Lecture 1: Prism Review and Application

Question 1

1. If a PLANO Cylinder is decentered along its Axis MERIDIAN, what is the PRISMATIC EFFECT?
2. If Decentration is PERPENDICULAR to the CYLINDER AXIS, you have to use what?

Answer 1

It will be ZERO!!

2. PRENTICE’s RULE!!

Question 2

What is Prentice’s Rule?

Answer 2

Prism = dF

Question 3

Decentration of Spherocylinders:

1. What method do we use?
   a. It’s an Approximation
   b. DOESNT take into consideration what exactly?

Answer 3

1. SIN SQUARED METHOD
   a. Only. Instead of F = Fsph + (Fcyl x sin^2(theta))
   b. the VERTICAL PRISM component induced by an OBLIQUE CYLINDER

Question 4

1. What is COMPOUNDING PRISM?

Answer 4

1. When 2 Prisms are combined to MAKE 1 EQUIVALENT PRISM.

Question 5

1. What is RESOLVING PRISM?

Answer 5

1. It’s PRISM w/an OBLIQUE BASE ORIENTATION and expressed as 2 PRISMS w/their BASES PERPENDICULAR to EACH OTHER

Question 6

What can we use in Lab if a Patient Needs COMPOUNDED FRESNEL PRISMS?

a. What does it calculate?
b. What does it Maintain?
c. What does it allow a SLIGHT VARIATION in?

Answer 6

1. Prism Rotation Nomograph
   a. Fresnel Prism base orientation
   b. Exact Vertical Prism
   c. In Horizontal Prism

Question 7

Prism Edge Thickness

1. Finding the Thickness difference b/w the prism base and Apex allows the PRISM AMT to be calculated.

What’s the EQN?

Answer 7

P = 100g(n-1)/d

P = Prism Amt

g = thickness difference b/w apex and base

n = lens index

d = distance b/w apex and the base