Keratitis
Correct answer: B. Glaucoma
Glaucoma involves progressive optic neuropathy often
associated with elevated intraocular pressure, leading to
characteristic visual field loss.
8. The macula is primarily responsible for:
A. Peripheral vision
B. Color discrimination
C. Central high-acuity vision
D. Night vision
Correct answer: C. Central high-acuity vision
The macula, particularly the fovea, contains a high density
of cones, enabling detailed central vision and fine visual
tasks.
EXAMINATION (NBEO) EXAM PRACTICE QUESTIONS
AND CORRECT ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALE 2026 Q&A| INSTANT DOWNLOAD PDF
1. Which layer of the cornea is primarily responsible for the
majority of its refractive power?
A. Epithelium
B. Bowman’s layer
C. Stroma
D. Endothelium
Correct answer: C. Stroma
The corneal stroma accounts for most of the cornea’s
thickness and is the primary contributor to its refractive
power due to its organized collagen fibrils and uniform
hydration. The epithelium and endothelium play important
protective and fluid-regulating roles but contribute
minimally to refraction.
2. Which cranial nerve controls pupillary constriction?
A. CN II
B. CN III
C. CN IV
D. CN VI
Correct answer: B. CN III
The oculomotor nerve (CN III) carries parasympathetic
fibers to the sphincter pupillae muscle, causing pupillary
constriction. CN II is sensory (vision), while CN IV and VI
control extraocular muscles.
3. The most common cause of painless vision loss in older
adults is:
, A. Cataract
B. Acute glaucoma
C. Retinal detachment
D. Optic neuritis
Correct answer: A. Cataract
Cataracts cause gradual, painless vision loss due to lens
opacification and are the leading cause of reversible vision
impairment worldwide in older adults.
4. Which structure is responsible for aqueous humor
production?
A. Trabecular meshwork
B. Ciliary body
C. Iris
D. Schlemm’s canal
Correct answer: B. Ciliary body
The ciliary processes of the ciliary body actively produce
aqueous humor, which maintains intraocular pressure and
nourishes avascular ocular structures.
5. Which visual field defect is most associated with pituitary
adenoma?
A. Right homonymous hemianopia
B. Bitemporal hemianopia
C. Central scotoma
D. Altitudinal defect
Correct answer: B. Bitemporal hemianopia
Pituitary adenomas compress the optic chiasm, affecting
crossing nasal retinal fibers and resulting in loss of
temporal visual fields in both eyes.
, 6. The primary function of the retina’s rods is:
A. Color vision
B. High-acuity vision
C. Low-light vision
D. Depth perception
Correct answer: C. Low-light vision
Rods are highly sensitive photoreceptors responsible for
scotopic (dim light) vision but do not detect color or
provide high spatial resolution.
7. Which condition is characterized by increased intraocular
pressure and optic nerve damage?
A. Cataract
B. Glaucoma
C. Macular degeneration
D. Keratitis
Correct answer: B. Glaucoma
Glaucoma involves progressive optic neuropathy often
associated with elevated intraocular pressure, leading to
characteristic visual field loss.
8. The macula is primarily responsible for:
A. Peripheral vision
B. Color discrimination
C. Central high-acuity vision
D. Night vision
Correct answer: C. Central high-acuity vision
The macula, particularly the fovea, contains a high density
of cones, enabling detailed central vision and fine visual
tasks.
