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Soflex ND GP lenses
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Fitting the Soflex ND
Moodi Kupperman B.ScSoflex
04/11/23 2
GP Lenses in your Clinique
Advantages to your customer
Improved corneal health Sharp, stable and clear vision Easy to handle Economic and easy cleaning process Comfortable throughout entire day Long lens life
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GP Lenses in your Clinique
Advantages for you Less chair time More profit Customer loyalty Less health problems for your customer’s eye
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100 years from glass to GP, contact lens History
• 1508 Leonardo da Vinci illustrated the concept of contact lenses
• 1823 British astronomer Sir John Herschel conceptualized practical lens design
• 1887 First contact lens manufactured from glass, and fitted to cover the entire eye
• 1939 Contact lenses first made from plastic• 1948 Plastic contact lenses designed to cover only the
eye's cornea• 1971 Introduction of soft contact lenses• 1978 Introduction of GP contact lenses• 1981 FDA approved new soft contact lenses for
extended (overnight) wear• 1986 Overnight wear of GP contact lenses became
available• 1987 Introduction of disposable soft contact lenses• 1987 GP contacts available in next-generation
fluorosilicone acrylate materials
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Polymer (in Greek) = Poly - many, Meros - parts
Fluoro-Silicone-Acrylate
Fluorine, Silicone =Oxygen permeability
Methacrylic acid
(Hema)= Wetting agents
MethylMethAcrylate
(MMA)=
Mechanical and
optical stability
Silicone Methacrylic Acid Methylmethacrylate
Fluroine HEMA MMA
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RGP Lens Properties
• Oxygen permeability / Oxygen Transmissibility• Surface characteristics
– Wettability, reactivity• Dimensional stability• Flexural resistance• Hardness• Fracture resistance• Specific gravity• Index of refraction• Machining capabilities
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Oxygen Transmissibility
Dk - Is the materials permeability to oxygen.
Dk/t - Is the materials oxygen transmissibility
t - Is the thickness of the lens.
The higher the Dk/t number the greater
the oxygen transmissibility!
O2O2
O2
O2O2
O2O2
O2
0.10 mm
O2O2
O2
O2O2
O2O2
O2
0.20 mm
O2
O2
O2
O2O2
O2
O2
O2
O2
Standards for measuring Dk• Coulometric
• Polarographic• ISO Fatt • ISO Fatt (revised)• mm Hg• hPa
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S4=32
HDS=58
HDS100Bxo
Optimum Extra=100
MeniconZ=168
S3=18
Optimum Comfort=
65
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Other Techniques for Measuring In Vivo Oxygen Transmissibility
• Overnight Corneal Swelling• Biochemical corneal changes• Epithelial mitosis• Corneal sensitivity• Limbal vascular response
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Limbal Redness
Low Dk CLLow Dk CL High Dk CLHigh Dk CL
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Silicone Fluorine
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Measurement of the Material Wetting Properties In Vitro
Sissile Drop –
in air
Captive Bubble –
in water
Wilhelmy Plate –
Dynamic in water
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RGP Surface Modification
• Bulk properties• Molecular
membranes• Plasma treatment
Plasma polymerization
Monomer
Treated Surface
Untreated Surface
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Manufacturing Induced Non-Wetting - Residual Blocking / Polishing Pitch
RGP Surface Modification
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Manufacturing Induced Non-Wetting - Excessive Solvent Exposure
RGP Surface Modification
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Manufacturing Induced Non-Wetting - Excessive Heat Exposure
RGP Surface Modification
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Plasma Treatment
SurfaceContaminant
OxygenPlasma
The oxygen plasma hits the lens surface with such force that it breaks-up any surface contaminants such as waxes,
polishing pitch and residual residue left on the lens.
