How Hard Is the ABO Exam?

The format and the passing score

The NOCE has 125 multiple-choice questions in 2 hours, and only 100 of them count; the rest are unscored pretest items. That is about 58 seconds per question: plenty for a recall question, tight for multi-step optics math. For the full format and domain breakdown, see how many questions are on the ABO exam.

You need a scaled score of 70 to pass, and that is not the same as 70% correct. Raw scores are converted to a scale that holds every version of the exam to the same standard, so there is no fixed number of questions you can afford to miss. Aim to be comfortably above the line on realistic practice tests rather than hovering near it.

What ABO-NCLE publishes about pass rates

ABO-NCLE publishes single-year pass rates. For 2024 it reported 64% for the ABO basic exam and 59% for the NCLE basic exam (the CLRE). The advanced exams were lower: 52% for ABO Advanced and 42% for NCLE Advanced.

Rates move from year to year, and a pass rate cannot tell you how you will do. Treat it as a sign that the exam deserves real preparation, and be wary of pass-rate figures that don't name a source.

Where candidates lose points

Optics math. Ophthalmic Optics is the largest domain, at 25 of the 100 scored questions. Transposition, Prentice's rule, decentration, vertex compensation and spherical equivalent each take a minute or more, and one arithmetic slip or sign error turns a concept you know into a wrong answer. Many working opticians rarely do these calculations by hand, so the skill is rusty on exam day.

Prism. Base direction, splitting and combining prism, the direction of prism induced by decentering plus and minus lenses, and vertical imbalance at the reading level all need a clear mental picture, not memorized phrases. Slab-off is a classic trap: conventional slab-off goes on the more minus (least plus) lens.

Standards. ANSI Z80.1 tolerances for prescription lenses and ANSI Z87.1 rules for safety eyewear are pure memorization, and the numbers are easy to confuse. Under Z87.1, for example, a basic-impact prescription safety lens needs a minimum thickness of 3.0 mm (2.5 mm if its most plus meridian is +3.00 D or more), while 2.0 mm is the high-impact minimum.

Topics outside your daily work. Students fresh from a program may know anatomy, laws and lens theory well but find practical troubleshooting scenarios harder; for experienced dispensers it can be the reverse. The exam samples all six domains, so gaps on either side cost points.

Pacing and reading. With under a minute per question, getting stuck on one calculation costs time you need elsewhere. Answer choices are often close, so a misread meridian, unit or base direction turns a known fact into a miss. Transposing +0.75 -1.75 × 065, for example, gives -1.00 +1.75 × 155. A choice of -1.00 +1.75 × 065 differs only in the axis, and +1.00 +1.75 × 155 only in the sign of the sphere, so a rushed reading can pick either.

A study plan that targets the hard parts

Week 1: take a practice test cold and sort your misses by domain. Our free ABO practice test gives you a 20-question mock drawn from every category each day.

Weeks 2–4: optics and prism first, because they carry the most points and use the most time. Work problems by hand every day with new numbers, then check them with the optical calculators. Read the prism study guide until you can sketch the base direction for any decentration without thinking.

Weeks 5–6: ophthalmic products, dispensing and instrumentation, then standards. Build a one-page sheet of ANSI Z80.1 tolerances and Z87.1 safety rules and review it every few days; the ANSI study guide is a good starting point.

Weeks 7–8: at least two timed, full-length practice runs under exam conditions, with a review of every miss. Register for your window before its deadline, but schedule your Prometric appointment once your practice scores sit comfortably above the 70% practice target (a study benchmark, not the scaled passing score), not the first time they touch it.

Stretch or shrink the plan to fit your starting point: newer candidates may need longer, and experienced opticians who only need math and standards work may need less. For a fuller schedule, see how to study for the ABO exam.

If you don't pass, you can retest 14 days after your exam date, with three attempts before a 90-day wait, and each attempt costs the full $225 fee. Use the content-area feedback on your score report to aim the next round of study.

Frequently asked questions

Keep reading

• ABO-NCLE Exam Dates and Registration
• The ABO Practical Exam: What It Is and How to Prepare
• Pantoscopic Tilt: What It Is and How to Fit for It
• What Is ABO Certification?