As a rule, particularly in higher power lenses, the multifocal should be turned around to measure the Add power in the lensometer.  This is because of the difference between front vertex power and back vertex power. 

All of the following are characteristics of a lens to correct simple myopia except:

How many optical centers does a  Single Vision lens of +2.00 -1.00 x180 power have?

According to the NCRP Report #160,

Short Answer Answer the question below correctly listing the acronym for all points. What does ALARA stand for? 

A _____________D lens has a focal length of 1600 mm.

When a single personnel monitoring device is worn, it should be worn at the

One joule of energy absorbed in each kilogram of absorbing material defines the

  The quantity of x-rays or gamma rays required to produce a given amount of ionization in a unit mass of air defines the

All of the following would be effective structural protective barrier materials EXCEPT