Ophthalmic Optics Mt 2

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| Attempts: 1,928 | Questions: 87 | Updated: Mar 21, 2025
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1. A prism will shift an image towards its ______.

Explanation

A prism will shift an image towards its apex. This is because a prism works by refracting light, causing it to change direction. When light enters a prism, it is bent towards the base of the prism. As a result, the image formed by the prism is shifted towards the apex, which is opposite to the direction of the base. Therefore, the correct answer is apex.

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About This Quiz
Ophthalmic Optics Mt 2 - Quiz

The 'Ophthalmic Optics MT 2' quiz assesses understanding of fundamental optical principles, such as reflection, refraction, and the behavior of light through prisms and lenses. It is designed to enhance knowledge of how light interacts with materials, crucial for fields like optometry and optical engineering.

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2. A prism will bend light rays towards its ________.

Explanation

A prism will bend light rays towards its base. This is because when light enters a prism, it undergoes refraction, which is the bending of light as it passes from one medium to another. The angle at which the light bends depends on the angle of incidence and the refractive index of the prism. In a prism, the base is the wider side, and it has a larger surface area for the light to interact with. As a result, the light rays are bent towards the base of the prism.

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3. For a negative lens, it is essentially like 2 prisms with their bases facing ____.

Explanation

A negative lens is essentially like two prisms with their bases facing outward. This means that the lens has a thinner center and thicker edges, causing light rays to diverge or spread out. When light passes through a negative lens, it bends away from the center, creating a virtual image that is smaller and upright compared to the object. The outward facing bases of the prisms in the negative lens cause the light to spread outwards, resulting in the divergence of light rays.

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4. The Seg Inset is the distance between the distance OC and the near OC

Explanation

The statement is true because the Seg Inset refers to the distance between the distance OC (the optical center of the lens) and the near OC (the near optical center of the lens). This distance is important in determining the positioning of the lens in relation to the wearer's eyes and is used in the fitting process of eyeglasses or contact lenses.

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5. A +3.50D lens is decentered 4 mm in and 5 mm down.  What is the resultant prismatic effect?

Explanation

A +3.50D lens decentered 4 mm in and 5 mm down will result in a prismatic effect of 1.4 prism diopters horizontally and 1.75 prism diopters vertically.

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6. What does DBL stand for?

Explanation

measured between the inner edge (edge closest to the lens) of the bridge

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7. Splitting prisms unequally can help to equalize lens thicknesses when lens powers between the 2 eyes are not equal

Explanation

Splitting prisms unequally can help to equalize lens thicknesses when lens powers between the 2 eyes are not equal. This is because prisms can be used to correct for differences in the refractive power of the eyes. By splitting the prisms unequally, the thicker lens can be placed in front of the eye with the lower power, helping to equalize the thicknesses of the lenses. This can improve visual acuity and comfort for individuals with unequal lens powers in their eyes. Therefore, the statement is true.

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8. If there is no prism prescribed for a patient, the PRP will be at the same location as the OC of the lens

Explanation

Prism Reference Point (PRP) is defined as the pont where the OC of the lens should be

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9. The longest vertical height of the frame is called the:

Explanation

The correct answer is B measurement. The question is asking for the term used to describe the longest vertical height of the frame. The term used for this is "measurement."

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10. Because the eye muscles are yoked, prism placed before one eye affects both eyes

Explanation

The statement is true because the eye muscles are yoked, meaning they work together to control the movement of both eyes. When a prism is placed before one eye, it causes a shift in the visual field for that eye, which in turn affects the alignment and movement of both eyes. This is because the brain coordinates the movements of both eyes, so any change in one eye will impact the other eye as well.

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11. For a positive lens, it is essentialy like 2 prisms with their bases facing ____.

