Presentation on theme: "SOFT LENS MATERIAL FITTING & FOLLOW-UP EVALUATION"— Presentation transcript:
1SOFT LENS MATERIAL FITTING & FOLLOW-UP EVALUATION University of Missouri-St. Louis College of Optometry
2Advantages Initial comfort Little lag Simple to fit Inventory Quick adaptationOccasional wearHard to dislodgeDifficult to get trapped FBRarely causes tearingCosmesis
3Disadvantages Bacterial contamination/greater risks with noncompliance Care?DurabilityProne to depositsReduced oxygen permeability with hydrogel materialsQuality of visionDifficult to verifyLimitations of correction
4MaterialsChemical monomers linked to form chains of polymers, cross-linked looselypolyHemaAdd other monomers to improve HEMAMAA, MMA, GMA, PVASilicone Hydrogels
5Monomer Characteristics HEMA – hydrophilic, soft, wettable, low DkEGDMA – Stable, low DkMAA – hydrophilic, pH sensitiveMMA – Hard, no Dk, machinable, optical clarity, stableNVP – Hydrophilic, wettable, high water uptake, High Dk, pH sensitive
6Monomer Characteristics GMA – Wettable, deposit resistant, low DkPVA – Hydrophilic, high water uptake, Deposit resistantSilicone – hydrophobic, High Dk
7The Science Behind the Lenses HEMA-based materialsPositivesEasily fabricated into CL’sRelatively cheap to produceHighly flexibleDimensionally stable to changes in pH & temp.NegativesReliance on H2O to transport O2Limitation to amount of O2 transmitted to corneaCorneal oxygen deficiencyFor the most part, HEMA is an excellent material from which to make soft contact lenses.The one huge negative, however, is the reliance on water to transmit oxygen through the lens material to the cornea. This factor, which significantly limits the amount of oxygen available to the cornea, may over time lead to chronic corneal hypoxia and an array of signs and symptoms known collectively as “corneal oxygen deficiency”. This will be discussed in greater detail in a moment, but first let’s examine the limitations brought about by HEMA’s dependence on water to transmit oxygen.
8O2 transport – HEMA materials This illustration is used to simulate the movement of oxygen molecules through the contact lens to the underlying cornea. With conventional HEMA –based materials, oxygen molecules are transmitted through the material by means of the water portion of the polymer.
9Silicone Hydrogels Available Focus Night & DayO2 Optix & Air Optix AquaAV AdvanceAV OasysPureVisionBiofinityMaterialLotrafilcon ALotrafilcon BGalyfilcon ASenofilcon ABalafilcon AComfilcon ADk14011060103101128Dk/t17513886147160Water content24%33%47%38%36%48%Powers+6 to -10+8 to -12+6 to -12-0.25to -10BCR8.4, 18.104.22.168, 8.78.4, 8.88.3, 8.6ReplaceMonthly2-4 weeks2 weeks
10Silicone Hydrogels Available AvairaO2 Optix CustomPremi OMaterialEnfilcon ASifilcon AAsmofilconADk10082129Dk/t125117161Water content46%32%40%Powers-0.25 to -6+20 to -20BCR8.57.4 to 9.2Replace2 weeks3 months
12Pure Vision (B&L) Performa surfacing process Do not use abrasive cleaners, H2O2, MiraflowGlassy islandsAvailable in toric & multifocalDW/EW/CW
13Focus Night & Day, Air Optix Aqua O2 Optix & O2 Optix Custom (Ciba) No restrictions on care solutionsPlasma coatingSurface chemically uniformUniformly coated with hydrophilic polymerN&D DW/EW/CW, Air & O2Optix DW/EW, O2 Optix DW, Air Optix for Astigmatism
14Acuvue Advance & Oasys (Vistakon) AV2 design, UV blockerNo coating, Hydraclear wetting agent on surface and throughout lensAV Adv. DW, Oasys DW/EWToric and Multifocal
15Biofinity & Avaira (CooperVision) Company reports no surface treatment or wetting agentsAquaform comfort scienceDW at this time
16Lens Surface Modifications Silicone elastomer materials generally display:Decreased surface wettabilityIncreased lipid interactionAccentuated lens bindingRequire “surface modification”Another important aspect of silicone hydrogel technology is the surface treatment of the lenses. One of the challenges historically to the development of silicone hydrogel lenses is the fact that silicone, by nature, is a very dry, hydrophobic material, and exposed silicone surface at the surface of a contact lens will lead to decreased wettability, increased lipid interaction and accentuated lens binding. In order to render the surfaces hydrophilic, the surface of all silicone hydrogel lens must be “modified” in some manner.
