Contact Lens Ii

Front 1

New Lecture: 1 Astigmatism and Toric Soft Lens Fitting

Front 2

why is it important to transpose an Rx into minus cyl, if you have one in plus cyl, before you call it into the contact lens company

Back 2

becuase their phone operators are just people off the street and don't have a background in the profession. they will probably record it as in the minus cyl form even if you say that it is plus cyl.

Front 3

what is simple myopic astigmatism

Back 3

one meridian is focused on the retina and one meridian is focused in front of the eye

Front 4

why would this pt be hard to fit with a toric CL: PL-1.00X090

Back 4

because they already probably have pretty good acuity unaided. so, you need to know their uncorrected acuity before you get started.

Front 5

if you don't correct cyl, and just do spherical equivalent, they pt may see 20/25 or 20/30, but when they put their glasses back on and realize how much better they see with glasses, they are likely to drop out of CLs

Front 6

what percent of pts with a prescription have at least 0.75 D of astigmatism?

Back 6

45%

Front 7

what is simple hyperopic astigmatism

Back 7

light focuses on the retina in one meridian and behind the retina in the other meridian.

Front 8

what is compound myopic astigmatism

Back 8

both meridians focus in front of the retina

Front 9

what is compound hyperopic astigmatism

Back 9

both meridians focus behind the retina

Front 10

what is mixed astigmatism

Back 10

one meridian focuses in front of the retina and one meridian focuses behind the retina

Front 11

why would a person with mixed astigmatism be hard to fit with toric CLs

Back 11

because they are probably seeing pretty well without correction, so it wouldn't be that much of an improvement

Front 12

why would rxing CL to a latent hyperope who has never been corrected before be beneficial

Back 12

because you can slowly give them more plus every 2-4 weeks without having to replace their glasses over and over again.

Front 13

name and describe the two types of astigmatism based on corneal shape

Back 13

regular: the two steepest meridians are 90 degrees apart irregular: two steepest meridians are not 90 degrees apart

Front 14

what type of lenses do individuals with irregular astigmatism need

Back 14

a RGP (or a thick soft lens with a high modulus) to mask their irregularity

Front 15

name four benefits of RGPs

Back 15

they mask corneal astigmatism, they usually provide the sharpest acuity, they are very healthy, they are more economical for the pt

Front 16

how long can pts usually wear soft CL vs. hard CLs (long term)

Back 16

soft: you don't see many wearing them continuously for 20 years (they have dropped out) hard: you frequently see them wearing GPs for 40-50 years continuously

Front 17

how can keratometry tell you about potential acuity

Back 17

if the keretometric mires are distorted, you know that they have an irregular cornea and they are not going to correct down to 20/20 with glasses

Front 18

why type of astigmatism is easies to fit with RGPs? what type is the hardest?

Back 18

with the rule (WTR) is the easiest. against the rule (ATR) is the hardest (great candidate for toric soft lenses)

Front 19

what is residual astigmatism

Back 19

astigmatism still present after correction of a refractive error

Front 20

how do you calculate residual astigmatism (after putting on an RGP)? how do you determine residual astigmatism clincally? why could these two numbers differ?

Back 20

Calculate: measure their corneal astigmatism with keratometry. any astigmatism in their correction after you take out the corneal astigmatism is their calculated residual astigmatism Clinically: put on a rigid lens (which eliminates corneal astigmatism) and do JCC -can differ because keratometry only measures central 3 mm of the cornea. true total corneal astigmatism could be different.

Front 21

why does a spherical RGP correct for astigmatism? when would a spherical RGP not correct all of the pts cylinder?

Back 21

1. because the tears accumulate between the lens and the cornea in just the right shape to make the cornea artificaially spherical (tear lens). 2. if there were residual cyl inside the eye that the RGP couldn't correct for.

Front 22

name three ways that soft toric CLs are designed so that the axis does not rotate while the lens is on the eye

Back 22

prism ballast, dual slab-off, truncation

Front 23

what is prism ballast and how does it keep toric CLs from rotating on the eye

Back 23

the overall shape of the CL is shaped like a base down prism. works by the "watermelon seed effect". the upper lid pushes the lens down when they blink like when you squeeze a watermelon see between your fingers and it shoots in the direction of the thicker middle part. Not a matter of gravity; still works when the pt is standing on their head.

Front 24

how much prism is in a prism ballasted toric lens? what problems can arise from this?

Back 24

1 to 1.5 prism diopters. if one eye is a toric prism ballasted lens and the other eye is spherical the pt may come back complaining that their vision is not right. if you place a 1.5 BD trial lens in front of the other eye it should correct their problem. -use another method of keeping the lens from rotating if they only have astigmatism in one eye

Front 25

what is double slab-off stabalization and how does it keep a toric lens from rotating

Back 25

it is like a prism-ballast lens, but there is a thin zone at the top and the bottom (which interacts with the lower lid). this mode works well and is comfortable because of the thin zone at the bottom

Front 26

virtually all CLs have an optical zone and a "carrier zone". the carrier zone is where interaction with the lids occurs.

Front 27

what does it tell you if your patient is seeing haloes through the CLs you rx and you can't fix it.

Back 27

they are seeing outside of the optical zone of the lens and you need to go to a custom lens where you can adjust the size of the optical zone.

Front 28

how much astigmatism do you need to start correcting for with toric CLs

Back 28

0.75 D of astigmatism and above, correct with toric CLs. lens will mask a little bit of astigmatism.

Front 29

what is the most important factor as far as the fit of a soft CL

Back 29

matching the sagital depth of the CL with the sagital depth of the eye

Front 30

what cyl powers do most off-the-rack CLs come in

Back 30

0.75, 1.25, 1.75, 2.25 -if you are inbetween values go with the lesser amount. the lens will mask a little of the cyl; also, if the lens rotates a little it will be less of a problem if there is less cyl in the lens.

Front 31

if the spectacle Rx is -8.75-3.25X180, what is the power of the CL at the corneal plane if vertex distance is 12 mm

Back 31

-8.00-2.50X180 -remember to vertex each meridian seperately

Front 32

when you vertex correct a myope, does the cyl increase or decrease? what about a hyperope?

Back 32

myope: decrease hyperope: increase

Front 33

the toritrack calculator; what other factor does it take into consideration when calculating CL power from spectacle Rx besides vertex distance.

Back 33

the modulus of the lens. the higher the modulus, the more like a RGP lens the soft lens will act. so a higher modulus lens will need less cyl correction that you would think if you didn't take this into consideration. this information was gatherd imperically (based on tons and tons of data though).

Front 34

how accurately can a slit-lamp reticle measure corneal diameter and other lesions

Back 34

to the nearest 0.2 mm -topagrapher measures horizontal visable iris diameter (HVID) to the nearest 0.1 mm

Front 35

what is the average HVID

Back 35

11.8

Front 36

is HVID or corneal curvature more important as far a selecting a base curve for a soft CL

Back 36

HVID (or corneal diameter) is the most important factor in determining sagital depth of the eye and base curve selection.

Front 37

soft CL fitting guides generally say if they have a cornea higher than a curvature use the steep base curve; if below use the flat base curve. these guidelines are based off a typical 11.8 diameter cornea. remember corneal diameter is a more important factor in selecting a base curve of a soft CL than corneal curvature; so, if your patient has a larger or smaller than average cornea they may require a flat base curve even though they have a steep cornea, or vice versa.

Front 38

how do you determine the diameter of a toric soft contact lens you should use

Back 38

you want the CL to be 1 to 1.5 mm larger than the cornea on each side. so, you add an average of 2.5 mm to the corneal diameter and that should be about the diameter you want the CL. -you only want 1 mm of coverage for a spherical soft CL. you need more coverage for a toric lens because it will help stabilize the lens and keep it from rotating.

Front 39

there are a lot of poor fitting spherical soft CLs that come in to the office year after year and like their contacts just fine. you don't see that with toric contacts. you need to have a much better fit on a toric soft CL for the pt to accept it.

Front 40

is the average asian cornea larger or smaller than causasian

Back 40

smaller

Front 41

what is the danger with putting a tight fitting soft CL on the pt

Back 41

they will love how they feel, but when you put a tight lens on the eye, with the materials we have today oxygen permiability is not the issue, but metabolic waste and tear exchange is of concern.