Explanation

see lecture 8 pg. 1

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12. Because the add power will always be positive, the power that you measure through the near add will always measure:

Explanation

-Less minus on a nearsighted Rx
-More plus on a farsighted Rx

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13. The goal is to use the smallest lens blank possible that will still fit in the frame

Explanation

The goal of using the smallest lens blank possible that will still fit in the frame is true. This means that when selecting a lens for a frame, the aim is to choose the smallest lens blank that can be cut and shaped to fit the frame properly. This helps to minimize the weight and thickness of the lens, making it more comfortable for the wearer and ensuring a better fit within the frame.

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14. What is refraction based on?

Explanation

Refraction is based on the index of the material. The index of refraction is a property of a material that determines how much the speed of light changes when it passes through that material. When light travels from one medium to another with a different index of refraction, it bends or changes direction. This bending of light is known as refraction. The amount of bending depends on the difference in the indices of refraction between the two materials. Therefore, the index of the material is the determining factor for refraction to occur.

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15. How does one calculate the Frame PD (FPD)?

Explanation

also equals the distance btw the GC of the frame

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16. A 20 pd BU prism will displace an image by what distance at a viewing distance of 5m?  In what direction will the imave be displaced?

Explanation

x/5m = 20cm/1m
x= 100 cm
--> images are displaced toward apex

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17. Your patient's right eye is misaligned with his left eye so that the right is higher than left.  What is the direction of the prism base that you would prescibe for the right eye?

Explanation

point apex toward deviating eye and base will therefore be opposite

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18. What is the name of an instrument that is a tower of mini-prisms that are 1mm thick.

Explanation

many prisms act as one large prism

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19. If a positive lens is shifted temporally what prismatic effect will that produce?

Explanation

Shifting a positive lens temporally refers to moving it horizontally. When a positive lens is shifted horizontally, it creates a base-out (BO) prismatic effect. This means that light rays passing through the lens will be deviated outward, causing an apparent shift in the position of the object being viewed.

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20. How much prism is induced if a +6.50 lens before the right eye is decentered 3mm nasally?

Explanation

induced prism = (0.3)(6.5)= 1.95

*because we are dealing witha (+) lens, and the OC is decentered nasally, the eye will be positioned such that there will be a BI prism

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21. 1 prism diopter = _____ degrees

Explanation

1 rad = 57 deg, 1 pd = 1/100 rad --> 1 pd = 0.57deg

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22. Cement Seg MFs are cement segments that are glued onto the distance portion of lenses

Explanation

The statement is true. Cement Seg MFs refers to cement segments that are attached to the distance portion of lenses. This implies that these segments are used to enhance the distance vision of the individual wearing the lenses.

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23. Indicate the disadvantages of Fresnel Prisms

Explanation

light weight and cheap

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24. Another term for the lens size is:

Explanation

The term "lens size" refers to the measurement of the lens. Therefore, "A measurement" is another term that can be used to describe the lens size.

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25. The larger the lens blank, the thinner the lens will be

Explanation

The larger the lens blank, the thicker the lens will be
-If lens blank is too small it won't fit into frames and if it is too big it may be too thick

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26. As n _____, the speed of light _______.

Explanation

As the value of n increases, the speed of light decreases. This is because the speed of light in a medium is inversely proportional to the refractive index (n) of that medium. When the refractive index increases, it means that the medium has a higher density, causing the speed of light to decrease. This phenomenon is known as the refraction of light.

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27. With horizontal prisms, similar bases are _______.  With vertical prisms, similar bases are ________.

Explanation

With horizontal prisms, similar bases are added because the bases are aligned horizontally and when they are combined, their areas are added together. On the other hand, with vertical prisms, similar bases are subtracted because the bases are aligned vertically and when they are combined, the area of the top base is subtracted from the area of the bottom base.

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28. Prentice's Rule depends solves for:

Explanation

Prentice's Rule is a formula used in optometry to calculate the amount of prism induced by a lens. It states that the prism induced is equal to the power of the lens multiplied by the distance away from the optical center (OC) of the lens in centimeters. Therefore, Prentice's Rule solves for the amount of prism induced, not the power of the lens or the distance away from the OC.

