Pass your ABO or NCLE with confidence.

Exam-style practice questions, timed mock exams, and clear explanations for every answer, written for opticians.

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6 months of access · One-time payment · Independent prep, not affiliated with ABO-NCLE

Independent: not affiliated with ABO-NCLE or IJCAHPO. Last reviewed Oct 22, 2026.

ABO: measure a frame with the boxing system

Tap the glasses to see an optician measurement

Read the ABO certification guide
NCLE: read a contact lens blister label

Tap the blister pack to open it and read the label
Read the NCLE certification guide
COA: take K readings with a keratometer

Tap the keratometer to measure the cornea
Read the COA certification guide

Sample question · Ophthalmic Optics · Vertical imbalance

A patient wears OD −3.00 D sphere and OS −1.00 D sphere. When reading, they look through points 10 mm below both optical centers. What is the vertical prismatic imbalance?

Show the worked answer

Answer: B, 2.00Δ

Apply Prentice's Rule to each eye with 10 mm = 1.0 cm. OD: 1.0 × 3.00 = 3.00Δ; OS: 1.0 × 1.00 = 1.00Δ. Both are minus lenses viewed below the optical center, so the base points away from the optical center — base down in both eyes. When the bases are in the same direction, subtract: 3.00 − 1.00 = 2.00Δ of vertical imbalance. If the bases were in opposite directions you would add them instead.

Read the Prentice’s Rule guide

The three exams

Formats from ABO-NCLE and IJCAHPO. Each guide links to the official source.

ABO, NCLE, and COA exams compared
Exam	Who it’s for	Format	Content areas	Study
ABO Basic , by ABO-NCLE	Opticians who dispense eyeglasses	125 questions · 2 hours	6 domains: optics, products, dispensing, standards	Guide to the ABO Basic exam Practice ABO Basic questions FAQ about the ABO Basic exam
NCLE Basic , by ABO-NCLE	Opticians and technicians who fit contact lenses	125 questions · 2 hours	8 domains: prefitting, fitting, dispensing, follow-up	Guide to the NCLE Basic exam Practice NCLE Basic questions FAQ about the NCLE Basic exam
COA® , by IJCAHPO	Ophthalmic assistants working with an ophthalmologist	200 questions · 180 minutes	22 content areas, history-taking to tonometry	Guide to the COA® exam Practice COA® questions FAQ about the COA® exam

Study topics

Guides with worked examples, each paired with practice questions.

Prentice’s Rule

Induced prism from lens power and decentration, base direction, vertical imbalance.

Guide: Prentice’s Rule · ABO practice
Lens transposition

Plus- and minus-cylinder form, power crosses, spherical equivalent.

Guide: Lens transposition · ABO practice
Keratometry basics

Reading K values, millimeter-to-diopter conversion, corneal astigmatism.

Guide: Keratometry basics · NCLE practice
COA study plan

A plan weighted by IJCAHPO’s 22 content areas, with an example 8-week schedule.

Guide: COA study plan · COA practice
Exam fees and passing score

The 2026 ABO and NCLE fee, retake and change costs, and how passing is decided.

Guide: Exam fees and passing score · All exam FAQs
Careers in eye care

How people become opticians and ophthalmic assistants.

Guide: Careers in eye care · State licensing

See the optics

Two concepts every candidate meets, as diagrams you can operate.

How a lens bends light

Plus (convex) lens: parallel rays bend toward the axis and converge at the focal point F behind the lens.

The duochrome (red-green) test

Equal on both sides: the red and green images straddle the retina evenly. This is the balanced endpoint.

Calculators

Prentice’s Rule calculator Prism and base direction from lens power and decentration, with the working shown.
Transposition calculator Plus- and minus-cylinder form, with the power cross.
All free tools and simulators Lensometer, keratometer and tonometer simulators plus every optics calculator.

Key exam guides

How hard is the ABO exam?The official pass rate and what makes it challenging.
ABO and NCLE exam dayID, arrival, breaks and the on-screen calculator.
ABO exam in a weekA 7-day final review plan by content area.
ABO exam formulas cheat sheetEvery core optics formula with a worked example.
How hard is the NCLE exam?The official pass rate and the heaviest content areas.
NCLE exam formulasVertex, keratometry and tear-lens math with worked examples.
COA exam cost and passing scoreIJCAHPO fees, retest costs and how the exam is scored.
How to become an opticianTraining, certification and licensing, step by step.
Optician license by stateWhich states license opticians and what they require.

The full ABO course

Self-paced ABO Basic exam prep on learn.optical.education.

11 chapters by content area
Chapter quizzes with explanations
Two full-length timed mock exams
6 months of access

$59 one-time, for 6 months of access

See what’s inside

The NCLE Basic and COA® courses are available too, $59 each. See all courses

Secure checkout by Stripe. Independent: not affiliated with ABO-NCLE. No pass guarantee.

Does your state license opticians?

Licensing is set state by state. We’ve verified 13 states on official board websites. Search our state guide for the board, the official link, and the date we checked.