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Neurology and Neuroscience > Visual System - Optics > Flashcards

Visual System - Optics Flashcards

1
Q

What is refraction?

A

light passes from one medium into another (velocity and direction changes)

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2
Q

What is the index of refraction?

A

n=speed of light in a vacuum/speed of light in a medium

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3
Q

The angle of incidence is equal to?

A

angle of reflection

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4
Q

The angle of incidence is > or < than what?

A

angle of refraction depending on the direction of the light

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5
Q

What types of lenses are there?

A

convex

concave

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6
Q

What is an application of converging lenses?

A

camera uses a lens to focus an image on film

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7
Q

Emmetropia

A

adequate correlation between axial length and refractive power
parallel light rays fall on the retina

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8
Q

Ametropia

A

mismatch between axial length and refractive power

parallel light rays don’t fall on the retina (myopia, hyperopia, astigmatism, presbyopia)

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9
Q

What is myopia?

A

Parallel rays converge at a focal point anterior to the retina

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10
Q

What are causes of myopia?

A

excessive long globe (more common)

excessive refractive power

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11
Q

What are symptoms of myopia?

A

Blurred distance vision
Squint in an attempt to improve uncorrected visual acuity when gazing into the distance
Headache

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12
Q

List treatments of myopia.

A

correction with diverging lenses, with contact lens, by removing the lens to reduce refractive power of the eye

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13
Q

What is hyperopia?

A

Parallel rays converge at a focal point posterior to the retina

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14
Q

What are the causes of hyperopia?

A

excessive short globe (axial hyperopia) : more common

insufficient refractive power (refractive hyperopia)

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15
Q

What are symptoms of hyperopia?

A

visual acuity at near tends to blur relatively early

asthenopic symptoms : eyepain, headache in frontal region, burning sensation in the eyes, blepharoconjunctivitis

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16
Q

What is amblyopia?

A

eye fails to achieve normal visual acuity, even with prescription eyeglasses or contact lenses

17
Q

List treatments of hyperopia.

A

correction with converging lenses/with` +ve lens + cataract extraction/with contact lens/with intraocular lens

18
Q

What is astigmatism?

A

Parallel rays come to focus in 2 focal lines rather than a single focal point

19
Q

Astigmatism etiology

A

hereditary

20
Q

What is the cause of astigmatism?

A

refractive media is not spherical–>refract differently along one meridian than along meridian perpendicular to it–>2 focal points

21
Q

What are symptoms of astigmatism?

A

Asthenopic symptoms (headache , eyepain)
blurred vision
distortion of vision
head tilting and turning

22
Q

How to treat regular astigmatism?

A

Regular astigmatism : cylinder lenses with or without spherical lenses (convex or concave), Sx

23
Q

How to treat irregular astigmatism?

A

rigid cylinder lenses, surgery

24
Q

Near response triad?

A

Adaptation for Near Vision

Pupillary Miosis (Sphincter Pupillae) to increase depth of field
Convergence (medial recti from both eyes) to align both eyes towards a near object
Accommodation (Circular Ciliary Muscle) to increase the refractive power of lens for near vision

25
Q

What is presbyopia?

A

Naturally occurring loss of accommodation (focus for near objects), distant vision intact

26
Q

Presbyopia onset from what age?

A

40

27
Q

Presbyopia is corrected by?

A

reading glasses (convex lenses) to increase refractive power of the eye

28
Q

What type of convex lenses are used for treatment of presbyopia?

A

reading glasses
bifocals
trifocals
progressive power glasses

29
Q

What type of spectacle lenses are used for treatment of presbyopia?

A

Monofocal lenses : spherical lenses , cylindrical lenses

Multifocal lenses

30
Q

For who might contact lenses be helpful?

A

cosmetic , athletic activities , occupational , irregular corneal astigmatism , high anisometropia , corneal disease

31
Q

What are disadvantages to contact lenses?

A

careful daily cleaning and disinfection , expense

32
Q

What are possible complications of contact lenses?

A

infectious keratitis , giant papillary conjunctivitis , corneal vascularization , severe chronic conjunctivitis

33
Q

Intraocular lenses

A

replacement of cataract crystalline lens

give best optical correction for aphakia , avoid significant magnification and distortion caused by spectacle lenses

34
Q

Types of surgical correction for optical issues

A

Keratorefractive surgery :RK, AK, PRK, LASIK, ICR, thermokeratoplasty
Intraocular surgery : clear lens extraction (with or without IOL), phakic IOL

Neurology and Neuroscience (15 decks)

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