WO2004090612A1

WO2004090612A1 - Method and device for producing soft contact lenses

Info

Publication number: WO2004090612A1
Application number: PCT/EP2004/003242
Authority: WO
Inventors: Birte Jansen; Kristian Hohla
Original assignee: Technovision GmbH Gesellschaft für die Entwicklung medizinischer Technologie
Priority date: 2003-04-10
Filing date: 2004-03-26
Publication date: 2004-10-21
Also published as: DE10316576B3; EP1616214A1

Abstract

The invention relates to a method and a device (1) for producing and finishing contact lenses, in particular customer-specific contact lenses. According to said invention, material is removed from the surface (3) of a pre-formed contact lens blank (2) using ultraviolet laser radiation (21). The inventive method is characterised in that: the contact lens blank (2) is first hydrated; the blank is then at least partially desalinated prior to the material removal by laser; and the blank remains hydrated during the material removal by laser.

Description

Method and device for making soft contact lenses

The present invention relates to a method and an apparatus for producing soft contact lenses, in particular customer-specific contact lenses.

So far, soft contact lenses have been produced in a turning or casting process. For the turning process, small, polymerized plastic plates are first produced, from which the later contact lens is turned. It is easier to manufacture soft contact lenses using a casting or molding process. The still liquid contact lens material is poured into a mold, the so-called mold, which corresponds to the negative of the later contact lens. The material, which is based, for example, on a silicone base, is then polymerized directly in the mold.

In both manufacturing processes, a hard lens is first produced, which is then hydrated. After hydration, two identical contact lenses with the same basic parameters only have an accuracy of +/- 0.125 diopters in their refractive index (the refraction) and approx. +/- 0.2 mm in their inner radius (the so-called basic parameters). Initially identical lenses can therefore cause different refractions in the eye.

This becomes a major problem when customizing multifocal lenses for a specific person. Such multifocal or multifocal lenses have several different focal lengths and can be used to correct presbyopia. It is also difficult to adapt lenses to improve the visual acuity, since these lenses must have precisely specified optical properties. An improvement in the visual acuity is particularly desired by people with more severe higher aberrations in their eye system or a beginning keratoconos.

Multifocal lenses would have to be made individually for each customer to take into account the special properties of their eyes. The most accurate results would be achieved if the customer placed a blank contact lens on the eye, carried out a measurement of the refractive properties of the eye-contact lens system, then removed the lens from the eye and reworked it according to the previous measurement. In particular, the position would have to be measured as precisely as possible that the contact lens occupies on the eye. The optical properties of the eye can only be corrected in a targeted manner if the position of the multifocal lens on the eye is not only very reproducible, but is also taken into account during post-processing.

Post-processing of the contact lens blank has not been possible so far. After the contact lens is hydrated, it can no longer be processed by a turning process because it is too soft and therefore no longer provides sufficient resistance for processing. It was initially thought of dehydrating the contact lens blank again. However, this is hardly possible since uniform drying would have to be achieved so that the contact lens blank does not warp. As an alternative, post-processing was carried out on identical contact lens blanks before they were hydrated, taking into account a swelling factor. However, it has already been stated that two identical contact lenses on the eye can behave differently. In particular, it is possible for the reworked contact lenses to assume a different position on the eye than the contact lens initially measured on the eye. In addition, this procedure leads to considerable storage and time expenditure.

In any case, it would be preferable to rework the contact lens blanks in the hydrated state. For some time now, attempts have been made to rework hydrated contact lenses by laser ablation. Ultraviolet laser radiation is mostly used, for example from excimer lasers, since the transparent contact lens material hardly absorbs laser beams in the visible wavelength range.

The post-processing of hydrated contact lens blanks by laser ablation has so far not been able to produce satisfactory results. Small bubbles form in the lens material during laser processing, making the surface quality of the contact lens unacceptable for use in refractive optics. It was suspected that these bubbles are caused by the heating and evaporation of the water contained in the lens, because on the one hand relatively high energy densities have to be used when processing the contact lens materials and on the other hand water in the UV range has a high absorption coefficient. With that stands one faces a dilemma, since the water is inevitably absorbed in the contact lens when hydrated.

