Fitting Guidance & Training

Welcome to KeraSoft Fitting Guidance and Training

KeraSoft Thin is a soft contact lens designed to correct all types of Irregular Cornea conditions, delivering visual acuity comparable to that of rigid options. Excellent comfort ensures lenses can be worn all day, every day, whatever your patient wants to do.


Front surface asphere/aspheric toric
Large back optic diameter to allow full drapage
Adjustable periphery fits any corneal shape


The entire periphery can be steepened or flattened independently of the overall base curve. Available peripheries:

Please click image to enlarge


KeraSoft Thin is fitted using an 8 lens Fitting Set.

There are 6 STD(Standard) periphery lenses
ranging from 7.80 to 8.80 mm base curves

1 × 8.20: FLT2 periphery lens (nipple cones)
1 × 8.60: STP2 periphery lens (post surgical)


  Standard Diagnostic Fitting Set Parameters
Base CurveDiameterPeripheryPower


The fitting methodology for KeraSoft Thin has been updated and is now based on measurements taken from Tangential topography. This allows for a high rate of first time fits by guiding the ECP to the most appropriate initial trial lens.

This system is based on our propriety computer modelling system supported by data from practitioner fittings over a long period of time.

First Choice Lens – BASE CURVE

A good approximation of the Base Curve required can be calculated using the Tangential map on a topography machine. Tangential maps are more sensitive than axial maps and give better information regarding the mid periphery and periphery. For best results, use a Normalized map with 5mm zone included and numerical values displayed. For more information, go to the Using Tangential Topography page. This calculation does NOT work with the Axial (Sagittal) maps, as the mid periphery values are different.

First Choice Lens – Diameter

We recommend different diameters depending on the condition. The reduced overall thickness of KeraSoft Thin improves drapage over the cornea and reduces the need for peripheral changes. More complex shapes such as post graft and low cones benefit from larger diameters.

The guide below indicates where larger diameters or different peripheries are indicated.

Assessing the lens straight away

It is very important that the trial lens is observed on slit lamp immediately after insertion and the fitting assessment made within the first five minutes.

It is not recommended that the patient be sent out to let the lens settle for 15 minutes or more.

This is important for the following reasons:

  • Issues such as bubbles under the lens or fluting edges can be seen immediately – these can settle and disappear after a few minutes.
  • Soft lenses do not maintain their initial fitting characteristics over time. Lenses flex, stretch and settle – for example, a really flat lens can, over time, mould to the eye and bind to the surface, mimicking a tight lens.
  • The fitting guidance is based on the initial assessment being within the first five minutes and thus designed to minimise chair time and improve accuracy of fitting.


Fit assessment is carried out by assessing Movement – Rotation – Centration – Comfort – VA
All these characteristics work together to indicate whether a fit is steep, flat or optimal.

 Movement Up to 2mm is acceptable as long as the patient is comfortable
Rotation Laser mark should sit at 6 o’clock.
 Rotation of the lens that does not change on upward gaze is classed as stable, indicating a Tight fit.
 Rotation of the lens that changes on upward gaze is classed as unstable, indicating a Flat fit
 Centration Centered lens indicates an Optimal fit.
 Decentered or dropping lens indicates a Flat fit
Comfort An Optimal lens is comfortable. A Tight lens may be comfortable at first but will then start to be  uncomfortable. Non-settling discomfort indicates a Flat fit.

If the fit appears Tight or Flat, remove and choose the next appropriate base curve. If fit appears Optimal, move straight to over-refraction, using the spectacle refraction as the starting point. If this is difficult to obtain, use the topography astigmatism as a starting point.


Always assess the over-refraction straight away. Leaving lenses to settle for an hour or so will change fitting characteristics. Use 0.50DS steps or more when assessing sphere and cyl. It is often easier to assess the cyl before finalizing sphere correction, as large amounts of uncorrected astigmatism cause excessive ghosting.VA with a Tight lens will be better after the blink. VA with a Flat lens will be worse after the blink. VA should be atleast the same or better than spectacle refraction. If you attain a worse result, this means the fit is not optimal


Always use STD lenses before trying a lens with a different periphery.
Each periphery change is equivalent to 0.20 change in Base Curve.


If the First Choice Lens Rule gives a relatively flat Base Curve (eg. 8.60) and this is acting very fl at, use that value as the peripheral fit and go down at least 2 steps for the Base Curve (ie. 8.20 FLT2).


Topography does not tend to record the peripheral cornea, so the First Choice Lens Rule is likely to provide a lens that fits the central cornea but tends to flute at the edge.Keep the Base Curve as it is and tighten periphery by 1 or 2 steps or increase diameter to 15.00.

Kerasoft training overview

Download the KeraSoft Training PowerPoint presentations from our box account HERE

Internal Study

To investigate the efficacy of KeraSoft® Thin, an internal study was carried out comparing KeraSoft® Thin to IC on subjects already successfully adapted to the KeraSoft® IC lens. The results demonstrated that in all cases, comfort was the same or increased significantly by the thinner design. Fit was very similar to IC and 95% of subjects experienced equal or improved VA. This was all achieved by maintaining the same parameters for the fit, demonstrating that KeraSoft® Thin could be fitted from KeraSoft® IC Fitting Lenses or powered lenses. The small number who experienced worse VA represented 3 eyes out of a sample of 48. These subjects had central keratoconus and subsequent experience of the Thin design has shown that changing fit parameters in such cases will improve VA.

Internal Study