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CL > MT1 > Flashcards

MT1 Flashcards

1
Q

Leonardo Da Vinci

A

The first to describe neutralizing cornea with a new refractive surface. Drew schematic eye and described how an image one was formed.

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2
Q

Descartes

A

Described how placing a tube of water on the eye would give perfect vision. Came up with telescopes

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3
Q

Young

A

Father of optics. First to describe and measure astigmatism. Described how accommodation occurred by changing the lens. First to give scientific reason for color vision. Designed the hydradiascope.

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4
Q

hydradiascope

A

25 mm tube closed at one end by a biconvex lens filed with cold water and placed at orbital lens. Designed to study accommodation.

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5
Q

John Herschel

A

First to take a photograph onto glass. Described a contact lens with a posterior surface (fit cornea) and anterior surface (designed for RE)

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6
Q

Muller

A

Master glass blower and made artificial eyes. Made a CL for a patient with a exposure following malignant lid tumor. Wore this for 21 years. New one made every 12-18 months. Had no RE power.

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7
Q

When was the first CL invented

A

1888

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8
Q

What three people invented CL

A

Fick, Muller, Kalt,

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9
Q

Fick

A

First published work on CL. Experimented from molds from cadavers. Muller and Zeiss gave him Cl.

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10
Q

Muller CL maker

A

First to describe why contact lens created corneal edema.

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11
Q

Kalt

A

Developed first lens for keratoconus. Used base lens citing on keratometric measurements. 11m lens design. Made from segments from the bottom of test tubes.

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12
Q

Muller Company

A

Scleral lenses from blown glass. Had a greater patient tolerance since no sharp edges remained

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13
Q

Zeiss company

A

Ground glass scleral lens. First to produce a commercially available diagnostic set.

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14
Q

Dallos

A

First to make impression of living eyes using negocoll. First to describe toric and lenticular lens design.

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15
Q

When did PMMA become material of choice for Cl

A

1938

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16
Q

Feinbloom

A

The first to use plastic for cl. The central portion is glass and the scleral portion is plastic. First to describe bifocal cl.

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17
Q

Gyorffy

A

First to make completely plastic scleral contact lens.

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18
Q

Obrig

A

First to suggest using fluorosceine dye with cobalt blue to evaluate fitting relationship

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19
Q

Bier

A

First to describe a scleral lens that incorporated a transitional curve between the cornea and sclera portions to provide limbal clearance.

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20
Q

First way to make molding CL

A

Used negocol to mold the eye. Removed and made cl off of mold. Then you would modify the lens based off of the mold.

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21
Q

England

A

Deisgned first CORNEAL CL made of PMMA. However, patient was rejected.

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22
Q

Tuohy

A

Patient first Corneal CL. A mono curve design. Must be first 1.50D flatter than flat K.

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23
Q

Butterfield

A

Designed the first multi curve contact lens to better contour the true shape of the cornea.

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24
Q

Dickson, neil, Sohnges

A

Developed the Microlens. 9.5 mm in diameter with average thickness of .2 mm.

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25
Q

Wichterle

A

First soft CL. Used a wichterle’s spin cast system. Morrison and National patient development got rights.

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26
Q

Food and Drug

A

CL became a drug.

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27
Q

Bausch and Lomb

A

First hydrogel lens approved by FDA for the US market.

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28
Q

Heat disinfection

A

First way to clean CL

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29
Q

First chemical disinfection

A
  1. Solution sensitivity.
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30
Q

Lens care today

A

Multi-purpose solutions, hydrogen peroxide, UV systems

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31
Q

RGP material

A

PMMA–>CAB–>silicone acrylate–>fluorosilicone acrylate

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32
Q

Hyatt

A

invented celluloid plastic

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33
Q

History of CL plastics

A

PMMA–>CAB–>polystyrene–>fluropolymers–>silicone

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34
Q

PMMA

A

Very durable. Doesn’t change shape. Good weight and wetting. Howevery does not have oxygen transmission.

