American Board of Opticianry (ABO) Practice Test

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What does a distometer measure?

  1. The characteristic of a minus lens

  2. The limbus in conjunction with the cornea and sclera

  3. The blue portion of light on the visible spectrum

  4. The vertex distance

The correct answer is: The vertex distance

A distometer is a tool used to measure the vertex distance of a lens. The vertex distance refers to the distance between the back surface of a lens and the cornea of the eye. This distance is important in determining the proper fit of a lens and ensuring optimal visual acuity. The other options are incorrect because they refer to specific characteristics or parts of the eye, rather than measuring distance.