soft lens material fitting & follow-up evaluation university of missouri-st. louis college of...
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SOFT LENS MATERIAL FITTING & FOLLOW-UP
EVALUATION
University of Missouri-St. LouisCollege of Optometry
Advantages
• Initial comfort• Little lag• Simple to fit• Inventory• Quick adaptation• Occasional wear
• Hard to dislodge• Difficult to get trapped
FB• Rarely causes tearing• Cosmesis
Disadvantages
• Bacterial contamination/greater risks with noncompliance
• Care?• Durability
• Prone to deposits• Reduced oxygen
permeability with hydrogel materials
• Quality of vision• Difficult to verify• Limitations of
correction
Materials
• Chemical monomers linked to form chains of polymers, cross-linked loosely
• polyHema
• Add other monomers to improve HEMA
• MAA, MMA, GMA, PVA
• Silicone Hydrogels
Monomer Characteristics
• HEMA – hydrophilic, soft, wettable, low Dk
• EGDMA – Stable, low Dk• MAA – hydrophilic, pH sensitive• MMA – Hard, no Dk, machinable, optical
clarity, stable• NVP – Hydrophilic, wettable, high water
uptake, High Dk, pH sensitive
Monomer Characteristics
• GMA – Wettable, deposit resistant, low Dk
• PVA – Hydrophilic, high water uptake, Deposit resistant
• Silicone – hydrophobic, High Dk
The Science Behind the Lenses
• HEMA-based materials– Positives
• Easily fabricated into CL’s• Relatively cheap to produce• Highly flexible• Dimensionally stable to changes in pH & temp.
– Negatives• Reliance on H2O to transport O2
– Limitation to amount of O2 transmitted to cornea
– Corneal oxygen deficiency
2006-01-0004
O2 transport – HEMA materials
2006-01-0004
Silicone Hydrogels Available
Focus Night & Day
O2 Optix & Air Optix Aqua
AV Advance
AV Oasys
PureVision Biofinity
Material Lotrafilcon A
Lotrafilcon B Galyfilcon A
Senofilcon A
Balafilcon A Comfilcon A
Dk 140 110 60 103 101 128
Dk/t 175 138 86 147 110 160
Water content
24% 33% 47% 38% 36% 48%
Powers +6 to -10 +6 to -10 +8 to -12 +8 to -12 +6 to -12 -0.25to -10
BCR 8.4, 8.6 8.6 8.3, 8.7 8.4, 8.8 8.3, 8.6 8.6
Replace Monthly 2-4 weeks 2 weeks 2 weeks Monthly Monthly
Silicone Hydrogels Available
Avaira O2 Optix Custom
Premi O
Material Enfilcon A Sifilcon A AsmofilconA
Dk 100 82 129
Dk/t 125 117 161
Water content
46% 32% 40%
Powers -0.25 to -6 +20 to -20
BCR 8.5 7.4 to 9.2
Replace 2 weeks 3 months 2 weeks
Other Dk/t Values
• Soflens 38 = 21
• AV2 = 20
• Focus Monthly = 15
• Focus Dailies = 27
• SF 1 Day = 16
• Proclear = 30
Pure Vision (B&L)
• Performa surfacing process
• Do not use abrasive cleaners, H2O2, Miraflow
• Glassy islands• Available in toric &
multifocal• DW/EW/CW
Focus Night & Day, Air Optix Aqua O2 Optix & O2 Optix Custom
(Ciba)
• No restrictions on care solutions• Plasma coating• Surface chemically uniform• Uniformly coated with hydrophilic polymer• N&D DW/EW/CW, Air & O2Optix DW/EW,
O2 Optix DW, Air Optix for Astigmatism
Acuvue Advance & Oasys (Vistakon)
• AV2 design, UV blocker
• No coating, Hydraclear wetting agent on surface and throughout lens
• AV Adv. DW, Oasys DW/EW
• Toric and Multifocal
Biofinity & Avaira(CooperVision)
• Company reports no surface treatment or wetting agents
• Aquaform comfort science
• DW at this time
Lens Surface Modifications
• Silicone elastomer materials generally display:– Decreased surface wettability– Increased lipid interaction– Accentuated lens binding
• Require “surface modification”
2006-01-0004
Surface Modifications
O2OPTIX NIGHT & DAY
PureVision ACUVUE Advance ACUVUE OASYS