The Cleaning stage
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Plasma Treatment
• Electron ejected from a gas (oxygen)• Bombard the contact lens surfaces• The reaction between the gas molecules
and the surface silicon molecules alters the hydrophobic silicon surface chemistry to one that is significantly more hydrophilic
The Surface
Modification Stage
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BEFORE AFTER
Plasma Treatment
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Base Curve Radius Stability
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Flexural Resistance
• In Vitro
Laboratory measurement
• In Vivo
Residual astigmatism
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RGP Surface Scratches
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Fracture resistance
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Superior Lens Position Inferior Lens Position
Centered Lens Position
Material name
Specific Gravity
Menicon z 1.200
Optimum Extra
1.160
HDS100 1.100
Bxo 1.270
Optimum Comfort
1.170
HDS 1.160
S4 1.140
S3 1.126
Specific gravity
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Material Index and Add Power
• Higher index materials can be made thinner while maintaining the same refractive power
low n
high n
Material I/R Add Pwr
PMMA 1.490 +1.75
HDS 1.449 +1.25
HDS 100 1.453 +1.25
Menicon Z 1.440 +1.25
Bxo 1.415 +0.75
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Raw Material PropertiesMaterial
nameWetting Angle
Oxygen Permeability
(Dk)
Hardness (Rockwell R)*
Refractive Index
Specific Gravity
Menicon z 24 160 1.440 1.200
Optimum Extera 3 100 100.0 1.431 1.160
HDS100 42 100 1.442 1.100
Bxo 49 100 112.0 1.415 1.270
Optimum Comfort 6 65 105.5 1.437 1.170
HDS 14.7 58 1.449 1.160
S4 12.8 32 1.446 1.140
S3 30 18 1.470 1.126
PMMA 0 1.490
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All Soflex gas permeable lens design are available in all the
above materials !!!
Ski, Soflex ND, Tri, OP2, OP5, OP8
OPT, SPHRD……
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The Soflex ND
• Soflex - ND is our Polish Free flexible Gas Permeable contact lens which is incredibly comfortable for customers to wear and convenient for practitioners to fit.
• The lens base curve has a unique aspheric optic zone and continuous periphery that controls the edge lift and rounds the edge. This revolutionary design allows maximum comfort and easy fitting.
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The Soflex ND
Soflex’s Soflex - ND is produced on computer controlled diamond turning lathes using advanced raw materials. This combination together with Plasma treatment gives the lens excellent wettability, high oxygen permeability and reliable parameter stability.
Fast Tool Servo
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Polish Free
• High reproducibility rate• Excellent optics• Accurate parameters• Stable parameters• High quality surface finish• High comfort all day long
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Fitting the Soflex ND1. Initial data gathering2. Lens Fit Analysis3. Ordering of the Soflex – ND, RGP lens
Rh Rv Axis Sph Cyl Axis HVID BUT
R
L
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Initial data gathering
• Recent routine refraction – note the visual acuity and back vertex distance.
• Full eye examination including a slit-lamp assessment.
• Keratometry and/or Topography
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Initial data gathering
Tips:- Measurements are required of the Horizontal Visible Iris
Diameter (HVID), the vertical palpebral aperture, and the pupil diameter in various illumination conditions.The HVID gives an initial clue as to the overall lens diameter, usually approximately 2 mm less than HVID.
- The position of the eye lids is important.The Soflex - ND lens should be fitted using the lid attachment method
- Tear film quantity and quality assessment using the slit lamp.
Observing the tear prismTear break-up time with fluorescein
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A suitable Soflex - ND lens is selected from the Trial Set Box based on the available information and inserted into one eye. An assessment and note of the lens fit and performance is made. Suitable modifications may be suggested to improve the fit and these may be discussed.
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Lens fit analysis The first choice Soflex - ND lens has a Back Optic Zone Radius of curvature (BOZR) nearest to the flattest keratometry ‘K’ reading.
An aspheric lens design is more likely to closely follow the mid-peripheral corneal contours, to spread the lens pressure on the cornea more evenly and to improve comfort.
For this lens design the lens BOZR on flattest ‘K’ is preferable.
An aspherical design lens can often mask corneal astigmatism better.
Tip:For each 0.75D corneal astigmatism reduce 0.05mm from lens BC(steeper)
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Effect of Lens Thickness
• If a lens has a back vertex power (BVP) of greater than +4.00D, the lens front surface shape and thickness may affect the fitting. A steeper fit would often be needed
• If the lens power is a high minus power of greater than -7.00D, the center of gravity is posterior to the corneal apex and the lids can grasp the relatively thicker lens transitional zone to lift the lens. A flatter fit and larger diameter would often be needed.
