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

04/11/23 3

GP Lenses in your Clinique

Advantages for you Less chair time More profit Customer loyalty Less health problems for your customer’s eye

04/11/23 4

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

04/11/23 6

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

04/11/23 7

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

04/11/23 8

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

04/11/23 10

S4=32

HDS=58

HDS100Bxo

Optimum Extra=100

MeniconZ=168

S3=18

Optimum Comfort=

65

04/11/23 11

Other Techniques for Measuring In Vivo Oxygen Transmissibility

• Overnight Corneal Swelling• Biochemical corneal changes• Epithelial mitosis• Corneal sensitivity• Limbal vascular response

04/11/23 12

Limbal Redness

Low Dk CLLow Dk CL High Dk CLHigh Dk CL

04/11/23 15

Silicone Fluorine

04/11/23 16

Measurement of the Material Wetting Properties In Vitro

Sissile Drop –

in air

Captive Bubble –

in water

Wilhelmy Plate –

Dynamic in water

04/11/23 18

RGP Surface Modification

• Bulk properties• Molecular

membranes• Plasma treatment

Plasma polymerization

Monomer

Treated Surface

Untreated Surface

04/11/23 19

Manufacturing Induced Non-Wetting - Residual Blocking / Polishing Pitch

RGP Surface Modification

04/11/23 20

Manufacturing Induced Non-Wetting - Excessive Solvent Exposure

RGP Surface Modification

04/11/23 21

Manufacturing Induced Non-Wetting - Excessive Heat Exposure

RGP Surface Modification

04/11/23 22

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

04/11/23 23

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

04/11/23 24

BEFORE AFTER

Plasma Treatment

04/11/23 26

Base Curve Radius Stability

04/11/23 28

Flexural Resistance

• In Vitro

Laboratory measurement

• In Vivo

Residual astigmatism

04/11/23 30

RGP Surface Scratches

04/11/23 32

Fracture resistance

04/11/23 34

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

04/11/23 36

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

04/11/23 39

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

04/11/23 40

All Soflex gas permeable lens design are available in all the

above materials !!!

Ski, Soflex ND, Tri, OP2, OP5, OP8

OPT, SPHRD……

04/11/23 41

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.

04/11/23 42

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

04/11/23 43

Polish Free

• High reproducibility rate• Excellent optics• Accurate parameters• Stable parameters• High quality surface finish• High comfort all day long

04/11/23 44

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

04/11/23 45

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

04/11/23 46

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

04/11/23 47

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.

04/11/23 48

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)

04/11/23 49

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

04/11/23 50

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

04/11/23 51

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.

04/11/23 52

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

04/11/23 53

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

04/11/23 54

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.

04/11/23 55

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.

04/11/23 56

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.

04/11/23 57

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.

04/11/23 58

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.

04/11/23 60

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) 

Thanks

Questions