# CHPT 3: LENS FORM

A ___ is perfectly round

sphere

A ___ ___ or lens can be thought of like the top one third of a tennis ball.

spherical cornea

what lens produces a single focal point for all he light passing through it?

spherical cornea (lens)

when a person's cornea is misshapen they have ??

a astigmatism

A ___ has two different curves, instead of being the same in all areas.

cylinder

___ is a notation of position in relation to the cornea and the corrective lens

axis

what kind of lens is this - the front surface of the lens is tapered away from the center

aspheric

___ ___ is the formula used to switch between the two different ways of writing a prescription

flat transposition

___ is used to alter the perceived image of an object so that the brain interprets it as being in the right place

prism

the use of ___ is a balance of ___ and power

prism, balance

if we alter the position of the apex we will alter the perceived ___ of the object being viewed

position

if we alter the power (thickness) of the prism we will alter the percieved ___ the object position will move

distance

When we place that point in front of the patients eye that point on the lens that fills the prism required in a written prescription that point becomes ___

MRP

what is MRP

lens major reference point

P = hcm X D
what formula is this?

prism prentice's formula

P = hcm X D
what does the P stand for?

the amount of prism created

P = hcm X D
the distance from where the wearer is actually looking the lens and where they should be looking (the lens OC) in centimeters*
this definition fits what term in the equation?

hcm

P = hcm X D
D stands for?

the lens diopter power in the meridian than you are checking

since we work in millimeters you must divide you answer by___ when using the prism ___ formula

10, prentice's

are these canceling or compounding effects - in regards to Prism Prentice's Formula?
BU/BU

canceling

are these canceling or compounding effects - in regards to Prism Prentice's Formula?
BU/BD

compounding

are these canceling or compounding effects - in regards to Prism Prentice's Formula?
BD/BD

canceling

are these canceling or compounding effects - in regards to Prism Prentice's Formula?
BI/BI

compounding

are these canceling or compounding effects - in regards to Prism Prentice's Formula?
BI/BO

canceling

are these canceling or compounding effects - in regards to Prism Prentice's Formula?
BO/BO

compounding

___ questions are done with the power of 180

PD

___ questions are done with power at 90

OC