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SF2 - Test 1 > 4 - Grover - Visual Optics > Flashcards

4 - Grover - Visual Optics Flashcards

1
Q

Refraction

Refractive Index

A

Bending of light caused by change of velocity of light as it crosses interface between two substances

Refractive Index = Speed in Air / Speed in Substance

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2
Q

Convex Lens

A

Convex Lens converge parallel light rays

At center of lens, light not bend, angle of incidence increases moving out, leads to greater refracting

- - -

Bends light to single point behind lens

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3
Q

Concave Lens

A

Concave lens diverge parallel light rays

Center of lens not bent, increasing angle of incident towards edge, greater refraction

- - -

Concave lens bens light away from a single point

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4
Q

Cylindrical Lens

A

Concave or Convex in only one axis

Light refracted towards or away from a line, not a point

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5
Q

Cylindrical Lenses combined at right angles?

A

Have same focuses effect as one spherical lens

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6
Q

Focal Length

How does it change with distance of source?

Convexity impact on Focal Length?

A

Distance behind convex lens at which light rays converge

- - -

The closer th source, the greater the focal length

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7
Q

Refractive Power: Diopter

A

Diopter = 1 m / Focal Length (m)

+1 Diopter = 1 m Focal Lenth

+2 Diopter = 0.5 m Focal Length

  • 1 Diopter diverges light equal to which Concave focuses (focal point on same side as source)
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8
Q

How is refractive power “neutralized”

A

Combinding Concave and Convex lenses with equal focal strengths (diopters)

Ex. +1 Concave and -1 Convex

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9
Q

Refractive Power - Cylindrical Lenses

A

Focal Line - Horizontal = Axis of 0 degrees

Focal Line - Vertical = Axis of 90 degrees

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10
Q

Refractive Interfaces of Eye

A

Air - Surface of Cornea

Back of Cornea - Aqueous Humor

Aqueous Humor - Surface of Lens

Back of Lens - Vitreous Humor

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11
Q

Greatest Refractive Power in Eye?

A

2/3 Air and Cornea

1/3 Lens

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12
Q

Accommodation

A

Change in refractive power by changing curvature of lens

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13
Q

Range of Accommodation in Lens

A

20 d - 34 d

Only in young children, range decreases with age

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14
Q

Nature of Lens in Resting Conditions

A

Ligaments Tense = Lens Flat = Less Power

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15
Q

Nature of Lens in Contracted Conditions

A

When contracted ligaments are pulled anterior/medially, releasing tension, more convex = more power

Circular fibers function like a sphincter

Contracted = Relaxed Ligaments = More Convex = More Power

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16
Q

How is lens accomodation controlled?

When does it activate?

Is it volunary or reflexive?

A

Parasympathetic Control

Ciliary Muscles regulated by parasympathetic nervous system

Parasympathetic activity causes ciliar muscles to contract = ligaments relaxed = more convex = increased power

- - -

Adapts (fires) for viewing nearby objects

Decreases for viewing far away objects

- - -

Voluntary AND Reflexive

17
Q

Accomodation Change with Age?

A

Ability to accommodate decreases

Age - Range

0-10: 14 D

50: 2 D
70: 0 D

18
Q

Iris

Control?

A

Controls amount of light entering the eye

Autonomic Nervous system has reflex control

Can also affect depth of focus

Sympathetic Activation - Pupil Dilation (mydriasis)

Parasympathetic Activation - Pupil Constriction (miosis)

19
Q

Depth of Focus (Depth of Field)

A

Range of distance over which objects remain in focus

Objects nearer or further from point of fixation are in varying degrees of focus

20
Q

Pupil Diamete effect on Depth of Field

A

Small Pupil = Long Depth of Focus (little scattering outside plane of focus)

Large Pupil = Short Depth of Focus (scattering outside plane of focus)

21
Q

Near Triad (Near Reflex)

A

When eyes fixate on nearby object:

C.A.M.

Convergence: Center object on fovea

Accomodation: Focus object

Miosis: (pupil contriction) to maximize depth of focus

22
Q

Argyll Robertson Pupil

A

Bilateral small pupils that constrict when patient focuses on near object, but do not contrict when exposed to bright light

Strongly associated with neurosyphyllis

23
Q

Clinical: Emmetropia

A

Normal (emmetropic) eye

Parallel light rays are in sharp focus on retina when ciliary muscle is completely relaxed

24
Q

Hyperopia vs Myopia

A

Hyperopia (Farsightedness) - Short eyeball, or weak lens, degraded vision for near objects

Focal point beyond retina

Myopia (Nearsightedness) - Long eyeball, or strong lens, degraded vision for far objects

Focal point in front of retina

***Just remember you got that Myopia, long eyeball, and strong lens

25
Q

Correcting Errors of Refraction

A

Hyperopia (can see far) - Correct with ADDED refractive power

+ D (Concave)

- - -

Myopia (can see near) - Correct with REDUCED refractive power

- D (Convex)

- - -

Just remember your prescription.

26
Q

Astigmatism

A

Light from one plane is focused at a different distance that light from a secon plane due to uneven curvature of cornea

- - -

Must be corrected with spherical and cylindrical lenses

27
Q

Intraocular Pressure

A

Created by fluid within eye

Aqueous Humor: In front and sides of lens (free flowing)

Vitreous Humor: Between lens and retina (gelatinous)

Exachange via diffusion

28
Q

Formation of Aqueous Humor

A

Continuously formed and reabsorbed

Secreted by Ciliary Body (ciliary processes)

- - -

Balance between formation and reabsorption determines intraocular pressure

29
Q

Formation of Aqueous Humor - Process?

A

Formed on surface of Ciliary Processes by Secretory Epithelial Cells

Similar mechanisms for secretion of aqueous humor and CSF

30
Q

Path of Aqueous Humor?

A
  1. Between suspensory ligaments
  2. Through pupil into anterior chamber
  3. Into angle between cornea and iris
  4. Through trabecular meshwork
  5. Out of eye through canal of Schlemm
  6. Into venous circulation
31
Q

Glaucoma

A

Damage to the optic nerve (retinal ganglion cells)

Associated with intraocular pressure

Typical Cause: Decreased Outflow of aqueous fluid, elevated pressure may compress optic nerve

32
Q

Two Types of Glaucoma

A
  1. Angle-Closure (narrow angle) Glaucoma:

Iris blocks flow of intraocular fluid, rapid rise in pressure, rapid damage to optic nerve

  1. Open Angle Glaucoma:

Flow of intraocular fluid impeded at trabecular meshwork, more common, slower rise

33
Q
A

SF2 - Test 1 (20 decks)

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