100+ Free NBEO Part I Practice Questions

Pass your NBEO Part I Applied Basic Science (ABS) exam on the first try — instant access, no signup required.

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Question 1

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What is the function of horizontal cells in the retina?

They transmit signals directly to the optic nerve

They provide lateral inhibition in the outer plexiform layer, enhancing contrast and spatial resolution

They form the blood-retinal barrier

They produce the vitreous humor

to track

2026 Statistics

Key Facts: NBEO Part I Exam

~300

Exam Questions

Two 3-hour sessions

6 hrs

Total Test Time

Full day exam

$575

Exam Fee

NBEO

~90-95%

First-Time Pass Rate

Estimated

Year 2

Typically Taken

After 2nd year of OD program

NBEO Part I has approximately 300 questions in two 3-hour sessions (full day exam). It covers anatomy and physiology (30%), optics (20%), pharmacology (20%), microbiology and pathology (15%), and biochemistry (15%). Typically taken after the second year of optometry school. A criterion-referenced scaled score determines passing. Required for optometry licensure in all U.S. states.

Sample NBEO Part I Practice Questions

Try these sample questions to test your NBEO Part I exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which cranial nerve innervates the lateral rectus muscle?

A.CN III (oculomotor)

B.CN IV (trochlear)

C.CN V (trigeminal)

D.CN VI (abducens)

Explanation: The abducens nerve (CN VI) innervates the lateral rectus muscle, which abducts the eye. The mnemonic 'LR6SO4' reminds us that the lateral rectus is innervated by CN VI and the superior oblique by CN IV. All other extraocular muscles are innervated by CN III (oculomotor nerve).

2What type of lens is used to correct myopia?

A.Convex (plus) lens

B.Concave (minus) lens

C.Cylindrical lens

D.Prism lens

Explanation: Myopia (nearsightedness) occurs when the eye's optical power is too strong relative to its axial length, causing images to focus in front of the retina. A concave (minus/diverging) lens reduces the total optical power, moving the focal point back onto the retina. Convex (plus) lenses are used for hyperopia, cylindrical lenses for astigmatism, and prism lenses for binocular vision disorders.

3Which layer of the cornea is responsible for maintaining corneal dehydration and transparency?

A.Epithelium

B.Bowman's layer

C.Stroma

D.Endothelium

Explanation: The corneal endothelium is a single layer of cells on the posterior corneal surface that actively pumps fluid out of the stroma via Na+/K+ ATPase pumps, maintaining the relative dehydration necessary for corneal transparency. Unlike the epithelium, the endothelium has very limited regenerative capacity in humans. Loss of endothelial cells below a critical density (~500-800 cells/mm²) leads to corneal edema and loss of transparency.

4What is the mechanism of action of topical beta-blockers (e.g., timolol) used to treat glaucoma?

A.Increase uveoscleral outflow

B.Decrease aqueous humor production by the ciliary body

C.Increase trabecular meshwork outflow

D.Constrict the pupil to open the drainage angle

Explanation: Topical beta-adrenergic antagonists like timolol lower intraocular pressure (IOP) by blocking beta-2 receptors on the ciliary body epithelium, reducing the production of aqueous humor. They do not significantly affect outflow. Systemic side effects include bradycardia, bronchospasm, and hypotension, making them contraindicated in patients with asthma, COPD, and certain cardiac conditions.

5Which microorganism is the most common cause of bacterial conjunctivitis in adults?

A.Pseudomonas aeruginosa

B.Staphylococcus aureus

C.Neisseria gonorrhoeae

D.Haemophilus influenzae

Explanation: Staphylococcus aureus is the most common cause of bacterial conjunctivitis in adults, followed by Streptococcus pneumoniae and Haemophilus influenzae. In children, H. influenzae is more prevalent. Pseudomonas is more commonly associated with contact lens-related keratitis. Neisseria gonorrhoeae causes hyperacute conjunctivitis, which is a medical emergency requiring immediate systemic treatment.

6The macula lutea gets its yellow color from which pigments?

A.Rhodopsin and iodopsin

B.Melanin and lipofuscin

C.Lutein and zeaxanthin

D.Hemoglobin and bilirubin

Explanation: The macula lutea (yellow spot) gets its characteristic color from the carotenoid pigments lutein and zeaxanthin, collectively called macular pigment. These xanthophyll carotenoids are concentrated in the Henle fiber layer and inner plexiform layer of the fovea. They serve as antioxidants and blue light filters, protecting the photoreceptors from phototoxic damage. Dietary intake of lutein and zeaxanthin is associated with reduced risk of age-related macular degeneration.

7What is the approximate refractive index of the human crystalline lens?

A.1.000

B.1.336

C.1.376

D.1.420

Explanation: The crystalline lens has an average refractive index of approximately 1.42 (ranging from about 1.386 at the cortex to 1.406 at the nucleus, creating a gradient index). This is higher than the surrounding aqueous (1.336) and vitreous (1.336) humors, giving the lens its converging power. The cornea has a refractive index of approximately 1.376. The gradient index structure of the lens reduces spherical aberration.

8Which photoreceptor type is primarily responsible for color vision and high-acuity central vision?