+7.00 -3.00 -7.00
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Lens Diameter The Soflex - ND lens Over All Diameter ( OAD ) is 9.60mm – Standard Diameter9.00 and 10.20 are also available upon request
• A large overall lens diameter may be preferred in order to help pupil coverage, to assist lens centration particularly if the palpebral aperture is wide, and in some cases to stabilize the lens fit if there is excessive lens movement.
• A small lens diameter is used where palpebral aperture is small
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Lens FitThe Soflex - ND lens fit is assessed after a drop of fluorescein is instilled, the patient blinks several times and the fluorescein pattern observed using the Burton lamp for a general view with the patient’s head in a natural position. The slitlamp with the cobalt blue filter can be used for a more detailed view of the lens fit pattern and tear flow. The lens centration, movement and fit should be noted, both in the primary position of gaze and on various eye movements.
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Fluorescein pattern Flat fit
• An apical bearing fluorescein pattern reflects a flat fitting relationship. Photo shows a Flat Pattern. This relationship can ultimately result in corneal distortion in the region of bearing.
This can be easily managed via selecting a steeper base curve radius.
An apical bearing
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Fluorescein pattern Steep fit
• An apical clearance fluorescein pattern reflects a steep fitting relationship. Photo shows a Steep Pattern. This can cause peripheral seal off, resulting in poor tear exchange and possibly adherence. Select a flatter base curve radius to improve the fitting relationship.
An apical clearance
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Fluorescein pattern Normal fit
• Strive for an alignment ("even") fluorescein pattern. This is not necessarily equal to an "On K" base curve selection due to the asphericity of the cornea. Photo shows an Alignment Pattern.
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A good fit shows - Satisfactory lens centration.- With lids held apart, the lens should slowly drop downwards. - With normal lid position, the lens peripher should not move
beyond the limbus.- Alignment type fluorescein pattern shows alignment or slight
apical clearance over the central 7.00mm region, mid-peripheral
touch and edge clearance of about 0.50mm width.
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Lens ordering • The ocular refraction (Oc.Rx) at the corneal plane can be calculated from the
spectacle prescription and the back vertex distance (BVD). See Back Vertex Correction table
( There should be an approximate change of 0.37D for every 4.00 diopters of power. )
• Trial Lens:
Soflex – ND 9.60 7.80 -3.00
• Over refraction: -5.25
• Soflex – ND 9.60 7.80 -8.00 / Raw Material / Clinique name / Px name
The ordered lens specification must be clearly written.
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Choice of the raw material
The Soflex - ND is manufactured from “state of the art” raw material Optimun Comfort as a standard. This material has excellent wettability and deposit resistance, high oxygen transmissibility and very good physical properties, however we are also able to manufacture the lens from other materials depending on your patients needs.
Tip: The choice of RGP lens material will depend on physiological characteristics of the patient.
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Lens ParametersLens Specifications:
Material DK Tint
Optimum Comfort 65 x 10 -11 @ 35º Blue,Green
Surface Treatment: Plasma
Base Curve : 7.00 to 8.40mm
Diameter: 9.60, 10.20mm ( 9.00mm )
Central Thickness: 0.16 mm @ -3.00DS
Sphere Power: Any
Back Design: Medium Asphericity + Blended Bevel
Front Design – Spheric: Sphere + Lenticular
For diameters and base curves outside the standard range, please inquire
04/11/23 59
Cleaning and disinfecting• Cleaning and disinfecting the Soflex - ND
lenses is an important procedure that must be performed immediately every time lenses are removed. Cleaning is necessary to remove mucous, film and residue on the lens surface, while disinfecting is used to prevent germs from causing eye infections. There are many different brands of lens care products available for GP contact lenses.
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Follow up• The practitioner is reminded that successful Soflex -
ND lens fitting is not just obtaining a contact lens of correct curvature and power, but includes educating the patient in the appropriate wear and care of the lens and continuing to monitor the eye at the regular aftercare visits.
Tip: Remember - Follow up regime is essential
04/11/23 61
Fitting tips
Fitting Tip Checklist
• Parameter Changes - Change base curve radius (BCR) a minimum of +/-0.1mm ( from the Trial Set ) - Change overall diameter a minimum of
0.6mm • To maintain the same fitting relationship:
- Select 0.05mm flatter BCR for every 0.6mm increase in diameter (i.e., if large pupil size)
- Select 0.05mm steeper BCR for every 0.6mm decrease in diameter (i.e., small fissure size)
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