KeraSoft® IC Technical Fitting Guide - UltraVision Group

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& ALL IRREGULAR CORNEAS
Technical Fitting Guide
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KeraSoft ® IC Technical Fitting Guide
Introduction
The KeraSoft ® IC is a soft contact lens designed to fit all stages of keratoconus and other irregular cornea types e.g. PMD,
post graft and post refractive surgery. This Award winning design is available in a choice of 2 materials; lathe cut Silicone
Hydrogel (SiH) (74% water content) and high water content Hydrogel (77% water content).
Fitting Set
BCOR DIA PERIPH Power
7.80 14.50 STD Plano
8.00 14.50 STD Plano
8.20 14.50 STD Plano
8.40 14.50 STD Plano
8.60 14.50 STD Plano
8.80 14.50 STD Plano
8.20 14.50 FLT2 Plano
8.60 14.50 STP2 Plano
Base Curve 7.40mm to 9.40mm (0.20 steps)
Diameter 14.00mm to 15.50mm (0.50 steps)
Lens Design
Periphery
Options
Sector
Management
Control
Power Range
Lathe-cut SiH (Filcon V 3) UltraVision 77% (Filcon II 2)
Water Content 74% 77%
Dk
Overall Diameter
14.50mm
Front Optic Zone
8mm
Laser Mark
(Broken line on left lens)
•
Back Optic Zone
12.50mm
Peripheral
Curves
Inversion Mark
60 x 10 -11 (cm 2 /sec)[ml0 2 /(ml x
mmHg)]
Design
53 x 10 -11 (cm 2 /sec)[ml0 2 /(ml x
mmHg)]
Handling Tint Clear Clear
Wear Modality 3 month, daily wear 12 month, daily wear
Pack Size Single lens, 2-pack Single lens
The KeraSoft ® IC has a front surface toric design, with a front optic
zone diameter of 8mm. The spherical back surface has tricurve
geometry with a large back optic diameter of 12.50mm for the
standard 14.50mm diameter lens. A wide range of base curves and
diameters are available (see below).
The periphery of the lens can be manipulated independently of the
base curve. Additionally, if required, the periphery can be altered in
one or two sectors only, the size and angles of which can be defined
by the practitioner (Sector Management Control).
Each lens has a vertical laser mark at the 6 o’clock position; a full line
indicates the lens is for the right eye and a broken line indicates the
left. Additionally, there is a dot (the inversion mark) located to the right
of the laser mark (when looking at the lens from the front surface) and
this allows the practitioner to ensure the lens is not inside out.
Stabilisation is achieved using prism ballast with balanced overall
thickness. All Fitting Lenses are prism ballasted to ensure that they fit
in the same way as the final powered lens.
The fitting set comprises 6 x lenses with a Standard periphery (STD), 1 x lens with a Flat periphery (FLT2) and 1 x lens with
a Steep periphery (STP2) and is supplied in 77% high water content hydrogel.
Fitting Set Parameters
Parameter Range
Front surface Asphere or Aspheric Toric prism
ballasted with balanced overall thickness
Wavefront aberration control
Standard, STEEP1, STEEP2*, STEEP3*, STEEP4*
(*Reverse Geometry),
FLAT1, FLAT2, FLAT3, FLAT4
Periphery can be invidividually customised to allow
Steeper and Flatter sectors, with a continuous blend
between the two sectors
Sphere: +30.00DS to -30.00DS
Cylinder: -0.50 to -15.00DC (in 0.25 steps)
Axis: 1° to 180° (in 1° steps)
KeraSoft ® IC prescription lenses can be
supplied in either lathe cut Silicone Hydrogel
material or high water content Hydrogel.
All Fitting Lenses are supplied in the high
water content hydrogel material only.
Lenses can be ordered in either material
without the need to change parameters or
power.
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How to determine the First Choice Fitting Lens
Fitting of the KeraSoft ® IC is based on the mid peripheral and peripheral corneal shape, not the central K readings, much
like “normal” soft lenses. In this respect, fitting KeraSoft ® IC differs significantly from fitting corneal RGP lenses as they use
fitting rules related to the central corneal curvature.
