W6 Unwanted Vertical Prism

Question 1

Unwanted vertical prism is a result of a …

Answer 1

misplacement of lens height

Question 2

Unwanted horizontal prism is a result of a…

Answer 2

misplacement of the PD.

Question 3

a difference in vertical prismatic effects between the two eyes due to a vertical misplacement of the OC (or PRP). This misplacement causes the image in each eye to be seen on two different planes. The larger the vertical imbalance the greater the separation between the two object planes

Answer 3

Unwanted vertical prism

Question 4

Unwanted vertical prism is commonly referred to as:

Answer 4

Vertical Imbalance

Question 5

These reduce the chances of unwanted vertical prism

Answer 5

measuring and requesting an accurate OC height
preadjusting the frame prior to performing patient measurements
calculating and performing vertical decentration correctly

Question 6

Center and spot the lens with the strongest 90 meridian power.

Switch to the weaker lens and center horizontally, ensuring that only vertical prism is displayed.

Read the prism amount, base direction, and spot the location of the prism being read.

Perform the millimeter test if the prism displayed is greater than 0.33^ diopters.

Move the frame table to center the lens vertically and spot the optical center.

Measure the vertical distance between the PRP (the vertical prism point) and the OC.

If the distance is greater than 1mm the lens fails ANSI vertical tolerance.

Answer 6

How to measure unwanted vertical prism

Question 7

When applying ANSI vertical prism tests,
…
the prism and millimeter tests must be passed in order to pass ANSI

Answer 7

One of

Question 8

Unwanted vertical prism is measured in the … lens and that can be either the right or left lens depending on the lens power.

Answer 8

Weaker lens