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Questions and Answers
What does Single Vision correct?
What does Single Vision correct?
What does Multifocal lenses do?
What does Multifocal lenses do?
What is a Bifocal lens?
What is a Bifocal lens?
A lens having two focus strengths.
What does a Trifocal lens pertain to?
What does a Trifocal lens pertain to?
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What is the purpose of Calculating Prismatic Effects?
What is the purpose of Calculating Prismatic Effects?
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What is the formula given in Prentice's Rule?
What is the formula given in Prentice's Rule?
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What does Vertical Imbalance refer to?
What does Vertical Imbalance refer to?
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What factors are involved in the minimum blank size formula?
What factors are involved in the minimum blank size formula?
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What does ANSI stand for?
What does ANSI stand for?
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What is the role of the FDA?
What is the role of the FDA?
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The distance between lenses is referred to as ______.
The distance between lenses is referred to as ______.
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Study Notes
Optical Terms and Definitions
- Single Vision: Corrects vision for one distance only.
- Multifocal: Lenses that correct vision with two or more prescriptions.
- Bifocal: A lens with two different focus strengths for viewing at different distances.
- Trifocal: A lens with three different focus strengths.
Optical Measurements and Instruments
- Calculating Prismatic Effects: Achieved by altering edge thickness during lens surfacing or by de-centering the optical center.
- Lensmeter: An instrument for verifying eyeglass prescriptions and marking lenses.
- Lens Measurement Devices: Includes lens clocks, calipers, millimeter rulers, and circumference gauges for accurate measurements.
- Digital Measurement System: Provides digital readings for measurements such as pupillary distance (PD) and segment height.
Prisms and Compensation
- Compounding Prism: Combining two or more prisms in various configurations (BI & BI, BO & BO, BU & BD).
- Cancelling Prism: Specific combinations like BI & BO or BD & BD that neutralize prism effects.
- Prentice's Rule: Formula (P=hcm x D) calculates the prism created based on lens movement and power in the error meridian.
- Vertex Compensation: When a plus lens is moved away from the eye, it appears to gain plus power.
Centration Techniques
- Horizontal Centration: Measured using pupillary distance (PD).
- Vertical Centration: Measured using the optical center (OC).
- Centration Formula: Calculated as Given PD/OC - Human PD/OC to determine lens positioning.
Lens Power and Measurement
- Power in Oblique Meridians: Calculated using Dt= (sina)²x Dc +Ds to find the total power required considering both cylinder and sphere powers.
Hand Tools for Eyewear Adjustment
- Screwdrivers: Different types designed for specific tasks, like the scratchless screwdriver for delicate lenses.
- Pliers: Various pliers such as lens axis pliers and temple angling pliers are used to adjust frame fittings without damaging them.
- Files: Used for different purposes including filing plastic frames and screw heads.
Frame and Face Shape Considerations
- Frame Fit: Importance of balance and comfort for various face shapes (e.g., larger frames for inverted triangle shapes).
- Face Shapes Guidelines: Specific recommendations for frame types based on face shape to ensure proper aesthetics and comfort.
Regulatory Bodies
- ANSI (American National Standards Institute): Develops voluntary consensus standards in the U.S.
- ASTM (American Society for Testing and Materials): Focuses on developing testing standards.
- EPA (Environmental Protection Agency): Federal agency for environmental protection programs.
- OSHA (Occupational Safety and Health Administration): Standards for workplace safety and health.
- FDA (Food and Drug Administration): Ensures foods and drugs are safe for public use.
- FTC (Federal Trade Commission): Protects consumers from deceptive advertising.
Exam and Measurement Techniques
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Measuring Segments:
- Bifocal: Measure from the bottom lid to the frame bevel.
- Trifocal: Measure from the lower edge of the pupil to the frame bevel.
- Progressive: Measure from the center of the pupil to the bottom of the frame.
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Key Measurements:
- A and B measurements: Horizontal and vertical depth of frames, respectively.
- DBL: Minimum distance between lenses.
- ED: Effective diameter determined by the longest radius of the lens.
Frame Fitting Considerations
- Bridge Pressure: Weight distribution on the nose, affecting comfort.
- Ear Pressure: Critical for achieving comfort through correct adjustment.
Additional Terms
- Datum Line: Reference point for lens measurements.
- Minimum Blank Size Formula: Helps determine the size of lens needed based on the effective diameter.
- Fitting Triangle: Proper fitting should touch three key points for balanced pressure distribution on the face.
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Description
This quiz consists of flashcards that cover essential optical terminology used in lens prescriptions. Each card defines a key term related to vision correction, including single vision, multifocal, bifocal, and trifocal lenses. Test your knowledge on these important concepts relevant to optics and optometry.
