DK1882206T3

DK1882206T3 - Glasses

Info

Publication number: DK1882206T3
Application number: DK05800157.9T
Authority: DK
Inventors: Brian Lever
Original assignee: Br Fusion Ltd
Priority date: 2005-05-19
Filing date: 2005-11-02
Publication date: 2015-08-10
Also published as: GB0512724D0; GB0510258D0; PT1882206E; ES2543713T3

Description

DESCRIPTION

[0001] The present invention relates to spectacles and to a method for the assembly of spectacles.

[0002] The following is a more detailed description of a known pair of spectacles with reference being made to the accompanying Figure 1, which shows the pair of spectacles 1 including two rims 3, and two lenses 2. Each lens 2 is surrounded by a respective rim 3, but this may not necessarily be the case and each rim 3 may only partially surround the associated lens 2, depending on the style of the spectacles. The spectacles 1 further comprise spectacle mounts which allow the spectacles 1 to fit a wearer's face. The spectacle mounts shown in Figure 1 comprise a bridge piece 4 which is connected between the rims 3, which is shaped to fit above the bridge of a wearer's nose and which carries pads 16 that support the spectacles on the wearer's nose, and two opposing side pieces 5 each of which extend from a respective outer side of each associated rim 3. Each of the side pieces 5 comprise a lug 6 and a temple piece 7 shaped or shapable to a wearer's ear. The temple piece 7 may be joined to the lug 6 by a hinge 8 (as is shown in Figure 1) or may be moulded together with the lug 6 to form a single piece depending on the style of the spectacles 1.

[0003] Rimless spectacles, in which the rims are omitted and in which the spectacle mounts (i.e., in Figure 1, the bridge piece and the two lugs) are connected directly to the lenses, have increased in popularity as they are very lightweight, as they allow the lenses to be cut to any required shape, and as they are relatively inconspicuous in comparison to spectacles including rims.

[0004] Rimless spectacles are constructed by attaching the bridge piece to a nasal side of each lens and attaching each side piece to a temporal side of a respective lens.

[0005] There are several known methods of attaching the bridge piece and side pieces to a lens. In the case where spectacle mounts are made of wire, the most common method involves drilling, for each end of the bridge piece and side pieces, a respective hole through the lens at the appropriate position and cutting a slot extending inwardly of the edge of the lens, close to the hole. In this case, the ends of the spectacle mounts (i.e. the bridge piece and side pieces), where they are to be attached to the lens, are looped around a screw that is inserted through the associated hole and then bent around the edge of the lens to fit with the slot, thereby limiting the movement of the wire with respect to the lens.

[0006] Another known method used with spectacle mounts that are formed from metal strip is described with reference to Figure 2, which shows a partial view from above of spectacles showing the attachment of spectacle mounts to lenses 2. In this method, a screw 10 is attached to each end of the bridge piece and the end of each side piece (not shown) at which the side piece is attached to the associated lens 2. For each spectacle mount, the screw 10 is pushed through an associated a hole which is drilled into the lens 2 at the required attachment point. If the spectacle mounts are made of wire, the arrangement is adapted by turning the wire end of each spectacle mount around the screw 10 that is inserted through the hole from the front of the lens. A plastic washer 11 is then inserted to the rear of the lens 2, followed by a thin metal washer 12, a lock nut 13, and finally a cap nut (or dome headed nut) 14 to lock the screw 10 into place.

[0007] These spectacle mounts can also be shaped to fit to the rear of the lenses, in which case the washers and nuts are arranged as necessary to reduce and spread the pressure on the lenses.

[0008] Other known methods for use with rimless spectacles include mounting each of these spectacle mounts by the use of two drilled holes in the lens at the required attachment point and then securing the spectacle mount to the lens with two screws and associated nuts each side of the lens. A lug may be attached to a lens by cutting a slot at a side of the lens into which the attachment end of the lug is inserted, the attachment end of the lug having been bent to stay in place without the use of screws.

[0009] Other methods can be used to attach such spectacle mounts to a lens in rimless spectacles - such as by the use of pins attached to such a spectacle mount which can be inserted into either the front or edge of the lens, or a combination of pins and plastic inserts which are forced together with pliers to hold the pins in place.

