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CL > MT1 CL2 > Flashcards

MT1 CL2 Flashcards

1
Q

Regular Astigmatism

A

Meridians are 90 degrees apart

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2
Q

Ways to stabilize SCL

A

Prism ballast, peri-ballast, dual slab off, truncation, toroidal back surface

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3
Q

How is CL different for myope

A

less sphere and cylinder

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4
Q

how is CL different for hyperope

A

more sphere and cylinder

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5
Q

What are ranges for cyl

A

.75 to 2.25. Go up in .50 steps.

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6
Q

Prism ballast

A

Allows the watermelon effect (the lens to squeeze CL down with upper eyelid). Have 1-1.50 BD.

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7
Q

Peri Ballast

A

Prism lens with prism taken from central.

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8
Q

Double Slab off

A

Only prism left in the central portion. The top and bottom edges are very thin. Lids stabilize. Overall thinner lens. use with tight lids or small fissures.

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9
Q

Truncation

A

have a small amount of prism ballast and cut the edge off. This is a last resort as poor comfort.

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10
Q

Back surface toric

A

Tori on back of lens. Done to line up with patient;s own astigmatism to stabilize.

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11
Q

How much rotation is one clock hour?

A

30 degrees of rotation

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12
Q

Young

A

First to describe astigmatism in his own eye

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13
Q

Donders

A

First to study and classify different RE conditions. I.e. myopia, hyperopia, astigmatism.

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14
Q

Typical axis in dx set

A

Full circle in 10 degree steps.

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15
Q

What will a SCL do that a GP lens will not

A

neutralize lens cyl. GP only neutralizes cornea cyl.

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16
Q

Are patient very sensitive to axis good SCL topic wearers?

A

NO.

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17
Q

How do SCL normally Ride

A

Temporal. Due to nasal sclera being slightly more elevated

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18
Q

Affects of SCL decenterization

A

Optic center not in correct place.

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19
Q

Normal corneal diameter

A

11.8 mm

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20
Q

Scleral drop of torics

A

Typically 1.25. Want more stabilization

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21
Q

When to vertex

A

If above 4 D

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22
Q

How to allows go about correcting the astimatism

A

UNDER correct

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23
Q

Cause of decreased vision if marker at 6 o’clock

A

RE, overtaxing errors, lens draping effect, cylinder masking, Tear lens effects.

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24
Q

Induced astigmatism and rotation

A

increases with amount of degrees rotated.

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25
Q

What is SCORx not repeatable

A

Suspect a poor fit, everted lenses, switched lenses.

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26
Q

The aging eye

A

reduced tear production, loss of contrast, reduced transparency of lens and cornea, decreased pupil size, increased lid flaccidity, inability to cope with reduced light, reduction in retinal sensitivity, greater visual expectation.

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27
Q

What RE epidemiology change do we see with aging

A

more hype ropes.

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28
Q

Presbyopic options

A

Single vision lenses with near add, mono vision, center near design, center distance design, segmented design, concentric CD design.

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29
Q

How many presbyopes use the Distance CLs and reading glasses?

A

43%

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30
Q

how much of the population does mono vision work for?

A

70%

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31
Q

which eye is which with monovision

A

dominant eye=distance

nondominant=near

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32
Q

Criticism of monovision

A

decreased stereopsis, decreased depth perception, legal consideration

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33
Q

Poor monovision

A

amblyopes, topic SCL wearers, critical visual requirements.

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34
Q

swinging plus test

A

give them +1.50 and see which is more comfortable.

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35
Q

what are complaints with failing monovision

A

decrease in stereopsis or ghost images at distance

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36
Q

Are new or previous CL wearers more successful with monovision

A

Those that have previous experience

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37
Q

Does add factor into success of monovision

A

no

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38
Q

Modified Monovision

A

Center distance for distance and center near for near. Vision is 20/30 at distance i near instead of 20/60.

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39
Q

Who does simultaneous vision work best for

A

Younger is better. Older cannot filter out (above 48)

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40
Q

Pupil size of 50

A

3.5

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41
Q

Pupil size and simultaneous vision

A

If pupil too small may not be able to see more than one zone

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42
Q

Where is line of sight in eye

A

nasal to geometric center.

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43
Q

Decentered Optics

A

Let lens go where CL with go and put optics up and 1 mm nasal. Will get perfect vision.