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35
Q

Corneal edema and PMMA

A

Central corneal clouding due to decreased oxygen transmission. The basal layer has greatest metabolism and decreased oxygen causes it to separate from bowman’s. This is a great corneal abrasions. Occurs from overwear syndrome.

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36
Q

Spectacle Blur

A

Wearing Contact lens causes the cornea to warp and then when the patient puts on their glasses they cannot see.

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37
Q

Endo changes with PMMA

A

polymorphism and polymegaism

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38
Q

Hypoxia and Cornea

A

The endothelium releases lactic acid in response to hypoxia. This is what hurts the endothelium.

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39
Q

Cellulose Acetate Butyrate (CAB)

A

A great failure but a great step.

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40
Q

Silicone Contact lenses

A

Pure silicone lenses have the highest oxygen permeability in a cl. Only used with pecs with aphasia. Has a surface TX that is hard to support with an adults tear film. DK=340

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41
Q

DK

A

How much oxygen can get through a cl

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42
Q

Polymer

A

All other Cl are polymers (made of many different parts)

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43
Q

Silicone Fluorine

A

Used for oxygen premeability

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44
Q

Methacrylic acid/ Hema

A

Wetting agents

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45
Q

Methylmethacrylate

A

mechanical and optical stability

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46
Q

Oxygen Transmissiblity

A

A material oxygen tranmission is known as its Dk/t. t=lens thickness. DK=oxgen permeability.

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47
Q

Oxygen permeability

A

D=diffusion. Inherent ability of material that allow oxygen to diffuse through holes or voids in plastic
K=solubility. Degree to which oxygen is absorbed within or on a material

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48
Q

Diffusion

A

Physical spaces within the material

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49
Q

Solubility

A

Absorbed within a material.

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50
Q

What material do we use today

A

Flurosilicone acrylate

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51
Q

Measurement of oxygen transmission in vitro

A

polygraphic technique.

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52
Q

Measurement of oxygen transmission in vivo

A
  1. Equivalent oxygen percentage. Lens placed on a rabbit. 2. Can also measure overnight corneal swelling. (no cl to get a baseline and then with a cl) More swelling with lower DK. 3. Biochemical corneal changes 4. epithelial mitosis 5. corneal sensitivity 6. Limbal vascular response
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53
Q

Oxygen Flux

A

The actual amount of oxygen that diffuse through a contact lens and is available to cornea

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54
Q

Oxygen availablility

A

The driving force of oxygen through a contact lens. Reduced at higher altitudes.

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55
Q

Oxygen tension

A

Driving force of oxygen through a contact lens

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56
Q

Minimal lens and TF thickness

A

Lens=100 TF=10-20

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57
Q

Why does cornea wet?

A

Due to micorvilli that holds mucin material

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58
Q

Ways to measure wetting properties

A

Sissile drops, captive bubble, wilhelmy plate

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59
Q

Plasma treatment

A

Should use on all gas perm. lenses. Gets rid of waxy material. Cleans the lens and increase wetting. Will then ship wet.

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60
Q

HydraPEG

A

A coating that makes contact lens more hydrophilic. Only lasts about 2 months.

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61
Q

Dimensional stability

A

Base curve radius stability. PMMA is more stable. How well contact lens keeps shape

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62
Q

Flexural/Fracture resistance

A

The lens should not fluxuate. Should hold shape with blinking.

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63
Q

Flexural resistance measurement

A

In vitro: Lab. mesaurements.

In vivo: residual astigmatism

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64
Q

CL hardness

A

How many scratches the lens gets. Polish scratches for comfort.

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65
Q

Lens specific gravity

A

The weight of the lens. Solubility diffusion lens are the heaviest. AKA those made of fluorine are more heavier.

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66
Q

Index of refraction of lens

A

Only use material with high n for multi-focal cl. (allows more add power to be derived) Styrene was used but low DK so not popular.

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67
Q

Machining Properties of lens

A

Should be able to maintain the lens. UV resistance and heat resistance.

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68
Q

Optium solution

A

Very good product. hard to get though

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69
Q

Lanoline based products

A

Lenses won’t wet with left over debris. Must wash hands with non cold cream based soap.