A device and a method for reworking contact lenses using ultraviolet laser radiation are known from US Pat. No. 5,331,132. A mask is placed on the back of a contact lens, which is subsequently removed by means of the radiation from a UV laser in order to produce certain surface structures in the contact lens. However, US 5,331, 132 makes no information about the material of the contact lens. In particular, it therefore does not make any statements as to how the disadvantages described above could be remedied when reworking soft contact lenses.

The present invention has for its object to provide a method and an apparatus with which contact lens blanks made of soft contact lens material can be reworked in a structurally simple manner and with a satisfactory surface quality.

This object is achieved by a method with the features of claim 1 and a device with the features of claim 9.

The invention is based on the surprising finding that very good surface qualities can be achieved with laser ablation if the hydrated contact lens blank is at least partially desalted before laser ablation. The hydration itself must be done in physiological saline, which typically has a salt content of around 7%. In this way, the salt content in the contact lens is adjusted to the salt content in the tear film, because otherwise water is extracted from the tear film or the contact lens due to osmosis as soon as the contact lens is put on the eye. So while the blank contact lens is being measured on the eye, it necessarily has a certain salt content. As soon as this salinity is reduced, post-processing with laser radiation leads to excellent results. The remaining water content in the contact lens blank does not represent an obstacle, since the removal parameters remain largely constant even if the blank partially dries. By completely desalting the hydrated contact lens blank, it should be possible to achieve even better surface qualities during laser ablation.

For desalting, the hydrated contact lens blank can, for example, be placed in a desalination liquid or rinsed with such a liquid.

Distilled water has proven to be a particularly inexpensive and yet effective desalination liquid.

When performing the laser ablation, at least the surface of the contact lens blank to be processed is preferably in air. The contact lens blank is therefore no longer completely immersed in the desalination liquid. This has the advantage that the removed lens material can be quickly removed from the contact lens, for example by means of an air stream, without being deposited as a debris on the surface of the contact lens. With a contact lens immersed in liquid, the removal of the removed material would be more difficult. Therefore, either the desalinated contact lens blank is lifted out of the liquid, or the liquid is at least drained so far that the surface of the contact lens to be processed is in air.

It has already been stated that a refractive measurement is carried out on the eye-contact lens system when the hydrated contact lens blank has been placed on the eye. It is even more advantageous to carry out a wavefront measurement of the optical system consisting of the eye and the contact lens as part of the refractive measurement, since the optical properties of the eye can be corrected particularly well if the data of such a wavefront measurement are taken into account during laser ablation. A wavefront measurement should be carried out in particular if multifocal lenses are to be manufactured.

It was also stated that the position of the contact lens on the eye should be taken into account during post-processing. In order not to have to rely on estimated values, it is advisable to measure the position of a hydrated contact lens blank in one eye before laser ablation and then to carry out the post-processing on the basis of the measured position data. It is favorable if the decentration and / or the axial position of the contact lens are measured on the eye during this position measurement. The decentering indicates how far the center of the contact lens deviates in the horizontal and vertical directions from the center of the pupil of the eye. Toric (cylindrical) contact lenses have a so-called cylinder axis, which corresponds to the direction of their minimum or maximum refractive power. The axial position of such lenses describes which rotational position the contact lens preferably assumes on the eye with regard to its cylinder axis. If the decentering and the axial position of the contact lens are known, then all position data are available.

The device according to the invention not only has a laser for carrying out the material removal and a desalination device for desalting a hydrated contact lens blank, but also a positioning device. It is used to hold the contact lens blank to be machined at a defined position in relation to the laser beam used for machining. This makes it possible to process the blank contact lens precisely on the basis of the previously measured refractive data and / or position data.

