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Refracting Skills > unit 1 (week 2) > Flashcards

unit 1 (week 2) Flashcards

1
Q

With the rule

A

Steepest corneal meridian is near the verticle
Flattest corneal meridian is near the horizontal
Figure 8 shape

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2
Q

Against the rule

A

Steepest corneal meridian is near the horizontal
Flattest corneal meridian is near the verticle
Bow tie shape

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3
Q

Regular astigmatism

A

Refractive error is constant over the refracting surface
When the axis is 90 degrees apart

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4
Q

Irregular astigmatism

A

Refractive error varies over the refracting surface
When the axis is anywhere between 180 and 90

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5
Q

5 types of regular astigmatism

A

-Simple myopic astigmatism
-Compound myopic astigmatism
-Simple hypermetropic astigmatism
-Compound hypermetropic astigmatism
-Mixed astigmatism

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6
Q

Mixed astigmatism

A

One line focus lies in front (negative) and one lies behind (positive) the retina

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7
Q

Simple myopic astig

A

One line image is formed in front of the retina and one on the retina
Once principal power of the correcting lens is negative and the other is plano

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8
Q

Compound myopic astig

A

Both line images are formed in front of the retina
Both principal power of the correcting lens are negative

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9
Q

Simple hyperopia astig

A

One line image is formed behind the retina and one ON the retina
One principal power of the correcting lens is positive and the other plano

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10
Q

Compound hyperopic astig

A

Both line images are formed behind the retina
Both principal powers of the correcting lens are positive

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11
Q

Subjective refraction

A

Results depends on the patients ability to discern changes in clarity
Ex. phoropter, trial frame

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12
Q

Objective refraction

A

Results depends puerly on the examiners judgement to determine the optimum optical correction
Ex, Retinoscopy, autorefractor

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13
Q

Subjective refraction 3 phases

A
  1. To correct the spherical element of the refractive error
  2. The determination of the astigmatic error (if present)
  3. Balancing and/or modification of the refractive correction to ensure optimal visual performance and patient comfort
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14
Q

Symptoms of uncorrected myopia

A

Clear near vision, blurred distance vision
Near sighted

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15
Q

Symptoms of uncorrected hyperopia

A

Blurred near vision, good distance
Far sighted

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16
Q

Does objective refraction determine the initial element of refraction

A

Yes - doing an auto refraction or using the retinoscope makes it alot easier to get the rx, without doing this it would take much longer to find

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17
Q

If a pxs PD is smaller than phoropter PD

A

Minus lenses will induce BI prism
Plus lenses will induce BO prism

18
Q

If a pxs PD is larger than phoropter PD

A

Minus lenses will induce BO prism
PLus lenses will induce BI prism

19
Q

Any lens moved away from the eye becomes more positive or negative?

A

Positive

20
Q

How does autorefractor work

A

-Infred light source is projected into the eye
-The reflection passes out to reach a light sensor
-The calculation of refractive error is based on analysis of how the eye influecnes the infared radiation

21
Q

How will an autorefraction results be most accurate

A

With cycloplgia or good accomodative control

22
Q

What errors are most common in autorefractor

A

Poor fixation
Accommodative fluctuation (proximal accommodeation in young people)
Media difficulties (cataract)

23
Q

Disadvantages of autorefractor

A

-May over minus
-Good fixation required: errors with nystagmu / poor attention span
-Errors with media opacities - cataracts, asteroid hyalosis, corneal changes
-Errors with small pupils
-Errors with some case of pseudophakia, high ametropia, amblyopia (lazy eye) or reduced central acuity

24
Q

Advantages of autorefractor

A

-Reliable alternative to retinoscopy
-Good accuracy after cycloplegia - better than retinoscopy when pupil is dilated - reflex can be misleading
-Useful if subjective unlikely to be reliable ; learning difficulties / cognitive impairments
-Easy for assisting staff
-Fast and efficient - can use in large scale screening ex/school

25
Q

What can tomey MR-6000 measure

A

Topography
Refractin
Keratometry
Tonometry
Pachymetry
Dry eye analysis tool

26
Q

When doing auto refraction it is important to double check the measruments to see if..

A

Has a standard deviation of less than 0.25 and within 10 degrees

27
Q

WHo is good to use retinoscope on

A

Pxs who are unavailable to cooperate in a subjective refraction - Babies and pxs with mobility issues
-Young children
-Development delay
-Low vision
-Non english speaking pxs
-Malingeres (pretending/faking)

28
Q

What parts of the eye can a retinoscope view

A

lens
iris
cornea

29
Q

Static retinoscopy

A

Accomodation is controlled or suppressed

30
Q

Dynamic retinoscopy

A

Accomodation is allowed to occur

31
Q

how does retinoscope work

A
  • a streak of light is shone into the pxs eye and the practitioner observes the movement of light refelcted from patients retina (reflex)
32
Q

If the reflection is moving with the retinoscope..

A

It means the px is hyperopic so correct with plus lens

33
Q

If the reflection is moving against the retinoscope

A

It means the px is myopia so correct with minus lenses

34
Q

How do you know you reached the endpoint of retinoscope

A

Occurs when the pupil fills or glows with light

35
Q

Working distance

A

Impossible for the practitioner to work at infinity
The usual working distance is an arms length (50-66cm)

36
Q

Preparing the retinoscopy

A

Adjust the trial frames
-match the distance pd
-level
-panto and vertex should be at sensible values
Add lens to the trial frames
-spheres should be places in the back cells

37
Q

Do you need to be in light or dark room for retinoscopy

A

Dark room - so pupil dilates which makes the reflex more visible

38
Q

When working on the visual axis w retinsocope

A

Work within 5 degrees of the visual axis
Use your right eye to test the patients right eye and use your left eye to test that pxs left eye

39
Q

Fogging

A

Fog the fixating eye to ensure accommodation is relaxed
-If overdone can induce accommodation
-SHould be less than 2D
-Check for againt movement along all meridians in the fixating eye

40
Q

Basic method for retinoscopy

A
  1. Initial lens selection
  2. Identification of the principal meridians
  3. Neutralisation of the refractive error along the principal meridians
41
Q

Working distance of 66cm would need what lens

A

+1.50Ds

42
Q

A working distance of 50cm will need what lens

A

+2.00DS

Refracting Skills (7 decks)

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