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coa vocabulary > Chapter 5: Optics and Refractive States of the Eye > Flashcards

Chapter 5: Optics and Refractive States of the Eye Flashcards

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1
Q

Optics

A

The branch of physical science that deals with the properties of light and vision

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2
Q

Physical Optics

A

The study of optics that describes the nature of light in terms of its wave properties

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3
Q

Geometric Optics

A

The area of optics that deals with the transmission of light as rays and is concerned with the effect of lenses on light and the production of images

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4
Q

Electromagnetic Radiation

A

Radiation produced through the combination of electrical and magnetic forces, includes rays from the shortest to the longest wavelengths, both visible and invisible

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5
Q

Opaque

A

Refers to a substance that completely blocks light from passing through it

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6
Q

Translucent

A

Refers to a substance that transmits light, but significantly interferes with its passage

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7
Q

Transparent

A

Refers to a substance that transmits light without disrupting its passage

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8
Q

Refracted

A

Refers to the change in directions of a light when it passes from one medium to another

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9
Q

Optical Density

A

A lens property that increases the effectiveness to bend light

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10
Q

Refractive Index

A

The ratio of the speed of light in a vacuum to its speed through a specific substance
Formula= Speed of light in vacuum divided by the speed of light in a specific substance

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11
Q

Prism

A

A triangular piece of glass or plastic with flat sides, an apex, and a base.
When light passes through a prism, it is bent in a different direction (towards the base)
Refractive power depends on refractive index and size of its apex angle. 1 prism D deviates light 1cm

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12
Q

Plane

A

Flat

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13
Q

Apex

A

The top of the prism; pointed

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14
Q

Base

A

The bottom of the prism; wider

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15
Q

Converge

A

To come together

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16
Q

Diverge

A

To spread apart

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17
Q

Convex Lens

A

A piece of glass or plastic in which one or both surfaces are curved outward
Also called a Positive, or Plus Lens

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18
Q

Concave Lens

A

A piece of glass or plastic in which one or both surfaces curve inward
Also called a Negative Lens, or Minus Lens

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19
Q

Parallel

A

Refers to rays that travel side by side in the same direction, neither diverging nor converging

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20
Q

Principle Axis

A

The pathway of a light ray that strikes the center of a lens of any shape and passes undeviated through the lens material

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21
Q

Principle Rays, Or Axial Rays

A

A light ray that strikes the center of a lens of any shape and passes undeviated through the lens material

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22
Q

Paraxial Rays

A

Light rays that enter a lens system away from the center
In Convex lenses, Paraxial rays are brought inward to converge at some point along the Principle Axis
In Concave lenses, Paraxial Rays diverge away from the Principle Axis, and instead produce a virtual image

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23
Q

Focal Point

A

The point somewhere along the principle axis at which the paraxial rays from a distant source are refracted by a lens and converge in the case of a convex lens and diverge in the case of a concave lens

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24
Q

Plus Lenses

A

Also called a Convex Lens, or Positive Lens

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25
Q

Minus Lenses

A

Also called Concave Lenses or Negative Lenses

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26
Q

Virtual Image

A

The image formed by a concave lens when the paraxial rays from a distant source are refracted and diverge

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27
Q

Vergence Power

A

Also called Power, it is the measure of a lens’ ability to converge or diverge light rays

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28
Q

Focal Length

A

The distance between the focal point and the lens

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29
Q

Diopters

A

The unit of measurement of Power of a lens
D=1/f (focal length)

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30
Q

Accommodation

A

The change in the curvature of a crystalline lens that helps to focus images of objects close to the eye

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31
Q

Refractive State

A

The relative ability of the refractive components of the eye to bring objects into focus on the retina

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32
Q

Emmetropia

A

The refractive state of the eye that is able to focus correctly without the need for corrective lenses

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33
Q

Ametropia

A

The refractive state of the eye that is unable to focus correctly due to a refractive error and requires corrective lenses

34
Q

Refractive Error

A

A nonpathological deficiency in the eye’s optical system

35
Q

Presbyopia

A

The progressive loss of Accommodation, due to again

36
Q

Myopia

A

Nearsightedness=able to see close, but not far away
Light rays are focused in front of the retina (too much plus power)
Requires Concave lenses to correct

37
Q

Hyperopia

A

Farsightedness= able to see far away, but not close
Light rays are focused behind the retina (too much minus power)
Requires Convex lenses to correct

38
Q

Astigmatism

A

The refractive error of the eye whose corneal surface curvature is greater in one meridian than another
Both distant and near objects will appear distorted

39
Q

Spherical Cornea

A

A cornea whose curvature in all meridians is uniform

40
Q

Toric Cornea

A

A cornea whose surface curvature is not uniform
Light rays are not focused into a single point

41
Q

Principal Meridians

A

The meridians of maximum and minimum corneal curvature, these meridians are at 90 degrees from each other

42
Q

Regular Astigmatism

A

The most common form of astigmatism, in which the cornea resembles a football standing on one end of on its side

