American Board of Ophthalmology (ABO) Practice Exam

Disable ads (and more) with a membership for a one time $2.99 payment

Get ready for the American Board of Ophthalmology Exam. Review with flashcards, multiple-choice questions, hints, and detailed explanations to enhance your learning experience. Prepare confidently for your ophthalmology certification.

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

To what index are lens clocks calibrated?

1.50
1.53
1.56
1.58

The correct answer is: 1.53

Lens clocks are calibrated to an index of refraction of 1.53. This calibration is essential because it allows the instrument to accurately measure the surface curvature of lenses, particularly for eyeglasses and contact lenses. When using a lens clock, the measurements taken are based on the assumption that the lens material has a refractive index of 1.53. If the actual index of the lens material differs from this calibration, it could lead to inaccurate assessments of its curvature or thickness. For example, high-index lenses, which usually have refractions indices above 1.53, would yield underestimations of their true power if a lens clock calibrated to 1.53 were used. This understanding is critical for ensuring proper lens fitting and prescription accuracy, reinforcing the importance of the specific calibration point chosen for lens clocks.