prism basics

Question 1

a prism diopter

Answer 1

a unit that describes the power of a prism to produce a one-centimeter deviation in a ray of light at a distance of one meter from the lens. In other words, one prism diopter will bend a ray of light one centimeter at a distance one meter away.

Question 2

BI

Answer 2

(base-in—thickest part of the prism toward the nose)

Question 3

BO

Answer 3

(base-out— thickest part of the prism toward the temples)

Question 4

BU

Answer 4

(base-up)

Question 5

BD

Answer 5

(base-down)

Question 6

example of a prescription with a prism:

Answer 6

O.D. -2.00-0.25x080 .5Δ BO

O.S. -2.50-1.50x090 .5Δ BO

Question 7

Remember that

Answer 7

light bends toward the base of a prism as it passes through the prism—and the image a person sees moves in the opposite direction from the base (because the retina flips the image). So a doctor can direct the eye to turn in a desired direction by prescribing a certain amount of prism.