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44
Q

Multifocal for myopia

A

Distance in middle and near out. Works great with their large pupil. Use decentered optics.

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45
Q

What happens as keratoconus increases

A

Cornea thins and have an increase in myopia and regular or irregular astigmatism.

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46
Q

Is teratology more common in M or F

A

Equal

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47
Q

When does keratoconus normally begin

A

12 to 32

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48
Q

How many patient with KC undergo transplatn

A

10%

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49
Q

When to do transplant with KC?

A

When patient can no longer be fitted with cl, when cl no longer provide acuity visual acuity due to scaring, patients who require sharp vision for their job.

50
Q

Associated condition with KC

A

Atopic disease, general allergic disposition, eye rubbing, hereditary.

51
Q

Is keratoaconus nomoral symmetrical?

A

no!

52
Q

Hallmarks of KC

A

Decline in VA, increased myopia, change in cylindrical power and axis, squeezing of the eyelids artificially creates a pinhole, appearance of halos around street light.

53
Q

Puberty onset keratoconus

A

begins in early adolescence age 12-16. Usually bilateral but worse in one eye. The younger the patient the more severe the disorder.

54
Q

Late onset keratoconus

A

Usually begins in late 20s or early 30s. Both eyes can be affected the same. The incidence of progression reduces greatly with the age of onset.

55
Q

Karatoconus Fruste

A

A mild non progressive form KC. Can occur anytime throughout life. No positive tilt lamp finding associated with KC. Normal corneal thickness.

56
Q

Vertical striae

A

Seen with KC.

57
Q

Fleischer’s Ring

A

Iron outlines where ectasia taking place. Iron is where the tears meet.

58
Q

Munson’s Sign

A

See a droplet when patient looks down

59
Q

Increased visibility of corneal nerve fibers

A

occurs with KC. The n. fibers are dilated.

60
Q

Irregular superficial corneal opacities

A

Majority occur down from geometric center. Scaring=breaks in bowman.

61
Q

Cascade Hypothesis

A

stromal collagen fibers are degraded due to UV light, mechanical trauma, and atopic disease. Lead to disruption in bowman, thin the storm, and scarring.

62
Q

How to limit oxidative stress

A

UV protection, NSAIDS, allergy meds, best cl fit.

63
Q

Ruptures in descent’s membrane

A

occurs when thinning is so bad. 5% with KC get this. Get acute hydras.

64
Q

Resolving hydrops

A

Have FC acuity and most cases will resolve after 3 weeks. Can cause reduction in keratoconus after

65
Q

Diopter power diagnosis for KC

A

greater than 10D

66
Q

Corneal eccentricity for KC

A

> .80

67
Q

Inferior superior average curvature

A

Abnormal if >1.50 diopters

68
Q

Surface Asymmetry Index for KC

A

Abnormal if greater than 1

69
Q

Surface regularity index

A

abnormal if >1

70
Q

Corneal GP for KC

A

If patient have 350 nm or less of corneal elevation difference

71
Q

Scleral GP for KC

A

If patient have greater than 350 nm of corneal elevation difference

72
Q

3 point touch technique

A

Most commonly KC lens. Distribute CL weight evenly between the cone and cornea.

73
Q

Apical clearance with KC

A

want to vault cone and cornea to decrease damage.

74
Q

KC lens eccentricity

A

Range for .8 to 1.60. Remember circle is zero.

75
Q

Quadrant specific lens design

A

Can change eccentricity for each quadrant. Aspheric

76
Q

Aspheric lens

A

change curvature from central to periphery

77
Q

OR with KC

A

use +/- big steps.

78
Q

Contumacy Material for SCL

A

Lathe able (made to order), daily wear, DK=60. Water content is 74 to decrease corneal swelling.

79
Q

HEMA vs. SiHY

A

Need SiHY for KC lenses to decrease corneal swelling

80
Q

Determining BC for KC

A

Identify the mean K and add 1.0 mm.

81
Q

Hybrid lenses and KC

A

Soft skirt with hard front.

82
Q

Calculating scleral lens saggiato depth

A

Low angle=low sag. High angle=high sag.

83
Q

Soft KC fittingy by sagitall height

A

If lens diameter is 14.2 add 500 microns to saggital height at 14.2 sag. If lens diameter is 14.8 add 1,000 microns to 14.8 sag.

84
Q

Piggy back lens and staining in KC

A

stops the 3 and 9 staining.