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29. What is the different between compounding and cancellation?

Explanation

The correct answer is that compounding involves addition and cancellation involves subtraction. Compounding refers to the process of adding two or more values together, while cancellation refers to the process of subtracting one value from another. This explanation aligns with the definitions and concepts of compounding and cancellation in mathematics.

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30. The slower the light passes through a lens, the ____ it gets refracted.

Explanation

When light passes through a lens, it gets refracted or bent. The speed at which light travels through a medium determines the degree of refraction. The slower the light passes through a lens, the more it gets refracted. This is because the change in speed causes the light waves to change direction as they enter the lens, resulting in a greater bending effect. Therefore, the correct answer is "more".

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31. The distance between the optical center and the line of sight is the amount of:

Explanation

this amount of decentration is then used to calculate the amount of prism induced by decentration

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32. The major reference point (MRP) of the lens is where the prism amount is unequal to the amount that has been prescribed for the patient.

Explanation

The MRP is the point on the lens where the prism amount is equal to the amount that has been prescribed for the patient.

-When there is no prism called for in the prescription, the OC and the MRP are exactly the same

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33. How can we ensure that there is no unwanted, induced prismatic effects?

Explanation

To ensure that there are no unwanted, induced prismatic effects, it is important for the optical center to coincide with the line of sight. This means that the point where light rays converge in the lens should align with the direction in which the individual is looking. When the optical center and line of sight coincide, it helps to minimize any distortion or prismatic effects that may occur, providing a clear and accurate visual experience.

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34. Reflection is when light rays are redirected in a different direction, usually with a loss in amplitude

Explanation

Reflection is when light rays are redirected in a different direction, usually WITHOUT the loss of amplitude.
Refraction is the redirection of light rays due to the loss in amplitude.

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35. The coordinate system for prism is the same as with cylinder axis.

Explanation

Similar: the zero degree marks the start from the observer's right and increases CCW
Dissimilar: a zero degree prism base orientation differs from a 180 degree prism base orientation

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36. Indicate the incorrect match.

Explanation

40 1D
50 2D
60 3D

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37. In which occupations are round segments useful?

Explanation

Round segments can be useful in various occupations. Golfers can benefit from round segments as they are often used to shape the trajectory of the golf ball during a swing. Plumbers may use round segments to cut and shape pipes. Electricians can utilize round segments when working with wires and cables. Painter/artists may find round segments helpful for creating circular shapes or curves in their artwork. Therefore, all of the above occupations can make use of round segments in their respective fields.

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38. For a fused multifocal design, which area has the higher n?

Explanation

In a fused multifocal design, the area with the higher n refers to the refractive index. The refractive index determines how light is bent as it passes through a lens. Since the question is asking which area has the higher n, it means that the near area of the multifocal design has a higher refractive index compared to the distance area. This suggests that the lens is designed to provide better vision for near objects, such as reading or close-up tasks.

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39. What was the Datum System used for?

Explanation

useful when frames were small and symmetrical. by the 1950s frame shapes were more varies and asymmetrical and the Datum System was no longer accurate

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40. C will always be greater than A

Explanation

C will NEVER be greater than A

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41. When neutralizing a pair of glasses you measure +200-075x180. The near add power is +200, the sphere and cyl target lines would read ____ and ____ when viewed through the segment.

Explanation

Put the Rx into a power cross and add the near to each of the meridians

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42. The Segment Depth is the:

Explanation

The segment depth refers to the longest vertical dimension of the segment. This means that it measures the distance from the top edge of the segment to the bottom edge. It is important to determine the segment depth accurately in order to ensure proper fitting of the lens and to provide optimal vision correction for the wearer.

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43. How much power does a prism have if it is able to displace an image by 5cm at a viewing distance of 0.5m?

