ABO Cheat Sheet 2026

The 30 highest-yield ABO facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which contact lens care solution component is responsible for killing microorganisms? → Disinfectant (such as hydrogen peroxide or polyquaternium)
2. What is the approximate normal central corneal thickness in adults? → 520-560 microns
3. Which organization administers the ABO (American Board of Opticianry) certification examinations? → The American Board of Opticianry (ABO)
4. What is the primary advantage of silicone hydrogel contact lenses over conventional hydrogel lenses? → Significantly higher oxygen transmissibility (Dk/t)
5. Which of the following best describes 'prism thinning' in lens fabrication? → Decentering the lens blank to reduce edge thickness on one side
6. The power of a spherical refracting surface is calculated using which formula? → P = (n' - n) / r
7. Anisometropic amblyopia develops primarily because: → A significant refractive difference between the two eyes causes chronic blur in one eye
8. Which condition is characterized by a ring scotoma that most severely affects mobility and orientation rather than fine reading tasks in early stages? → Retinitis pigmentosa
9. Which parameter most directly influences the tear exchange beneath a rigid gas-permeable contact lens? → Edge lift (axial edge clearance)
10. Which refractive condition results from a cornea with greater curvature in the vertical meridian than the horizontal? → With-the-rule astigmatism
11. A patient whose exophoria is significantly greater at distance than at near most likely has which binocular vision condition? → Divergence excess (or simulated divergence excess)
12. Topical carbonic anhydrase inhibitors (e.g., dorzolamide) lower IOP by: → Reducing aqueous humor production
13. A dispensary employee accesses a patient's prescription records out of curiosity without a treatment, payment, or operations reason. This violates: → HIPAA minimum necessary standard
14. The minimum recommended Dk/t for daily wear soft lenses to avoid significant corneal hypoxia is approximately: → 24 × 10⁻⁹
15. Slab-off (bicentric grinding) is used in spectacle lenses to compensate for: → Vertical prism imbalance at near in anisometropic patients
16. When measuring the fitting height for a progressive addition lens, the measurement is taken from: → The pupil center to the lowest edge of the frame
17. A patient with 4.00 D of axial myopia has an eye axial length that is approximately how much longer than emmetropic? → 1.4 mm
18. Which type of bifocal segment provides the widest near reading area? → Executive (full-width) segment
19. When dispensing a frame to a patient with a high nose, which bridge adjustment is most appropriate? → Increase the splay angle of the nose pads
20. Which lens material property is most important in reducing lipid deposit formation on contact lenses? → Ionic surface charge (FDA Group IV materials)
21. What effect do variations in vertex distance have on a high-minus lens's effective power? → Increasing the vertex distance decreases the effective power
22. Which of the following mistakes will a four-point touch test miss? → Skewing
23. What is the function of the "add power" in bifocal lenses? → To provide additional magnification for near tasks in presbyopic patients
24. Under ANSI Z80.1 standards, the maximum allowable cylinder power tolerance for a lens with a prescribed cylinder of -2.00 D is: → ±0.09 D
25. A hypertropia is defined as a vertical deviation in which the deviating eye turns: → Upward
26. The ABO Code of Ethics requires opticians to represent their qualifications honestly. This means an optician should NOT: → Claim to hold an NCLE certification without having earned it
27. In retinoscopy, a 'with' motion of the reflex indicates what type of refractive error? → Hyperopia or insufficient minus correction
28. Which structure of the eye is primarily responsible for focusing light at different distances? → Crystalline lens
29. What is the primary risk factor for open-angle glaucoma in the United States? → Elevated intraocular pressure
30. Which ANSI standard governs the requirements for prescription ophthalmic lenses in the United States? → ANSI Z80.1