Front 42

Describe Mark and Pat Caroline's empiracle concept of effective K

Back 42

a way to determine what base curve you should start with when fitting a soft CL that takes into consideration corneal curvature as well as corneal diameter: -for every 1 mm larger than 11.8 mm add 5 D of corneal curvature to the K values and fit based on that "effective K" -if it is smaller, subtract from corneal curvature.

Front 43

how are off-the-rack CLs manufactured vs. custom CLs

Back 43

off-the-rack: all cast molded custom: all lathe cut

Front 44

how do you use lens orientation markers on toic soft CLs

Back 44

they are intended to be at a certian position. what is important is not that they are right at 6 o'clock or whatever, but that they are stable. they need to stay in the position they are at blink after blink in order for you to be able to fit them.

Front 45

what is the best way to see the lens orientation marker

Back 45

retro illumination is the best way to see them

Front 46

is the left/right LARS (left add right subtract) rule left or right from the practitioners or the patients perspective

Back 46

from the practitioners perspective

Front 47

how does LARS work

Back 47

a rule for toric soft CLs. if the axis marker is shifted to the left (from the practitioners perspective) then you add the amount it is shifted to the axis of the specticle rx (you can thin your beam and rotate it and measure the amount of rotation). if it is rotated to the right then you subtract that amount from the axis of the spectacle rx. -when you order the new lens, the orientation marker should be in the same position (right or left) that the origional lens was (NOT AT 6 O'CLOCK). -LARS is not a really good method to figure out the CL rx to order. you should do a sphero-cylindrical over refraction and calculate it scientifically if they have very much cyl. it's probably okay for low amounts of cyl.

Front 48

if you get a new toric CL pt and the orientation markers are off axis from 6 o'clock, you can not assume that the lens is rotated. because you don't know if the previous practitioner had corrected for that. you would need to look at the spectacle Rx and compare it to the CL Rx

Front 49

the higher the cyl the more blur if the lens rotates. the larger the rotation the more blur they will see.

Front 50

if the pt is seeing poorly through a toic CL, how do you figure out if it is because of the fit or because of the power in the lens

Back 50

look at the eye with the keratometer with the lens on. if the mires are clear, you think that the fit is good and you need to change the power. if the mires are distored, you know that the fit is poor and you need to fix this before you can know if you have the right power or not.

Front 51

if you have a toric CL fit and you do a sphero-cylindrical over refraction, how do you calculate the power to order

Back 51

use a calculator. toritrack has one. I believe in Dr. Citek's notes he gave us one.

Front 52

on a toric fit, what should you suspect if your result are not making sense

Back 52

you need to consider that they have switched the lenses. this is really important and will get you way down the wrong track if you don't consider it.

Front 53

what does it usually mean if you get a spherical equivalent of plano on a sphero-cylindrical over refraction on a toric CL

Back 53

usually means that the power is right on, but the axis is off.

Front 54

New Lecture: 2 Introduction to ToriTrack

Front 55

what incriments to typical off-the-rack toric axis come in

Back 55

010 degree incriments

Front 56

what are you looking for to assess the fit of a toric soft CL

Back 56

1. centration 2. limbal coverage 3. movement in primary gaze and up gaze 4. push up test 5. position and stabilization of orientation marker

Front 57

if you have an unstable sphero-cylindrical overrefraction (SCOR) name three things you should suspect

Back 57

1. poor fit 2. everted lens 3. switched lenses

Front 58

what should you suspect if you are getting numbers that don't make sense on the SCOR

Back 58

THAT THEY SWITCHED THE LENSES

Front 59

do you tend to see steep or flat corneas with microphthalmos

Back 59

steep

Front 60

what is the arc length calculator

Back 60

a calculator made by the company SpecialEyes. it takes HVID, flat K, and steep k, and calculates the appropriate base curve and diameter for a custom lens. I don't know the details of how the calculations are done, but Dr. Lampa recommends it for eyes that don't fit into standard off the rack soft lenses. Saved it as a file called: Specialeyes Calculator. In the Contact Lens II course.

Front 61

Start of new lecture: 3 Gas Permeable Contact Lens Management of Astigmatism.

Front 62

name three things you are looking for to indicate a good fit on a toric gas permeable lens

Back 62

1. clear the apex of the cornea 2. touch at 3 and 9 o'clock 3. unobstructed movement along the vertical meridian -0.75 to 1.00 D WTR cornea fitting relationship -note same as spherical GP fit

Front 63

describe the concep of eccentricity

Back 63

eccentricity is a rate of flattening. for example an eccentricity of 0 would be a sphere and an eccentricity of 1 would be a straight line (not sure of these facts). eccentricity can be greater than 1.

Front 64

how much is the idal clearance of a GP lens over the apex of the cornea

Back 64

about 20 microns

Front 65

why does it work to fit a spherical GP lens over some toric corneas

Back 65

because the lens creates a tear lens that compensates for the astimatism some of the time

Front 66

if you have a high astigmat, why can you not correct their vision with a spherical GP lens.

Back 66

because there is so much lift off at the inferior and superior cornea (WTR) that you will get "lens rock" which will cause the optics over the pupil to be unstable. Also, you get greater lid interaction which creates problems as well as lens flexure.

Front 67

what is lens rock

Back 67

the apex of the cornea touches the contact lens, but the cornea is so steep that the contact lens rocks back and forth like a seesaw

Front 68

what is lens flexure

Back 68

the contact lens physically bends, creating astigmagism that is not ground into the lens from the prescription

Front 69

what is the difference between apical and limbus-to-limbus astigmatism and how do you tell the difference based on the topography

Back 69

apical: astigmatism does not extend all the way across the cornea limbus to limbus: astigmatism extends from one limbus all the way across the cornea to the other limbus. -if there is a single color that goes 360 degrees on topography then you have apical astigmatism

Front 70

the flourescene pattern of a GP lens on a cornea with apical astigmatism can look like the flourescene pattern of a spherical cornea. -see answer for picture

Front 71

if you measure a lot of astigmatism on keratometry you may be able to still fit a spherical GP lens on the person because it might be apical astigmatism, in which case the lens would fit as if the eye were spherical

Back 71

insert text here

Front 72

how do you want the base curves of a GP lens to fit on an astigmatic cornea

Back 72

in the horizontal meridian you want the lens just steeper than the cornea (maybe 0.25 D) and you want the lens 0.75 to 1.00 D flatter than the cornea in the vertical meridian. this creates unobstructed vertical movement of the lens when they blink. -minic a 1 diopter WTR cornea

Front 73

what amount of cyl do you need to start doing a toirc GP at

Back 73

1.50 to 2.00 D of cyl or more and you usually need to do a toric GP lens

Front 74

it is possible for a toric GP lens to rotate 360 degrees and not affect the pts vision (details later in notes)

Front 75

how do you determine if there is lens flexure clinically

Back 75

do ketratometry over the top of the lens. if there is astigmatism on the fron surface and it is supposed to be spherical, then there is lens flexure.

Front 76

what is spectacle blur

Back 76

a GP lens can change the shape of the cornea slightly, so that when they put on their glasses (which are made to correct the natural shape of the cornea) they see some blur. -can happen when you put a spherical lens on a toric cornea.

Front 77

consider that if you have a pt come in with a poor fitting GP lens that the lens could be changing the shape of their eye. So, if you take them out of there lens for a while, their cornea will return to the normal shape.

Front 78

name 5 types of toric GP lenses

Back 78

1. base curve toric 2. spherical power effect 3. cylindrical power effect 4. front surface toric 5. thin-flex

Front 79

for a base curve toric GP lens, is the toricity on the front or the back of the lens

Back 79

only on the back. the front is spherical.

Front 80

does a spherical power effect GP lens have the toricity on the front or the back surface of the lens

Back 80

both front and back

Front 81

does it matter if a spherical power effect toric GP lens rotates on the eye as far as the vision through the lens

Back 81

no, it can rotate 360 degrees and it won't change the vision through the lens (SPHERICAL power effect)

Front 82

does a front surface (or F1) toric GP lens have the toricity on the front or the back surface

Back 82

the front. the back is spherical.