Explanation

deviation/viewing distance = x/1 m (solve for x)

5cm/0.5m = x/1m
x=10 cm or 10 pd

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44. The amount of prism induced requires knowledge of what factor(s)?

Explanation

Prentice's Rule: induced prism = d(cm) x F
F= power of lens

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45. When do we use the Sine-Squared Method?

Explanation

The Sine-Squared Method is used when the prescription (Rx) has an oblique axis. This method helps in calculating the power of the lens accurately, taking into account the angle of the oblique axis. By using this method, the lens can be properly aligned and adjusted to provide the correct vision correction for the patient.

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46. What is the most preferred bifocal design due to less distortion?

Explanation

The most preferred bifocal design due to less distortion is the flat top design. This design is known for providing a smooth transition between the distance and near vision areas, minimizing any distortion or blurriness. The flat top design also offers a larger reading area compared to other designs, making it more comfortable for the wearer to read or perform close-up tasks.

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47. The full prism power must be placed on the eye that is deviated

Explanation

The full prism power can be placed before one eye or can be divided equally or unequally between the two eyes

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48. How many optical centers do Executive bifocals have?

Explanation

monocentric; results in NO IMAGE JUMP when shifting gaze from distance to near

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49. If a patient requires 4 BO total.  Indicate what possible prisms they can use.

Explanation

The patient can use either 2 BO OD and 2 BO OS prisms or 1 BO OD and 3 BO OS prisms.

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50. As the ledge sticks out more for a flat top, the seg narrows

Explanation

The ledge sticks out more as the seg widens

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51. Curved top are usually ______ and executives are usually ______.

Explanation

Curved top: compromise btw minimizing distortion for near vision and a cosmetically appealing lens
Executive: largest reading area but the most cosmetically unappealing

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52. What is the opticla difference between grinding in prisms and prism by decentration?

Explanation

Both grinding in prisms and prism by decentration are methods used to correct vision problems. However, in terms of optical difference, there is no distinction between the two methods. This means that both methods can achieve similar optical outcomes and correct vision aberrations effectively.

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53. Round segments only come in fused form

Explanation

Round segments can come in fused or bifocal form

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54. In the Box System, the longest horizontal length is considered the _____ when referring to the frame and the _____ when referring to the lens

Explanation

In the Box System, the term "eye size" is used to refer to the longest horizontal length of the frame, while the term "lens size" is used to refer to the longest horizontal length of the lens.

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55. The geometric center is another name for the optical center.

Explanation

The GC is the point on the horizontal midline that is halfway btw the 2 vertical lines bordering the lens. This is not the same as the OC. If you put 2 lines through your 'box' the intersection would be the GC.

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56. One should orient the prism apex away from the deviating eye to place the image where the deviating eye is looking

Explanation

Orient the prism apex TOWARD the deviating eye to place the image where the deviating eye is looking

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57. There are many different materials available for fused glasses designs.

Explanation

For FUSED glasses, you can only use glass

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58. Segment Widtch is measured from:

Explanation

Segment width is measured across the widest portion of the segment. This means that the measurement is taken from one side of the segment to the opposite side, specifically at the point where the segment is widest. This measurement provides an accurate representation of the width of the segment, disregarding any other factors such as corners or frames.

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59. The Minimum Blank Size (MBS) equals:

Explanation

MBS = ED + total decentration + 2mm

Total Decentration= the difference between the FPD and the pt's PD

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60. If a negative lens is shifted inward what prismatic effect will that induce?

Explanation

When a negative lens is shifted inward, it induces a Base In (BI) prismatic effect. This means that the light rays passing through the lens are deviated towards the center of the lens, causing the image to appear shifted towards the nasal (inner) side.

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61. Indicate the clinical uses of prisms.