Although topography serves as a valuable tool for recognising corneal types, KeraSoft ® IC can be fitted, without the benefit
of topography, using standard, lathe cut soft lens fitting techniques. Utilising the slit lamp, valuable information can be
gained by assessing the overall corneal shape which can then guide the choice of the first Fitting Lens. Thereafter,
assessment of the lens performance on eye will supply sufficient information for the fit to be refined.
Corneal Shape
To assist corneal shape assessment, it is helpful to look at the corneal profile as this can guide the choice of the first Fitting
Lens. To observe the corneal profile, ensure the patient is looking straight ahead, move the eye piece and illumination unit
of the slit lamp 90 degrees from the usual straight ahead position, separate the lids and observe the cornea from the side.
For conditions that cause irregular cornea, the resultant shape of the cornea is partly determined by the original shape of
the cornea before ectasia developed or surgery was performed.
Below are some representations of corneal shapes as represented by topographical mapping. It should be noted that a
normal cornea is fairly uniform in shape whereas an irregular cornea will demonstrate extremes of steepness and flattening
within relatively small areas. Keratoconic and pellucid corneas can also (rarely) demonstrate steep areas other than in the
inferior position.
(1) Normal Cornea (2) Steep Central/ 3) Steep central or (4) Steep inferior/Very (5) Flat central/Normal
Steep Periphery inferior/Flat periphery Flat superior periphery to steep periphery
Mild to Moderate Keratoconus with relatively normal corneal shape (Type (1) above)
These corneas have reasonably normal characteristics in the mid periphery and can be fitted with lenses of
base curves in the range 8.40 – 8.80 STD in the same way as normal corneas. However, mild keratoconus can
be deceptive if the peripheral cornea was relatively steep before ectasia developed and may need to be fitted
as Type (2).
Cornea with steep central/inferior area and steep mid-periphery/periphery (Type (2) above)
This
type
of
cornea
demonstrates
steep
central
K readings
and
a relatively
steep
mid
peripheral
and
peripheral
curvature, even compared to a “normal” cornea. The corneal profile appears to have steep “sides” and this
corneal shape is best fitted with base curves between 7.80 and 8.00 STD from the Fitting Set. 7.40 and 7.60
base curves are available on request for more advanced cones.
Cornea with steep central/inferior area and relatively flat mid-periphery/periphery (Type (3) above)
The mid periphery in these corneal types tends to be even flatter than normal corneas and it is advised to start
with Fitting Lenses in the range 8.40 – 8.60 STD. For “nipple cones”, the difference between central and mid
peripheral areas is even more extreme and suggested first choice Fitting Lens is 8.20/14.50/FLT2, which has
a periphery equivalent to an 8.60 STD Fitting Lens.
Low Cone/Pellucid Marginal Degeneration (Type (4) above)
Both these corneal types present in a similar way, with relatively normal central K readings and against the rule
astigmatism. Corneas tend to be very flat superiorly and are significantly curved in the inferior area. Lenses in
the 8.60 – 8.80 STD range are a good starting point.
If all lenses tend to flute inferiorly, try the 8.60/14.50/STP2 Fitting Lens. If this improves the fit but causes
fluctuating vision, an SMC lens with a steep periphery in the inferior portion only may be necessary. For more
information, see the section on adjusting the periphery.
Reverse Geometry Corneal Shapes (Type (5) above)
These corneal types are usually post surgical: post graft and post refractive surgery
It is useful to note that although topography machines may record the central area as “blue” (flat) and the
periphery as “red” (steep), in fact the periphery may be quite normal, in terms of curvature. The mapping is
simply indicating the relationship between the curvatures of the two areas.
It is suggested that such corneas are fitted with the 8.60/14.50/STP2 lens from the Fitting Set, as this lens
most closely matches the corneal shape. However, if the cornea had a relatively flat periphery before surgery,
it may be best to begin with an 8.60 – 8.80 STD periphery lens.
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KeraSoft ® IC Fitting Procedures
The fit of a KeraSoft ® IC lens is assessed utilising the
following 5 characteristics: Movement, Rotation, Centration,
Comfort and VA.
All of these characteristics have equal importance when
assessing fit. Even if 4 other fitting characteristics appear to
be optimal, if VA is sub optimal, then the fit is not correct.