43
Q

Irregular Astigmatism

A

The less common form of astigmatism, in which the corneal surface losses its uniformity secondary to scarring or other pathology

44
Q

Types of Corrective Lenses

A

Glasses, contact lenses, refractive surgery, or surgical implantation of a corrective lens

45
Q

Spherical Lens

A

A concave or convex lens whose curvature is uniform

46
Q

Bifocals

A

A lens that has 2 powers, typically one for correcting distance vision and one for correcting near vision

47
Q

Trifocals

A

A lens that has 3 powers: one for correcting distance vision, one for correcting intermediate vision, and one for correcting near vision

48
Q

Multifocal Lenes

A

Any lens that has more than one power

49
Q

Add

A

The portion of the multifocal lens that provides correction for near vision

50
Q

Cylindrical Lenses

A

A lens that has curvature in only one meridian, commonly used to help correct Astigmatism

51
Q

Axis

A

The meridian perpendicular to the meridian with the curvature in cylindrical lens

52
Q

Spherocylinder Lens

A

A combination of spherical and cylindrical lenses
Also called a Toric Lens
Does not refract light rays into a single point, but into 2. The clearest point is called the Circle of Least Confusion

53
Q

Toric Lens

A

Also called a Spherocylinder Lens

54
Q

Lensometry

A

The measurement of certain qualities of lenses by use of a lensometer

55
Q

Refraction

A

The process of measuring a patient’s refractive error. Combination of Refractometry and Clinical Judgement
Steps: Retinoscopy, Refinement, Binocular balancing

56
Q

Retinoscopy

A

The use of a Retinoscope to determine a refractive error
1st step in Reffraction

57
Q

Refinement

A

The subjective 2nd step of Refraction, requiring patient participation and responses, which confirms the information produced with Retinoscopy
Also called Subjective Refractometry or Manifest Refractometry

58
Q

Binocular balancing

A

A procedure performed on both eyes at once to ensure that the optical correction determined by refractometry for distance vision does not include an uneven overcorrection or undercorrection

59
Q

Cycloplegic Refraction

A

Refractometry performed with the use of a drug that temporarily paralyzes the ciliary muscle, thus blocking accommodation
Done in children frequently

60
Q

Manifest Refraction

A

Refractometry performed without the use of cycloplegic drugs

61
Q

Objective Refractometry

A

Also called Retinoscopy

62
Q

Retinoscope

A

A handheld instrument for measuring refractive error, consists of a light source and a viewing component, and is used in conjunction with a phoropter or trial lenses

63
Q

Fixate

A

To gaze steadily at something

64
Q

Plano Mirror Effect

A

The flat lighting effect of a retinoscope that produces slightly divergent rays

65
Q

Concave Mirror Effect

A

The lighting effect of a retinoscope that produces convergent rays

66
Q

With Motion

A

The retinoscopic reflex movement that is in the same direction as the movement of the streak of light from a retinoscope
Typically seen in a Hyperopic eye

67
Q

Against Motion

A

The retinoscopic reflex movement that is in the opposite direction from the movement of the streak of light from the retinoscope
Typically seen in Myopic eyes

68
Q

Neutralization Point

A

The lens power that is the approximate correction for a refractive error. This is the goal of Retinoscopy

69
Q

Trial Lens Set

A

A set of various hand-held lenses introduced before a patient’s eye to select the appropriate corrective lenses
These lenses can be set into a trial frame set

70
Q

Phoropter, or Refractor

A

An instrument for determining a corrective lens prescription; stores a range of trial lenses that can be dialed into position

71
Q

Subjective Refractometry

A

Also called Refinement

72
Q

Cross Cylinder

A

A special lens consisting of 2 cylinders of equal power, one minus and one plus, with their axes set at right angles to each other; used for determining the axis and power of an astigmatic correction

73
Q

OD

A

Right eye (oculus dexter)

74
Q

OS

A

Left eye (oculus sinister)

75
Q

OU

A

Both eyes (oculus uterque)

76
Q

Transposition

A

The conversion of a lens prescription from a plus-cylinder to a minus-cylinder
Steps:
1. Algebraically add cylinder power to sphere power
2. Reverse sign of cylinder power
3. Add/Subtract 90 degrees from axis

77
Q

Lensmeter

A

An instrument for measuring the prescription of glasses
Also called Lensometer, Vertometer, or Focimeter
Steps:
1. Focus eyepiece
2. Position lens on the stage
3. Measure sphere power (3 thin lines)
4. Measure cylinder power (3 thick lines)(Turn dial towards you for plus cylinder or away from you for minus cylinder)
5. Note axis
6. Measure multifocal power by repositioning glasses (thick to thick lines, or thin to thin lines)
7. Measure Prism (if present)

78
Q

Vertometer

A

A device for measuring the distance between the posterior surface of the glass lens and anterior surface of the eyeball
Also called Distometer

79
Q

Keratometry

A

The measurement of corneal curvature

80
Q

Keratometer, or Ophthalmometer

A

An instrument used to measure corneal curvature

coa vocabulary (17 decks)

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