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70
Q

Progent and unqiue PH

A

Best cl invention for cleaning.

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71
Q

Gas permeability lenses schedule

A

Begin with 4 hours on Day 1. Increase wearing 2 additional hours a day.

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72
Q

Steps to GP lens fitting

A
  1. lens diameter 2. Base curve radius 3. lens power
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73
Q

Average corneal diameter

A

11.8 mm

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74
Q

Why measure average corneal diameter on obliique

A

As cornea longer horizontally than vertically.

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75
Q

If HVID (horizontal visible iris diameter) 11.4 mm or less?

A

9.0 mm diameter lens

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76
Q

If HVID 11.5 mm or greater

A

9.5 mm diameter lens

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77
Q

How much clearance do you want on flat K

A

20 microns

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78
Q

Which meridian will have more tears?

A

The vertical as it has more bend so more tears can come in.

79
Q

How much tears under cl on horizontal

A

19 in the middle and 6 on the side.

80
Q

Base curve evaluation

A

The center of the lens should vault the central cornea. The lens should and on the mid peripheral cornea along the horizontal meridian (3+9 o’clock). The lens should have unobstructed vertical movement.

81
Q

Where will the lens land on the eye

A

At the point of highest elevation. Will naturally life at 12 and 6.

82
Q

HVID greater than 12.2

A

large

83
Q

HVID 11.4-12.1

A

Normal

84
Q

HVID less than 11.4

A

small

85
Q

+ numbers/red on cornea topography

A

Higher than spherical

86
Q
  • numbers/blue on cornea topograph
A

lower than spherical

87
Q

Difference between horizontal and vertical height on cornea

A

Take both the numbers. DO not worry about negative or positive. Just add them.

88
Q

If we place a rigid lens on flat K how many times will it be correct?

A

50% of the time

89
Q

Cornea eccentricity

A

Amount of cornea flattening that occurs

90
Q

Eccentricity of sphere

A
  1. As flatter eccentricity increases.
91
Q

Lens that is too flat

A

Will fit too high. Have low central clearence

92
Q

How much central clearance do you want

A

20 microns (10-25)

93
Q

Lens that is too steep

A

Excessive apical clearance. May have bubbles and drift low.

94
Q

Normal cornea ____ in the periphery

A

Flattens

95
Q

Peripheral curves

A

Allows cl to move over eyes as pt. moves eye. Fit will change with cl gaze. Can ask lab to make peripheral curves more flat or steep.

96
Q

Step 3 of corneal fit

A

Overrefraction.

97
Q

WTR Astigmatism

A

Horizontal meridian: touch at 3 &9

Vertical meridian: clearance at 12 and 6

98
Q

ATR Astigmatism

A

Horizontal: clearence at 3 & 9
Vertical: clearance at 12&6

99
Q

Where does cl clear?

A

Clear at the power meridian

100
Q

Base curve radius

A

primary radius on the POSTERIOR surface of the lens

101
Q

On flat K lifts off of the _____ meridian

A

power axis

102
Q

fluroscene staining

A

Darker=lens closer to cornea

Green=more clearance.

103
Q

What type of astigmatism is ideal for RGP

A

WTR. Can move vertically

104
Q

How much tears do we want along horizontal meridian with WTR

A

About 20 microns

105
Q

How much TF do we want along periphery with WTR

A

7 microns

106
Q

How much do we want in vertical with WTR

A

40 microns. Allows it to move.

107
Q

Atlas

A

Takes cornea topography and allows you to superimpose a cl. Can adjust cl so it has 20 microns of clearance

108
Q

Secondary and periphery curves

A

Has increased clearance. Allows eye to move

109
Q

Posterior optical zone

A

Shows you have far the optical zone extends. The chord diameter over which the base curve extends. Not to edge of lens. Only goes to peripheral curves

110
Q

Sagittal Depth

A

Distance between the flat plane of a given diameter and the highest point of a concave surface of the CL

111
Q

The larger the OZ the _____ the sagital depth

A

greater

112
Q

The smaller the OZ the ____ the sagital depth

A

Smaller

113
Q

Secondary curve width

A

.2-1 mm.