Always assess fit within 5 minutes of insertion
It is important to assess KeraSoft ® IC within 5 minutes of
insertion, as the movement at this time equates to the
movement after 8 hours wear. It should be noted that it is
possible for lenses that are fitting flat to be very mobile after
5 minutes but become immobile after 30 minutes and this
can erroneously be interpreted as being a tight fit.
Dynamic Assessment Routine
The slit lamp routine below is designed to capture information on Movement Rotation and Centration and can be used to
assess fit using the Fitting Procedure below. It is important to assess fit first in straight ahead gaze and then in upward gaze
followed by lateral gaze movements. The resultant lens behaviour can be used to determine the fit as seen below. The laser
mark and the visible FOZ can be utilised to assist in fit assessment (see pictograms).
Assess fit in straight ahead and upwards gaze and assess lag on lateral gaze movements
Straight
ahead Gaze
Optimal Lens Fit Characteristics
MoRoCCo gives optimal VA
Using the above routine and characteristics of tight and flat fits below, it is possible to refine the fit with the “Traffic Light”
fitting system on the next page.
As a useful aid, the following tables list typical characteristics of a Tight Fit and a Flat Fit when fitting KeraSoft ® IC:
Characteristics of Tight Fit Characteristics of a Flat Fit
Mo
Ro
Upward
Gaze
Lag on
right/left
Gaze
• Movement: Is it limited, optimal or excessive?
• Rotation: Is the laser mark vertical or rotated?
Is the Rotation relatively stable or erratic?
• Centration: Is the FOZ central or decentred?
• Movement: Is it limited, optimal or excessive?
Mo
Ro
• Rotation: Does the laser mark stay in same position as straight ahead?
Is the Rotation relatively stable or erratic?
• Centration: Is FOZ central, dropping to limbus or below limbus?
• Does the lens move off the cornea?
• Does the lens lag excessively?
• Does it remain reasonably central?
Little movement on straight ahead gaze. Lenses
may move more on upward gaze.
Stable rotation of 15 - 20 degrees or more on
straight ahead and upward gaze. 30 degrees
rotation or more indicates a poor fit.
C Lens is usually central.
Co
Tight lenses are comfortable but often become
uncomfortable after a few hours, often in a
particular position.
VA A tight fit will give clearer vision after blink.
Movement 1mm - 2mm
Note: Up to 3mm post blink is acceptable, providing the
patient is comfortable
Rotation should be minimal with the laser mark as
close to the 6 o’clock position as possible
C Lens should be central
Co Lens should be consistently comfortable
VA Visual Acuity should be steady with little fluctuation
Mo
Ro
C
Co
VA
0-1mm
1-3mm
>3mm
Movement Rotation Centration
A
G G
G A A
R
R
R R
R
Movement more than 3mm on straight ahead gaze
and may flute at one position.
Unstable, erratic rotation of 15 - 20 degrees or more
on straight ahead gaze. Laser mark will swing on
upward gaze.
Lens decentres and FOZ drops to limbus or below
on upward gaze.
Flat lenses are generally edgy and uncomfortable
and this does NOT settle with time.
A flat fit will give worse vision after blink. This does
not settle with time.
A
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KeraSoft ® IC Fitting Procedure
The chart below utilises a “traffic light” system to indicate when the fit is optimal, requires re-assessment or is incorrect and
should be removed immediately. As mentioned previously, it is best if the lens fit assessment begins within 5 minutes of lens
insertion. It is not advisable to insert a lens and send the patient out for it to settle without first assessing the fit on a slit lamp,
as a flat lens can become immobile after approximately 30 minutes and this can be mistaken for a tight fit.
Presence of significant air bubbles that do not settle is an indication of a tight fit and obvious fluting is an indication of a flat
fit. In both instances, the first lens choice should be reassessed.
Procedure
Select and insert a lens using the First Choice Fitting Lens Guide. If in doubt, begin with 8.20/14.50/STD.
Assess lens fit within 5 minutes using the Dynamic Assessment Routine outlined on the previous page.
If fit is in RED zone, remove lens and then select next Fitting Lens 1 - 2 steps steeper or flatter.
If fit is in GREEN or AMBER zone, begin over refraction whilst the lens settles further.
If VA is in RED zone, remove and reconsider first lens choice, rechecking corneal profile and topography.
If VA is in AMBER zone, determine whether fit is steep or flat, then adjust by 1 step.
