Miscellaneous

Miscellaneous

Time and time again, there is a possibility of producing lenses which lie outside our standard lens range. In each individual case, our Technical Customer Service Centre checks whether the production of the required non-standard version is meaningful and possible from the production viewpoint. You can obtain an overview of possible specially produced lenses here.

1. Thickness

Non-standard Thickness

Non-standard Thickness

It is sometimes advisable to increase the edge thickness of plus lenses for glazing rimless frames. If the optician expressly specifies that the order is for a Supra or rimless frame with screw connections, ZEISS will automatically produce a minimum edge thickness of 1.5 mm.

If an exactly specified thickness is required in the area where the drill hole is made,
the following information is required:

  • centration
  • lens shape
  • frame data
  • position of drill hole
  • dioptric and prismatic powers


ZEISS can then use this information to produce the optimum lens for your requirements.
Principle of thickness determination as for OPTIMA

Thickness matching for Anisometropia

Thickness matching for Anisometropia

A marked difference between the dioptric powers of the right and left eyes may result in a major difference in lens thickness. For patients with pronounced anisometropia, it is possible to match the front curvature and/or the centre or edge thickness of the lens with the lower power to that with the higher power.

Tips for the optician:
If this is required, a comment to this effect should be made on the lens order. If, however, the thickness matching is to be exactly calculated, ZEISS requires the following data:

  • centration
  • lens shape
  • frame data
  • dioptric and prismatic power


The same principle like calculating OPTIMA

Iseikonic Lenses

Iseikonic Lenses

For the correction of aniseikonia (different images between right and left eye), ZEISS produces special lenses with an increased curvature and centre thickness. In this way it is possible to achieve the required shape factor (effective magnification) and hence improved binocular vision.

Tip for the optician:
The comment "Iseikonic lenses" should be made on the lens order.

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2. Curvatures

Non-standard curvatures

Non-standard curvatures

Single vision lenses without an aspheric front curve can be produced with non-standard curvatures. Lenses with a flatter or greater curvature are usually ordered for cosmetic or fashion reasons. Flatter curvatures can sometimes result in poorer visual quality.

Tips for the optician:
If the required front surface radius is specified in the lens order, we start by checking its technical feasibility.
The comment "extra flat" suffices if you wish to order exceptionally flat lenses. In every case, an aspheric or atoric lens is preferable to an "extra flat" design to ensure that optimum visual quality is provided.

Examples are diving goggles, iseikonic and biconvex / biconcave lenses

Diving Goggles

Diving Goggles

For diving goggles, ZEISS produces special glass plano-convex and plano-concave lenses which are cemented onto the inside of the diving goggles. The range of products available includes both single vision and bifocal lenses for diving goggles.

Tips for the optician:

Giving the patient’s centration data and back vertex distance, the goggles should be sent to ZEISS Aalen, Germany for glazing.

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3. Diameter

Optimised Diameters

The thickness of plus lenses is heavily dependent on the diameter ordered

Optimised Diameters

For plus lenses, it is often advisable to order a diameter which deviates from the standard diameters given in the price list. In this way, a thinner lens can be produced than with the next highest standard diameter.
Remember: the smaller the diameter, the thinner a plus lens becomes. For single vision lenses, optimised diameters of as small as 38 mm are possible. The size of the optimised diameter is selected by the optician so that the lens is as large as required and as small as possible.

Special case for optimised diameter: OPTIMA
Special case for non-standard diameter: Decentred single vision lenses

Decentred Single Vision Lenses

Single vision lenses, with the exception of aspheric or atoric lenses, can be pre-decentred. This is advisable if the standard diameters available do not permit exact centration.
The required pre-decentration is calculated as follows and is specified in mm in the lens order:

Pre-decentration
Decentred Single Vision Lenses
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4. Toughening

Toughening of Glass Lenses

Glass lens (blue) before ion exchange in salt melt (red)

Toughening of Glass Lenses

Chemical toughening increases the resistance of glass lenses to breakage (exceptions: ZEISS Single Vision Sph Mineral 1.7, ZEISS Single Vision Sph Mineral 1.8 and ZEISS Single Vision Sph Mineral 1.9). An ion exchange process in the lens surface causes compressive strain which increases the resistance of the lens to breakage. Subsequent coating (AR coating) leads to a reduction in the breaking strength achieved in this process.

Toughening of Glass Lenses

After ion exchange

ZEISS limits this toughening process to edged lenses in order to rule out the possibility of a subsequent grinding process negatively influencing the breaking strength achieved by chemical hardening.

In some countries the use of thermally toughened glass is more common and it is recommended that safety spectacles are purchased as a complete appliance in order to guarantee the effectiveness of the device.

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5. Frosted Lenses

Frosted or Occluded Lenses

Frosted Lenses
To cover an eye which a patient does not want to be visible for cosmetic or other reasons, all lenses in the ZEISS product range can be frosted on their front surface.

Occluded Lenses
If an eye is to be excluded from vision for medical reasons, this can be achieved with an occluded lens. As the front surface is only roughened, the outline of the eye can still be seen from the outside - unlike frosted lenses.

6. Franklin Split Lenses

Franklin Split Lenses

In some countries, plastic executive or Franklin split lenses are often used to reduce accommodation in children. Executive or Franklin split lenses are special bifocals without image jump which provide a very wide zone for near vision. They are produced by cementing together two lens halves, one the distance portion and one the near portion.

7. Prismatic Powers

Prismatic Powers

Prismatic lenses are produced "true to prescription" by ZEISS. This means that, during wear, the user experiences exactly the prescribed power in the major reference point of the lens. Due to the different ray path present during measurement in the focimeter, a different value is measured than that ordered. To allow accurate checking with the focimeter, the measured value is printed on the lens packet.

8. Bifocal Lenses

Bifocal Lenses

Magnifying bifocals

Non-standard Additions
For additions over 6.00 D, magnifying bifocals are preferable to standard lenses.
Further information about: Low Vision Devices

Prismatic effects in the Distance and Near Portions
All bifocal and progressive lenses by ZEISS can be produced with prism by surface tilting. This results in the same prismatic effects for the distance and near portions.
If different prisms are required for distance and near, a prism segment can be cemented onto a Punktal base.

9. With "Inset 0"

Progressive Lenses with Inset 0

Progressive Lenses with "Inset 0"

For presbyopic spectacle wearers whose eyes do not converge in near vision, individualised progressive lenses from ZEISS - ZEISS Progressive Individual 2 - can be ordered without an inset. The progressive lenses are then specially computed for this situation. The distance and near reference points then lie directly underneath each other in the vertical axis.

Note for the optician:

These individualised progressive lenses are ordered by specifying "Inset 0".

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