Refraction Lecture Powerpoint Flashcards Preview

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Flashcards in Refraction Lecture Powerpoint Deck (32):
1

Presbyopia is a ____ refractive error

FALSE

2

Hyperopia

Far-sightedness, eyeball is too short (axial) or cornea is not curved sufficiently (curvature), corrected by a convex lens (positive power) that increases the eyes refractive power by converging the light

3

Myopia

Near-sightedness, eyeball is too long (axial) or cornea is excessively curved (curvature), corrected by a concave lens (negative power) that reduces the eyes refractive power by diverging the light rays

4

The majority of refraction is done by....

...the cornea (fine tuned by the lens)

5

What is the shape of the lens for distance viewing?

Flat

6

The lens of the eye cannot make a ___ shape but can go ____ to view distances

concave, flat

7

Myopia is corrected by what type of lens? What about hyperopia? Astigmatism?

Concave, convex, cylindrical

8

Most common cause of amblyopia and 3 other common onees

-Strabismus
-Refractive disorder
-cataract
-ptosis

9

Refraction

Ability of eye to bend light so image is focused on the retina

10

Concave lens

A lens with negative optical power that causes the dispersing of oncoming light, used in nearsighted patients

11

Convex lens

A lens with positive optic power that causes converging of the oncoming light, used in farsighted patients

12

Ametropia (refractive errors)

Optical imperfections that prevent the eye from properly focusing light causing blurred vision, including nearsightedness, farsightedness, or astigmatism, very common up to 1/3 of patients >40, worldwide common cause of poor visual acuity and blindness

13

Worldwide #1 cause of blindness

Cataracts

14

Visual acuity

Diagnosed via a snellen chart, a patient with less than 20/25 in either eye has impaired visual acuity, done by healthcare professional often in children and then annual beyond 61

15

Treatments of ametropia (3)

-Eye glasses
-Contact lens
-Lasik surgery (refractive surgery)

16

Orthoptist

Specialize in diagnosis and treatment of binocular vision problems such as strabismus

17

Factors influencing light focusing on the retina

-Cornea is extremely curved
-Refraction thru the aqueous humor is minimal
-Lens accommodates and can adjust accordingly
-Refraction thru vitreous humor is minimal
-Length of eyeball matters to bring focus to the

18

Emmetropia

When the eye is able to bring distant objects to a point of focus on the retina without a refractive aid

19

Presbyopia

A loss of lens elasticity preventing it from becoming as convex that causes difficulty seeing near things (rolling lens, flat lens is no problem), not considered a true refractive error

20

When an object is close, the lens refractive power must ____

increase (accommodate)

21

Elderly must read things by holding the media....

....farther away than a child would

22

___% of people have a refractive error (ametropia)

70%

23

Astigmatism

Misshapen cornea resulting in 2 or multiple focal lines that focus in front, behind, or on the retina

24

OD

Right eye

25

OS

Left eye

26

Sphere, cyl, axis, add

-Refers to the degree of optical error in the glasses
-corresponds to astigmatism
-corresponds to astigmatism
-Added to bifocals to adjust in presbyopia

27

LASIK

Laser assisted in situ keratomileusis, used for hyperopia, myopia, and astigmatism, laser alters shape of the cornea, can have complications including dry eyes, overcorrection or undercorrection, induced astigmatism, wrinkles in flap, or halos

28

Amblyopia

Disorder of visual development caused by optical, physical, or ocular alignment defect in childhood, brain selects better image to the eventual detriment of vision in the other eye (lack of development in the visual pathway), most common cause of uniocular vision loss in patients less than 45 years of age, if not treated before age of 7 permanent visual loss occurs

29

Esotropia

When the strabismis affected eye moves inward

30

Exotropia

when the strabismis affected eye moves outward

31

Cataract

Clouding of lens obstructing passing light, leading source is aging, can be congenital, traumatic, or drug induced, prevented with sun glasses, has loss of visual acuity and contrast sensitivity, as well as an absent red reflex

32

Cataract treatment (1)

-Surgical removal of lens and replacement with plastic lens (that can't accommodate like the natural one but can sometimes have different optic settings)