Explanation

Prisms can be used clinically to reduce eye turns, enhance binocularity/stereopsis, and redirect the image to the patient's fovea to achieve similar retinal images. By reducing eye turns, prisms help correct strabismus and improve eye alignment. They also enhance binocularity and stereopsis, which are important for depth perception and visual integration. Additionally, prisms can be used to redirect the image to the patient's fovea, which can be beneficial in cases of visual field loss or macular degeneration, ensuring that the patient receives a clear and focused image.

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62. What is the height of the intermediate portion for a trifocal lens usually?

Explanation

The height of the intermediate portion for a trifocal lens is usually 7mm.

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63. Indicate the advantages of a Fresnel Prism.

Explanation

Fresnel prims are LIGHT WEIGHT

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64. How does one deterine the 'reference eye'?

Explanation

The 'reference eye' can be determined by identifying the eye with the most power in the 90 meridian. This means that the eye has the highest level of refractive power in the vertical axis. The power in the 90 meridian is important in determining the astigmatism correction needed for a person's vision. By identifying the eye with the most power in this meridian, eyecare professionals can accurately prescribe the appropriate corrective lenses for the individual.

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65. 1 prism diopter = ______ radians

Explanation

The given answer is 1/100. This implies that 1 prism diopter is equal to 1/100 radians.

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66. What components are used to specify a prism?

Explanation

A prism is specified by two components: the base direction and the power. The base direction refers to the orientation of the prism's base, which can be either up, down, in, or out. The power of the prism determines the amount of deviation or bending of light that occurs when it passes through the prism. These two components together define the characteristics and functionality of a prism.

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67. A +4.00D lens is ordered for the right eye.  The Rx calls for 2 BI prism before the right eye.  How should the lens be decentered?

Explanation

The lens should be decentered nasally by 2 pd. This means that the lens should be shifted towards the nose by 2 prism diopters. Decentering the lens nasally helps to correct the eye's alignment and improve visual clarity.

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68. How did the Box System update the Datum System?

Explanation

from these additional vertical lines, other measurements could be attained

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69. When is it apprpropriate to use Prentice's Rule?

Explanation

Prentice's Rule is used to calculate the induced prism in a lens when there is decentration. Decentration refers to the displacement of the optical center of the lens from the visual axis. In this case, when the decentration is perpendicular to the cylindrical axis, Prentice's Rule is appropriate to determine the induced prism. This rule helps in determining the amount and direction of prism that needs to be incorporated in the lens to correct for the decentration.

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70. What type of bifocals have no ledge?

Explanation

No ledge because the distance and near are the same curvature but have a different n for the different portions

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71. A patient is prescribed vertical prisms.  He is wearing 3 pd BU OD and 3 pd BU OS.  What is the total prismatic effect?

Explanation

The question states that the patient is prescribed vertical prisms, but it does not mention the power or direction of the prisms. It only provides information about the patient wearing 3 pd BU OD and 3 pd BU OS, which indicates that the patient is wearing 3 prism diopters base up in both eyes. However, the question does not specify whether these prisms are vertical or horizontal prisms. Therefore, based on the given information, it is not possible to determine the total prismatic effect.

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72. The effective diameter is the distance from the geometric center to the furthest pont on the frame.

Explanation

The effective diameter (ED) is the distance from the geometric center to the furthest pont on the frame TIMES 2. Usually a diagonal measurement and can be the same as the A in some frames.

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73. Segment Height is measured from:

Explanation

Segment Height is measured from the bottom of the frame to the top of the segment. This means that the measurement starts at the lowest point of the eyeglass frame and extends upwards to the highest point of the segment. It is important to measure segment height accurately in order to ensure that the segment of a bifocal or progressive lens is positioned correctly for optimal vision correction.

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74. A patient is prescribed horizontal prisms.  She is wearing 2 pd BI OD and 3 pd BO OS.  what is the total prismatic effect?

Explanation

The patient is prescribed horizontal prisms, with 2 pd BI OD (base in) and 3 pd BO OS (base out). The total prismatic effect is calculated by adding the prism values together. In this case, the total prismatic effect is 1 pd BO (base out).

