medical.swisslens.ch

Fitting advice

Fitting "HydroCone" is very straightforward and efficient. Fittings can be made in one of two ways:

1. Fitting with a fitting set:

The fitting set contains 6 contact lenses
  • 3 for grade 1-2 keratoconus - HydroCone 12  (DIA 14.00, BC 7.80/8.00/8.20)
  • 3 for grade 3-4 keratoconus - HydroCne 34 (DIA 13.70, BC 7.60/7.80/8.00)
It is recommended to start with the medium base curve and then if necessary to choose the flatter or steeper curve depending on the observed behavior of the trial lens.

2. Fitting with an individual Trial Lens:

The initial trial lens is determined by Corneal topography, the vision and the classification of the Ketatoconus. This lens is then observed in situ and modified and re-ordered with the appropriate parameters. Trial lenses are supplied with a plano cylinder. The final contact lens is ordered using the findings of an Auto Refractor combined with the usual subjective/objective refraction results. A fitting guide service is available. Download calculator

Fitting advice

The HydroMed for post-LASIK is easily fitted with a time saving set of simple fitting lenses. For post keratoplasty and irregular corneas, it is advisable to determine the first trial lens using our fitting advice service.

Fitting with a fittng set:

The bi-curve "HydroMed" is developed specifically for post-LASIK (refractive surgery) conditions and the fitting set contains 4 contact lenses (DIA 14.20, BC 8.90, 9.20, 9.50, 9.80). The appropriate fitting lens is selected using Corneal topography as a guide. 

Fitting with a Trial Lens:

  The initial trial lens is determined by Corneal topography, the vision and condition classification. This lens is then checked in situ and modified and re-ordered with the appropriate parameters. Trial lenses are supplied with a plano cylinder, The final contact lens is ordered using the findings of the Auto Refractor combined with usual subjective/ objective refraction results. A fitting guide service is available. A good underwashing of the contact lens is recommended to ensure a sufficient tear exchange and best correction of irregularities on the corneal anterior surface. If the expected visual performance is not achieved with the regular thin lens design, the optical zone can be optimized on the front surface to compensate. Download calculator

Fitting advice

The fitting with trail lenses is generally recommended. Selecting  the appropriate geometry: For Keratoconus grades 1 or 2, and/or a topography > 6.5 mm select the "HydroConeK12" as initial lens For Keratoconus grades 3 or 4 and/or a topography < 6.5 mm select the "FlexConeK34" as initial lens Modifications Increase the lens diameter according to the off-centring of the cone If the lens does not stay in place (centrally too flat or too steep) adjust r0 accordingly If the "K12" should sit to steep in the periphery, switch to "K34" by using the equal r0. If the "K34" should sit too flat in the periphery, switch to "K12" use an equal r0. If the back-surface geometry does not lead to a satisfied fit, or a special topography is required; the back surface can be individually parameterized using the "Orbiflex SxS".

Fitting advice

The use of trial lenses is generally recommended
Selecting the appropriate geometry:
There are 3 different edge designs: M (medium, standard), S (steep) and F (flat).
Start with the medium design "M" and flatten or steepen in accordance with the flourorescein observations
If the back-surface geometry does not lead to a satisfactory fit, or a special topography is required, the back surface can be individually parameterized using the "Orbiflex SxS".

Baby contact lens - Fitting advice

The diameter of the cornea of a newborn is on average 9.5mm. Corneal growth is completed at the end of the second year of life (approx. 11.7 mm). Measuring lenses: DIA = 12.50; BC: 7.40 / 7.80 / 8.20 Principles of fitting: Pediatric contact lenses, as with all lenses should show stable fitting behaviour. The Central optical zone should cover  the entire area of the pupil. Since infants typically spend more time on their backs when compared to an adult, the centering of the lens will be different. Another key factor is the handling of the contact lens - to attach and to remove the lens: a small overall diameter simplifies this procedure.

Required measurements:

  • K  Readings
  • IRIS Diameter (DHIV)
  • Refraction

Choice of trial lens

  • BC HH radii + 0.30 mm
  • Diameter = IRIS diameter + 1, 50 mm
  • Strength: HSA to "0" when glasses refraction
The cornea flattens as it grows, therefore the BCOR should be modified when the infant grows older. Young infants may not be cooperative in the consulting room, so the following guidelines may be useful:
Age BCOR (mm) Diameter (mm) Power (dpt.)
0-3 Month 7.40 12.00 +40.00
3-6 Months 7.60 12.50 +36.00
6-9 Months 7.80 13.00 +33.00
9-12 Months 8.00 13.00 +30.00

Fitting recommendations:

  • The contact lens should fit centrally in front of the pupil with approx. 1mm of movement upon blink.
  • Choose the smallest diameter to meet these criteria.
  • A small bubble may be observed upon insertion which is quite normal, the bubble should disapear after a few blinks.

Flat adjustment:

The push-up test helps determine how well the lens is centering. If the lens stays de-centered or gets stuck beneath the upper eyelid  then increase the overall diameter by 0.50 mm or reduce the BCOR by 0,3 mm. These adjustments can be made in combination.

Steep adjustment:

A steep lens will display lack of movement, in the centre is a bubble for longer than 10 minutes. You can dissolve this effect by increasing the BCOR. Generally a slighlty flat fit is preferable to a steep fit.

Tight fit:

A tight fitting contact lens will not respond correctly to the push up test. Observations will show reduced lens movement as well as possible eye redness and irritation. The lens may also become de-centered getting itself stuck on another part of the eye. Higher than average centre thickness is normal with high plus powered lenses, however smaller diameters associated with baby lenses help to dissolve the problem. Should  the centre thickness be problematical to the fitting of the lens then flatten the BCOR by 0.50 mm RX assessment: It is recommended using retinoscopy to perform a refraction. After a few hours in situ cylindrical elements of the prescription can be determined  (also by using a retinascope). Astigmatism powers are  available but rarely used on young infants.