Operation

Set up

Sytem Components
OptiSpheric^® IOL setup follows the requirements of the ISO 11979 standard for the different parameters to be measured.

An illuminated target is at the focus of a collimator, so that parallel light is incident upon the IOL.
All targets needed for full characterisation of the IOL are mounted in a manual or fully automated reticle changer. Double slits are used for power determination, single slit, cross or pinhole are used for MTF measurement.
The collimator is an achromatic objective lens that is virtually free of aberrations for the wavelength band transmitted by the filter. The filter is transmitting green light with a narrow band transmittance peak at 546.1 nm.

A microscope with a high numerical aperture allows for imaging of the target on a high resolution CCD-Camera connected to the PC. The complete measurement head, including the microscope and the sensor, is mounted on a motorized stage featuring micro step operation for fast and accurate autofocus.

OptiSpheric^® IOL can be customized to measure at different wavelengths. An instrument version measuring all parameters over the visible spectral range is available.

Sample holders

In-air measurement holder
When measuring in air, the IOL is placed in a suitable holder designed for different kinds of sample diameters and haptics shapes. The aperture, typically of 3 mm can be adjusted to diameters from 1 to 6 mm. The IOL holder itself is clamped by a self centering mount with a diameter range of 3-35 mm equipped with accurate translation facilities in X, Y-directions.

In-situ measurement holder
When measuring in situ, the intraocular lens must be inserted in a model eye simulating the effect of the real human eye.
Two types of model eyes can be used, both compliant to the ISO 11979 standard. They are composed of two parallel plates delimitating the area filled with saline solution.

The IOL is placed in between these two plates
on a sample holder including the aperture
stop. An achromatic doublet simulates the
eye cornea.

Standard Model Eye
The standard model eye is a small, easy to use holder which is positioned into the self centering mount.

Advanced Model Eye
The advanced model eye additionally allows for 35°C heating of the fluid chamber and tilting of the lens holder up to 5° in order to simulate the behavior of a tilted IOL when inserted in the eye.
Additionally it brings advanced adjustment features:

• Translation in X and Y directions of the sample inside the model eye
• Translation in X and Y directions of the complete model eye regarding to the optical axis
• Aperture sizes modification
• Easy removable cornea lens since MTF and optical power of IOLs must be measured in two different conditions: with and without cornea lens.

High volume production testing holder
In case of testing in a high volume production environment the system can be factory configured with a tray system which allows for the fully automatic measurement of a multitude of IOL. This tray system which contains a motorized high precision XY linear stage is proposed for in-air as well as in-situ measurements.

During the measurement an automatic classification of all IOL in different quality classes is done according to user defined pass fail criteria. A classification map is displayed at the end of each tray measurement allowing for an easy sorting of the lenses.

Measurement of complex Intra ocular lenses

The latest generation of IOL: aspheric, toric, diffractive, multifocal lenses are measured as well by OptiSpheric^® IOL.
In case of multifocal lenses, different image planes are measured. When moving the microscope and CCD camera troughout the focusing range, several images are found by the system.
The powerful automatic focusing routine allows focusing consecutively the image analyzer to the multiple image planes of multifocal lenses.

Toric lenses for example have too different radii of curvature along sagittal and tangential directions. They form two images in two distinct planes which are easily found by moving the imaging microscope. The use of a cross target in such a case also allows seeing both symmetry directions.

When a lens provides images in different focal planes which are quite close one to each other, the quality of the image in one plane is affected by the residual background of a second image plane. This affects directly the MTF. One can also choose to measure the image quality in each focal planes individually by removing the background effect.

OptiSpheric^® IOL software provides in this case a correction function based on an apodization principle which removes the background of neighbour focal planes at dedicated spatial frequencies without changing the image of the focus under test.

Measurement of very long EFL (small diopter powers)

From the standard OptiSpheric^® IOL covering an EFL range up to 250 mm to the OptiSpheric 2000 covering a measurement range up to 2000 mm, our customers can select further intermediate product versions in order to optimally meet their specific requirements from very small diopter powers to very large ones.

If one prefers to use a smaller stage, small diopters (leading to long EFL) can still be measured by using a well known additional lens shor tening the imaging distance.
The power of he optical system formed by the known lens and the IOL is determined and from this the power of the IOL itself is calculated.

High volume production testing

To respond to customer needs for testing of large quantities of lenses in production environment, TRIOPTICS developed an OptiSpheric^® IOL station working with a motorized tray system and fully automated measuring procedure.
Once a lens tray with 30 to 60 lens seats is kinematically placed on a transport frame with two translation precision stages the OptiSpheric^®IOL PRO software positions each lens on the optical axis of the instrument, performs an accurate focussing, calculates and displays the measurement data and produces on request a Pass/Fail result. This is particularly well suited for the production testing of IOL.