Prism II Flashcards
If prism in the OD is located in vector III, which direction would the prism be located?
Down and out
If prism in the OD is located in vector I, which direction would the prism be located?
Up and in
If prism in the OS is located in vector I, which direction would the prism be located?
Up and out
If prism in the OD is located in vector II, which direction would the prism be located?
Up and out
If prism in the OS is located in vector II, which direction would the prism be located?
Up and in
If prism in the OS is located in vector III, which direction would the prism be located?
Down and in
If prism in the OD is located in vector IV, which direction would the prism be located?
Down and in
If prism in the OS is located in vector IV, which direction would the prism be located?
Down and out
If a patient is complaining of symptoms of walking up-hill, what type of prism would they be experiencing?
Base down
If a patient is complaining of symptoms of vertical objects appearing shorter, what type of prism would they be experiencing?
Base up
If a myopic patient receives glasses whereby the optical center are wider than their PD, what type of prism will they experience?
Base in
If a hyperopic patient receives glasses whereby the optical center are wider than their PD, what type of prism will they experience?
Base out
If a myopic patient views above the optical center of the lenses, what type of prism will they experience?
Base up
If a hyperopic patient views below the optical center of the lenses, what type of prism will they experience?
Base up
Which of the following would represent canceling prism?
a.) 2 BU OD / 2 BD OS
b.) 2 BU OD / 2 BD OD
c.) 2 BI OD / 2 BI OS
d.) 2 BO OD / 2 BO OS
b.) 2 BU OD / 2 BD OD
Which of the following would represent compounding prism?
a.) 2 BU OD / 2 BD OS
b.) 2 BD OD / 2 BD OD
c.) 2 BI OD / 2 BO OS
d.) 2 BO OD / 2 BO OS
a.) 2 BU OD / 2 BD OS
A patient presents with an rx of the following:
OD -8.00 sph 6 BU / OS -8.00 sph 2 BD
After consulting with the prescriber, it is determined that it would be appropriate in order to make the glasses more cosmetically pleasing and weight balanced, it is acceptable to split the prism. What would the appropriate rx be after splitting the prism?
OD 8.00 sph 4 BU / OS -8.00 sph 4 BD
Given a compound prism of 3 BI and 2 BU in the OD, what would be the resultant prism be?
3.61 - classic Pythagorean theorem right here
A patient presents with an rx of the following:
OD -12.00 sph 10 BU / OS -12.25 sph
After consulting with the prescriber, it is determined that it would be appropriate in order to make the glasses more cosmetically pleasing and weight balanced, it is acceptable to split the prism. What would the appropriate rx be after splitting the prism?
OD -12.00 sph 5 BU / OS -12.25 sph 5 BD
Given a compound prism of 3 BI and 2 BU in the OD, where would the resultant prism be located?
33.69 degrees - SohCahToa
Where is the thickest point on a prism?
Base
Where is the thinnest point on a prism?
Apex
Describe what a prism does to incident white light. Include both dispersion and deviation.
It makes white light into a rainbow via dispersion, and it deviates the light to a steeper angle.
When viewed through a prism that is held base down, the image of an object will be?
Base up
Two rays of light that are parallel to each other before they enter a prism will do what?
Be deviated but stay parallel
When a prism is held with the base to the left, the image viewed through the prism will do what?
Go to the right
The factors that affect how much a ray will be deviated by a prism are what?
The power of the prism, the thickness of the base, and the distance from the object.
If a pair of glasses with a plus rx is made so that the wearer is looking above the optical center of the lens, what type of prism will the wearer experience?
Base down
A pair of minus lenses is cut so that the optical centers are farther apart than the wearer’s pupils. What type of prism will the wearer experience?
Base in prism
When the glasses wearer looks down through the the bottom of plus lenses, what type of prism will the wearer experience?
Base up prism
If the doctor asks for BO prism and the glasses rx has a minus power, where should the OC be with respect to the wearer’s pupil, and why?
The OC should be decentered in from the patient’s pupils, so that they are looking through base out prism
How much prism is in effect 3mm above the OC of a 2.50 DS lens?
Prentice’s rule: P = hd = .3 x -2.50 = -0.75. 0.75 BU