Front 83

what is a bi-toric GP lens

Back 83

a lens that has toricity on BOTH the front and the back surface. if it only has one toric surface, it is a toric lens, but not a bi-toric lens

Front 84

what does the front surface toricity of a spherical power effect GP lens correct for

Back 84

only astigmatism induced by the material of the CL

Front 85

what is the back surface of a spherical power effect GP lens designed to do

Back 85

create a 0.75-1 D WTR relationship with the cornea

Front 86

for a spherical power effect lens, do we need to specify the power on both the front and the back surface of the lens

Back 86

no, the lab will calculate the power that needs to be on the front of the lens

Front 87

what are the indications of a spherical power effect GP lens design (1)

Back 87

corneal toricity is equal to spectacle astigmatism (vertexed)

Front 88

why does a spherical power effect lens not induce astigmatism if it rotates on the eye.

Back 88

because as the lens rotates a tear lens develops that compensates for any induced astigmatism

Front 89

how do you tell if a lens is a spherical power effect lens clinically

Back 89

if the difference in the base curves you measure with the radioscope is the same as the astigmatism you measure with lensometry, it is a spherical power effect lens.

Front 90

is F1 and F2 the front or the back surface of a GP lens

Back 90

F1: front F2: back

Front 91

if you have a refraction of -1.00-3.25X180 and Ks of 44.00 @ 090/41.00 @ 180, what are the parameters of the lens you should design if you are using a spherical power effect design?

Front 92

on a toric GP lens the steeper base curve is always associated with the more minus powered meridian.

Front 93

does the cylindrical power effect design have toricity on the front or the back surface of the lens

Back 93

both

Front 94

what are the indications for a cylindrical power effect GP lens design

Back 94

corneal cylinder NOT equal to refractive cylinder

Front 95

how can you tell clinically if a lens is a cylinder power effect design

Back 95

toricity in the lensometer is NOT equal to the difference between the two base curves

Front 96

do you need to specify the perameters on the front and back surface of a cylinder power effect design

Back 96

no, just the back surface; the lab will figure out the front surface

Front 97

is spherical power effect or cylinder power effect design more common

Back 97

spherical power effect is much more common

Front 98

is stability an issue for a cylinder power effect design? why or why not?

Back 98

yes, if the lens rotates, it will induce astigmatism. this is because you are correcting for residual astigmatism, which can not be compinsated for by a tear lens.

Front 99

if you have a MR of +7.25-4.00X160 and Ks of 42.25@070/39.00@160, what are the perameters you should innitially order if you are designing a cylinder power effect lens

Front 100

which of the toric GP lens designs do you need to specify an axis and why

Back 100

the only one you need to is a F1 toric. the other designs rotate into place, but the F1 toric has all the toricity on the front surface and is spherical on the back surface.

Front 101

does a base curve toric lens have toricity on the front or the back of the lens

Back 101

toric back surface; spherical front surface.

Front 102

what are the indications of a base curve toric design

Back 102

refractive cyl is 1.5 times greater than corneal cyl

Front 103

do front surface (F1) toric lens designs have toricity on the front or the back of the lens

Back 103

spherical back surface, toric front surface

Front 104

do front surface toric lens designs correct residual astigmatism

Back 104

yes

Front 105

how do front surface toric lens designs keep the lens from rotating

Back 105

prism ballast 1-2 D, truncation.

Front 106

when are front surface toric lens designs indicated

Back 106

1. when optimum fit can be achieved with a spherical lens design 2. when refractive cyl. is significantly greater than corneal cyl

Front 107

for a front surface toric lens design does it affect the pts vision if the lens rotates

Back 107

yes, you are correcting for residual astigmatism inside the eye

Front 108

does a thin-flex toric GP lens design have trocitiy on the front or the back of the lens

Back 108

neither; spherical front AND back surface

Front 109

Start of new lecture: 4 No-Nonsense Management of the Presbyope with Contact Lenses

Front 110

name some changes that happen to the eye as it ages (6)

Back 110

1. reduced tear production 2. loss of contrast sensitivity 3. reduced transparency of the lens and cornea 4. decreased pupil size 5. increased lid flaccidity (affects CL wear) 6. reduction in retinal sensativity

Front 111

what factor will help you overcome the obstacles of fitting a presbyope with multifocal/monovision CLs

Back 111

high pt motivation to avoid reading glasses -need to set pt expectations

Front 112

name three options for correcting a presbyope with CLs

Back 112

1. correct distance with CLs and have them use reading glasses 2. monovision 3. multifocal CLs

Front 113

why is it difficult to get multifocal optics into a CL

Back 113

because the only optics that are being used by the pt are the optics over the pupil. so you have to cram multifocal optics into about a 5 mm optic zone.

Front 114

what is the advantage of the method of correcting presbyopia with CLs where you have the pt wear distance correcting CLs and reading glasses over the top of them? what is the disadvantage?

Back 114

optics. your acuity will be better because of the problems associated with multifocal optics into a contact lens -you need your near vision pretty much all the time, so the pt will have to have reading glasses with them everywhere they go.

Front 115

why should you start correcting a presbyope with distance CLs and reading glasses over the top

Back 115

setting pt expectations. there vision will be the best through this modality, but it is really frustrating having to take reading glasses on and off everywhere you go. everything you do from there through is going to compromise their vision, whether it's monovision or multifocal CLs, so it's important that they are really motivated enough to make these other methods work. -if you take a presbyope and put them straight into multifocal lenses they will complain bitterly about their loss of distance acuity

Front 116

what percent of pts are able to adjust to monovision

Back 116

70%

Front 117

how long does it usually take a pt to adjust to monovision

Back 117

varies a lot. averge is about 1 week.

Front 118

can you train yourself to adapt to monovision

Back 118

studies indicate no. you are either wired to be able to adjust to this modality or not.

Front 119

how far out do we use stereopsis to determine depth

Back 119

15 feet. beyond this we determine depth by other visual cues such as overlapping contours, speed of motion, etc. (monocular cues). this is why monocular pts can function at a fairly high level in their environment.

Front 120

what do you need to warn pts about before starting monovision therapy

Back 120

that their near stereopsis is going to suffer. look at their profession, are they a carpenter etc.

Front 121

what could you do to compensate for the decreased stereopsis that pts will experience with monovision

Back 121

you could rx glasses to wear over the top of their monovision CLs that will correct both eyes for distance (for driving etc) -provide this Rx to the pt regardless of whether they fill it or not (they will rarely fill it)

Front 122

Pat finds that there is a low grade type of amblyopia, that only is uncovered when the pt tries monovision and is not able to supress one eye. the person is usually 20/20 in one eye and 20/20- in the other eye.

Front 123

name three types of people who are poor candidates for monovision and why

Back 123

1. amblyopes 2. toric SCL wearers (NOT an absolute contraindication) throughout the day a normal toric SCL wearer will have the CL on one eye roate, and their perception will switch to the other eye. this is not possible with SCL monovision. (consider a spherical GP that won't induce astig. on rotation) 3. pts with intense visual demands. using binocular vision is easier than putting all of the demands on one eye. so, pts will feel tired at the end of the day if they have intense visual demands and are forced to use only one eye. (binocular pts tend to be able to read longer than one eyed pts)

Front 124

how do you chose which eye to use for distance and which for near in monovision

Back 124

most pts prefer to use dominant eye for distance and non-dominant eye for near. start here, however, some people are the opposite (especially people who do a lot of near work).

Front 125

describe the most definative method for determining dominant eye

Back 125

swinging plus test: put full correction in front of the pt. then put a +1.50 lens in front of one eye, and then the other, while the pts is viewing the 20/20 line. most patients will have a definant preference.

Front 126

if you have a new monovision pt that is seeing blur at distanct, what should you try to correct it

Back 126

increase the plus power in the eye adjusted for near. if the blurred eye is interfering with the perception of distance acuity, increasing the blur in that eye may shift the perception at distance entirely to the eye corrected for distance. (try +0.50 D on the near eye)

Front 127

why is uncorrected astigmatism more of an issue for a presbyope than a non-presbyope

Back 127

because if you have accommodation you are able to adjust your focus point to the circle of least confusion. a presbyope is not able to do this.