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75. An angle of 1 radian results in an arc with an equal length to the _______.

Explanation

see lecture 7 pg.2

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76. 1 radian =

Explanation

1 rad = 360/2pi or 57 deg

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77. What factors affect the induced prism due to decentration?

Explanation

The factors that affect the induced prism due to decentration are the cylinder power and the axis orientation. The cylinder power refers to the strength of the astigmatism correction in the lens, while the axis orientation refers to the angle at which the cylinder power is oriented. Both of these factors contribute to the amount and direction of the induced prism when the lens is decentered. The sphere power, on the other hand, does not directly affect the induced prism due to decentration.

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78. What factors are important for measuring the prism power at the center?

Explanation

Prism Power = 100(g)(n-1)/d

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79. A prism is able to displace an image by 4 degrees.  What is the power of the prism?

Explanation

4 deg = (4)(1.75pd) = 7pd

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80. What 3 measurements are used in the Box System?

Explanation

The Box System is a method used to measure eyeglasses frames. It involves three measurements: eye size, bridge width, and temple length. The eye size refers to the width of the lenses, the bridge width is the distance between the lenses, and the temple length is the length of the arms that go over the ears. These measurements are important in ensuring that the eyeglasses fit properly and comfortably on the wearer's face.

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81. What type of materials are commonly used for One Piece MFs?

Explanation

One Piece has a ledge because the distance and near portions are made of the same material but have DIFFERENT CURVATURES

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82. The prism diopter is the unite for prisms and it represents:

Explanation

The prism diopter is a unit used to measure prisms. It represents both the angle of deviation in degrees and the amount of image displacement. The angle of deviation refers to the amount of bending or deviation of light as it passes through the prism. The amount of image displacement refers to the shift in the position of an object when viewed through the prism. Therefore, the prism diopter represents both the angle of deviation and the amount of image displacement.

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83. A patient is prescribed horizontal prisms.  She is wearing 2 pd BO OD and 2 pd BO OS.  what is the total prismatic effect?

Explanation

The patient is prescribed horizontal prisms with a base out (BO) direction. She is wearing 2 pd BO in the right eye (OD) and 2 pd BO in the left eye (OS). The total prismatic effect is calculated by adding the prismatic powers of both eyes together. Therefore, the total prismatic effect is 2 pd BO + 2 pd BO = 4 pd BO.

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84. Which widths are available in round segments?

Explanation

The available widths in round segments are 22, 25, and 28.

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85. What seg widths do flat top/D segs come in?

Explanation

Flat top/D segs come in various widths, including 22, 25, 28, 35, and 45. These widths refer to the size of the segments used in flat top or D-shaped diamond tools. Different widths are available to accommodate different cutting or grinding needs, allowing users to choose the appropriate size for their specific application.

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86. A patient is presribed vertical prisms.  He is wearing 2 pd BU OD and 2 pd BD OS.  What is the total prismatic effect? (2 answers possible)

Explanation

The patient is prescribed vertical prisms, with 2 pd BU OD (base up in the right eye) and 2 pd BD OS (base down in the left eye). The total prismatic effect is the sum of the prism powers in each eye. Therefore, the total prismatic effect is 4 BU OD (2 pd BU OD in the right eye) and 4 BD OS (2 pd BD OS in the left eye).

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87. Select the material and available seg widths for Ultex series.

Explanation

The correct answer is glass,22,32,38,40. This means that for the Ultex series, the available materials are plastic and glass. The available segment widths are 22, 32, 38, and 40.