17Surface Modifications All photos 5 x 5 micron resolutionPermanent, chemically bonded plasma treatment for a smooth, continuous surfaceO2OPTIXNIGHT & DAYEach company has developed its own means of accomplishing this, but the techniques, and therefore the surface characteristics of the various lenses, vary significantly. The differences in the surfaces can be visually appreciated using very high magnification imaging techniques such as atomic force microscopy (AFM), as shown in these photos.CIBA Vision utilizes a unique, patented process called “plasma polymerization” which results in a permanent, chemically bonded plasma treatment for a smooth, continuous surface. B&L also utilizes a plasma treatment for its PureVision lenses, but this process, called “plasma polymerization” differs from the CIBA Vision process in that the silicone components on the surface of the lenses are transformed into hydrophilic silicate compounds surface, forming glassy, island-like, discontinuous silicate “islands which do not completely cover the surface.The ACUVUE Advance and ACUVUE OASYS materials have no permanent plasma treatment, relying instead on an internal wetting agent (Hydraclear™) which is designed to provide a hydrophilic layer at the surface of the material. (Source: Jones L and Tighe B. Silicone Hydrogel Contact Lens Material Update – Part 2, editorial, 2004(August).)PureVisionACUVUE AdvanceACUVUE OASYSSurface made up of silicate islands that do not completely cover the surfaceNo permanent plasma treatment
18Surface Modifications Focus N&D, O2 Optix, Air OptixO2 Optix CustomPureVisionAV Advance,AV OasysBiofinity, AvairaPremiOCiba VisionBausch & LombVistakonCooperVisionMeniconPlasma coatingPlasma oxidationInternal Wetting agent-polyvinyl pyrrolidone (PVP)NoneNanoglossCiba Vision -gas plasma technique to apply a uniform plasma coating, approximately 25 nm thick with high refractive index. The gas plasma technique is also used by Bausch and Lomb to apply a plasma oxidation surface treatment. PremiO reports similar surface modification.
19BiofinitySiloxane molecules attract and bond to surrounding water molecules, continuouslywetting and lubricating the material (Courtesy CooperVision)
20Modulus “Stiffness” Makes it easier to handle Masks astigmatism? Modulus impacts the “stiffness” of a lens material, and is defined as… The comparative modulus measurements of the currently available silicone hydrogel lenses are listed here. However, it is important to note that, like Dk, modulus describes only a material parameter, and is therefore also related to thickness. A thin lens of relatively high modulus could be less “stiff” than a thick lens of lower modulus.
22Modulus Material Hydrogel/SiHy Modulus (MPa) HEMA Hydrogel 0.50 AV AdvanceSiHyAvaira0.5AV OasysBiofinityPremiO0.9O2Optix/Air Optix1-1.2PureVisionFocus N&D
23An increased Dk is linked with an increase in modulus SiH Dk & MODULUSAn increased Dk is linked with an increase in modulusNight&DayO2OptixPurevisionModulus (MPa)biofinityOasysAdvanceDkCourtesy CooperVision
24Comfort?Silicone hydrogel lens materials are different from conventional HEMA-based materialsSome patients will experience increased “awareness” when refitThere has been a considerable amount of discussion regarding “comfort” when refitting patients from low-Dk/t lenses to silicone hydrogels. It is important to note that, as a category, silicone hydrogel lenses are “stiffer” than conventional HEMA-based materials, and therefore some patients may indeed report an increased awareness of the lenses for a time following refitting. (This is not typically a factor with new fits as the patient has no reference point from which to make a comparison.)
25Dailies with AquaRelease (Ciba) AV 1Day Moist (Vistakon)
26Water content = weight of water in lens/ total lens weight X 100
27Water Content Range of water content 24-79% HEMA by itself has 38% waterPlays a role in determining:Dk/t, durability, stability, deposit formation, pore size
30Dk/t and H2O Conventional Lenses Silicone Hydrogels These relationships are beautifully illustrated in this graph. As can be seen, increasing water content of conventional lenses does slightly increase the resultant Dk/t, but still to a very low level. With the silicone hydrogel lenses shown, Dk/t levels climb significantly with increased silicone content of the lenses and generally decreasing water content.(One may also wonder how the Acuvue OASYS can have a higher water content than O2OPTIX and PureVision, yet still have a higher Dk/t. That has to do with the different center thicknesses of the lenses, and will be discussed further in a later portion of this presentation.)ACUVUE® OASYS™NIGHT & DAY®Biomedics®Soflens®66ACUVUE®2ACUVUE® Advance™PureVision®O2OPTIX™Frequency® 55.Conventional LensesSilicone Hydrogels
31FDA Classification Group 1 – nonionic, low water Group 2 – nonionic, high waterGroup 3 – ionic, low waterGroup 4 – ionic, high waterGroup 5 - ???????