Permanent, chemically bonded plasma treatment
for a smooth, continuous surface
Surface made up of silicate islands that do not completely
cover the surface
No permanent plasma treatment
All photos 5 x 5 micron resolution
2006-01-0004
Surface ModificationsFocus N&D, O2 Optix, Air Optix
O2 Optix Custom
PureVision AV Advance,
AV Oasys
Biofinity, Avaira
PremiO
Ciba Vision Bausch & Lomb
Vistakon CooperVision Menicon
Plasma coating
Plasma oxidation
Internal Wetting agent-
polyvinyl pyrrolidone (PVP)
None Nanogloss
Biofinity
Siloxane molecules attract and bond to surrounding water molecules, continuously wetting and lubricating the material (Courtesy CooperVision)
Increased Modulus
• Mucin Balls
• GPC/CLPC
• SEALs
• Edge Fluting
ModulusMaterial Hydrogel/SiHy Modulus (MPa)
HEMA Hydrogel 0.50
AV Advance SiHy 0.4-0.43
Avaira SiHy 0.5
AV Oasys SiHy 0.6-0.72
Biofinity SiHy 0.75-0.8
PremiO SiHy 0.9
O2Optix/Air Optix SiHy 1-1.2
PureVision SiHy 1.1-1.25
Focus N&D SiHy 1.4-1.52
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
40 60 80 100 120 140 160
O2Optix
Purevision
Oasys
Advance
Mod
ulus
(MPa
)
Dk
SiHDk & MODULUS
Night&Day
An increased Dk is linked with an increase in modulus
biofinity
Courtesy CooperVision
Comfort?
• Silicone hydrogel lens materials are different from conventional HEMA-based materials
• Some patients will experience increased “awareness” when refit
2006-01-0004
Dailies with AquaRelease(Ciba)
AV 1Day Moist(Vistakon)
Water content = weight of water in lens/ total lens
weight X 100
Water Content
• Range of water content 24-79%
• HEMA by itself has 38% water
• Plays a role in determining:
Dk/t, durability, stability, deposit formation, pore size
Silicone Hydrogels
• Hema – Hydrophilic
• Silicone – Hydrophobic
• Dk-Hema = 10
• Dk-Silicone = 250
Dk compared with % Water
27
55
28
55
32
66
26
58
86
47
101
36
138
33
147
38
175
24
0
20
40
60
80
100
120
140
160
180
Dk/t H20
Dk/t and HDk/t and H22OO
Conventional Lenses Silicone Hydrogels
ACUVUE®
OASYS
™
PureV
isio
n®
NIGHT
& DAY
®
Frequen
cy® 5
5.
Bio
med
ics
®
Soflens
® 66
ACUVUE® 2
O 2O
PTIX™
ACUVUE
®
Advance
™
2006-01-0004
FDA Classification
• Group 1 – nonionic, low water
• Group 2 – nonionic, high water
• Group 3 – ionic, low water
• Group 4 – ionic, high water
• Group 5 - ???????
Groups 2 & 4 avoid
• Heat disinfection
• Sorbic acid/potassium sorbate
• Deposit-prone patient
Oxygen Permeability
• Increases with water content in HEMA lenses
• Increases as water content decreases in Silicone Hydrogels
• Oxygen transmission increases with decreases in CT
• Dk ranges 8.3 to >100• Tear exchange 1-2%
Oxygen Profiles (-3.00 sph.)
2006-01-0004
Examples
• Hydrocurve II 45%, Dk 12, CT .05, Dk/t 24
• Hydrocurve II 55%, Dk 22, CT .05. Dk/t 44
• Optima 38, Dk 8.5, CT .06, Dk/t 14
• Optima FW, Dk 8.5, CT .035, Dk/t 24
• B&L 70, Dk 33.8, CT .1, Dk/t 33.8
Wettability
• Aids in lid closure and comfort
• Contaminants adhere to surface
• Increase sensitivity to preservatives
Internal Wetting Agents
• Polyvinyl pyrrolidone (PVP)
• Polyvinyl alcohol (PVA)
Material Selection• Patients with Ocular Compromise• Refractive Error including astigmatism• Deposit-prone patients• Age• Lens Handling• Part-time Wearers• Compliance• Oxygen requirements• Patient’s Interest• Dry Eye
Soft Lenses for Dry Eye
• Proclear• Extreme H2O• AV Advance• Preference• CSI• Dailies with
Aquarelease• AV 1 day Moist
• O2 Optix/Air Optix Aqua
• Focus N&D• AV Oasys• Purevision• Biofinity• Frequency ?
