Resolving Prisms and Bi-Centric Lenses

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Questions and Answers

What angle measurement is represented in this context?

130.5°

150.0°

143.13° (correct)

125.25°

The value of y represents the vertical meridian component.

False

What does CAH likely symbolize in this context?

Cosine of angle A over Hypotenuse

The value y represents the _____ Meridian component.

Horizontal Signup and view all the answers

Match the components with their meanings:

CAH = Cosine of angle A over Hypotenuse BO = Base of an Oblique angle BI = Height of an Oblique angle y = Horizontal Meridian component Signup and view all the answers

What is the prescription strength of the spectacle lenses in Example 3?

-3.75/+5.00 x 90 Signup and view all the answers

The spectacles became aligned after the patient dropped them.

False Signup and view all the answers

What sport was the patient playing when the spectacles fell?

volleyball Signup and view all the answers

The prescription of the lenses can be represented as _______ x 90.

-3.75/+5.00 Signup and view all the answers

Match the following terms related to resolving prisms:

Resolution = Clarity of vision Prism = Optical element that refracts light Misalignment = Improper alignment of optical components Spectacles = Eyewear to correct vision Signup and view all the answers

What does the abbreviation PE stand for in the context of eye treatment?

Prismatic Effect Signup and view all the answers

Both methods aim to eliminate or standardize the prismatic effect.

True Signup and view all the answers

Which method is considered more appropriate for eye treatment and why?

Making the two eyes the same PE is more appropriate because it standardizes the visual experience. Signup and view all the answers

To improve vision, one method aims to make the two eyes the same _____ effect.

prismatic Signup and view all the answers

Match the methods of addressing prismatic effects with their main focus:

Take away all prismatic effect = Eliminate variations in vision Make the two eyes the same PE = Standardize visual experience Signup and view all the answers

What does the term 'bi-centric' mean in the context of lenses?

Having two optical centers Signup and view all the answers

A bi-centric lens has only one point of no prismatic effect.

False Signup and view all the answers

What is the name given to a point where there is no prismatic effect?

Optical center Signup and view all the answers

Compounding of prisms refers to putting together two prisms to form one prism that is the equivalent of both, and this process is known as __________.

putting together Signup and view all the answers

Match the following definitions with their terms:

Compounding = Putting two prisms together Resolving = Breaking an oblique prism into components Optical center = Point with no prismatic effect Bi-centric lens = Lens with two optical centers Signup and view all the answers

What formula is used to get 'c' when resolving prisms?

P = cF on H and on V Signup and view all the answers

The eye is looking towards the horizontal meridian in the example provided.

False Signup and view all the answers

In the example provided, what is the value of the resultant PE?

5∆ BU and BO @ 143,13 Signup and view all the answers

To resolve prisms, the formula used is P = cF on _ and on _.

H, V Signup and view all the answers

Match the following terms with their appropriate descriptions:

P = Prism diopter measurement c = Constant related to the prism F = Force or impact on the eye RE = Resultant eye position Signup and view all the answers

Study Notes

Resolving Prisms

Example 1:
- Prescription: +5.00/-3.00 x 90
- Resultant Prism: 5∆ BU and BO @ 143.13°
- Question: Patient is looking towards the vertical and horizontal meridians.
- Solution: Decenter the lens or place a prism into the spectacle lens.
Example 2:
- Scenario: Patient uses spectacles while playing volleyball, they fall and misalign.
- Problem: The spectacles are misaligned and need to be corrected.
- Goal: Eliminate all prismatic effects in both eyes and make their prismatic effect the same.
- Solution: Two methods are available, the most appropriate one is not specified.
- Calculations:
  - To determine the horizontal meridian component (y) of the prismatic effect, use the formula P = cF for both horizontal and vertical components.

Bi-Centric Lenses

Definition: Bi-centric lenses have two optical centers.
Explanation:
- Bi means two, Centric means centers.
- At the optical center of a lens, there is no prismatic effect.
- Therefore, a bi-centric lens will have two points with no prismatic effect.
Example:
- Scenario: Before placing a prism, a patient is looking at a point 1 cm above the optical center.
- Action: A 4∆ BU prism is placed to eliminate the 4∆ BD (caused by the eye looking at a different point).
- Result: The patient's eye is looking at a point that has both 4∆ BD and 4∆ BU, resulting in zero prismatic effect.
- Conclusion: The point with zero prismatic effect is called the optical center. Since the lens already has its own optical center, and the prism creates another point with no prismatic effect, a bi-centric lens is created.

Compounding and Resolving of Prisms

Compounding: Combining two prisms with different powers and base orientations to create one equivalent prism.
- This process involves adding the vertical and horizontal components to find the resultant in an oblique meridian.
Resolving: Converting an oblique prism into two prisms perpendicular to each other.
- This involves breaking down the oblique prism into its vertical and horizontal components.
Methods: Two primary methods for resolving and compounding prisms are not detailed in the text.

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Description

This quiz covers the principles of resolving prisms, including calculations for correcting misalignment in spectacle lenses. Learn about bi-centric lenses and their significance in optometry. Test your knowledge on how to eliminate prismatic effects for optimal visual clarity.