[0010] The assembly of rimless spectacles that contain fixing parts such as screws, pins, nuts or plastic inserts may be problematic for those assembling spectacles for use, as opticians often throw away these fixing parts when putting spectacles on display so that when such spectacles are sent to be assembled for use there is extra cost and unnecessary delay in the assembly process if these parts have to be purchased separately. Further, the fixing parts may also become loose or otherwise move out of alignment, the fixing parts may obscure a wearer's area of vision, and the fixing parts may cause an obstruction when the lenses are cleaned. The fixing parts also tend to put pressure on the lens which can crack or distort the lens around the assembly point. It is often not possible to adjust rimless spectacles which are produced by the methods described above for pantoscopic tilt (i.e. the tilt of the lenses about a horizontal axis when the spectacles are worn) and the head width of a wearer, and they require a skilled technician to assemble, thereby tying up skilled staff on what is a very slow job.

[0011] In addition to the known methods described above for attaching the spectacle mounts described above with reference to Figure 1 to the lenses in rimless spectacles using mechanical fixing means, it is known to attach such spectacle mounts using adhesive. A slot or hole may be cut into the lens at the appropriate location and, where the spectacle mounts are made of wire, the wire of the mount to be attached is bent to engage with the hole. The wire is then fixed into place in the hole using adhesive. The hole in the lens is of a size so as to create a “tight" fit (an interference fit) for the wire, and consequently mounts affixed using this method are known to put great pressure on the lens, causing the appearance of stress marks on soft lenses such as high index, photochromatic and polycarbonate lenses. Further, adhesives used to affix the mounts using this method have their own associated drawbacks. One known system uses a two component adhesive which attacks polycarbonate and may lead to cracking of polycarbonate lenses, while another known system uses an adhesive which cures in the presence of ultraviolet light which is messy and time consuming to both assemble and clean.

[0012] EP-A-0718660 relates to rimless spectacles. Each lens has two nasal-side fixing parts and two temple-side fixing parts, each of which fits into a respective hole in the lens. Fixing parts have substantially the same sides as the lens. An adhesive is provided in the holes prior to inserting the fixing parts.

[0013] US-A-3577394 discloses an adhesive which cures without appreciable shrinkage at room temperature.

[0014] US-A-2784215 discloses an adhesive that has a very low change in volume during polymerisation.

[0015] FR-A-2849510 discloses a spectacle assembly comprising two lenses and a plurality of spectacle mounts, each including a fixing part sized to fit into a hole formed in an associated one of the lenses to connect the mount to the lens, the fixing part being held in the associated hole by an adhesive, wherein each of the lenses has a single nasal-side spectacle mount including a single linear fixing part sized to fit into a single linear nasal-side hole formed in the lens to connect the mount to the lens and a single temple-side spectacle mount including a single linear fixing part sized to fit into a single linear temple-side hole formed in the lens to connect the mount to the lens, [0016] According to the invention, there is provided a spectacle assembly as defined in claim 1 [0017] According to the invention, there is also provided a method of fixing a lens to a spectacle mount as defined in claim 13.

[0018] According to the invention, there is still further provided the use of an adhesive for the assembly of spectacles as defined in claim 17.

[0019] Some embodiments of the invention will now be described in detail, by way of example, with reference to the accompanying drawings in which:

Figure 3 shows a bridge piece for use in the assembly of rimless spectacles;

Figure 4 shows the bridge piece of Figure 3 when attached to lenses;

Figure 5 shows one end of a side piece for the rimless spectacles of Figures 3 and 4;

Figure 6 shows the side piece of Figure 5 attached to a lens and shows how the angle of the side piece with respect to the lens can be adjusted to any required position;

Figures 7A, 7B, 7C and 7D are partial views of an end of the side piece of Figures 5 and 6 and of the associated lens showing successive stages in the attachment of the side piece to the lens; and

Figure 8 is a view from above the spectacles showing the bridge piece of Figures 3 and 4 and the side piece of Figures 5 and 6 positioned for connection to the lenses.

[0020] In the drawings, like elements are generally designated with the same reference numeral.

[0021] Referring first to Figure 3, the bridge piece 15 comprises a bridge 23 for connection to the lenses and arms 19 extending from the bridge 23 and each carrying a respective pad 24 at an end remote from the bridge 23. Each end of the bridge 23 carries an associated pin 25. The bridge piece 15 may be formed from metal as a single piece, or may be formed by separate parts and then joined together, for example by soldering or welding.

