7.1 Refractive Error Flashcards

COA refractive error

1
Q

Define refractive error

A

Light is not bent perfectly to hit the retina precisely

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2
Q

Myopic refractive error

A

Light hits IN FRONT of the retina

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3
Q

Hyperopic refractive error

A

Light hits BEHIND the retina

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4
Q

Emmetropic refractive error

A

Trick question! NONE. Emmetropes have NO REFRACTIVE ERROR as the light hits retina perfectly

the white here if light hit retina perfectly

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5
Q

Which has the MOST refractive power: cornea, crystalline lens, or retina

A

Cornea 2/3rd refractive power of whole eye (think light hits big dome: large surface area)

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6
Q

What spectacle lens in front of emmetrope helps light to hit retina?

A

Plano DS (needs nothing as light already hits retina)

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7
Q

What spectacle lens in front of myopic eye helps light to hit retina?

A

Minus lens aka CONCAVE

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8
Q

What spectacle lens in front of hyperopic eye helps light to hit retina?

A

Plus lens/ AKA CONVEX

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9
Q

Is an EMMETROPIC eye long or short?

A

Neither! It’s perfect length for light to hit retina perfectly

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10
Q

Is a MYOPIC eye long or short?

A

Long (the retina is so far away the light end short and can’t reach that long)

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11
Q

Is a HYPEROPIC eye long or short?

A

Short (the retina is bunched too close so the light surpasses it)

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12
Q

Myopia aka

A

Nearsightedness (sight of the near, none of the far)

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13
Q

Hyperopia aka

A

Farsightedness (sight of the far, none of the near)

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14
Q

Mnemonic for Myopia refractive error

A

MINUS Myopia Increased length Nearsightedness Upclose Short light to retina

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15
Q

Concave corrects what refractive error

A

Minus lens is concave, corrects myopia

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16
Q

Mnemonic for hyperopic refractive error

A

PLUS Past the retina Long away sight Unique Short eye

17
Q

Convex corrects what refractive error

A

Plus lens is convex, corrects hyperopia

18
Q

With the rule astigmatism is @ what meridian in the plus cyl (vs minus cyl)

A

090 plus cyl (vs 180 in minus cyl)

19
Q

Against the rule astigmatism is @ what meridian in plus cyl (vs minus cyl)

A

180 in plus cyl (vs 090 in minus cyl)

20
Q

What lens corrects for astigmatism

A

Cylinder

21
Q

Oblique astigmatism

A

Range of 30deg on either side of 180 or 90,if outside that it is oblique

22
Q

Irregular astigmatism

A

Two meridians are not 90 deg away from each other (think looks like L instead of figure 8)

23
Q

Oblique astigmatism vs Irregular astigmatism

A

Oblique is Outside range of 30deg to either side of 90 or 180, Irregular is isosceles triangle is not 90 deg between each meridian

24
Q

Define presbyopia

A

Cilliary body muscles to crystalline lens get week with age, won’t all lens to bend, blows out near vision

25
Q

Monocular precautions

A

Protect one good eye with shatter resistant lenses (polycarbonate spectacle lenses)

26
Q

Aphakia is

A

No implant to replace when the crystalline lens came out (uncommon)

27
Q

Pseudophakia means

A

Implant inside eye after crystalline lens removed after cataract surgery (super common almost 100%)