When an optimal GREEN fit is achieved, allow to settle for 15 - 20 minutes then finalise over-refraction and take note of BVD.
Movement
Rotation
Centration
Comfort
VA
Hints and Tips
Movement
Optimal Fit
(Green)
Re-assess Fit
(Amber)
1-3mm Vertical Post Blink 3mm
Up to 3mm acceptable if patient is
comfortable
3mm - try one step steeper
Incorrect Fit
(Red)
Too Mobile OR Immobile Lens that
Moves with Push-up
If lens too flat - try 2 steps steeper
If lens too tight - try 2 steps flatter
Laser Mark - Vertical 15 - 20 Degrees >20 Degrees
Up to 15 degrees stable rotation acceptable
if fitting 1 lens steeper or flatter does not
reduce the angle
Central
Minimal decentration acceptable if visual
acuity is good
Erratic swing on blink - Flat fit
Limited swing on blink - Tight fit
Decentres on Straight Ahead Gaze /
FOZ Drops to Limbus on Upward Gaze
Erratic swing on blink - Flat fit
Limited swing on blink - Tight fit
FOZ Edge Drops Below Limbus on
Upward Gaze
Try lens 1 step steeper Try lens at least 1 step steeper
Good Comfort General Discomfort Very Uncomfortable
Consistently good comfort
Lens feels edgy - Flat fit
Discomfort in one location - Tight fit
Comfort does not improve with time
No Fluctuation Fluctuation with Blink Very Poor Vision
Visual acuity should not fluctuate on blink
Worse after blink - Flat fit
Clearer straight after blink - Tight fit
Poor vision not improved by any
over-refraction
A lens that is fitting too flat, may initially be mobile and then can become immobile after approximately 20 minutes due to
the lens decentring and aligning with flatter areas of the cornea. However, the lens will usually move easily with Push-Up
test. This is why it is important to assess the fit within 5 minutes.
Lenses that are fitting tightly and show little movement on straight ahead gaze, may appear to move well on upward gaze
due to lid interaction with the lens edge. Be guided, in this instance, by the movement on straight ahead gaze.
Rotation
For an irregular cornea, a significantly rotated lens indicates that the fit is not correct. It is desirable for the laser mark to be
as vertical as possible.
A lens that is fitting tightly will produce a stable rotation; i.e. it will remain in approximately the same position when the
patient looks straight ahead and then looks upward.
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A lens that is fitting flat will demonstrate rotation that is unstable: i.e. it may change position over time and on upward gaze
will swing back towards the vertical in an erratic fashion.
For some corneas, there will always be some rotation, whichever lens is fitted, in which case the optimal fit must be
determined solely by the other characteristics.
Centration
The FOZ of the KeraSoft ® IC lens can be used to judge centration and movement. A decentred lens that appears to be fitting
well in all other respects will often induce ghosting and patients may report that they have improved acuity if they turn their
head. This usually indicates the lens is fitting flat and visual symptoms are caused by the decentred optics.
On upwards gaze, if a lens drops so that the FOZ rests on the limbus or falls below it, this indicates a lens is fitting too flat.
If the FOZ falls below the limbus, then try a lens 2 steps steeper. If all Fitting Lenses tend to show that the FOZ decentres
downwards towards the limbus, this implies marked inferior curvature of the cornea, in which case an SMC design might be
the appropriate option to use.
Significant lag on lateral gaze movements will confirm a lens is fitting too flat. If the lens moves significantly off the cornea,
then try lens 2 steps steeper. For moderate lag, try 1 step steeper.
Comfort
This characteristic is very valuable in assessing fit.
A lens that is fitting flat will feel generally edgy in the eye. Optimal and tight fits will both feel comfortable; however, a lens
that is fitting tightly will gradually start to feel uncomfortable at the flattest point of the cornea and the patient will be able to
indicate this area quite easily.
If patients have become accustomed to contact lenses that are uncomfortable, they may feel that a KeraSoft ® IC Fitting Lens
is comfortable, even if it is fitting too flat. However, they can still differentiate between lenses that are fitting steeper and
flatter when given the option.
VA
Visual Acuity with a plano Fitting Lens, and an over refraction in place, is an excellent indicator of fit. This is why it is
suggested that over refraction is started as soon as the fit is in the AMBER or GREEN zone.
