centring

Interactive demo: Fitting ZEISS lenses

1. Anatomic Fitting

After the preliminary anatomic fitting of the spectacles, the selected frame should be

• fitted to a corneal vertex distance of between 12 and 16 mm and
• display a (tilt) pantoscopic angle of between 8° and 12°.

If not specified individually for customised lenses, ZEISS lenses are designed for these parameters. These recommended values cannot always be observed due to special anatomic conditions or to an unusual frame shape. The optician should then take this into account in refraction and the lens order.

2. Lateral Centration

Lateral centration of ZEISS lenses without prismatic power

Lateral Centration for ZEISS Lenses without Prismatic Power

The centration distance should correspond to the interpupillary distance when the patient is looking into the distance (distance PD).
This applies to all ZEISS lenses:

• Single vision lenses for distance and near
• Officelenses, the proximity lens
• Progressive lenses
  
• Bifocal and trifocal lenses it is standard practice to use the segment tops as reference points in lateral centration. These are each marked at a distance of 2.5 mm nasally from the distance PD.
  

3. Vertical Centration

1. Natural head posture
2. Head posture for marking the vertical centration according to the "centre-of-rotation requirement" (frame plane perpendicular)

Vertical Centration of ZEISS Lenses

Single vision lenses and Office lenses
The "centre of rotation requirement", i. e. the lens is centred when its optical axis runs through the eye’s optical centre of rotation, should be met in the fitting of single vision lenses and office lenses. There are two ways of determining the vertical centration:

• The patient raises his head until the frame plane is perpendicular. The pupil centres are then marked, with the patient’s eyes in the zero visual direction (looking straight-ahead).
  
• With the patient’s head and body in a natural posture, the positions of the pupil centres are marked for the zero visual direction (looking straight-ahead).
  
  

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4. ...with Prismatic Power

Centration of ZEISS Lenses with Prismatic Power

In prismatic prescriptions the centration points determined must be displaced by 0.25 mm per 1 cm/m in the opposite direction to the prism base. This takes into account the movement of the eyes in prismatic lenses.

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5. ...with i.Terminal 2

Centration with i.Terminal 2

The computer-assisted i.Terminal 2 fitting system can be used to determine all centration data with extreme precision using two video images, with the patient’s head and body in a natural posture. The correct position of the centration points is calculated and displayed on the basis of the applicable centration requirement, the dioptric power and the lens type.

Not all products, services or offers are approved or offered in every market and approved labelling and instructions may vary from one country to another. For country specific product information, see the appropriate country website.