Front 128

how could you use orthokeratology to create a monovision type correction

Back 128

hyperopic orthokeratology correction in on eye

Front 129

what is simultaneous vision

Back 129

the distance, intermediate and near optics are placed over the pupil simultaneously. the brain selects the light rays that are in focus for the pts viewing distance. -screen door analogy: when you look through a screen door you are paying attention to the outside scene; but you can also shift your attention to the screen its self. (analogy kind of works) -opposite is called alternating vision

Front 130

what are the two types of simultaneous vision designs used today

Back 130

annular center-near or center-distance.

Front 131

how does age impact a pts ability to wear simultaneous vision CLs and why

Back 131

as they age their pupils get smaller. you want about half the area over the pupil for distance and half for near. it gets harder to do this as the pupil gets smaller.

Front 132

what is the term used for the decrease in pupil size with age

Back 132

senile miosis

Front 133

Cooper vision proclear multifocal descign is a simultaneous vision design that is center distance in one eye and center near in the other eye. this lens seems to give the pt the best vision. may be referred to modified monovision. with regular monovision you are 20/20 in one eye and about 20/200 in the other eye. with this method you are 20/20 in one eye and 20/40 in the other eye.

Front 134

it is much easier to fit multifocal optics into a GP lens. you get much better optics than a soft lens.

Front 135

an aspheric GP multifocal lens needs to be fit really steep in order to land at 3 & 9. also it needs to center really well to get the distance optics over the pupil.

Front 136

are most soft multifocal CLs center near or center distance? how about GP multifocals?

Back 136

95% of soft are center near. GP lenses are usually center distance.

Front 137

how many microns of apical clearance do you need beofre you will see a bubble on a GP lens? how many microns before you loose sight of the pupil?

Back 137

90 microns or more for a bubble. you lose sight of the pupil at around 50 microns.

Front 138

what can happen to the shape of the cornea when the pt wears an aspheric GP multifocal design

Back 138

you get a steepening effect on the cornea. hyperopic orthokeratology effect. they will get spectacle blur.

Front 139

what is the most popular type of multifocal contact

Back 139

aspheric GP

Front 140

how does the amount of aspehricity relate to the amount of add power you get in a multifocal GP lens

Back 140

the greater the aspehericity the greater the add power effect

Front 141

old manufacturing techniques required that the asphericity of a multifocal GP lens be put on the back of the lens. now we can put in on both the front and the back surface of the lens because of advances in technology. this will decrease the spectacle blur caused by aspheric multifocal GP lenses. you can put all the apshericity on the front surface of the lens.

Front 142

why is it important for aspheric multifocal GP lenses to be large diameter

Back 142

you need the lens to center really well, because when you decenter aspheric optics you get really bad higher order abberations.

Front 143

what does changing the index of refraction of the material aspehric GP multifocal lenses are made of do

Back 143

if you make a lens with a higher index of refraction you can get a greater amount of add power out of the same curvature.

Front 144

how does the size of the pupil affect the amount of add power you get out of an aspheric GP multifocal lens

Back 144

the greater the size of the pupil the more add power you get out of the lens

Front 145

translating multifocal lenses are not simultaneous vision. they have seperate optics for distance and near.

Front 146

how do translating multifocal GP lenses work

Back 146

they rest on the lower lid, and they are like a segmented bifocal design, so that when you look down you are looking through the add portion of the lens.

Front 147

what anatomical feature is important to take into consideration before fitting a pt with a translating bifocal GP lens

Back 147

the position of the lower lid and its relation to the pupil. if it is too far down, the pt will have to lower their eye exteremely far to see through the add portion of the lens. you want a lower lid that positions at the lower limbus or above.

Front 148

how do you fit a tanslating bifocal GP design

Back 148

the back surface is spherical, so you fit just like you would any other spherical GP lens.

Front 149

where do you want the segment line of a translating bifocal lens to align

Back 149

right at the inferior portion of the pupil

Front 150

if you are trying to simulate the lighting of normal room illumination in the slit lamp to evaluat the pupil size in a contact lens wearer, what type of light would you use

Back 150

the blue filter at a real dim setting.

Front 151

if you fit a translating GP multifocal lens too tight, the lens will stick on the eye and not translate as it should

Front 152

how do they keep a translating multifocal GP lens from rotating on the eye

Back 152

1.5 to 2 diopter of prism ballast. you can change the prism ballast if the lens is riding high or not returning to position as it should.

Front 153

do translating bifocal GP lenses tend to decenter nasal or temporal and why? is the adventagous or disadventagous?

Back 153

nasal. because the lid closes in a wave like motion starting temporl and going nasal in order to push the tears towards the punctum. -this is actually adventagous because when the pt converges to read they are in the center of the near optic

Front 154

what do you do if a translating GP multifocal lens is rotating temporal

Back 154

call the lab and have them adjust the orientation of the prism ballast to put the lens at 6 o'clock or slightly nasal.

Front 155

what is a concentric design (De Carle design)

Back 155

cut the entire lens for near vision. then cut a small circular area for distance in the very center of the lens. it work as a translating bifocal design. the eye moves into the near power of the lens when the pt looks either up or down.

Front 156

Start of New Lecture: 5 Keratoconus - CL Design and Fitting 2010

Front 157

what is the incidence of keratoconus

Back 157

1 in 2,000

Front 158

why are many of the keratoconus referals that we get from refractive surgery centers

Back 158

because there are few contraindications to refractive surgery and keratoconus is one of them -they do a good job of screening these individuals

Front 159

does keratoconus occur more commonly in women or men

Back 159

equal

Front 160

are there any systemic conditions associated with keratoconus

Back 160

none

Front 161

are there any other ocular problems associated with keratoconus

Back 161

none

Front 162

what age does the onset of keratoconus typically occur

Back 162

between the ages of 12 and 32 (usually about age 15)

Front 163

what is the etiology of keratoconus

Back 163

we really don't know

Front 164

can we treat keratoconus very well

Back 164

yes!

Front 165

what percent of people with keratoconus will undergo corneal transplant surgery

Back 165

10%

Front 166

what are the top three conditions that comprise corneal transplant patients

Back 166

1. pseudophakic bullous keratopathy 2. corneal endothelial conditions (such as Fuch's dystrophy) 3. keratoconus

Front 167

how long will keratoconic patients require contact lens therapy

Back 167

for the rest of their life

Front 168

is keratoconus usually unilateral or bilateral

Back 168

it is very rare that the conidition is unilateral. however, one eye is usually more effected than the other.

Front 169

describe the onset of keratoconus

Back 169

usually begins as a decrease in vision in one eye and then spreads to the other eye in a year or two.

Front 170

name the three types of keratoconus

Back 170

1. puberty onset keratoconus 2. late onset keratoconus 3. keratoconus fruste

Front 171

how does the age of onset of keratoconus relate to the severity of the condition

Back 171

the younger the onset the more severe the condition

Front 172

how does puberty onset keratoconus compare to late onset keratoconus in respect to the age of onset, symmetry and the severity of the condition

Back 172

Puberty onset: 12 to 16, asymmetrical, more severe Late onset: 20's and 30's, tend to be more symmetrical, less severe

Front 173

what type of keratoconus is the most common

Back 173

keratoconus fruste

Front 174

what is keratoconus fruste

Back 174

a mild, non-progressive form of keratoconus (KC). onset anytime of life. no slit lamp findings associated with KC, and normal corneal thickness. they are often best corrected to 20/25.

Front 175

what is the most important part of a corneal topography

Back 175

the area over the pupil, because that is what the pt sees

Front 176

why are keratoconus pts not able to be corrected with glasses

Back 176

because the curvature of the cornea is asymmetrical. so we correct them with a rigid gas permeable lens.

Front 177

is a pt with keratoconus fruste able to have refractive surgery

Back 177

no, not in this country

Front 178

why do some keratoconus pts end up getting a corneal transplant

Back 178

if the cornea begins to scar and impact best correct visual acuity (worse than 20/40)

Front 179

describe the progression of puberty onset keratoconus

Back 179

if the age of onset was 15, there will be rapid progression for 7 or 8 years (we will have to change lenses a lot), but then the condition will stabilize in the early 20s. -there can be acute relapses after this period though

Front 180

National Keratoconus Foundation: good resource for pts with keratoconus (requested pamphlet from them)

Front 181

what are striae

Back 181

vertical stretch marks that occur in the deep layers of the stroma that occur in keratoconus. they are very diagnostic for keratoconus (very few other conditions can cause them), they are also one of the first signs you will see.

