PRODUCT INFORMATION - Fitting Guide
KeraSoft®3 Fitting System
The KeraSoft®3
fitting system is straight forward and similar to conventional soft
lens techniques. The back curves are expressed in Series form
(Series A, B, C, D) which correspond to the BCOR values expressed
below. For keratoconus initial trial lenses are chosen based on
practitioner assessment of the stage of advancement. Keratometry
readings may be of limited use if the the cornea is distorted.
Corneal topography may be useful in assessing the peripheral cornea
and indicating which first trial lens to use.
First Lens Recommendation
| Cone Advancement | Series | Equivalent BCOR | Approx. K readings |
|
Advanced |
A | 8.00 | Steeper than 6.20 |
|
Moderate - Advanced |
B | 8.20 | 6.20 - 6.60 |
|
Moderate |
C | 8.40 | 6.60 - 7.00 |
|
Early |
D | 8.60 | 7.00 - 7.40 |
Trial Lenses
The 8 trial lenses in the fitting set are available in a range of powers (see table below) to assist in fitting and to give the patient useful vision whilst the lens is settling. The trial lenses are supplied in the same Silicone Hydrogel (SiH) material as the final lens.The trial lenses have a prismatic aspheric toric front surface in the same form as the final prescription lenses. Thus fitting the trial lens gives a very reliable indicator of the final lens performance and resultant visual acuity.
| Series | Diameter | BVP |
|
A (8.00) |
14.50 | -14.00 and -12.00 |
| B (8.20) | 14.50 | -10.00 and -8.00 |
| C (8.40) | 14.50 | -6.00 and -4.00 |
| D (8.60) | 14.50 | -2.00 and Plano |
The SiH Material
| Properties | Attributes |
| Naturally hydrophilic SiH | Excellent wetting |
| Lathe cut | Wide range of powers |
| 74% water content | High comfort level |
| DK 60 | Increased oxygen transmission |
| Modulus 0.38 | Faster settling time |
| High water retention | Long wear times |
Lens Care
These lenses are compatible with all current chemical and oxidative systems. Care should be taken to follow solution manufacturers' instructions.Fitting Procedure for Keratoconic Eyes
| Step 1 | Fit spherical trial lens from the KeraSoft®3 trial set according to the recommendation table, matching power as near as possible. |
| Step 2 | Allow to settle for 5 - 10 minutes and then assess initial fit. If there is too little lens movement and large bubbles, go flatter. (NB Try dispelling any bubbles by sliding lens to side and back again). If there is excessive movement, go steeper. |
| Step 3 | When a good fit is achieved, allow to settle for 20 - 25 minutes and then over-refract to ascertain sphere and cyl. |
| Step 4 | Order Rx single lenses stating lens series and power used, over refraction (over Rx) and BVD. |
| Step 5 | The patient can wear the lenses for up to 90 days, after this time, the Rx should be stable and the final lens can be ordered as a single lens, a 2-pack or a 4-pack. |
Fitting Considerations and Adjustments
Initially on fitting the lens, bubbles may form. These should settle fairly quickly. If they do not and there is little lens movement, this may indicate a tight fit. In other respects, the fitting assessment is the same as for a normal soft lens - there should be post blink movement of not more than 1mm and the lens should have a good positive return to the central position after manual displacement.As an alternative to changing series, the lens can also be steepened by going to 15.00mm or flattened by going to 14.00mm. The Horizontal Visible Iris Diameter (HVID) should be taken into account when deciding the final diameter of the lens. For cyls over 3.00DC, a minimum lens diameter of 14.50mm should be used.
Over Refraction
The Over Refraction should be assessed in the normal way. The final correction should always be measured using standard refractive techniques, detailing sphere, cyl, axis, add and BVD.Ordering
Once you have a stable over refraction, order a single powered lens. To ensure prescription is totally settled, the patient can use the lens for up to 90 days before the final lens or pack is ordered.The single lens option has a fitting warranty, however no exchange is possible on the 2-pack or 4-pack options.