A tank is preferably provided in the device for the desalination liquid so that a sufficient amount of the liquid is always available.

It is expedient if the device itself has at least one measuring instrument for measuring the position data of a contact lens, for measuring a wavefront and / or for measuring the surface topography of an eye. Using an internal processor, this data could be used directly to control the post-processing of the contact lens blank.

An exemplary embodiment of the invention is illustrated below with the aid of a drawing. In detail shows

Figure 1 is a schematic representation of an apparatus for performing the method according to the invention for producing soft contact lenses. Figure 1 shows schematically the most important components of a device 1 for reworking preformed contact lens blanks 2. A contact lens blank 2, which consists of a soft contact lens material and from whose surface 3 a volume 4 is to be removed, is located in a positioning device 5. Die Positioning device 5 has two approximately semicircular holding jaws 6. On the mutually facing sides of the holding jaws 6, a notch 7 is provided, in which at least the outer edge of the contact lens blank 2 can be received. The contact lens blank 2 shown lies on a support 6a which is approximately adapted to the curvature of its inner surface and supports the soft contact lens blank 2 in a dimensionally stable manner. The notch 7 is shaped so that it also supports the support 6a.

The two holding jaws 6 can be removed from one another for inserting and removing the support 6a and a contact lens blank 2 into the notch 7. For this purpose, a hinge is provided between them, for example, or they are mounted on rails and can be moved linearly away from one another. In the processing position shown in FIG. 1, the holding jaws 6 enclose the contact lens blank 2 at its edge and clearly define its position.

The holding jaws 6 form the bottom of a basin 8, which is also delimited by side walls 9. A desalination liquid 11 can be filled into the basin 8 from a tap 10. The strength of the liquid flow can be adjusted via a metering device 12. The desalination liquid 11 stored in a tank 13 is preferably distilled, mineral-free water.

Except for an overflow 14, the desalination liquid 11 can only flow out of the basin 8 through an outlet opening 15 between the holding jaws 6. The outlet opening 15 is located in the support under the contact lens blank 2. On the way from the basin 8 to the outlet opening 15, the desalination liquid 11 must either seep through the partially permeable contact lens blank 2 or at least wash it around. The desalination liquid 11 flowing through the outlet opening 15 or the overflow 14 is collected by a collecting basin 16. The liquid 11 can be pumped back to the tank 13 via a feed line 18 by means of a pump 17. Instead of one, several outlet openings 15 can also be provided. Another component of the device 1 shown in FIG. 1 is a laser 20 for reworking the contact lens surface 3. Usually, it is a UV laser, for example an excimer laser. The laser beam 21 emerging from the laser 20 is guided over two adjustable scanner mirrors 22 which can be pivoted about axes which are perpendicular to one another. By moving the scanner mirror 22, the focus of the laser beam 21 can be directed to any points on the surface 3 of the contact lens blank 2.

The operation of the device 1 according to the invention is described below. First, a contact lens blank 2, which consists of a transparent plastic, is preformed in a manner known per se. Then the contact lens blank 2 is hydrated in physiological saline. The volume of the contact lens blank 2 increases and the material becomes soft. The saline solution has a salt content of about 7% to adapt to the composition of the tear film of eyes.

The hydrated, soft contact lens blank 2 is placed on a person's eye. The position is determined as precisely as possible, i.e. the decentering and the axial position, which the contact lens blank 2 preferably occupies on the eye. It can be averaged over a plurality of measuring points, for example.

In order to facilitate the position measurement of the contact lens, a laser engraving can be provided on it, which extends over the optical zone of the contact lens, that is to say when the contact lens is put on, it lies above the pupil of the user. The laser engraving can be generated either by unloading through an aperture or by moving a very small laser focus over a scanner 22 to generate the engraving directly. Any shapes are conceivable for the engravings. For example, they can be designed as intersecting or intersecting, dotted lines. These lines can e.g. in the form of a Y, a cross or a star in the optical center of the contact lens.