Front 182

topography is not the most important tool in diagnosing keratoconus because many other conditions (even variations of normal) have a steeper inferior cornea and a flatter superior cornea. some feel the vertical striae are more important in diagnosis

Front 183

what is a Fleischer's ring

Back 183

a copper deposition seen in keratoconus. often not a complete 360 degree ring.

Front 184

what percent of the time do you see a Fleischer's ring in keratoconus

Back 184

50%

Front 185

what could you do to see a Fleischer's ring clinically

Back 185

try looking with the cobalt blue filter.

Front 186

does the number of corneal nerves increase in keratoconus

Back 186

no, they just become more visible

Front 187

name 7 slit lamp findings associated with keratoconus

Back 187

1. vertical striae 2. fleischer's ring 3. increased visability of the corneal nerve fibers 4. corneal opacities and scars 5. corneal thinning 6. ectatic reflex (changed appearence of the red reflex) 7. munson's sign

Front 188

why would treating seasonal allergies help keratoconic pts

Back 188

because they will pretty agressively rub their eyes, which can lead to (or worsen) corneal scaring in this condition.

Front 189

corneal thinning does not happen until late stages of keratoconus. so, abscence does not indicate that they don't have keratoconus

Front 190

dispite the fact that a cornea can thin from 550 microns to 20 microns in keratoconus, it is extremely rare for those corneas to have an external rupture. this is because the lamella are still there, but the space between them is reduced. internal rupture (or hydrops) however, is not as uncommon.

Front 191

what is corneal hydrops

Back 191

a complication of advanced keratoconus in which Descemet's membrane ruptures resulting in acute corneal edema. it is due to stretching of descemet's membrane as the cornea steepens.

Front 192

describe the subjective symptoms pts will call in with if they have had acute corneal hydrops

Back 192

extreme pain and complete loss of vision.

Front 193

describe the pathophysiology of corneal hydrops

Back 193

as the cornea steepens, descemet's membrane becomes stretched to the point that it tears. then aqueous rushes in and you have massive edema. bullous lesions form and pop, which is painful.

Front 194

describe the prognosis associated with corneal hydrops

Back 194

in the majority of cases the endothelium repairs its self and pumps the aqueous out and there is a good recovery. if not, a corneal transplant is required. if there is a recovery, the cornea usually flattens dramatically after hydrops, which is beneficial.

Front 195

how does the retonoscopic reflex change with keratoconus

Back 195

you will see a scissor reflex. this is a very early finding (along with vertical striae)

Front 196

scissor reflex on retinoscopy is a good indicator of an irregular cornea

Front 197

how can keratometry detect an early sign of keratoconus

Back 197

you will not be able to get the bottom right right single. this is a very good diagnostic sign (so is retinoscopic reflex)

Front 198

pathfinder corneal analysis: a program on most topographers that screens for keratoconus

Front 199

describe the curvature of the cornea in keratoconus

Back 199

there is inferior steepening (usually just below the pupil). and there is often a superior flatening.

Front 200

pts that fall into the keratoconus fruste category can be fit with traditional GP lenses that they wear full time

Front 201

what is a pretty average corenal curvature

Back 201

43 D

Front 202

if you have less than ______ microns of clearence of a GP lens over the apex of the cornea it will look like it is touching when it is really not (picture in answer)

Back 202

10 microns

Front 203

if you have a GP lens that looks like it is touching the apex of a keratoconic cornea, how can you tell if it is or not

Back 203

if the lens is centered it is NOT touching the cornea. if there is less than 10 microns of clearence, it will look like it is touching when it is not (that is the case in this picture)

Front 204

when fitting a CL for keratoconus you need to look at the flattest part of the cornea, not the steepes part. because that is where the lens is going to rest. if you have a steep inferior area where there is a lot of pooling that is okay because if you were to steepen it, you would be tightening it and putting unwanted pressure on the superior cornea. (picutre in answer of inferior pooling)

Front 205

how do you tell if you have fit a CL to tight on a keratoconic pt

Back 205

they will have decreased wearing time because of comfort

Front 206

how do you know when you need to move into a keratoconic CL from a traditional GP lens in a pt with keratoconus

Back 206

when the apex of the cornea is touching the contact lens (this will cause scaring). you can tell when the cornea is touching the CL because the lens will be decentered.

Front 207

keratoconic CL are often fit with an aspheric design because of their flat peripher and steep central shape

Front 208

does a keratoconic CL tend to ride low or high

Back 208

low; because it centers on the apex which is typically inferior

Front 209

on a keratoconic cornea, the far periphery has a fairly normal curvature. so, if you can get the lens to land in the peripher and vault the cornea you should be in good shape. (large diameter aspheric lenses can be used)

Front 210

how do you fit a keratoconic CL

Back 210

there can be a range of curvature of the cornea of 40 D, so the though part is selecting a base curve. get a KC fitting set and start every pt with the middle base curve; remeber it can only be too flat too steep or just right. keep diving the set in half based on whether the lens is too flat or too steep until you find a good fitting lens. -an alternative is you can do topography and simulate a lens on the eye to see how it fits

Front 211

how much clearance between the cornea and the CL do you want when fitting a keratoconic specific CL

Back 211

25 to 50 microns (a bit more than normal)

Front 212

fitting keratonic patients with a contact lens simulator on a topographer works amazingly well; but hardly anyone is doing it (acording to Pat)

Front 213

what is a reverse geometry lens design

Back 213

every lens has a standard 43 D base curve. however it differs in how high that base curve is vaulted above the base of the eye

Front 214

what is the advantage of the reverse geometry lens in terms of its power vs. other methods of correcting keratoconus

Back 214

the reverse geometry lens requires less minus power. with a really steep base curve you often end up having to put -26 D in the lens (traditional keratoconic CLs). with a reverse geometry lens you have a significant minus tear lens (FAP) so you close to zero or plus.

Front 215

what perameter of a reverse geometry lens do you adjust

Back 215

the height. if you have a bubble you lower the lens. if you are touching the cornea you raise the lens.

Front 216

how could you fit a soft lens on a keratoconic pt

Back 216

a traditional soft lens will mold to the shape of the eye and not create a tear lens that corrects for the irregular surface of the cornea. if you significantly increase the thickness of the soft lens it can act as a rigid lens. Mark Andre has made some like these; I'm not sure if they are on the market or not.

Front 217

reverse geometry lenses: I think the design was made my Pat; I'm not sure if they are on the market or not.

Front 218

what is the advantage of a soft contact lens that would work for keratoconus

Back 218

comfort. the most important thing for a keratoconic is wearing time. they are effectively blind if they can not wear the lens. they need to wear it from the time they get up to the time they go to bed. so if we can increase the comfort and thus the wearing time, that is much more important than the fact that they wouldn't see as well as they would through a RGP

Front 219

is it easier for a pt to adjust to wearing an RGP on one eye, or both eyes

Back 219

both eyes. it is extremely difficult for a pt to adjust to having an RGP on just one eye

Front 220

what design of CL is most commonly used for keratoconus

Back 220

aspheric

Front 221

what is a piggyback lens design

Back 221

a soft contact lens on the eye, with a GP lens that is placed on top of it and adheres to it

Front 222

what type of lens would you use in a piggyback system for keratoconus and why

Back 222

acuvue oasys. because it has a very low modulus and can therefore mold to the shape of the eye. it can fit a normal 43 D cornea as well as a 80 D keratoconic cornea.