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A prism will shift an image towards its ______.
A prism will bend light rays towards its ________.
For a negative lens, it is essentially like 2 prisms with their bases...
The Seg Inset is the distance between the distance OC and the near OC
A +3.50D lens is decentered 4 mm in and 5 mm down.  What is the...
What does DBL stand for?
Splitting prisms unequally can help to equalize lens thicknesses when...
If there is no prism prescribed for a patient, the PRP will be at the...
The longest vertical height of the frame is called the:
Because the eye muscles are yoked, prism placed before one eye affects...
For a positive lens, it is essentialy like 2 prisms with their bases...
Because the add power will always be positive, the power that you...
The goal is to use the smallest lens blank possible that will still...
What is refraction based on?
How does one calculate the Frame PD (FPD)?
A 20 pd BU prism will displace an image by what distance at a viewing...
Your patient's right eye is misaligned with his left eye so that...
What is the name of an instrument that is a tower of mini-prisms that...
If a positive lens is shifted temporally what prismatic effect will...
How much prism is induced if a +6.50 lens before the right eye is...
1 prism diopter = _____ degrees
Cement Seg MFs are cement segments that are glued onto the distance...
Indicate the disadvantages of Fresnel Prisms
Another term for the lens size is:
The larger the lens blank, the thinner the lens will be
As n _____, the speed of light _______.
With horizontal prisms, similar bases are _______.  With vertical...
Prentice's Rule depends solves for:
What is the different between compounding and cancellation?
The slower the light passes through a lens, the ____ it gets...
The distance between the optical center and the line of sight is the...
The major reference point (MRP) of the lens is where the prism amount...
How can we ensure that there is no unwanted, induced prismatic...
Reflection is when light rays are redirected in a different direction,...
The coordinate system for prism is the same as with cylinder axis.
Indicate the incorrect match.
In which occupations are round segments useful?
For a fused multifocal design, which area has the higher n?
What was the Datum System used for?
C will always be greater than A
When neutralizing a pair of glasses you measure +200-075x180. The near...
The Segment Depth is the:
How much power does a prism have if it is able to displace an image by...
The amount of prism induced requires knowledge of what factor(s)?
When do we use the Sine-Squared Method?
What is the most preferred bifocal design due to less distortion?
The full prism power must be placed on the eye that is deviated
How many optical centers do Executive bifocals have?
If a patient requires 4 BO total.  Indicate what possible prisms...
As the ledge sticks out more for a flat top, the seg narrows
Curved top are usually ______ and executives are usually ______.
What is the opticla difference between grinding in prisms and prism by...
Round segments only come in fused form
In the Box System, the longest horizontal length is considered the...
The geometric center is another name for the optical center.
One should orient the prism apex away from the deviating eye to place...
There are many different materials available for fused glasses...
Segment Widtch is measured from:
The Minimum Blank Size (MBS) equals:
If a negative lens is shifted inward what prismatic effect will that...
Indicate the clinical uses of prisms.
What is the height of the intermediate portion for a trifocal lens...
Indicate the advantages of a Fresnel Prism.
How does one deterine the 'reference eye'?
1 prism diopter = ______ radians
What components are used to specify a prism?
A +4.00D lens is ordered for the right eye.  The Rx calls for 2...
How did the Box System update the Datum System?
When is it apprpropriate to use Prentice's Rule?
What type of bifocals have no ledge?
A patient is prescribed vertical prisms.  He is wearing 3 pd BU...
The effective diameter is the distance from the geometric center to...
Segment Height is measured from:
A patient is prescribed horizontal prisms.  She is wearing 2 pd...
An angle of 1 radian results in an arc with an equal length to the...
1 radian =
What factors affect the induced prism due to decentration?
What factors are important for measuring the prism power at the...
A prism is able to displace an image by 4 degrees.  What is the...
What 3 measurements are used in the Box System?
What type of materials are commonly used for One Piece MFs?
The prism diopter is the unite for prisms and it represents:
A patient is prescribed horizontal prisms.  She is wearing 2 pd...
Which widths are available in round segments?
What seg widths do flat top/D segs come in?
A patient is presribed vertical prisms.  He is wearing 2 pd BU OD...
Select the material and available seg widths for Ultex series.
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