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Which test uses the corneal light reflex to estimate the angle of strabismus by observing the position of the light reflection on the cornea?

Worth 4-dot test

Maddox rod test

Hirschberg test

Cover-uncover test

to track

2026 Statistics

Key Facts: AOC C.O. Exam

Exam Components

Written (Pearson VUE, June) + oral/practical (September)

$800

Total Board Fee

AOC — covers both written and oral/practical

24 months

Fellowship Required

AOC-accredited program, ≥2,000 clinical hours

45 CE

Recertification Credits

Per 3-year cycle (30 in core topics)

2–3%

Amblyopia Prevalence

Most common childhood visual impairment

7–10 yrs

Critical Period

Peak amblyopia treatment window

The AOC C.O. board examination has two components: a written computer-based exam at Pearson VUE in June and an oral/practical exam each September. The $800 fee covers both parts. Eligibility requires completing a 24-month AOC-accredited orthoptic fellowship. Content spans ocular motility, strabismus classification, sensory testing, amblyopia management, neuro-ophthalmology, nystagmus, and ocular anatomy. Recertification requires 45 CE credits every 3 years (30 in core topics). The credential is required to practice as a Certified Orthoptist in the United States.

Sample AOC C.O. Practice Questions

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

1Which test uses the corneal light reflex to estimate the angle of strabismus by observing the position of the light reflection on the cornea?

A.Cover-uncover test

B.Hirschberg test

C.Maddox rod test

D.Worth 4-dot test

Explanation: The Hirschberg test uses a penlight to produce a corneal light reflex and estimates the angle of strabismus by observing the location of the reflex on the cornea. A reflex centered on the cornea indicates orthophoria. A reflex displaced nasally suggests exotropia, and a temporal displacement suggests esotropia. Each millimeter of displacement from center corresponds to approximately 7 prism diopters (or 15 degrees) of deviation. It is a rapid screening tool, especially useful in non-cooperative patients.

2Which test uses prisms to neutralize the corneal light reflex displacement and thereby quantify the angle of strabismus?

A.Krimsky test

B.Alternate cover test

C.Stereoacuity test

D.Bruckner test

Explanation: The Krimsky test quantifies the angle of strabismus by placing a prism in front of the deviated eye (or the fixating eye) until the corneal light reflex is centered on both corneas simultaneously. The power of the prism needed to center the reflex equals the magnitude of the deviation. It is often used in patients who cannot maintain fixation for a cover test, such as very young children or those with deep amblyopia.

3A patient fixates a target at 40 cm. The right eye is covered and the left eye is observed to make a refixation movement from an inward to a straight-ahead position. What does this finding indicate?

A.Left exotropia

B.Left esotropia

C.Right hypertropia

D.Orthophoria

Explanation: When the left eye moves outward (from inward to straight-ahead) upon uncovering or as the right eye is covered, it indicates the left eye was deviated inward (esotropia) before it was forced to fixate. The left eye moved from its deviated esotropic position to fixation on the target, which is an outward refixation movement. This finding is consistent with left esotropia in the cover-uncover test.

4The alternate cover test (prism and alternate cover test) measures which type of deviation?

A.Manifest deviation only (tropia)

B.Latent deviation only (phoria)

C.The total (maximum) deviation, including both manifest and latent components

D.Only the phoric component after dissociation

Explanation: The prism and alternate cover test (PACT) measures the total deviation by fully dissociating the eyes (breaking fusion), allowing measurement of both the manifest component (tropia) and the latent component (phoria). The cover-uncover test reveals only the manifest tropia. The PACT provides the maximum angle of deviation and is the gold standard for quantifying strabismus. It cannot distinguish between the magnitude of tropia versus phoria components separately.

5During the Worth 4-dot test, a patient with bifoveal fusion will report seeing how many dots?