Front 223

how does a piggyback system compare to a synergeyes style lens

Back 223

they are very similar. with a piggyback system you can use a lens with a very high Dk. the Dk of the skirt of a synergeyes lens is around 2. -synergeyes is right now releasing a new lens with a skirt Dk of 80

Front 224

the problem with the synergeyes is that with the low Dk skirt hardly any of Pat's patients are able to wear them long term (3 or 4 out of a coupel hundred). -they also had an unexplainable tendancy to adhere to the eye (this was releaved if you drilled three holes in the lens, but the contact lens company would not allow it; the 3 of his patients that are still able to wear the lens are able to because they drilled holes in the lens)

Front 225

describe the care and application associated with a piggyback CL system

Back 225

clean with clear care (because it is approved for all soft and hard lenses). -you put the soft lens on the eye and then wet the rigid lens with an artificial tear, not a conditioning solution (the preservatives in the RGP solution is not compatable with the soft lens)

Front 226

how do you fit a piggyback lens system

Back 226

put the soft lens on the eye and perform keratometry or topography over the soft contact and fit as though the surface over the soft lens were the cornea -the soft lens will smooth out some of the irregularities in the cornea

Front 227

how does the prevelance of keratoconus compare to pelucid marginal degeneration

Back 227

for every 25 pts with keratoconus you will see 1 with pellucid marginal degeneration

Front 228

is pelucid marginal degeneration a type of keratoconus

Back 228

yes

Front 229

what is the shape of the cornea over the pupil in pelucid marginal degeneration

Back 229

there is high against the rule astigmatism over the pupil. this is imporant to know. it is almost always dead on at 90 degrees.

Front 230

if you have a pt come in with greater than 2 D of against the rule astigmatism, what pathological condition do you need to be suspicious of

Back 230

pellucid marginal degeneration

Front 231

are patients with pellucid marginal degeneration correctable with glasses why or why not

Back 231

yes, often refractable to 20/20. because although there is an irregular shape to the cornea, the cornea over the pupil makes an almost perfect against the rule astigmatic shape. it can be as high as 22 D, but as long as it is not irregular, we can correct it with lenses -there will however be problems associated with putting that high of an amount of cylinder into spectacles -note that if the pattern over the pupil (kissing pigeon) is not centered over the pupil, they won't be correctable to 20/20. this is sometimes the case.

Front 232

describe the difficulties associated with fitting RGPs for a pt with pellucid marginal degeneration

Back 232

often use a piggyback system. there is high against the rule astigmatism, which doesn't fit well; also, fitting a toric lens would be difficult because the steep and flat meridians are often not perfectly linear.

Front 233

why do surgens not like doing corneal transplant surgery on pts with pellucid marginal degeneration

Back 233

when they do a normal transplant for a keratoconic eye the use a percision instrument to cut out the old tissue, but the kidney-shaped transplant required for pellucid have to be hand cut the old and new cornea and a lot of astigmatism of usually induced.

Front 234

can pelluicd marginal degeneration pts be fit with soft CLs, why or why not?

Back 234

in the early stages they can. remember the optics over the pupil make a nice against the rule pattern. so, if they have lower amounts of against the rule cyl they can be corrected with toric soft CLs. the problem is that when they start getting larger amounts of cyl even a small amount of rotation will cause distortion for the pts vision.

Front 235

what is the most common CL fitting style Pat uses to correct pellucid marginal degeneration

Back 235

piggyback system

Front 236

is pellucid marginal degeneration usually unilateral or bilateral

Back 236

usually bilateral, but one eye is usually effected worse than the other. similar to keratoconus.

Front 237

how pervelant is keratoglobus

Back 237

you probably go your whole carear and see 1 or less of these pts

Front 238

what is keratoglobus

Back 238

the ENTIRE cornea thins and bulges forward

Front 239

what two types of CL systems work on keratoglobus

Back 239

piggyback, or a scleral lens

Front 240

is posterior keratoconus a type of keratoconus

Back 240

we don't know

Front 241

what is posterior keratoconus

Back 241

a normal 43 D front surface of the cornea with a thinning that only affects the posterior surface -it is EXTREMELY rare

Front 242

if you have a pt with keratoconus that you are not able to correct down to 20/20, and there are no scars or anything that could be attributed to this, what could be causing their decrease in vision and why does that occur

Back 242

could be due to changes on the back surface of the cornea. remember that the ectasia is happening on both the front and back surface of the cornea, and that GP lenses only mask the irregularity on the front surface of the eye.

Front 243

what is a fibroplastic nodule

Back 243

forms in keratoconus. it is an elevated nodule of fibroplastic epithelium that stick out from the cornea. it has the same color and appearence as a salzman's nodule. it is easily debraded by a rigid lens and cuts down the pts wearing time significantly

Front 244

how do you treat a fibroplastic nodule

Back 244

lay down a soft bandage CL in a piggyback system and the nodule will dissapear. if it continues to debrade, then refer them for a superficial keratectomy (surgen removes superficial layers of the cornea with a spud and then applies a bandage CL)

Front 245

are fibroplastic nodules recurrent

Back 245

if they are removed by superficial keratectomy it is rare that they will come back.

Front 246

what are Intacs (intrastromal rings)

Back 246

small plastic rings that a surgen will insert into the stroma of the cornea to either flatten or steepen the cornea. doesn't work nearly as well as refractive surgery, so never cought on for myopia control, but some surgens will put them in keratoconic pts in a attempt to flatten the cornea (one half ring inferior and no ring superior). technique does really work and makes it much harder for us to fit CLs on these pts. the rings can be removed.

Front 247

riboflavin is a new technique that attempts to strengthen the stroma to prevent progression of keratoconus. still under development. right now under investigation by FDA

Front 248

New Lecture: 6 Specialty Lens Designs for the Irregular Cornea

Front 249

does the cornea flatten or steepen after a trauma? why?

Back 249

it will flatten. because in its natural state that are a lot of forces pulling on the cornea in every direction. when you put a laceration into your skin a V shaped divot forms and heals that way, the tissue does not come completely back to gether. the cornea acts the same way, you are actually adding tissue to the eye in that V shaped divot. as you add tissue to the eye you are flattening it.

Front 250

how does the amount of flattening that occurs when you have a corneal laceration change as you approach the visual axis

Back 250

the closer to the visual axis the greater the amount of flattening.

Front 251

describe the physiological mechanism involved in radial keratotomy

Back 251

you intentionally insert a laceration in the cornea to induce flattening.

Front 252

with an irregular cornea from trauma, if you have a shperical peripheral cornea all you need to do is put a spherical rigid CL that fits in the periphery and vaults over the cornea.

Front 253

if you see an old laceration and that area of cornea is actually steepened what is going on

Back 253

when the surgically repair a laceration they have to pull the cornea together tightly so that fluid does not excape. when they pull the cornea together like that it will actually steepen that area of the cornea.

Front 254

what is phototherapeutic keratectomy

Back 254

Phototherapeutic keratectomy (PTK) is a type of eye surgery that uses a laser to treat various ocular disorders by removing tissue from the cornea. PTK allows the removal of superficial corneal opacities and surface irregularities. It is similar to photorefractive keratectomy which is used for the treatment of refractive conditions. The common indications for PTK are corneal dystrophies, scars, opacities, bullous keratopathy.[1]

Front 255

how do you tell clinically if a corneal scar would be able to be treated with phototherapeutic keratectomy

Back 255

use slit lamp to determine the depth of the scar. if it is in the anterior 1/3 or 1/4 of the cornea then they might be a candidate for the therapy

Front 256

what is the benefit of phototherapeutic keratectomy over corneal transplant

Back 256

you can remove a scar with out the potential serious consequenses associated with corneal transplant.

Front 257

is a pt with band keratopathy a good candidate for phototherapeutic keratectomy? why or why not?

Back 257

yes, because it is a disorder that occurs at bowman's membrand and is not too deep to be treated with this therapy.

Front 258

how does phototherapeutic keratectomy affect refractive error

Back 258

you are removing tissue from the cornea, so they will become more hyperopic. if the pt was plano, they will now be hyperopic.

Front 259

when did sucessful corneal transplant surgeries begin and what allowed that to happen

Back 259

in the 1950s. they had been attempting them long before this, but the availability of effective steriod medications in the 50s allowed the surgeries to be sucessful without rejection.

Front 260

do corneal transplant rejections still happen today

Back 260

yes, however, they are identified and effectively treated very quickly. they are still relatively common, but not a serious as in the past because of our effective methods of treating rejection with steroids in the beginning stages.

Front 261

why do they try to match the age of the doner and the recipeint on a corneal transplant surgery

Back 261

because in a young cornea the tissue is more stretchable and will tend to bulge under the pressure of an adult eye. you don't want an infant cornea in an adult.