114
Q

Peripheral curve width

A

.1-.4 mm.

115
Q

Secondary curve radius

A

Flatter radius of curvature adjacent to the base curve. .7-1.50 mm flatter than the base curve radius.

116
Q

Peripheral curve radius

A

The outer most curve on the posterior surface. It is designed to clear the peripheral cornea and limbus. Always 11.50 mm

117
Q

What is the peripheral curve radius

A

11.50 mm

118
Q

Peripheral curve types

A
  1. Spherical radius
  2. Aspheric radius-gradually flatten the cornea and easy to duplicate
  3. Tangent angle-cornea periphery described as a straight line.
119
Q

Do you read cl based off of front or back vertex power?

A

Must ask the lab what they do

120
Q

SAM

A

Steeper add minus

121
Q

FAP

A

Flatter add plus

122
Q

Lens thickness

A

Need to avoid bending with blinking.

123
Q

Specific gravity with plus vs. minus

A

plus=more ant=rides down more

Minus=more post=rides up more

124
Q

Anterior Optical Zone

A

Radius of curvature of the anterior lens surface which determines the Refractive power. Has both a radius of curvature and a diameter. Normally lab determines.

125
Q

Lenticular Flange

A

An increase or decrease in the anterior edge thickness to aid in lens positioning. Creates more or less lid interaction.

126
Q

Myo-flange

A

An increase in peripheral lens thickness to aid in raising low riding lenses (i.e. plus lens design) Plus power lens with minus periphery. Allow greater lid/lens interaction.

127
Q

Hyper-flange

A

A decrease in peripheral lens thickness to aid in lowering high riding lenses (i.e. high minus lens) The decrese in edge thickness results in less lid interaction. Occurs with any lens greater than -3D.

128
Q

Lenticulation

A

Where there is anterior optical zone curve and then lenticular curve (myo, hyper, or plano)

129
Q

Edge Design

A

Represents the junction between the anterior and posterior lens surface. The edge profile is instrumental to the overall comfort of the lens.

130
Q

Edge Design zones

A

Anterior zone, apex, posterior zone

131
Q

Prism Ballast

A

Incorporates a thicker inferior portion of the lens periphery. Use to orient lens (i.e. bifocal). Top portion thinner than bottom. No prism effect. Allows the upper lid to squeeze the lens downward by watermelon effect. (upper lid pushes down)

132
Q

Truncation

A

The removal of inferior portion of a lens to aid in the meridional orientation of a lens. Used in some toric and bifocal lens designs. More stability when rest at bottom of lid. Not very common today

133
Q

Fenestrations in CL

A

Holes need to help with CL removal. Used to be used to allow more oxygen in but not down today.

134
Q

Special Considerations with CL

A

Pregnancy (vision will change), diabetes, allergies, HIV (concerned with ability to fight infection), Arthritis, refractive surgery, active eye dz, dry eyes, conjunctival injection, lid margin disease (CI for successful CL wearing. MGMT of condition prior) Photophobia

135
Q

Spectacle vertex distance

A

12 mm

136
Q

A contact lens will require a _____ focal length than spectacles with myopia

A

Longer. ADD. Less minus.

137
Q

A contact lens will require a _____ focal length than glasses with Hyperopia

A

Shorter. MINUS. More plus.

138
Q

When does vertex distance matter?

A

When it is greater than +/- 4D

139
Q

Converting D –> R

A

D = 1.3375-1/radius in m

140
Q

Lacrimal lens theory

A

Lacrimal lens=TF, fluid lens. Reference to flat k. Lacrimal lens shape determines the BC to cornea relationship.

141
Q

When does SAMFAP not apply

A

When changing diameter or optical zone.

142
Q

When does SAMFAP apply

A

when changing the base curve

143
Q

Residual Astigmatism

A

When a non-flexing rigid contact lens is placed on the cornea, it can be assumed to mask or negate the corneal cylinder. Lenticular cal will come through though, therefore need consider potential for residual astimgatim.

144
Q

Does Javal’s rule apply to cl?