A.2 dots

B.3 dots

C.4 dots

D.5 dots

Explanation: A patient with normal bifoveal fusion sees 4 dots (2 red and 2 green) with the Worth 4-dot test. The red filter over one eye allows only the 2 red dots to be seen, while the green filter allows only the 2 green dots plus the white dot (which passes through both filters, so it appears as a composite color). Seeing 5 dots indicates diplopia (suppression absent), 2 dots indicates suppression of the green-filtered eye, and 3 dots indicates suppression of the red-filtered eye.

6Which of the following best describes the accommodative convergence to accommodation (AC/A) ratio?

A.The amount of convergence per unit of divergence

B.The amount of convergence (in prism diopters) elicited per diopter of accommodation

C.The ratio of esotropia angle at near versus distance

D.The amount of divergence per unit of accommodation

Explanation: The AC/A ratio expresses the amount of accommodative convergence (in prism diopters) that is elicited per diopter of accommodation (in diopters). A normal AC/A ratio is approximately 4:1 to 6:1 prism diopters per diopter. A high AC/A ratio is characteristic of accommodative esotropia and explains why deviation is larger at near. It is measured clinically using the gradient method (changing lenses by a known amount and measuring the change in deviation) or the heterophoria method.

7A child presents with esotropia of 35 prism diopters at distance and 45 prism diopters at near, corrected by full cycloplegic refraction (+3.50 OU). The residual near deviation after glasses is 10 prism diopters. What is the most likely diagnosis?

A.Basic (non-accommodative) esotropia

B.Fully accommodative esotropia

C.Partially accommodative esotropia

D.Intermittent exotropia

Explanation: Partially accommodative esotropia is characterized by esotropia that is reduced, but not eliminated, by full hyperopic spectacle correction. In fully accommodative esotropia, the deviation is completely corrected with glasses. Since a residual 10-prism-diopter esotropia persists after correction in this case, the diagnosis is partially accommodative esotropia. The accommodative component is eliminated by the glasses, but a non-accommodative component remains that may require surgery.

8Congenital (infantile) esotropia typically presents with which of the following features?

A.Large angle esotropia over 40 prism diopters, onset before 6 months of age, and high hyperopia

B.Large angle esotropia over 30 prism diopters, onset before 6 months of age, and minimal hyperopia

C.Small angle esotropia, onset at age 2-3 years, and high hyperopia

D.Onset after age 1, associated with hyperopia, and fully correctable with glasses

Explanation: Congenital (infantile) esotropia is characterized by onset before 6 months of age, a large constant angle (typically greater than 30-40 prism diopters), and minimal to moderate hyperopia (usually not significantly more than age-expected). It is NOT typically associated with high hyperopia (which characterizes accommodative esotropia). Associated features include cross-fixation, dissociated vertical deviation (DVD), latent nystagmus, inferior oblique overaction, and absent binocularity. Surgical correction is the treatment of choice.

9Anomalous retinal correspondence (ARC) is best described as:

A.Normal correspondence between the two foveas

B.An adaptation where an extrafoveal point in the deviated eye develops a common visual direction with the fovea of the fixing eye

C.Complete suppression of the deviated eye

D.Diplopia caused by strabismus

Explanation: In anomalous retinal correspondence (ARC), an extrafoveal point (anomalous retinal element) in the deviated eye develops a common visual direction with the fovea of the fixing eye. This is an adaptation to strabismus that allows the brain to fuse the images despite the ocular misalignment. ARC eliminates diplopia but results in abnormal binocularity. It is detected using the Bagolini striated lens test, the Worth 4-dot test, and the synoptophore. ARC can complicate strabismus surgery outcomes and postoperative alignment assessment.

10The Titmus stereotest uses polarized vectographic targets. What is the minimum level of stereoacuity measurable with the Titmus fly test?

A.40 arc seconds

B.100 arc seconds

C.3000 arc seconds

D.400 arc seconds

Explanation: The Titmus fly (or Wirt fly) test measures gross stereopsis at 3000 arc seconds. This is the largest (coarsest) target in the Titmus test, making it useful for detecting grossly reduced or absent stereopsis. The graded circles range from 800 down to 40 arc seconds. The Random Dot Stereotest (Randot, Lang, TNO) uses random dot stereograms that eliminate monocular cues, providing a more rigorous assessment of true cortical stereopsis. Patients with ARC or monofixation syndrome may pass the Titmus fly at 3000 arc seconds but fail random dot tests.