Front 262

what type of suture is most commonly use in corneal transplant surgery and why

Back 262

a double running suture. because they can adjust the tension more easily to best control the amount of astigmatism after the surgery. -the other technique is the interrupted sutures. they are not connected, individual sutures.

Front 263

if you want to flatten an area of a cornea on a corneal transplant would you want to losen or tighten the sutures in that area

Back 263

losen

Front 264

how soon do they remove the sutures in a corneal transplant

Back 264

they usually leave them in indefinately. epithelium will heal over the top of the suture.

Front 265

how long does healing for a corneal transplant take? Why?

Back 265

6 months to 1 year. it takes so long because there is no vascular supply to the cornea.

Front 266

what other ocular conditions tend to occur secondary to corneal transplant surgery and why

Back 266

glaucoma and cataracts. they often need to be on steroids for the rest of their life. -corneal transplant is not a trivial procedure.

Front 267

why is it a good idea to put of surgeries as long as possible

Back 267

because advances in surgical techniques in our profession happen rapidly.

Front 268

what is the key to fitting a corneal transplant pt

Back 268

use a large diameter lens. remember that out past the edge of the transplant is the pts normal cornea. if you use a large enough diameter lens to land on their normal cornea you will have a much easier fit.

Front 269

95% of corneal transplant pts will be able to be fit in a large diameter corneal lens. the rest will need to be put into a scleral lens.

Front 270

to fit irregular corneas (corneal transplant pts) you need a fitting set of large diameter lenses used for fitting irregular corneas.

Front 271

why is an aspheric design important for large diameter lens on a steep cornea

Back 271

because of the eccentricity of the eye, if you use a large diameter spherical lens you will have an extremely large amount of apical clearance. you need to use an aspherical design with a sperical center and an aspheric periphery (flattens in the periphery) to decrease the excessive apical clearance

Front 272

what is mean topographical curvature

Back 272

a rough method for using a topographer to determine the starting base curve on an irregular cornea if you don't have a good idea of where to start. the topographer finds the steepest part of the cornea and makes it red, and it finds the flattest part of the corena and makes it blue. you chose the curvature in the very center of this scale and use it as your starting point: mean topographic curvature. it's not great, but can work okay.

Front 273

why would a pt have an anterior chamber IOL following trauma

Back 273

if too much of the capsule is damaged.

Front 274

Medmont: software that uses corneal topography and simulates what the flourescene pattern would look like on the eye as you adjust CL perameters. a pretty neat way to design a GP lens without wasting the pts time.

Front 275

every single condition that affects the anterior surface of the eye has the potential to leave the cornea with an irregular surface.

Front 276

what is the average amount of astigmatism leaft in the US after penetrating keratoplasty

Back 276

6 D

Front 277

large diameter corneal contact lenses for irregular corneas are about 11 mm. scleral lenses are about 13-18 mm in diameter.

Front 278

are scleral lenses comfortable? why?

Back 278

they are suprisingly comfortable because they don't move on the eye and they rest on the sclera which has relatively few nerve endings compared to the cornea.

Front 279

what is a plateau topography

Back 279

occurs in kertaocnic pts (not other conditions) who have undergone corneal transplant surgery. the periphery is a normal curvature and the central cornea becomes flat. it looks like the topography of someone who has had LASIK or something.

Front 280

what is peripheral keratometry

Back 280

a method of measuring curvature of the peripheral cornea with a keratometer if you don't have a topographer. Pat Caroline did a study on peripher keratometry at Pacific. remember that the keratometer is measuring a 3 mm zone, so it is a rough estimate.

Front 281

why do you get large corneas in congenital glaucoma

Back 281

the elasticity of the stoma in a young cornea is very great. if you place a corneal transplant form a child on an adult it will bulge because of this elacity. therefore, if you have glaucoma as a child it will stretch the cornea making it larger than normal.

Front 282

name two signs of corneal transplant rejection

Back 282

1. a distinct line of cellular compromise, known as Khodadoust line, which has the potential to advance across the entire cornea 2. hazing or decrease of VA due to edema

Front 283

how often do pts experience a corneal transplant rejection

Back 283

it is actually rare that they will not experience at least a minute rejection at some point. today, steroids reverse almost all of these rejections.

Front 284

what percent of pts undergoing modern LASIK surgery will lose 2 lines of acuity or more as a result of the surgery? what percent will have permanent problems with glare etc.

Back 284

1% lose 2 lines of acuity. 5% have other problems.

Front 285

name 5 types of refractive surgery and an example of each

Back 285

1. tissue subtraction: LASIK 2. tissue addition (prosthetic): intacs 3. tissue incision/coagulation: radial keratotomy/photoagulation 4. tissue replacement: corneal transplant 5. intraocular implant: IOL -LASIK is obviously the most common

Front 286

what layer of the cornea does radial keratotomy go down to

Back 286

descemet's membrane

Front 287

in radial keratotomy is it common for one side of the incision to raise above the other. this creates a surface that is difficult to stabilize CLs over, the lenses are likely to pivot.

Front 288

www.orthotool.com: a program for designing contact lenses

Front 289

what types of CL systems (2) would work for a person who has had refractive surgery (and a high refractive error before surgery) and why would they be needed

Back 289

reverse geometry or a piggyback system with a high plus (because of the thickness) soft lens. with the plateau shape of the cornea a spherical back surface on a CL would create a bubble. reverse geometry allows you to have a flatter base curve that is just vaulted above the cornea; a high plus soft lens would have a flatter base curve on the back surface (the plus power would be compinsated for with the rigid lens).

Front 290

on an irregular cornea you want the lens to land 4 mm to either side of the center of the cornea. just take a topographer and count out four squares from the center and measure the curvature there and that is where you will want the CL to land.

Front 291

the parameter that you change on a reverse geometry lens is the height of the reverse curve. it come in increments of 25 microns.

Front 292

why is it inadvisable for a person to have refractive surgery when there is a chance that their refractive error might progress further

Back 292

because the amount of tissue that you would need to remove to correct 1 or 1.5 D of myopia progression is so small that it is highly likely that they would remove too much tissue and make them hyperopic.

Front 293

how would hyperiopic refractive surgery work

Back 293

you would remove tissure around the center of the cornea, but not in the center of the cornea.

Front 294

what type of CL design would work well with a hyperopic LASIK pt

Back 294

aspheric, steep in the center and flat in the periphery.

Front 295

New Lecture: 7 Management of the Irregular Cornea with large Diameter Lenses

Front 296

describe the comfort of a piggyback lens system

Back 296

supposed to be more comfortable than straight GP lens. good for people who have worn soft CLs in the past and would have a hard time adjusting to a GP lens. -if the lens discomfort is due to the GP lens moving on the eye, then a piggyback system will improve comfort. if discomfort is due to the lid interaction with the edge of the lens, then piggyback system won't improve comfort much.

Front 297

piggyback system can be used to help manage peripheral GP complications such as VLK (vascularized limbal keratitis)

Front 298

oxygen permeability due to lens thickness (related to power) does not change a lot with sylicone hydrogels. it is more a factor with hydrogels and hema based lenses.

Front 299

picture

Front 300

first hybrid lens was the Saturn II. it had a low Dk center and a monocurve design. second hybrid lens was the SoftPerm, it also had a low DK center, but a bi-curve design.

Front 301

what is the name of the only hybrid lens on the market today

Back 301

SynergEyes

Front 302

name the the six types of the SynergEyes lens

Back 302

A: astigmatism M: multifocal KC: keratoconus PS: post surgical (reverse geometry design) ClearKone: moderate to severes keratoconus (reverse geometry design) Duette: sylicone hydrogel skirt (about to be released)

Front 303

the SynergEyes lens has a high Dk center. the skirt, however, is low Dk. they are currently releasing a new lens with a sylicone hydrogel skirt that should have a higher Dk though. -the synergeyes lenses have an aspheric back surface

Front 304

the synergeyes lenses have 2-3 skirt base curves

Front 305

synergeyes lenses are laser marked with the type of synergeyes lens and the base curve of the skirt and the base curve of the center

Front 306

how do you fit the synergeyes lens

Back 306

center curve is usually fit 1 to 1.5 steeper than flat K. you fit them steep. there is a calculator to determine how to fit these lenses.