After the contact lens blank 2 has been placed on the eye, a low-intensity helium-neon laser is used to irradiate the eye. The laser light is reflected from the retina of the eye. On the way back through the contact lens blank 2, the laser light is scattered on the engraving. On one on the surface 3 of the contact lens blank 2, the focus is clearly visible, the engravings are dark in front of the pupil, which is very bright due to the reflected laser light. The strong contrast between the bright pupil and the dark engravings makes it possible to evaluate the image using a computer and to determine the coordinates of the engravings. Using the coordinates of the engraving, the decentration and the axial position of the contact lens can be calculated relative to the center of the pupil.

In addition to the position measurement, a refractive measurement is carried out on the eye-contact lens system. In this case, preferably not only the remaining ametropia, but if possible also the wavefront of the optical system consisting of eye and contact lens blank 2 are measured. Here, too, it is possible to center over a plurality of measuring points.

A great advantage of the position measurement just described using the coordinates of small, preferably punctiform, engravings is that the wavefront of the eye-contact lens system can be measured through the engraving. The wavefront measurement is based on a point light source on the retina. This light can originate, for example, from the radiated HeNe laser. The small engravings on the surface of the contact lens blank 2 do not interfere with the wavefront measurement, especially since the wavefront measurement does not focus on the surface 3 of the contact lens blank 2. The position measurement and the wavefront measurement can thus be carried out simultaneously.

From the refractive measurement it can now be determined in what way the contact lens blank 2 has to be modified in order to achieve a desired refractive effect. For example, one goal can be that the wavefront emerging from the eye-contact lens system is a plane wavefront as close as possible. The target wavefront may have a slight coma to correct presbyopia. A processor calculates where and how much material has to be removed from the surface 3 of the contact lens blank 2 in order to achieve the desired refractive effect as closely as possible. From the calculated removal profile or removal volume 4 and known removal parameters of the laser 20, it can then be calculated how the laser beam 21 passes over the surface 3 of the contact lens blank 2. must be performed to remove the volume 4. The calculated path is stored in a control file for controlling the scanner mirror 22.

According to the invention, the contact lens blank 2 is at least partially desalted before the reworking. First, the holding jaws 6 of the positioning device 5 are moved apart, so that the contact lens blank 2 can be inserted into the notch 7. Thereupon, the holding jaws 6 are moved towards one another to such an extent that the contact lens blank 2 is seated in a fixed position and is secured against slipping out of this position, without however being deformed.

The metering device 12 is opened, so that desalination liquid 11 from the tank

13 is filled into the basin 8 via the tap 10. A layer of desalination liquid 11 is formed in the basin 8 above the contact lens blank 2. The desalination liquid 11 flows through or flows around the contact lens blank 2 and thereby removes salt stored in the contact lens blank 2. The desalination liquid 11 flows into the collecting basin 16 via the outlet opening 15. If the liquid level in the basin 8 rises too high, the desalination liquid 1 also flows via the overflow

14 and is then also collected in the catch basin 16. The pump 17 pumps the desalination liquid 11 back into the tank 13. In this way, the desalination liquid 11 can be used several times. Faucets are not shown, through which the desalination liquid 11 can be removed from the illustrated circuit in order to replace the entire desalination liquid 11 in the device 1 after a certain operating time.

After a certain rinsing time, the salt content in the contact lens blank 2 has been reduced to a sufficiently low level, for example to 0.3-1.0%. The metering device 12 is closed in order to stop the supply of further desalination liquid 11. The remaining desalination liquid contained in the basin 8 flows down through the outlet opening 15. The surface 3 of the contact lens blank 2 to be processed thus comes to rest in air again. In Figure 1, the surface 3 to be machined is the outside of the contact lens, i.e. the side that later turns away from the eye.

