1
Q
Work up during CL appointments
A
VA
Refraction
Corneal curvature (K’s, topography)
Corneal size (HVID)
Anterior segment
Posterior segment
2
Q
What are 3 reasons why CL may be worn
A
Visual correction
Cosmetics
Therapeutic/medical reasons
3
Q
OAD
A
Overall diameter
4
Q
OZD
A
Optic zone diameter
5
Q
BCR
A
Base curve radius
6
Q
BOZR
A
Back optic zone radius
7
Q
PCR
A
Peripheral curve radius
8
Q
PCW
A
Peripheral curve width
9
Q
What is the central region where vision is corrected?
A
Optic zone
10
Q
The optic zone is provided by what?
A
The base curve
11
Q
The outer portion of the lens that generally have flatter (prolate) curves than the central base curve
A
Peripheral curves
12
Q
Peripheral curves assist in the ______ of the lens and impact the ________
A
Centering, movement
13
Q
Edge profiles of CLs interact with the ______
A
Eyelid
14
Q
Edge profiles of CLs are imperative for what?
A
Comfort and centration
15
Q
HVID
A
Horizontal visible iris diameter
16
Q
HVID may also be called what?
A
White to white
17
Q
Average HVID
A
11.6mm
18
Q
Normal HVID
A
10-14mm
19
Q
OAD = _____ + ______
A
Optic zone diameter + peripheral curve widths
20
Q
What. Cue center and align appropriately to cornea to provide clear vision?
A
Base curve
21
Q
What is sagittal height?
A
The height of the cornea
22
Q
What is sagittal depth?
A
The depth of the lens needed to fit a cornea at a given height
23
Q
Steeper curves have a ______ sag
A
Greater sag
24
Q
Larger diameters have a _____ sag
A
Greater
25
The size f the cornea directly impacts what?
The sagittal height of the cornea
26
Larger HVID is correlated with ______ sagittal depth
Larger sagittal depth
27
Steeper cornea is correlated with _____ sagittal depth
Larger sagittal depth
28
Increased OAD of the lens causes _____ sagittal depth
Increased sagittal depth
29
Steepened BC and/or PC _______ sagittal depth
Increases
30
Hydrogel lenses are comprised of what?
HEMA
31
Are hydrogel contact lenses hydrophilic or hydrophobic?
Hydrophilic
32
Hydrogel CLs rely on _____ to allow oxygen through the lens
Water
33
The higher the water the more the _____
Oxygen
34
The lower the modulus (softer), the _______
Less elastic
35
What hydrogel lens additive increases oxygen by increasing water uptake?
NVP
36
What hydrogel lens additive increases wetting and resistance to deposits?
GMA
37
What hydrogel lens additive helps hydrophilic ability and water uptake?
PVA
38
Can additives be used in CLs to reduce transmission of UVA and/or UVAB?
Yes
39
Refractive index of hydrogel lenses
1.34 to 1.44
40
Negative charge is ionic and more prone to what?
Deposits
41
Neutral charge is non-ionic so it may not attract as many ______
Deposits
42
What are the four FDA hydrogel groups?
Group I: low water, non-ionic
Group II: high water, non-ionic
Group III: low water, ionic
Group IV: high water, ionic
(Low high low high, in in i i)
43
Group V of FDA hydrogel
Silicone hydrogel
44
Deposits occur more likely on what material and which group?
High water content and ionic material, group IV hydrogel
45
Why are th daily disposables lenses not a deposit resistant?
Because the don’t have the be since they are meant for only daily use
46
Increase water leads to ____ oxygen which causes more ______ lenses
Increased oxygen, more fragile lenses
47
Soft contact lens application disrupts what layer?
Anterior tear layer
48
Thicker contact lenses lose ___ water
Less water
49
Higher water lenses lose a _____ percentage of their water
Greater
50
_____ water, ____ lenses lose the most water
High water, thin lenses
51
What are the possible concerns with thin high-water lenses?
As the lenses dehydrate, corneal desiccation can occur as water is pulled from the cornea to the lens -> it is tarrying to equilibrate
52
How can corneal desiccation manifest?
Staining on cornea and conj
Stain that outlines wear of CL
Superior epithelial accurate lesion
53
As lenses dry, we gain more ______
Deposits
54
More deposits leas to decreased _____ and decreased _______
Decreased VA and decreased comfort
55
Silicone hydrogel (SiHY) lenses are comprised of _______ but ______ silicone
Hydrophobic but aerophilic silicone
56
SiHY lenses have poor ______ but very high _____
Poor wetting but very high oxygen
57
For hydrogels, high water content = _____ DK
High DK
58
For silicone hydrogels, high water content leads to _____ silicone content, which leads to ____ permeability
Low silicone content, low permeability (low DK)
59
Increase modulus leads to _____ conformation to the cornea
Less conformation
60
Patients with _________ tend to have increased signs and symptoms with contact lens wear
Ocular surface disease
61
Are daily wear lenses approved for overnight wear?
No
62
Extended wear lenses are approved for up to __ nights extended wear or ____ days of continuous wear
6 nights, 30 days (ONLY pure vision Night and Day)
63
What is a term I used to describe approved lenses for 30 days continuously?