Why decreased dryness in SiHy?
• Low Dk of hydrogels leads to hypoxia– Decreased corneal sensitivity, decreased tear
flow– Leads to inflammation and ocular surface
damage– Leads to lacrimal damage
Lens Design
• Lathe-cut
• Cast molded
• Spun-cast
• Lathe-cut back & spun-cast front
Optics
• Aspheric lenses to optimize spherical clarity or correct spherical aberration
• Focus N&D, Air & O2 Optix, PureVision, Frequency Aspheric, Biofinity, Avaira
FITTINGPatient Selection
Indications
• Spherical RE• Low astigmats• Lenticular astigmatism• Career enhancing• Occasional wear
• Inability to adapt to GP’s
• Responsibility• Motivation• Chronic GP
complications
Low astigmats
• Spherical equivalent
• Soft Toric
• Aspheric design
Career Enhancing
• Athletes
• Actors
• Models
• Eye Changing Tints
• Fountain of Youth
Responsibility
• Age restrictions
• Participation in the costs of the lens
• Most who sleep in their lenses do so frequently – average is 21 nights/month
• 41% of those sleeping in their lenses do so for more than 7 nights continuously– Many (28%) are wearing lenses
not approved for such use
• 84% of soft contact lens wearers accidentally fall asleep or nap with their lenses
Sleeping in lenses
(Source: CIBA Vision, data on file)(Source: CIBA Vision, data on file)
2006-01-0004
Contraindications
• Inflammation/Disease of Anterior Seg
• Systemic disease• Pregnancy• Poor hygiene• Lack of motivation• Irregular cornea• RK
• Chronic allergies• Chronic use
antihistamines• GPC• Astig.>1D• Work environment• Poor tears
Systemic diseases
• Epilepsy
• Diabetes
• Mental incompetency
Pregnancy complications
• Dry eyes
• Refractive changes- Corneal thickness changes
• Decreased corneal sensitivity
• Increased tear viscosity
Preliminary evaluation is important for determining
patient suitability
Case 1
35 y.o male banker
Desires CL’s for occasional sports activities
Case 2
24 y.o female
Wants CL’s 1st time
3 months pregnant
Case 3
Auto mechanic
Wants CL’s
Poor hygiene
Lens Selection
Lens Type
DW, FW, EW, CW
Replacement schedule
Tints
What is the patient interested in?
DW, FW, EW, CW
• Wear 12-14 hours a day
• Remove daily
• Occasional overnight wear
• Full time overnight wear
• 7 days/6 nights• 30 day wear
Educate and Set Proper Expectations- Making the switch
• Oxygen Transmission
• Corneal Health
• Modulus
• Replacement schedule
• Discuss going from hydrogel EW to SiHy EW or CW
• Give the patient 1-2 weeks
CW Patient Education
• Use appropriate solutions for SiHy’s
• Rub the lenses to clean, except ClearCare
• Do not swim in lenses and do not sleep in lenses after swimming
• Clean & disinfect upon removal
• Need back-up glasses with updated Rx
• Examine every 6 mths.
• Bring glasses and solutions to visits
• Remove when ill and do not sleep in them
• Must be 100% healthy to wear CW
• Remove if dirty or FB sensation to clean & disinfect
• Replace with fresh, clean lenses each month
• Showering in lenses?
Even in a BMW, you need to slow down when it is icy.