33Oxygen Permeability Increases with water content in HEMA lenses Increases as water content decreases in Silicone HydrogelsOxygen transmission increases with decreases in CTDk ranges 8.3 to >100Tear exchange 1-2%
34Oxygen Profiles (-3.00 sph.) Another way to illustrate this concept is by using color to represent the oxygen profile across the lens profile. Again, depending on the thickness profile of a given lens, lenses of seemingly similar “published Dk/t”, (at the center of a sph. lens), can have significantly different oxygen transmissibility profiles throughout the mid-peripheral and peripheral regions of the lens.Two important points to note:The cornea does not have the ability to move oxygen laterally or peripherally. Therefore, the amount of oxygen moving through a lens at a given point is what is available to the corneal tissues directly beneath.The limbal region is of particular interest due to the fact that it is the only source of stem cells in the eye, leading some experts to speculate on the long-term implications of contact lens-related hypoxia. (Barr JT, Fonn D, Bonanno JA, Cavanagh HD, et al. Elemental Need: Sustaining Limbal Health, Contact lens Spectrum Supplement, August 2005; p. 11.)
47ResponsibilityAge restrictionsParticipation in the costs of the lens
48Variability in Lifestyle Want to sleep overnight in their lenses on a regular basisEssentially every other SCL patient entering your office desires the freedom and flexibility of sleeping in their lenses, at least occasionally.25%54%21%Don’t want to sleep in their lensesWant to sleep overnight in their lenses occasionallySource: CIBA Vision, data on file, 2005.
49Sleeping in lensesMost who sleep in their lenses do so frequently – average is 21 nights/month41% of those sleeping in their lenses do so for more than 7 nights continuouslyMany (28%) are wearing lenses not approved for such use84% of soft contact lens wearers accidentally fall asleep or nap with their lenses(Source: CIBA Vision, data on file)
50Contraindications Inflammation/Disease of Anterior Seg Systemic diseasePregnancyPoor hygieneLack of motivationIrregular corneaRKChronic allergiesChronic use antihistaminesGPCAstig.>1DWork environmentPoor tears
57What is the patient interested in? Lens SelectionLens TypeDW, FW, EW, CWReplacement scheduleTintsWhat is the patient interested in?
58DW, FW, EW, CW Wear 12-14 hours a day Remove daily Occasional overnight wearFull time overnight wear7 days/6 nights30 day wear
59Educate and Set Proper Expectations- Making the switch Oxygen TransmissionCorneal HealthModulusReplacement scheduleDiscuss going from hydrogel EW to SiHy EW or CWGive the patient 1-2 weeks
60CW Patient Education Use appropriate solutions for SiHy’s Rub the lenses to clean, except ClearCareDo not swim in lenses and do not sleep in lenses after swimmingClean & disinfect upon removalNeed back-up glasses with updated RxExamine every 6 mths.Bring glasses and solutions to visitsRemove when ill and do not sleep in themMust be 100% healthy to wear CWRemove if dirty or FB sensation to clean & disinfectReplace with fresh, clean lenses each monthShowering in lenses?
61Even in a BMW, you need to slow down when it is icy. -Dr. Ghormley
81Patient Education Provide written instructions Don’t bombard them with infoGive them nuggetsProvide wearing scheduleTeach I & RProvide Informed ConsentTeach lens & case careTeach how to open blister pack
82Nuggets Use a rewetting drop prior to removal Dial toric lenses prior to removalFB under lens, pull onto sclera and blink back onUse viscous solution like daily cleaner to unroll edges
83Lens Insertion tips Fingers dry Make sure lens is not inverted Inspect lensPlace on sclera or directly on cornea
84Lens Removal tips Slide the lens off onto sclera Pinch off with the finger pads
90Case 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 & RTC in 2 wks with trial lens. Upon the return visit, engorged limbal vessels and conjunctival drag. What do you plan to do?
91Case 2 Focus Monthly wearer, DW basis Group 4, BCR 8.6 Using Complete, appears compliant but has depositsName other options for this patient?
92Case 3Your patient works at a computer at work. She uses frequent rewetting drops. She experiences dryness. What might be helpful for her?
93Case 4Patient is wearing AV lenses 2-3 weeks continuously. Some signs of edema.What lens options might you want to discuss with the patient?
94Case 5Patient is interested in obtaining soft extended wear tinted bifocal toric lenses.
95Case 6Patient 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.
96Case 7Patient desires to wear soft lenses; however, he desires very little care regimen.
97Case 8Patient 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?
98Case 9Patient 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.
99Case 10Patient 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?