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Opthalmology > Clinical Optics > Flashcards

Clinical Optics Flashcards

1
Q

what is eye refractive index?

A

manifestation of the refractory components of the eye (cornea, aqueous humour, lens and vitreous humour), their refractive indices and length of the eye

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2
Q

what is a refractive error?

A

occur when eye is unable to focus light

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3
Q

what are the clinical features of refractive errors?

A

Double vision, haziness, flare or halo around bright lights, squinting, headaches, eye strain

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4
Q

what is myopia?

A

short sightedness

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5
Q

what is hypermetropia?

A

long-sightedness

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6
Q

what are the causes of myopia?

A

Unclear
Hereditary component
Link between myopia, academia and occupation
Environmental?

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7
Q

what are the causes of hypermetropia?

A

Physiological – variation of normal, hereditary
Pathological – developmental abnormality, trauma
Functional – presbyopia, age

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8
Q

what are the causes of astigmatism?

A

Hereditary
Trauma or surgery
Keratoconus

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9
Q

what is the pathophysiology of myopia?

A

Parallel rays of light entering the cell focus at a point short of retina
Due to length – too long or
Refractive – too curved or lens too thick, corneal flattening

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10
Q

what is the pathophysiology of hypermetropia?

A

Rays of light entering eye focus at a point beyond retina

Eyeball is too short, or the lens/cornea become thinner + flatter

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11
Q

what is the pathophysiology of astigmatism?

A

Cornea has irregular curvature

Light enters at different points and are focused differently

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12
Q

how is myopia denoted?

A

(-) meaning negative lens is required to correct?

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13
Q

how is hypermetropia denoted?

A

(+) meaning positive lens are required to correct

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14
Q

what are the clinical features of myopia?

A

Blurry vision when looking at things far away

Increased risk of retinal detachment (retinal stretching)

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15
Q

what are the clinical features of hypermetropia?

A

Blurry vision when looking at shirt distances

Headaches, squinting

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16
Q

what are the clinical features of astigmatism?

A

Blurred vision at all distances
Headaches
Difficulty driving at night

17
Q

how is myopia treated?

A

Glasses (divergent/negative lens/concave)

Not required if asymptomatic

18
Q

how is hypermetropia treated?

A

If asymptomatic no treatment

Positive dioptric powered lens (converging)

19
Q

how is astigmatism treated?

A

Cylindered lens

20
Q

what is presbyopia?

A

Reduction of accommodation

21
Q

what is the cause of presbyopia?

A

ageing

22
Q

what is the underlying mechanism of presbyopia?

A

Lens become less elastic, ciliary body loses ability to contract

23
Q

what are the clinical features of presbyopia?

A

Difficulty with near vision

24
Q

what is the management of presbyopia?

A 
o	Convergent (+) lens
o	Simple reading glasses
o	Bifocal or varifocal lens
25
Q

what are the causes of squints?

A

refractive, non-refractive, mixed, nerve palsies, myogenic, cataract, paralytic, non-paralytic, retinoblastoma

26
Q

what is a exotropia squint?

A

Divergent squint (affected eye looks outwards) – divergent angle between eyes

27
Q

what is a esotropia squint?

A

Convergent squint (affected eye looks inwards) – convergent angle between eyes

28
Q

what is a hypertropia squint?

A

Upwards vertical squint (affected eye looks up) – one eye is lower to the other

29
Q

what is a hypotropia squint?

A

Downwards vertical squint (affected eye looks down) – one eye is superior

30
Q

what is a manifest squint?

A

Present all the time and is referred to as a “tropia”

31
Q

what is a latent squint?

A

On present on dissociation of the eyes and is referred to as a “phoria”

32
Q

what are the clinical features of squints?

A
  • Misalignment of the eye
  • Double vision
  • Eye strain
33
Q

how are squints diagnosed?

A
  • Visual Acuity
  • Alignment of the visual axes
  • Cover/Uncover test
  • Alternate Cover Test
  • Assess ocular movements
  • Fundoscopy
34
Q

what is the cover/uncover test?

A

o Cover the squinting eye. The unaffected eye will not deviate
o Cover the unaffected eye. The squinting eye will move to take up fixation
o Since eye movements are equal and opposite then as the squint moves to take up fixation, the unaffected eye also moves.
o Remove the cover from the unaffected eye. The unaffected eye will resume fixation and the squint will return to it’s original position.

35
Q

what is the alternate cover test?

A

Move the cover rapidly between the two eyes. This dissociates the eyes and will show if there is a latent squint.

36
Q

what is the management of squints?

A

3Os
o Optical – assess refractive state – spectacles for correction
o Orthoptic – patching good eye encourages use of the one which squint
o Operation - resection and recession of rectus muscles

Opthalmology (15 decks)

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