A

No only glasses

145
Q

Approximating power for corrective lens with residual astigmatism greater than .75D

A

Use equivalent sphere, proceed with caution, toric RGP, soft toric contact lens, over spectacles.

146
Q

How would you ID clinically that there was residual astimgatim during your RGP fitting?

A

Not getting Vas that are expected. Do cal rxn and then see if pick up cylinder and does better

147
Q

How would you clinically determine there was lens flexure?

A

Keratometry over rigid lens. Fix by asking maker to make lens thicker

148
Q

What if manifest ref cyl=165 and kcyl=180

A

Both are considered WTR. Treat them as the same

149
Q

What if manifest ref cyl=WTR and kcyl=obl

A

create obliquely crossed cylinders. Messy math. Rare and poor candidate for GP.

150
Q

How close should cl compare to actual ors in phoropter? What could be wrong if its not this close?

A

Ideally within .25-.37 D. K’s off, manifest off, cl base curve off, cl power off, calculation error

151
Q

What if cl way off from phoropter?

A

Vertify ors out of phoropter, verify cl, prescribe least minus possible, rely on true over rxn verified.

152
Q

Who accommodates and converges more in CL’s than spectacles?

A

Myopes

153
Q

Who accommodates and convergenes LESS in CL’s than spectacles

A

Hyperopes

154
Q

A 4.00D myopes has to accommodate _____ D more in Cl’s than spec?

A

.25D

155
Q

3 and 9 staining with Cl

A

Punctate epithelium staining. Trianglular shaped patches at 3 and 9 or 4 and 8. Shaped and position of PEE is dependent on the lens design and resting position. Conj. hyperemia localized in the horizontal meridian.

156
Q

3 & 9 staining symptoms

A

patients may be asymptomatic, may have an itchy sensation usually increase with wearing the time and persists after lens removal. Increasing lens awareness throughout the day. Dry eye symptoms.

157
Q

What causes 3 & 9 staining

A

Mechanical-related to the lens design or fabrication. Physiological-peripheral drying secondary to an unstable TF or edge thickness. May appear during the first few days of lens wear or after months of even years. Rarely disappears spontaneously more often increases in severity.

158
Q

TX for 3&9 staining

A

Artificial tears, decrease overal diameter, blend peripheral edge lift, flatten peripheral edge life.

159
Q

Vascularized Limbal Keratitis Symptoms

A

Moderate discomfort with some photophobia. Lens awareness and decreased wear time. Visualization of defect by the patient. Will tell you they have a white spot in their eye. This is 911.

160
Q

VLK Signs

A

Elevated epithelial lesion bridging the limbus. Will have stromal involvement. Diffuse ill defined border. Semi-opaque. Conj. injection. Edema and staining. Corneal vascularization.

161
Q

Early VLK TX

A

Reduced wearing time or stop wear. Begin lubricating drops. Redesign the lens (reduce diameter, flatten base curve, flatten peripheral curves) follow closely for recurrences

162
Q

Late VLK TX

A

Signifigant pt symptoms of pain. Increase conj. injection. Erosion of the elevated mass. Discontinue lens wear for 1-3 weeks. Treatment with combination of antibiotic/steroid (tobradex). Redesign lens. Consider piggyback (SCL under GP) if unable to discontinue GP wear.

163
Q

Post VLK neovascularization and scaring

A

Normally not a ton of scaring. If see BV and no prog. ask about it. It probably happened in the past. Pay attention to the periphery and decrease the lens diameter.

164
Q

VLK vs. phlyctenular keratoconjunctivitis

A

Similar in appearance to VLK. VLK is mechanical and heals in 3-5 days. Phlyctenulosis heals in 10-14 days. Phlyctneulosis staph hypersensitivity

165
Q

Salzmann’s Nodular Degeneration

A

Have blue-white opacities in periphery. Generally not inflamed unless associated with corneal degeneration.

166
Q

BLK vs pseudopterygium

A

Pseudo-conj stick to ulcer on eye. Not very common.