[0022] The pins 25 are formed by blocks of rectangular cross-section which project from the bridge piece 15. The pins 25 include opposed longer surfaces interconnected by shorter surfaces, the longer surfaces in the plane generally parallel to the length of the bridge 23. The pins 25 are approximately 1.25 mm deep and 2.45 mm wide. Each longer surface is grooved to provide a gripping formation, with the grooved part of each surface extending approximately 2.40 mm from the distal end. Of course, pins 25 with any suitable dimensions could be used and, although the pins 25 shown in Figure 3 would be oriented horizontally when spectacles are placed on a wearer's face, they could be oriented vertically to suit the particular style of spectacle. The grooved longer surfaces of the pins 25 comprise a cross-hatched pattern for a purpose to be described below. Each pin 25 has a plastically deformable neck 26 for a purpose to be described below.

[0023] The bridge piece 15 is connected to a pair of lenses 2 as follows, with reference to Figure 4. First, each lens 2 is formed with a hole at the nasal side of the lens 2 at the position wlnere it is required to attach the associated end of the bridge piece 15. Only a single hole 28 is required in each lens 2, to allow the attachment of the bridge piece 15 to the lens 2. The requirement of a single hole in the lens 2 is the same for the attachment of a side piece to the lens 2 as will be described below. The holes 28 are formed to have a cross-section that is the same as the cross-section of the pins 25 to give a "close" fit wlnere force is not required to insert a pin 25 into the associated hole 28, rather than a "tight" fit (or interference fit) wlnich is used in the known methods of spectacle assembly described above and in which force is applied to insert a pin 25 into the associated hole 28. The fit should be such as to allow a minimum sufficient amount of adhesive required to fix the bridge piece 15 to the lens 2, to be used.

[0024] The pins 25 are inserted into appropriately positioned holes 28 formed in the lenses 2 and secured by adhesive. The close fitting of a pin 25 in the associated hole 28 is an important aspect of the embodiment described, as the adhesive used to fix the bridge piece 15 to the associated lens 2 is specifically chosen to retain its volume when set, i.e. it will not shrink or expand upon setting, thereby enabling the adhesive to act as a buffer between the pin 25 and the lens 2. The adhesive buffer acts to substantially reduce or even eliminate the pressure around the assembly point, which produces the stress marks that are normally visible on rimless spectacles made with soft lenses. The buffering effect of the adhesive also enables the assembly of rimless spectacles using lens materials that are not currently considered to be suitable for rimless spectacles. For example, CR39 (hard resin) lenses are not usually used in rimless spectacles because of the brittle nature of the lens material, and lenses wth a very high index , such as 1.74 index , higher index and polycarbonate lenses, are often not suitable for rimless spectacles because of the considerable stress marks produced by assembly using known methods. Further, to avoid the problems related to the known methods of spectacle assembly which use adhesives, the adhesive used should be a single component adhesive which does not require the presence of ultraviolet light for curing and which does not attack polycarbonate.

[0025] A suitable adhesive which offers all of the above properties has been found to be a cyanoacrylate adhesive comprising an acetate group with a large molecule size. Cyanoacrylate adhesives are based on a wide range of different acetate groups with a range of molecule sizes and, in general, smaller molecule acetates produce adhesives with a greater overall strength and setting time. Polymerisation occurs under the influence of trace moisture contained in the atmosphere and, in the case of spectacle assembly, within the lenses, and this polymerisation sets the adhesive by neutralising the acidic stabiliser present in the unset adhesive. The presence of a large-molecule acetate group gives the cyanoacrylate adhesive the property of retaining its volume when set, thereby making such an adhesive particularly suitable for application in the assembly of rimless spectacles using the method described above. It has been found that an oxygen-containing acetate group, such as an alkoxyalkyl, in the cyanoacrylate adhesive has a suitable molecule size to give the adhesive the required volume-retaining property \Mien set, without compromising the advantages attributed to small molecule sized cyanoacrylate adhesives.

[0026] Particularly suitable adhesives for this application are Sicomet (RTM) 9010 and 9020, manufactured by Henkel Adhesives, which have a chemical basis of methoxyethyl cyanoacrylate.