A.Rod cells

B.Cone cells

C.Retinal ganglion cells

D.Bipolar cells

Explanation: Cone cells are responsible for photopic (bright light) vision, color perception, and high-acuity central vision. They are concentrated in the fovea, where they are packed at the highest density (~200,000/mm²). Three types of cones (S/blue, M/green, L/red) enable trichromatic color vision. Rod cells are responsible for scotopic (dim light) vision and peripheral vision, but they provide lower acuity and no color discrimination.

9Which topical ophthalmic medication is a prostaglandin analog used as first-line treatment for open-angle glaucoma?

A.Timolol

B.Latanoprost

C.Pilocarpine

D.Brimonidine

Explanation: Latanoprost (Xalatan) is a prostaglandin F2α analog that lowers IOP primarily by increasing uveoscleral outflow. Prostaglandin analogs are the most commonly prescribed first-line treatment for open-angle glaucoma due to their efficacy (25-35% IOP reduction), once-daily dosing, and favorable systemic side effect profile. Ocular side effects include iris darkening, eyelash growth, and periorbital fat atrophy.

10Herpes simplex keratitis is caused by which type of virus?

A.RNA retrovirus

B.Double-stranded DNA virus (herpesvirus)

C.Single-stranded RNA virus

D.Prion

Explanation: Herpes simplex virus (HSV) is a double-stranded DNA virus belonging to the Herpesviridae family. HSV-1 is the primary cause of ocular herpes, causing epithelial keratitis (dendritic ulcer), stromal keratitis, and endotheliitis. The virus establishes latency in the trigeminal ganglion and can reactivate, making recurrence common. Treatment includes topical or oral antivirals (e.g., ganciclovir, trifluridine, oral valacyclovir).

About the NBEO Part I Exam

NBEO Part I Applied Basic Science (ABS) tests foundational knowledge for optometry including ocular anatomy and physiology, optics, pharmacology, microbiology, pathology, neuroanatomy, and biochemistry as applied to vision science and clinical optometry.

Questions

100 scored questions

Time Limit

6 hours (two 3-hour sessions)

Passing Score

Criterion-referenced scaled score

Exam Fee

$575 (NBEO (National Board of Examiners in Optometry))

NBEO Part I Exam Content Outline

30%

Anatomy & Physiology

Ocular anatomy, neuroanatomy of vision, visual pathways, extraocular muscles, orbital anatomy, and ocular physiology

20%

Optics

Geometrical optics, physical optics, ophthalmic lenses, visual optics, aberrations, and optical instruments

20%

Pharmacology

Ocular and systemic pharmacology, drug mechanisms, glaucoma medications, anti-infectives, and anti-inflammatory agents

15%

Microbiology & Pathology

Ocular pathogens, immunology, infectious disease, ocular and systemic pathology, and inflammatory processes

15%

Biochemistry

Ocular biochemistry, visual cycle, tear film composition, lens metabolism, retinal biochemistry, and nutritional science

How to Pass the NBEO Part I Exam

What You Need to Know

Passing score: Criterion-referenced scaled score
Exam length: 100 questions
Time limit: 6 hours (two 3-hour sessions)
Exam fee: $575

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

NBEO Part I Study Tips from Top Performers

1Anatomy and physiology is the largest section (30%) — master ocular anatomy, neuroanatomy of the visual pathway, extraocular muscle actions, and orbital anatomy thoroughly

2For optics, practice calculations involving vergence, lens power, magnification, Prentice rule, and ray tracing until they become automatic

3Study pharmacology by mechanism of action — group drugs by class (beta-blockers, prostaglandins, CAIs, alpha-agonists) and know their side effects

4Create tables comparing ocular pathogens — bacteria, viruses, fungi, and parasites — with their characteristic clinical presentations

5Review biochemistry of the visual cycle (rhodopsin regeneration), tear film layers and composition, and lens metabolism (sorbitol pathway)

Frequently Asked Questions

What is NBEO Part I?

NBEO Part I, also called the Applied Basic Science (ABS) exam, tests foundational science knowledge for optometry. It covers ocular anatomy and physiology, optics, pharmacology, microbiology and pathology, and biochemistry. It is typically taken after the second year of the Doctor of Optometry (OD) program and is required for optometry licensure in all U.S. states and territories.

How many questions are on NBEO Part I?

NBEO Part I contains approximately 300 multiple-choice questions administered in two 3-hour sessions during a full testing day. The questions cover five content areas: anatomy and physiology (30%), optics (20%), pharmacology (20%), microbiology and pathology (15%), and biochemistry (15%). The passing standard is criterion-referenced, meaning it is based on a minimum competency level rather than a curve.

When should I take NBEO Part I?

NBEO Part I is typically taken after the second year of optometry school (between the second and third years), when basic science coursework has been completed. The exam is offered during specific testing windows throughout the year. Most OD programs integrate Part I preparation into their curriculum. Taking it on schedule is important as Parts I, II, and III must all be completed for state licensure.

How should I study for NBEO Part I?

Effective NBEO Part I study strategies include: reviewing ocular anatomy and neuroanatomy of vision (30% of exam), practicing optics calculations and lens problems, studying ocular pharmacology mechanisms and drug classes, reviewing microbiology (ocular pathogens) and immunology, and understanding biochemistry of the visual cycle and lens metabolism. Most students study 4-6 months alongside coursework. Use KMK review materials, practice questions, and study groups.