Front 307

name two high molecular weight fluroescene dies and what they are used for

Back 307

Flura-Safe and Fluroesoft. they are used as a fluroescene stain that won't stain soft contact lenses. -used with synergeyes.

Front 308

what do you need to let the pt know before putting on a lens with Flura-safe on it.

Back 308

that it is going to sting. and that it is the die, not the lens.

Front 309

what type of stain do you need to use to evaluate the fit of a synergeyes lens

Back 309

flura-safe or sluoresoft (high molecular weight die that won't stain the skirt)

Front 310

does flura-safe or fluroesoft contain anesthetic

Back 310

flura-safe contains anesthetic. fluoresoft does not. -remember that you can't asses comfort if there is an anesthetic in the eye.

Front 311

how much apical clearence are you trying for with a synergeyes lens

Back 311

50 microns.

Front 312

describe the method for instilling the flourescene to evaluate the fit of a synergeyes lens

Back 312

you need to remove the lens and apply the flourescene to the bowl of the lens. there is not enough tear exchange to just apply the drops to the eye and have the flourescene get underneath the lens.

Front 313

describe the technique for removing a synergeyes lens

Back 313

have the pt look straight ahead. grasp the lens right at the junction of the GP and the soft skirt (or use a DMV placed right at the junction of the GP and the skirt). may want to instill a drop of artificial tears to lubricate the eye and help the lens not to stick to the eye.

Front 314

synergeyes lenses don't decenter hardly at all

Front 315

what type of bifocal design is in the synergeyes M lens

Back 315

simultaneous vision: center add; they get both distance and near optics at the same time

Front 316

the synergeyes M (multifocal) comes with 2 segment sizes for the center add portion (remember it is a simultaneous vision design)

Front 317

what is the limitation of the synergeyes KC lens

Back 317

the synergeyes lens centers so well; we rely on most keratoconic lenses to decenter just a little bit. withough decentering it is possible for the lens to impinge on the slightly inferiorly decentered (usually) cone.

Front 318

if a GP lens looks like it might be touching the apex of the cornea, look really closely at that area on follow up to look for any epithelial changes

Front 319

synergeyes KC is not a reverse geometry design; synergeyes clearkone is a reverse geometry design.

Front 320

does changing the height of the reverse curve in a reverse geometry lens change the power of the lens

Back 320

no. SAM FAP relies on changing the curvature of the tear film, not the thickness of it.

Front 321

what type of solution can you use on a synergeyes lens

Back 321

you can not use a GP conditioner or cleaners on this lens. Clear care is solution of choice.

Front 322

what is the recommended replacement schedule for the synergeyes lens

Back 322

every 6 months

Front 323

why is it important to not impinge on the limbal area with a scleral lens design

Back 323

so you don't disrupt the limbal stem cells.

Front 324

what is the definition of a scleral lens

Back 324

if a GP lands on the sclera, we term it a scleral contact lens

Front 325

what is the typical range of diameters of scleral CLs

Back 325

13.5 to 18.2 mm

Front 326

why would a scleral lens be used for exposure disease

Back 326

because there is so little tear exchange, you can apply wetting agents to the bowl of the lens and they will stay over the cornea for a long time.

Front 327

what type of wetting agents do you use with a scleral lens and why

Back 327

you need a preservative free, pH balanced solution to put into the bowl of the lens before insertion because there is pretty much no tear exchange. you don't want a preservative solution in contact with the cornea for 8 hours straight. Unisol is the brand name recommended (it's hard to find)

Front 328

why is it not a good idea to have a radial keratotomy wound line that goes all the way to the limbus

Back 328

because vessels will follow the wound line toward the central cornea. after they found this out, they began making the incision stop short of the limbus.

Front 329

New Lecture: 8 Tinted & Prosthetic Contact Lenses

Front 330

CLs with colored irides to cover a disfigured iris are called prosthetic lenses

Front 331

name the three coloring methods for CLs

Back 331

1. translucent tints 2. opaque 3. UV absorbing

Front 332

what type of coloring method is a visability tint considered to be

Back 332

translucent tint

Front 333

there are two types of translucent tints: one is like a visability tint, the other is cosmetic

Front 334

does the tint of a translucent tint change with the power, or thickness, of the lens

Back 334

no, the tint is a uniform thickness put on the front surface of the lens and does not change with lens thickness.

Front 335

some soft CLs come with UV blockers and some don't. the same is true for GP lenses

Front 336

GP lenses with a UV blocker in them can be more difficult to evaluate the fit of because the UV protection can inhibit the excitation of the flourescene molecules. this may or may not be a problem for evaluating the fit of the lens.

Front 337

if you have UV protection in your CLs, does that eliminate the need for sunglasses

Back 337

no, the conjunctiva is still exposed.

Front 338

how will a translucent cosmetic tint change in color when on the eye. how about an opaque tint.

Back 338

a translucent tint will combine the color of the CL with the color of the iris. opaque lenses are darker and tend not to let light through.

Front 339

on the internet you can upload your picture and put different colored contacts on your picture to see how it looks. you can then upload the pictures to facebook and see what your friends think.

Front 340

what are the two methods for putting an opaque tint on a CL

Back 340

dot matrix: pattern of small dots on the front surface of the lens laminate construction: iris pattern painted on unhydrated HEMA button, then a layer of HEMA is placed over the drawing. then they hydrate the lens. theses lenses are extremely expensive ($350-450 per lens, wholesale)

Front 341

one thing you can do for pts who are light sensative (perhaps because part of the iris is missing) is paint the back surface of an opaque lens black. you can ether paint the entire back surface black or you can just paint behind the iris black and leave the pupil clear.

Front 342

do tints on CLs affect oxygen permeability

Back 342

generally not a consideration. if you have a laminate HEMA design it would be an issue.

Front 343

if a colored lens is not centered, this can affect vision because the pupil will be partially covered by the colored portion of the lens.

Front 344

it is important to set expectations for colored contacts. it doesn't really work for a dark eyed person to attempt to have blue eyes.

Front 345

how does the topographer affect pupil size

Back 345

it uses an infrared light, so it does not affect pupil size. this is a good way to measure pupil size for colored contacts.

Front 346

you can use tinted lenses to make a strab look like they are looking straight ahead.

Front 347

cosmetic fitting sets: the colored lenses are plano so the pt can try on the colors. they also have a set of lenses with no color, but all the different powers in the set so you can assess vision and fit. they will leave with the clear lenses and come back in a week for a follow up, wearing the clear lenses, just like a normal CL fit.

Front 348

there are companies that tint lenses. so, you can fit the pt with whatever lens you want, and sent the lens to the company and they will tint/paint the lens.

Front 349

you need to try out colored lenses in bright, dim, and normal room illumination to see how it affects the pts vision, because the size of the pupil on the contact is fixed. -try to match pupil size to their daily activities.

Front 350

what types of cleaning solutions can you use on a colored CL

Back 350

the main thing you want to avoid is any kind of alcohol based system (only one is called miraflow/extra strength daily cleaner). some people feel that peroxide solutions will cause color bleaching (Dr. Lampa feels that neither peroxide solutions or multipurpose systems will damage the color of the lens)

Front 351

there is some evidence that the altered surface of colored CLs changes the charge, which can lead to increased protein deposition

Front 352

custom hand painted CLs: you want to photodocument the eyes, so the artist can match the color of the eyes as well as possible. -what is helpful to have the pt do when doing this photodocumentation

Back 352

wear a neutral colored shirt (like grey or white) so as not to influence the color of the eyes. (have them put on your white coat)

Front 353

What are ChromaGen lenses

Back 353

they have a tinted center and are desinged to improve color vision

Front 354

there are certain vocations that are particularly exposed to artifical UV light: microbiology labs, welders, some technology sectors.

Front 355

there are office based tinting systems, where you can follow a "recipe" and tint contacts different colors. (called Softchrome)

Front 356

what material does not hold color very well

Back 356

silicone hydrogel -the CL companies may have found a way around this, but it is not released yet.

Front 357

how prevelant is aniridia

Back 357

very rare. 1 in 56,000-90,000 in the US