[0027] To assemble the spectacles, a very small amount of adhesive should be applied into the grooves of each of the longer surfaces of the pin 25 so that the adhesive sits slightly proud to the longer surfaces of the pin 25. An applicator such as a tooth pick or cocktail stick may be used to apply the adhesive so that it can be applied sparingly. The pins 25 are then inserted into place in the associated hole 28 in the lens 2. When a pin 25 is inserted into the associated hole 28, the adhesive will spread over the pin 25 and fill the space between the pin 25 and the lens 2. If any adhesive spreads onto the surface of the lens 2 it should be cleaned off using an appropriate solvent, applied using an optical wipe. Each pin 25 should be cleaned as required after the next pin 25 has been inserted into the associated hole 28, as the adhesive starts to set almost immediately.

[0028] The side pieces of the spectacles, to be described below, are fixed to the lenses in a similar fashion.

[0029] The adhesive should be left to set for about ten minutes, at which point the spectacles can be adjusted, if this is necessary. The spectacles can be adjusted for pantoscopic tilt, side angle and temple width as described below, using the appropriate tool such as nylon nose pliers. The spectacles can also be adjusted for any small drilling error as the spectacle mounts do not contain any mechanical fixing components which are easily broken. The deformable necks 26 allow the bridge piece 15 to be adjusted relative to the lenses 2 to allow the spectacles to be fitted correctly to a wearer.

[0030] The side piece 29 shown in Figures 5 and 6 comprises a pin 31 for attaching the side piece 29 to the lens 2, a lug 32 and a temple piece 33. The pin 31 is formed by a block of rectangular cross-section which projects from the side piece 29. The pin 31 includes opposed longer surfaces interconnected by shorter surfaces, the longer surfaces in the plane generally parallel to the length of the side piece 29. The pin 31 is approximately 1.25 mm deep and 2.45 mm wide. Each longer surface is grooved to provide a gripping formation, with the grooved part of each surface extending approximately 2.40 mm from the distal end. Of course, a pin 31 with any suitable dimensions could be used and, although the pin 31 shown in Figure 5 would be oriented horizontally when spectacles are placed on a wearer's face, it could be oriented vertically to suit the particular style of spectacle. The grooved longer surfaces of the pin 31 comprise a cross-hatched pattern. The pin 31 is connected to the remainder of the side piece 29 by a plastically deformable neck 30, allowing the angle of the side piece 29 to be varied with respect to the lens 2 as is shown in Figure 6 by the arrow A.

[0031] The connection of a side piece 29 to a lens 2 will now be described with reference to Figures 7Ato 7D. First, a hole 28 is formed in the lens 2 as described above for the bridge piece 15 with reference to Figure 4. A small amount of adhesive of any of the kinds described above with reference to Figure 4 is placed on the grooved longer surfaces of the pin 31 prior to the insertion of the pin 31 into the hole 28 in the lens 2, thereby securely attaching the side piece 29 to the lens 2. Preferably, and as shown in Figure 7B, a small gap 34 (typically 1 mm to 2 mm) is left between the side piece 29 and the face of the lens 2 in which the plastically deformable neck 30 is located to allow the pantoscopic tilt of the spectacles to be adjusted - as is show) in Figures 7C and 7D. A greater pantoscopic tilt can be achieved if a larger gap 34 is left between the side piece 29 and the lens 2, and the spectacles can be assembled as required for each individual wearer. The gap between the side piece 29 and the lens 2 also allows the temple width of the spectacles to be adjusted - and again the spectacles can be assembled with the gap 34 between the side piece 29 and the lens 2 suitable for allowing the plastically deformable neck 30 to provide the spectacles with a temple width as required by an individual wearer.

[0032] The side piece 29 may be formed from metal as a single piece, or the pin 31, the lug 32 and the temple piece 33 may be formed separately and then joined together, for example by soldering or welding. Depending on the style of the spectacles, the lug 32 and the temple piece 33 may be formed separately and then joined together with a hinge. The pin 31 and the lug 32 may be formed from metal as a single piece, or may be formed separately and then joined together, for example by soldering or welding.

[0033] The components of the spectacle mounts described above with reference to Figures 3 to 8 may be made from any suitable material, such as plastic or those metals which are commonly used for making spectacles and which are capable of being moulded. Examples of suitable metals are titanium, stainless steel, Monel (RTM) (a nickel-containing alloy), aluminium, EVO (RTM) (nickel-free steel), Breda (RTM) (a nickel-free alloy), nickel silver and memory metals (i.e. alloys with the ability to remember their shape).