167
Q

Pterygium

A

can complicate lens

168
Q

Pinguecula

A

Rarely progresses in size

169
Q

Dermoid

A

Round

170
Q

Papilloma

A

Diffuse

171
Q

Dellen

A

Local saucer like depression in the peripheral cornea. Caused by localized dryness result in stromal dehydration. Occasional occurs with 3&9 staining. May scar and become vascularized.

172
Q

Conjunctival xerosis or bitoto spot

A

White plaque area on conj. keratized cells. Can be associated with vit. A deficient (adult with gas perm. think gas perm). Patient are asymptomatic. Some minimal conj. injection towards the end of the day. Associated with long term conj. drying secondary to the bridging effect of the lens. Slightly elevated conj lesion. Located intra-palpebral. Keratinization of the conj. epithelium.

173
Q

Conjunctival xerosis or bitot spot tx

A

Consider the lens design, follow for changes in patient symptoms or clinical appearance.

174
Q

Lens Adhesion and patient symptoms

A

Happens with a flatter lens. Pt blink and it doesn’t move. Patient generally asymp. Patient may notice lens adherence in the morning.

175
Q

Lens adhesion and signs

A

localized ring like corneal distortion (rarely stains with fluorosceine), adhesion usually located in the periphery with one edge crossing the limbus, retention of debris and mucus beneath the stationary lens, mild punctate staining, fern-like pattern upon manipulation.

176
Q

Who does lens adhesion occur in?

A

25-80% of GP lens wearers in extended wear. Also occurs in DW. Patient dependent phenomenon. Lens suction does not play a role

177
Q

What create GP lens adhesion

A

Created by a thinning of the post lens tear film during sleep which creates a thin highly vicious mucus rich tear between the lens and the cornea. Upon opening the force of the eyelid may be insufficient to initiate lens movement. The lens may remain bound until the mucus film is diluted and thickened by the tears. Can also be solution dependent.

178
Q

What type of lenses are more often bound?

A

Flat, large, or loose.

179
Q

TX for lens adhesion

A

Lens design changes may or may not stop the binding. Change lens care products, Treat dry eyes, adherence will not show signs every day on a given pt.

180
Q

GP induced GPC

A

Can get GPC from GP. Can be due to mechanical reasons.

181
Q

Atomic Force Microscopy

A

Assess surface roughness at a monoscopic level. Look at surface after rubbing.

182
Q

What step of cleaning do pt. often miss?

A

Rubbing

183
Q

Dimple Veil

A

Small circular indentation in the epithelium. Correlate with area of bubbles trapped beneath the lens. Pt. is asymp. unless over optical axis

184
Q

Neurogenic ptosis

A

Caused, controlled or arising from the NS (congenital hornets)

185
Q

Myogenic ptosis

A

Dysgenesis or abnormal function of the legator muscle. Congenital, MG

186
Q

Mechanical ptosis

A

weight of the lids

187
Q

Aponeurogenic ptosis

A

rupture of the tendon of the legator muscle/disinsertion or thinning of the legator muscle aponeurosis. Due to surgery or GP wear.

188
Q

Aponeurogenic ptosis causes

A

forced lid squeezing-due to forced blink, rigid lens displacement of tarsus, blind induced lens rubbing, excessive forced used in soft lens handling.

189
Q

Non-aponeurogenic CL ptosis causes

A

Edema, blepharospasm, papillary conjunctivitis caused by CL

190
Q

Discontinuing CL wear and ptosis affect

A

Ptosis goes away but it has a rebound affect

191
Q

CL induced ptosis risk factors

A

high myopia, pt. age, long term GP use.

192
Q

DMV

A

May decrease ptosis. Less manipulation of the eyelid during ptosis.

193
Q

Rigid lens corneal edema

A

Historical problem but decrease with new technology. Long term, low grade edema. Slow progression. Mild moderate CCC with centric like epithelial changes to adjacent Bowman’s layer.

194
Q

Unexplained Red eye

A

Can be due to manufacturing compounds, surface debris toxicity, metharcylic acid toxicity. Can treat with surface treated GP or soft contact lenses.

CL (3 decks)

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