American Board of Opticianry (ABO) Practice Test

What is the standard for optical infinity usually measured as?

1. Geometric center

2. Converge

3. Provides approximately 43 diopters of power to an eye's refractive system

4. 20 feet

The correct answer is: 20 feet

The standard measure for optical infinity is typically represented as 20 feet. This is the distance at which a person with normal vision can see objects clearly without any further adjustments to their eye's focus. A geometric center is not used as the standard as it does not have a specific distance or measurement associated with it. The concept of convergence in relation to optical infinity is also incorrect as it refers to the angle at which the eyes must turn inward to fixate on a specific object. Measuring optical infinity as providing 43 diopters of power to a person's refractive system is also not accurate as diopters measure the curvature of a lens and not distance. Therefore, the most relevant and commonly used measurement for optical infinity is 20 feet.