[0034] Since the pin 31 of the side piece 29 has the same dimensions as the pin 25 of the bridge piece 15, this enables a single hole dimension setting of 1.25 mm x 2.45 mm to be inputted into the database of a drill used to drill the holes into the lenses for the assembly of the spectacles. Only minor adjustments will have to be made to the drilled holes as the pins are produced to be accurate to within 0.03 mm.

[0035] The pins 25, 31 are suitable for use with lenses 2 with a standard lens thickness of 2.0 mm to 2.2 mm. For a thicker lens a blind hole can be drilled from the front of the lens 2, meaning that there will be no hole on the surface of the lens 2 which is closest to the face of a wearer. This means that wrap-around type rimless sunglasses can be assembled with thick lenses using the described method. Such sunglasses may also be adjusted for pantoscopic tilt and head width, which is not usually possible with standard wrap-around type sunglasses.

[0036] As can clearly be seen from Figure 8, only a single hole 28 in the lens 2 is required to allow the fixing of each spectacle mount 15, 29 by location with the appropriate pin 25, 31. Each of the spectacle mounts 15,29 is fixed to the appropriate lens 2 by means of a single horizontal hole, or slot, 28, rather than by the methods known in the art in which two pins are located with two separate holes. The spectacle mounts 15, 29 can be produced with vertical pins if required to suit the style of spectacle.

[0037] The spectacle mounts described above with reference to Figures 3 to 8 are formed by a bridge piece and side pieces. Other spectacle mounts, and in particular hook arrangements which allow clip-on sunglasses to be attached to spectacles, may be assembled in the same way.

[0038] The spectacle mounts may also include delicate decorative parts, such as diamantes, as the spectacle mounts are fixed to the lenses by hand and no pressure is required to be applied to the spectacle mounts during the assembly of the spectacles.

[0039] The simple method described above for assembling rimless spectacles removes the need for skilled technicians to construct the spectacles, and also reduces the time taken to assemble the spectacles by a factor of four or five when compared to the known methods described above. This leads to an increase in the production volume and a decrease in the production cost of the spectacles.

REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description • EPQ71 βββΟΑ [0012] • US3577394A Γ00131 • US2 784215ArøQ 141 • FR284S510A [0015]

Claims

An eyewear device comprising: two lenses (2), each formed therein having a single linear nasal side hole (28) and a single linear thinning side hole (28), and a plurality of eyeglass sockets (15, 29), each comprising a a single linear block (25, 31) projecting therefrom, generally of rectangular cross-section and dimensioned to fit into one of the holes (28) formed in one of the associated lenses (2) to connect the socket ( 15, 29) to the lens (2), wherein each of the blocks (25, 31) is held in the associated hole (28) by means of an adhesive, the adhesive having, before the frame, a volume equal to the volume after the frame, wherein the fitting and adhesive are arranged so that each of the sockets (15, 29) is attached to the associated lens (2) and the adhesive acts as a bump between any of the blocks (25, 31) and the associated lens (2) for essentially reducing or eliminating pressure around the junction of the block (25, 31) and the lens, each of the holes (28) extending in the direction of the thickness of the lens and having a cross-section equal to the cross-section of the block (25, 31) contained therein wherein (15, 29) comprises a bridge piece (15), wherein the bridge piece (15) carries two blocks (25), each of which is located at one end of the bridge piece (15), and wherein the spectacle holders (15, 29) for each of the lenses further comprising a side piece (29), wherein the block (31) is provided at one end of the side piece (29), the block (31) being connected to the rest of the side piece (29) with a plastic deformable neck (30), wherein there is a gap (34) between the side piece (29) and a front of the lens (2) where the deformable neck (30) is arranged to allow the associated side piece (29) to change its direction relative to the the associated lens (2).

Device according to claim 1, wherein the block is provided with gripping forming.

Device according to claim 2, wherein the gripping means comprise a cross-shading ring.

The device or method of claim 3, wherein the block has longer surfaces which are associated with shorter surfaces, wherein the cross-shading is provided on the longer surfaces.

Device according to one of claims 1 to 4, wherein the hole (28) is a through hole.

Device according to one of claims 1 to 5, wherein the hole (28) is a blind hole.

Device according to one of claims 1 to 6, wherein the block (25) and the side piece (29) are formed together.