85
Q

Ideal fit for GP

A

.75D to 1D WTR astigmatism

86
Q

A GP spherical lens on a >2D topic cornea

A

Will have poor vision, poor contraption, lens flexure, stable fit, lens rocking on flat, corneal dessication

87
Q

Topography of good astigmatism with GP toric

A

want limbus to limbus.

88
Q

GP flexure on topic conrnea

A

will have inconsistent VA.

89
Q

Spectacle blur and GP

A

Spherical lens on topic cornea will mold the cornea and create less cylinder.

90
Q

When to consider topic GP

A

Significant amount of cornea toxicity or significant residual astigmatism.

91
Q

Topic GP options

A

Spherical power effect, cylindrical power effect, base curve topic, front surface topic, thin flex

92
Q

Spherical power effect lens

A

Biotic. Compensating power on front surface. Back surface for a good fit.

93
Q

When to pick Spherical power effect

A

corneal toxicity greater than 2. Residual astigmatism .75 to 1 with spherical GP. Corneal toxicity is equal to spectacle astigmatism (can rotate)

94
Q

Lens rotation and spherical power effect

A

Behaves like a spherical lens. Tear lens compensates for rotation.

95
Q

Advantages to spherical power effect

A

good for highly toxic. But expensive and many parameters to specify.

96
Q

How to know if a SPE lens

A

If change in BC=change in CL power

97
Q

If same meridian cylinder in OR

A

add to the power of steep meridian or add sphere if indicated. No longer a SPE design.

98
Q

Cylinder Power Design

A

Topic back surface and toric front surface. The front surface is greater than the back.

99
Q

Measurements with SPE

A

toxicity in lensometer=toricity in radiuscope

100
Q

Is toxicity in lensometer equal to toxicity in radarscope with CPE

A

NO.

101
Q

When to use CPE

A

Corneal toxicity greater than 2D. Corneal cylinder is not equal to refractive cylinder.

102
Q

Is stability important with CPE

A

YES.

103
Q

CPE is identical to SPE but

A

Compensating for residual astigmatism by adding extra cylinder in steep meridien.

104
Q

Base Curve Toric

A

Spherical front surface. Topic back surface

105
Q

When to use base curve topic.

A

Corneal toxicity greater than 2D. Refractive cylinder 1.5X greater than corneal topic or with non flexing spherical GP reveal residual cylinder (.75D or greater). No compensating optics on front surface for induced astigmatism or residual astigmatism.

106
Q

Base curve topic and acuity

A

Most pt. will not get optimal acuity. Relies on CL and tear lens to induce a minus cylinder. However, induced cylinder rarely corrects the residual.

107
Q

What relationship should refractive cylinder and corneal toxicity have with base curve topic?

A

Refractive cylinder should be 1.5X greater than corneal toxicity.

108
Q

Higher index of refraction and base curve toric

A

will induce greater cyliner

109
Q

123 rule

A

To get 1D of cylinder on the eye you will need 2D of toxicity on CL and you will measure 3 in the air.

110
Q

Topic Peripheral curves

A

Normally the peripheral curves of a topic lens will be spherical. Necessary if the peripheral pattern of the GP is minimal in one meridian

111
Q

Front surface toric

A

Prism ballast and trunction

112
Q

When to use FST

A

When an optimum lens fit can be achieved with spherical lens design. When refractive astigmatism is greater than corneal (.75D)

113
Q

Flexure

A

Thickness is critical. As lens becomes thinner the possibility increases. May negate value. Increases with corneal toxicity.

114
Q

Thin-Flex

A

Planned flex that corrects corneal toxicity. Neutralize 30% corneal astigmastims

115
Q

SynergyEyes Multifocal

A

use near segments surrounded by distance. However, have complications due to low DK skirt.

116
Q

SynergEyes Duette

A

Have a skirt with higher DK.

117
Q

Pupil size and add power

A

Lower add with lower pupil

118
Q

Add effect

A

Front surface yields higher add effect than back surface. Steeper BC yields higher add effect. Higher indices of refraction yield higher add.

119
Q

Flex lens GP design

A

Standard spherical or aspheric design. High Dk material. Minimal center thickness. Diameter is 1 mm smaller than cut out diameter.

120
Q

Soft perm Hybrid lens designs

A

Has a soft skirt. Will increase diameter but low DK so caused complication. Discontinued.

CL (3 decks)

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