The next step is the laser ablation of contact lens material. The scanner mirror 22 is controlled based on the previously calculated control file so that the Laser beam 21 is guided in the so-called flying spot method over the surface 3 of the contact lens blank 2. It is usually a pulsed laser 20, so that new coordinates of the scanner mirror 22 can be set between two laser pulses. If it is a UV laser, the material is removed photoablatively. By laser ablation, the contact lens blank 2 becomes the finished contact lens. After processing, it can be removed from the device 1 and only needs to be sterilized in physiological saline for a short time before it can be placed on the person's eye.

Starting from the illustrated embodiment, the manufacturing method and the device according to the invention can be modified in many ways. For example, it would be possible for a measuring instrument for measuring the position data of a contact lens on the eye, for measuring a wavefront of the eye-contact lens system and / or for measuring the surface topography of an eye to be integrated in the device 1.

Distilled water would not necessarily have to be used as the desalination liquid 11, but other, salt-extracting liquids would also be conceivable.

It was described above that the contact lens blanks 2 are rinsed using the desalination liquid 11 for desalting. However, a desalination effect can also be ascertained if the contact lens blanks 2 are only inserted or immersed in desalination liquid 11. Desalination liquid 11 could continue to be supplied during the laser ablation, e.g. drop by drop so that at least the edge of the contact lens blank 2 remains moist and the blank 2 is prevented from drying out.

The positioning device 5 does not necessarily have to have two holding jaws 6. Especially if the contact lens blanks 2 are only to be inserted into the liquid 11, shell-like positioning devices 5 would also be conceivable. In addition, the positioning devices 5 could be constructed in such a way that more than just one contact lens blank 2 can be accommodated in each of them, so that a whole series of similar contact lenses can be produced. Even if the laser 20 is preferably a UV laser, there are still alternatives. For example, a short or ultra short pulse laser with visible or infrared wavelengths could be used to perform a photodisruptive ablation process.

Finally, instead of the outside of the contact lens blank 2, the inside of it could also be machined, i.e. the later contact area to the eye. If the surface topography of the eye has been measured beforehand, the inner surface of the contact lens blank 2 could be adapted to this topography, for example.

Claims

Expectations

1. A method for producing soft contact lenses, in particular customer-specific contact lenses, material (4) being removed from the surface (3) of a preformed contact lens blank (2) by means of ultraviolet laser radiation (21), characterized in that the contact lens blank (2 ) is first hydrated, is at least partially desalted before laser ablation and remains hydrated during laser ablation.

2. Manufacturing method according to claim 1, characterized in that the hydrated contact lens blank (2) is completely desalted before laser ablation.

3. Manufacturing method according to claim 1 or 2, characterized in that the hydrated contact lens blank (2) is desalted by placing in or rinsing with a desalination liquid (11).

4. Production method according to one of the preceding claims, characterized in that distilled water (11) is used for desalting the hydrated contact lens blank (2).

5. Manufacturing method according to one of the preceding claims, characterized in that there is at least the surface to be machined (3) of the contact lens blank (2) when performing the laser ablation in air.

6. Manufacturing method according to one of the preceding claims, characterized in that the laser ablation takes place on the basis of the data of a wavefront measurement, which was previously carried out on one eye with the hydrated contact lens blank (2) placed thereon.

7. The manufacturing method according to at least one of the preceding claims, characterized in that the position of a hydrated contact lens blank (2) is measured in one eye before laser ablation and the measured position data are taken into account during laser ablation.

8. Manufacturing method according to claim 7, characterized in that in the position measurement, the decentering and / or the axial position of the contact lens blank (2) are measured relative to the pupil of the eye.

9. Device (1) for performing a manufacturing method according to one of the preceding claims, wherein the device (1) a desalination device (8-18) for desalting a hydrated contact lens blank (2), a positioning device (5) for positioning one to be processed Contact lens blank (2) and a laser (20).

10. The device according to claim 9, characterized by a tank (13) for storing a desalination liquid (11).

11. Device according to one of claims 9 or 10, characterized in that it has at least one measuring instrument for measuring the position data of a contact lens blank (2), for measuring a wavefront and / or for measuring an eye surface topography.