About the AOC C.O. Exam

The AOC Certified Orthoptist (C.O.) credential verifies clinical and teaching competencies in the evaluation and non-surgical management of ocular motility disorders, strabismus, amblyopia, binocular vision disorders, and nystagmus. Candidates must complete a 24-month AOC-accredited orthoptic fellowship (≥2,000 supervised clinical hours) before sitting for the two-part board: a computer-based written exam administered at Pearson VUE centers in June, followed by an oral/practical examination each September. The written exam is based on the AOC Syllabus of Orthoptic Instruction and the Core Competency: Essential Skills for Orthoptists, covering ocular anatomy, sensory/motor physiology, pharmacology, optics, visual acuity assessment, amblyopia, strabismus, nystagmus, eye movement disorders, and electrophysiology principles.

Questions

100 scored questions

Time Limit

Written exam in June (computer-based, Pearson VUE); oral/practical in September

Passing Score

Criterion-referenced passing standard set by AOC

Exam Fee

$800 (American Orthoptic Council (AOC) / Pearson VUE (written))

AOC C.O. Exam Content Outline

~30%

Ocular Motility and Strabismus Evaluation

Cover testing (unilateral and alternating), Hirschberg, Krimsky, prism and alternate cover test, simultaneous prism cover, ductions, versions, forced duction test, esotropia/exotropia subtypes (infantile, accommodative, partially accommodative, intermittent, sensory), Brown syndrome, Duane retraction syndrome, congenital fibrosis

~25%

Sensory Testing and Binocular Vision

Worth 4-dot, Bagolini lenses, Maddox rod and double Maddox rod, stereoacuity (Titmus/Randot/Lang/TNO), ARC vs. NRC, subjective/objective angle, fusional vergence amplitudes, prism bar, AC/A ratio (gradient and heterophoria methods), monofixation syndrome, 4Δ base-out test, suppression

~20%

Amblyopia Diagnosis and Management

Strabismic, anisometropic, deprivation, and organic amblyopia; critical period; patching protocols; atropine penalization; visual acuity testing in children (Teller Acuity Cards, LEA symbols, HOTV, preferential looking); Bruckner test; fogging for latent nystagmus patients

~15%

Neuro-Ophthalmology and Nystagmus

CN III, IV (Parks-Bielschowsky three-step), and VI palsies; INO and MLF; horizontal gaze palsy; PPRF lesions; skew deviation; DVD; nystagmus classification (jerk, pendular, latent, infantile, periodic alternating, spasmus nutans); null zone; Kestenbaum-Anderson surgery principles; albinism; optic nerve hypoplasia

~10%

Ocular Anatomy, Physiology, Optics, and Recertification

Extraocular muscle anatomy and primary/secondary/tertiary actions, innervation (CN III, IV, VI), Hering's law, Sherrington's law, cycloplegic refraction, refractive errors, Panum's fusional area, retinal disparity, AOC recertification requirements (45 CE/3 years, 30 core)

How to Pass the AOC C.O. Exam

What You Need to Know

Passing score: Criterion-referenced passing standard set by AOC
Exam length: 100 questions
Time limit: Written exam in June (computer-based, Pearson VUE); oral/practical in September
Exam fee: $800

Keys to Passing

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

AOC C.O. Study Tips from Top Performers

1Master the prism and alternate cover test — know the difference between the manifest angle (SPCT) and the total dissociated angle (PACT)

2Learn the AC/A ratio gradient and heterophoria calculation methods, and know when bifocal lenses are indicated (high AC/A with near > distance esotropia)

3Study all strabismus subtypes systematically: infantile esotropia features, accommodative vs. partially accommodative, Duane type I/II/III, Brown, Mobius, CFEOM

