Lecture 1 - Optical Characteristics Flashcards
How much will a typical patients tolerate a slight error?
+ or - 0.50 D of refractive error
How are Abbe Value and Chromatic Aberation related to one another?
Inversely Proportional
If you a lens has a low index value, what will happen to the Abbe value?
Abbe Value will increase
What is the heaviest lens material?
Glass
What is the lightest lens material?
Trivex
What is the imaginary line connecting the centers of curvature?
Optical Axis
T or F. Light passing through the OC is refracted?
False
Your mother-in-law’s lens PD and DBOC don’t match, what have you done to her glasses?
You have induced prism.
For prism, which way will white light refract?
Base
What type of light is refracted the most and which one is refracted the least?
Most - Violet
Least - Red
What is the primary concern for lens designers?
Marginal Astigmatism
For curvature of field, if marginal astigmatism is fully corrected, what can occur?
Peripherally viewing will decrease
What are the two types of distortion?
Minus - Barrel
Plus - Pincushion
Note: This occurs with lens magnifications through lens PERIPHERY
For people who drive at night, as a doctor what would be your primary concern for your patient?
Spherical Abberration
Light rays that are oblique to the optic axis and cause a comet like tale, what kind of effect or problem is this?
COMA. When you’re looking form the top, the bottom will look larger.
Note: Can be corrected via surgery
As your prescription changes from +2.00 to plano, what has happened to the shape of the lens?
It has flattened
Why is it specific to have a base curve and why not give a base curve for everything?
The clinical abberation would be too high
While looking at a horizontal line, you move a minus sphere lens down, what type of motion will it be Against or With?
With. Minus Sphere
Hint: Think of a concave lens and the line traveling towards the apex.
Using an astigmatic lens, you rotate the lens counterclockwise and you notice the line you look through it is going clockwise, what type of break is this?
Against. Plus lens
When looking at sphero-cylinder lense, what can break tell you and what can the motion tell you?
Break - Meridians
Motion - Power
Note: W will be the most plus or least minus of the two meridians
If an unknown lens shows “against” motion with no trial lens in place. You use a -3.00 trials lens in combination with the unknown lens shows “with” motion. What is the power of the unknown lens?
The power would be less than +3.00
Your patient has rotated his right lens 17 degrees clockwise in order to see better. Their original lens axis is 170 degrees. What is the new axis that you will prescribe?
7 degrees