Continuous wear
64
Single use contact lenses term?
Daily disposable
65
Term for contact lenses used for 2 weeks or less?
Disposable
66
Term used for contact lens used for 1 month up to semiannually?
Frequent replacement
67
Term used for contact lens replaced annually?
Conventional
68
What is critical in management of an OSD patient that is choosing a CL?
Follow up care with lens removal adn staining is critical to understand impact
69
Most GPs today are composed of what?
FSA
70
What are GP lenses composed of FSA/?
Adding fluorine increases wetting and increased deposit resistance e
71
Often as fluorine increases, _____ decreases, which makes the lenses _____
Hardness decrease, makes the lenses softer
72
After manufacture, GP lenses may receive a high-powered cleaning treatment known as what?
Plasma treatment
73
What does storing GP lenses wet do?
Improves initial wetting and dispensing experience
74
A perfectly wet table material will spread evenly across and look flat having a _____ angle
Low
75
An unwearable material will not spread. It will maintain its ptominaen spherical shape having a _____ wetting angle
High
76
____ degree angle = better wet ability
Lower
77
GP average index of refraction
1.42-1.48
78
GP/RGP high index of refraction range
1.51 to 1.54
79
Higher indices of refraction in GP/RGPs allow the lenses to be _____
Thinner
80
How does hydrapeg coating impact the wetting angle?
Reduces wetting angle
81
How does hydro peg coating impact impact lubricity and surface water retention?
Increases
82
How does hydrapeg coating impact TBUT?
Increases TBUT
83
How does hydrapeg coating impact protein deposits
Resists protein deposits
84
Ratio of mass to equal volume of water?
Specific gravity
85
_____ specific gravity may help keep heavy plus lenses from drooping
Lower specific gravity
86
Lathe manufacturing of CLs
Cut from hard plastic rod or button form is made
Soft lenses are rehydrated after cutting
Hydrogel, SiHY, or GP
87
Spin cast manufacturing of CLs
Liquid polymer is injected into a spinning mold
Mostly historical and costly
Hydrogel form only
88
Cast molding manufacturing of CLs
Separate mold created for each SKU
SiHY or hydrogel
89
DK = ?
Oxygen permeability
90
DK of Soft hydrogel lenses is correlated with_____ content
H2O content
91
DK in SiHY lenses is correlated with _____ content
Silicone content
92
DK in GP lenses is unique to the ____ composition of the lens
FSA composition of the lens
93
Low GP oxygen permeability values
<15
94
Mid GP oxygen permeability values
15-30
95
High GP oxygen permeability values
31-60
96
Super GP oxygen permeability values
61-100
97
Hyper GP permeability values
100 +
98
How does flexibility change with increasing oxygen permeability?
Decreases
99
Oxygen transmissibility = ____ / ___
DK/t
100
The thicker the lens the _____ the oxygen transmission
Lower
101
Amount og oxygen between cornea and lens
EOP - estimated oxygen percentage
102
EOP and DK/t needs are used to determine what?
The oxygen needs of the cornea with a goal to prevent corneal swelling
103
In the open eye situation or with daily wear, what DK/t or EOP minimums are needed?
DK/t of 24 or EOP of 10%
104
EOP and DK/t needs in closed eye or extended wear situations based on HM criteria?
DK/t of 87 or 17.9% EOP
105
DK/t need in closed eye or extended wear situations based on HB criteria
DK/t of 125
106
Overnight Edema DK/t and EOP requirements
DK/t - 87.0 +/- 3.3 or EOP 17.9%
107
What does oxygen help provide when wear in contact lenses?
-Prevent hypoxia
-prevent edema
-maintain mitosis
-maintain nerve fiber endings
-maintain appropriate corneal sensitivity
-maintain pH
108
What contact lenses mini the normal edema cycle and are approved for EW?
SiHY CLs
109
How does epithelial and stroma edema impact transparency
Decreases transparency
110
What CLs lead to this edema cycle:
-Minimal to no edema during the day
-minimal overnight edema
-overnight edema resolves during the day
No cl wear to thin hydrogel CLs and SiHy CLs worn on a daily wear basis only
111
Hypoxia changes:
-decreased transparency
-vacuoles
-folds
-vascularization
Block 15
flashcards
Decks in class (14)
# Cards
-
BV: Intro To BV And Motility102
-
Optics: Lensometry SV Lenses13
-
Optics: Lensometry Of Multifocals28
-
Optics: Prism28
-
Contacts: Intro To Basic CL111
-
Ant Seg: Uvea/scleral And Autoimmune Disease124
-
Post Seg: Anatomical Review And Intro To Disease142
-
Post Seg: Diagnostic Approach To Retinal Disease91
-
Post Seg: Reitnal Physiology40
-
Ant Seg: Embryology And Orbital Disease171
-
Optics: Prism In Toric Lenses8
-
BV: Vergences95
-
Ant Seg: Treatment Of Uveitis, Scleritis, And TED124
-
Post Seg: Diabetic Retinopathy177