Always ask the patient whether vision is better or worse after the blink. If Visual Acuity is clearer after the blink straight away,
reassess the fit on slit lamp as the lens may be too tight. Use other indicators, such as rotation and movement, to assess
whether to flatten lens by 1 or 2 steps.
If the Visual Acuity is worse after the blink, wait to see if this starts to improve with settling. If it does not, reassess the fit on
slit lamp as the lens may be fitting too flat. Use other indicators, such as rotation and centration, to assess whether to flatten
lens by 1 or 2 steps.
Significant ghosting of letters can indicate that the lens is decentred or that the cyl element is over, or under, corrected. If
retinoscopy is difficult, due to corneal distortion, auto-refraction or topography over the lens can be helpful in indicating
amount of cyl and its axis.
Manipulating the periphery
Up to 80% of all Irregular Cornea cases can be fitted with the standard periphery lens.
Due to its tricurve design, the STD periphery of the KeraSoft ® IC is flexible enough to accommodate most irregular corneal
surfaces. However, in the cases where this is not sufficient to obtain optimal fit, the peripheral radius of curvature can be
flattened or steepened independently of the base curve by up to 4 STEPS.
A change in the peripheral curve of a lens by 1 STEP is equivalent to providing the periphery of a lens with a base curve 0.20
steeper or flatter.
Certain corneal shapes (see below) nearly always benefit from a change in periphery and 2 lenses with non standard
peripheries are included in the Fitting Set for this purpose; 8.20/14.50/FLT2 and 8.60/14.50/STP2
8.20/14.50/FLT2
This configuration is useful in cases of keratoconus where there is a steep cone that flattens off markedly towards the
periphery, such as a Type 3 cornea (see above). For such corneas, standard periphery lenses will give a reasonable fit but
fluctuating Visual Acuity and often significant, stable rotation will be present.
The 8.20/14.50/FLT2 Fitting Lens will generally give better Visual Acuity. For more advanced cones, it is possible to order
steeper base curve Fitting Lenses with a FLT2 periphery.
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8.60/14.50/STP2
The STP2 lens is a useful first choice lens for Type 5 corneas (see above) such as post refractive surgery and post graft cases
where topography clearly indicates the corneal periphery is significantly steeper than the centre. This design represents a
reverse geometry shape, as all normal soft lens designs flatten slightly towards the periphery.
The 8.60/14.50/STP2 Fitting Lens will generally give better Visual Acuity than standard periphery lenses. For corneas with
significantly flat central areas, it is possible to order flatter base curve Fitting Lenses with a STP2 periphery.
For irregular corneas, changing the diameter to try and improve fit can often result in unwanted changes such as air bubbles.
Changing the periphery by one step can be used to improve the fit of a near optimal lens.
Note that changing the periphery from the standard configuration results in a reduction in the Back Optic Zone
Indications for using a FLAT periphery
Indications Actions Comments
If significant air bubbles are present near
the periphery but flatter lenses are too
mobile, decentre or cause discomfort
The cornea is a Type 3 shape (see
above) and there is generally very poor
Visual Acuity with any Fitting Lens
When fit is near optimal but VA is clearer
after the blink and flatter Fitting Lenses
are too mobile, decentre or cause
discomfort
It is unusual to require the FLT3 and FLT4 peripheries, as in most cases, improvement to the fit can be obtained by flattening
the base curve by 1 STEP whilst maintaining a FLT2 periphery. If this still does not improve fit, contact customer services for
advice with topography mapping if available.
Indications for using a STEEP periphery
Indications Actions Comments
Where there is obvious fluting in one
position but steeper lenses which
eliminate the fluting give fluctuating
Visual Acuity (clearer after the blink)
When fitting a Type 4 cornea (see
above) and flatter Fitting Lenses
decentre but steeper Fitting Lenses
produce fluctuating vision, (clearer after
the blink).
When fit is near optimal but VA is
worse after the blink and steeper Fitting
Lenses have too little movement and
give fluctuating vision, (clearer after the
blink).
Try the 8.20/14.50/FLT2 Fitting Lens
Ordering a FLT1 periphery will improve
Visual Acuity without destabilising the
fit.
Try the 8.60/14.50/STP2 Fitting Lens.