4Memorize extraocular muscle primary/secondary/tertiary actions and apply them to the Parks-Bielschowsky three-step test for CN IV palsy

5Practice interpreting Worth 4-dot responses: 4 dots = fusion, 5 dots = diplopia, 3 dots = RE suppression, 2 dots = LE suppression

6Understand the differences between stereo tests: Titmus fly (3000 arcsec, monocular cues present) vs. Randot/TNO (random dot, no monocular cues, confirms true cortical stereopsis)

7Know ARC — subjective angle = 0 in harmonious ARC while objective angle is non-zero; Bagolini lenses test ARC under natural viewing conditions

8Review amblyopia treatment protocols including PEDIG trial outcomes for patching vs. atropine, and the fogging technique for patients with latent nystagmus

9Study neuro-ophthalmology: INO (MLF lesion), sixth nerve palsy as false localizing sign in raised ICP, skew deviation pattern, and nystagmus null zone management

10Use the AOC Syllabus of Orthoptic Instruction as your primary content guide — it is the basis for both the written and oral/practical examinations

Frequently Asked Questions

What is the AOC Certified Orthoptist (C.O.) credential?

The Certified Orthoptist (C.O.) is the national credential granted by the American Orthoptic Council (AOC) to healthcare professionals who have completed an accredited orthoptic fellowship and passed board examinations. Orthoptists specialize in evaluating and non-surgically managing disorders of ocular motility, strabismus, amblyopia, binocular vision, and nystagmus in patients of all ages, typically working under ophthalmologist supervision.

What are the eligibility requirements for the AOC C.O. board exam?

Candidates must hold a bachelor's degree and complete a 24-month AOC-accredited orthoptic fellowship program (minimum 2,000 supervised clinical hours and 1,250 patient encounters). Advanced-standing candidates (with prior COT or COMT certification) may qualify with a minimum of 12 months. Program director recommendation is required before examination eligibility. International candidates must also pass the European Diploma for Orthoptists and demonstrate English proficiency.

What does the AOC board examination consist of?

The AOC board examination has two sequential parts: (1) a written exam administered electronically at Pearson VUE testing centers, scheduled during June, and (2) an oral/practical examination held annually in September. The written exam must be passed before the candidate may sit for the oral/practical. The total board examination fee is $800.

What content does the AOC written exam cover?

The written exam is based on the AOC Syllabus of Orthoptic Instruction and Core Competency: Essential Skills for Orthoptists. Core topics include ocular anatomy and neuroanatomy, sensory and motor physiology, pharmacology, optics, visual acuity assessment, amblyopia detection and treatment, nystagmus, strabismus evaluation and treatment (including special forms such as Brown, Duane, Mobius syndromes), and electrophysiology principles.

How do I maintain my AOC C.O. certification?

AOC recertification requires completing 45 continuing education credits per 3-year cycle. At least 30 credits must address core subject matter, and at least 10 of those 30 core credits must come from attendance at approved meetings (AACO, AOC, AAPOS, or similar organizations). CE can also be earned through peer-reviewed publications (10 credits), presentations (5 credits), journal quizzes, and webinars/virtual meetings.

How long does orthoptic fellowship training take?

Orthoptic fellowship training is a 24-month post-graduate clinical program (or a minimum of 12 months for advanced-standing students with prior ophthalmic medical credentials). Programs combine didactic coursework (anatomy, physiology, optics, pharmacology, pediatric ophthalmology) with supervised clinical training. Annual tuition typically does not exceed $5,000 per year. A list of AOC-accredited programs is maintained on the AACO website.

What clinical skills does an orthoptist need for the practical/oral exam?

The oral/practical examination assesses competency in: cover testing and prism measurement techniques, sensory testing (Worth 4-dot, Bagolini lenses, stereoacuity, Maddox rod), amblyopia evaluation and treatment planning, interpretation of ocular motility findings including cranial nerve palsies and restrictive strabismus, nystagmus assessment, and patient communication and clinical reasoning.