Device according to one of claims 1 to 6, wherein the block is formed apart from and then connected to the rest of the side piece (29).

The device according to any one of the preceding claims, wherein the adhesive is a single component adhesive.

Device according to one of the preceding claims, wherein the adhesive is a cyanoacrylate-based adhesive having an acetate group containing at least one oxygen molecule.

Device according to one of the preceding claims, wherein the acetate group is an alkoxyalkyl group.

Device according to one of the preceding claims, wherein the alkoxyalkyl group is specifically a methoxyethyl group.

A method of attaching a lens (2), shaped therein, each having a single linear nose side hole (28) and a single linear thinning side hole (28), to a plurality of spectacle frames (15, 29), wherein the sockets (15, 29) each comprising a single linear block (25, 31) projecting therefrom, generally of rectangular cross-section and dimensioned to fit into one of the holes (28) formed in one of the associated lenses (2). ) for connecting the sockets (15, 29) to the lens (2), the method comprising: wherein the block (25, 31) is held in the associated hole (2) by an adhesive, the adhesive having a volume prior to the mounting , which is the same as the volume after the frame where the fit and the adhesive are arranged so that each of the sockets (15, 29) is attached to the associated lens (2) and the adhesive acts as a buffer between each of the blocks (25, 31) and the associated lens (2) for substantially re reduce or eliminate pressure around the junction of the block (25, 31) and the lens, each of the holes (28) extending in the direction of the thickness of the lens and having a cross section equal to the cross section of that block (25, 31) contained therein, wherein the spectacle holders (15, 29) comprise a bridge piece (15), the bridge piece (15) carrying two blocks (25), each of which is at one end of the bridge piece (15), and the spectacle frames (15) , 29) further comprising a side piece (29), wherein the block (31) is provided at one end of the side piece (29), the block (31) being connected to the rest of the side piece (29) by a neck (30) which is plastic deformable, where there is a gap (34) between the side piece (29) and a front of the lens (2) where the deformable neck (30) is arranged to allow the associated side piece (29) to change the direction thereof in relation to the associated lens (2).

The method of claim 13, wherein the hole (28) is a through hole.

The method of claim 13 or 14, wherein the adhesive is a single-component adhesive.

A process according to any one of claims 13 to 15, wherein the adhesive is a cyanoacrylate-based adhesive having an acetate group containing at least one oxygen molecule and optionally wherein the acetate group is an alkoxyalkyl group, preferably a methoxyethyl group. .

Use of an adhesive for assembling glasses, comprising: two lenses (2) each having a single linear nose side hole (28) and a single linear thinning side hole (28), and a plurality of glasses sockets (15, 29). ), each comprising a single linear block (25, 31) projecting therefrom, generally of rectangular cross-section and dimensioned to fit into one of the holes (28) formed in one of the associated lenses (2). ), to connect the socket (15, 29) to the lens (2), wherein each of the blocks (25, 31) is held in the associated hole (28) by an adhesive, the fitting and the adhesive being arranged so that any of the sockets (15, 29) are attached to the associated lens (2), each of the holes (28) extending in the direction of the thickness of the lens and having a cross section equal to the cross section of that block (25, 31). ) contained therein, wherein the eyeglass sockets (15, 29) comprise a bridge piece (15), wherein the bridge piece t (15) carries two blocks (25), each of which is located at one end of the bridge piece (15), wherein the spectacle holders (15, 29) for each of the lenses further comprise a side piece (29), the block (31) is provided at one end of the side piece (29), where the block (31) is connected to the rest of the side piece (29) with a plastic deformable neck (30) where a gap (34) remains between the side piece (29). and a front of the lens (2) wherein the deformable neck (30) is positioned to allow the associated lateral portion (29) to change its direction relative to the associated lens (2), wherein the adhesive acts as a bump between any of the blocks (25, 31) and the associated lens (2) to substantially reduce or eliminate pressure around the junction of the block (25, 31) and the lens (2), wherein the adhesive prior to the frame has a volume that is the same as the volume after the frame.

Use according to claim 17, wherein the adhesive is a single component adhesive.

Use according to claim 17 or 18, wherein the adhesive is a cyanoacrylate-based adhesive having an acetate group containing at least one oxygen molecule and optionally wherein the acetate group is an alkoxyalkyl group, preferably a methoxyethyl group.