Ordering a STP1 periphery will improve
Visual Acuity without destabilising the
fit.
If Visual Acuity is improved with this
lens but the lens is too mobile or
rotates erratically, then Fitting Lenses
with steeper base curves with a FLT2
periphery can be ordered.
This has a similar effect to changing
to a 14.00 diameter lens on a normal
cornea.
If this improves the fit and Visual Acuity
but either the lens is still too mobile or
gives fluctuating vision, clearer after the
blink, then steeper or flatter base curve
Fitting Lenses with STP2 periphery can
be ordered.
This has a similar effect to changing
to a 15.00 diameter lens on a normal
cornea.
STP 3 and STP 4 peripheries may be required for post refractive surgery cases where the eye was previously significantly
myopic, due to a steep corneal shape, pre surgery. If topography indicates this is the case, then contact UltraVision’s
Customer Services to obtain specific Fitting Lenses.
If manipulating the periphery results in a lens that is still fitting too tight or too flat in one particular location, then the Sector
Management Control (SMC) design may be required.
6

Sector Management Control
In the case of significantly irregular corneas, there may be a
requirement to tighten or flatten a periphery in one location only.
This type of adjustment is possible using Sector Management
Control (SMC) and can be useful for PMD, low cones, advanced
keratoconus, post graft, post refractive surgery, surgery related
ectasias and even very high astigmatism on an otherwise normal
cornea.
An example of an SMC design for PMD would be to designate a
STD periphery to an area between 30° and 150° and a STP2
periphery to an area between 220° and 320°. The intermediate
areas are automatically blended. If this lens was being ordered
on an 8.60 base curve, the configuration would be:
8.60/14.50/STD/STP2 A1=30 A2=150 A3=220 A4 =320
The SMC can be completely customised to suit the particular cornea; for example, it could be flattened in the nasal area only
or be steepened superiorly and inferiorly in cases of high astigmatism.
Note: SMC is required in very few cases. This design is only used for the most unusual corneal shapes and it is
recommended to contact Customer Services for advice on the SMC periphery design before ordering. It is also useful, in
such cases, that topography maps of the cornea are supplied, in colour. Please note: Faxed monochrome maps cannot be
correctly interpreted.
Ordering
To order a KeraSoft ® IC lens, please use the order forms available on the CD or in paper form from UltraVision. Alternatively,
contact Customer Services with the following information:
Parameters Required Over Refraction Material Required
• Base Curve
• Diameter
• Periphery
• Power of Fitting Lens
If you wish to order powered lenses directly, ensure all rotation and BVD (Back Vertex Distance) are accounted for.
Note: A laser mark rotated more than 20 degrees may indicate that the fit is not optimal and we may ask you to look again
at the fit before ordering.
If the periphery is not specified in the order, it will be assumed that a STD periphery is required.
Examples of typical orders would be:
R: K IC / 8.20/14.50/-6.00/-4.50 x 35 / STD / laser mark 10° CW / 77% Hydrogel
(use notation CW – Clockwise; ANTI – anti-clockwise)
L: K IC / 8.80/15.00/ Plano/-5.00 x 110 / STP3 / laser mark vertical / SiH
From this information, a lens with fitting/exchange warranty can be issued.
Exchanges
• BVD of all lenses
(including all cyl lenses)
• Laser mark rotation and
direction
If an exchange lens is required, perform a fitting assessment on the current lens, using the Dynamic Assessment Routine.
Note the MOROCCO characteristics: Movement, Rotation, Centration Comfort and Visual Acuity (after blink) on straight
ahead and upward gaze. Also measure any over correction as accurately as possible and supply BVD.
Contact UltraVision’s Customer Services with this information and the original order number.
• SiH 74%
• Hydrogel 77%
ULTRAVISION INTERNATIONAL LIMITED, COMMERCE WAY, LEIGHTON BUZZARD, BEDFORDSHIRE, LU7 4RW, UNITED KINGDOM
Record No. 279
Issue 4
17.03.11
I N N O V A T I O N I N P R A C T I C E
Tel: +44 (0)1525 381112 Fax: +44 (0)1525 370091 UK Order Line: 0800 585115 (Freephone)
Email: orders@ultravision.co.uk Web: www.kerasoft.co.uk
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