-Dr. Ghormley
CW Wearing Schedule
• New CL patient – Immediate CW
• Follow-up: 1wk, 3wk, 6wk, 6mth
• DW SCL patient – 3 days DW, CW
• Follow-up: 10 days, 3 wk, 6wk, 6mth
• EW SCL patient – 1 week DW, CW
• Follow-up: 2wk, 3wk, 6wk, 6mth
Replacement Schedule
• Daily
• Weekly
• Every 2 weeks
• Monthly
• Every 2 months
• Quarterly
• Traditional/Conventional
Tints
• Handling
• Enhancing
• Opaque
• Opaque wild & crazy
Lens Inversion Markings
BCR
• 4-5D flatter than flat K
• Steepest BCR = flat K >45D
• Middle BCR = flat K 41-45D
• Flat BCR = flat K < 41D
Lens Diameter
• HVID +2 = Lens Diameter
• 13.8-15mm
Lens Power
• Vertex > + 4D
• Spherical equivalent for < 1D cyl
• Residual astigmatism = Refractive cylinder
Center Thickness
• Greater minus – Thinner
• Greater plus – Thicker
• Thicker lenses are easier to handle
• Thinner lenses provide greater oxygen transmission
Fitting Evaluation
Empirical vs. Diagnostic
Case 1
39.50/40.00 @90 OUOD –2.00D
OS –1.75-0.50 X180
Case 2
OD 43.00 Sph.OS 42.50/43.50 @90
OD –4.50OS –4.50-1.00X180
Fitting
• Insert lenses and let settle 10-15 minutes
• Assess position, coverage and movement
• Centration- centered
• Complete corneal coverage
• 0.5-1mm lag, Push-up test
Too tight
• Conjunctival drag
• Negative push-up test
• No movement
Too loose
• > 2mm lag
• Moving off cornea
• Decentered inferiorly
• Edge lift
• Slides inferior on superior gaze
Edge fluting
www.siliconehydrogels.org
Determine visual acuity and lens power by best sphere &
sphero-cylindrical over-refraction
Over-keratometry
• Flat Fit• Mire distortion which
becomes more distorted on blink
• Steep Fit• Clear mire on blink
which becomes distorted
• Assess Patient Comfort
• Dispense out of Inventory/Trials?
• Parameters required to order (BCR, Rx, Material name, diameter?, CT?, tint)
• Verify lens specifications prior to dispensing
Follow-Up Evaluations
Patient Education• Provide written instructions• Don’t bombard them with info• Give them nuggets• Provide wearing schedule• Teach I & R• Provide Informed Consent• Teach lens & case care• Teach how to open blister pack
Nuggets
• Use a rewetting drop prior to removal
• Dial toric lenses prior to removal
• FB under lens, pull onto sclera and blink back on
• Use viscous solution like daily cleaner to unroll edges
Lens Insertion tips
• Fingers dry
• Make sure lens is not inverted
• Inspect lens
• Place on sclera or directly on cornea
Lens Removal tips
• Slide the lens off onto sclera
• Pinch off with the finger pads
Informed Consent should cover:
• Specifies patient taught I&R, care
• Emergency phone number
• Risks
• Dr. copy & patient copy
Progress Evaluations
• Case Hx
• VA
• Over-Ks
• SLE lenses on & off
• K’s with lenses off
• Refraction
• RTC schedule
Case History
• Problems/complaints
• WT
• Solutions:
Are they compatible?
Have they switched?
Are they disinfecting, enzyming, cleaning?
Are they compliant?
SLE with lenses
• Clear, white eye
• Position
• Coverage
• Movement
• Defects in the lens
SLE without lenses
• Edema (microcysts, striae, polymegethism)
• Neovascularization
• Limbal engorgement
• Injection
• Lid eversion
• Fluorescein Evaluation (Rinse out)
Case 1A patient is fit in a Frequency 55 lens, base curve radius of 8.4mm, worn DW. It is a group 4 lens with a water content of 55%. It comes in base curve radii of 8.4, 8.7 & 9.0. RTC in 2 wks with trial lens. Upon the return visit, engorged limbal vessels and conjunctival drag. What do you plan to do?
Case 2
Focus Monthly wearer, DW basis
Group 4, BCR 8.6
Using Complete, appears compliant but has deposits
Name other options for this patient?
Case 3
Your patient works at a computer at work. She uses frequent
rewetting drops. She experiences dryness. What might be helpful
for her?
Case 4
Patient is wearing AV lenses 2-3 weeks continuously. Some signs of edema.
What lens options might you want to discuss with the patient?
Case 5
Patient is interested in obtaining soft extended wear tinted bifocal toric
lenses.
Case 6
Patient had ocular trauma to the left eye which resulted in a large distorted
pupil. The patient is unhappy with the cosmetic appearance. The iris
color of the OD is blue.
Case 7
Patient desires to wear soft lenses; however, he desires very little care
regimen.
Case 8
Patient is being fit for CL’s for the 1st time. She loves monovision;
however, she has trouble seeing the lenses when handling. What would
you do for her?
Case 9
Patient was fit in Focus Night & Day. They previously wore AV 2 for 1-2 weeks EW. They return for a 1 week check. They are complaining of lens awareness. SLE findings are normal.
Case 10
Patient is wearing PureVision lenses. At their 2 week follow-up visit you notice a mild
coating on the lenses. The patient is using Aquify with their lenses. Any thoughts on
what might be happening?
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