GB2301198A

GB2301198A - Capsule containing hydrogen peroxide catalase for contact lens disinfection

Info

Publication number: GB2301198A
Application number: GB9610678A
Authority: GB
Inventors: Chun Put Lau
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-05-22
Filing date: 1996-05-22
Publication date: 1996-11-27
Anticipated expiration: 2016-05-22
Also published as: GB2301198B; GB9610678D0

Abstract

A capsule 10 has a sealing layer 13 formed of e.g. contact lens polymer and contains hydrogen peroxide catalase 14. The capsule is used in a disinfection solution of hydrogen peroxide in which contact lenses are suspended. The layer 13 is designed to become automatically unsealed after about 3 hours to expose the catalase to neutralise the sterilising solution. The layer 13 thickness may be increased to increase unsealing time.

Description

DISINFECTION METHOD FOR CONTACT LENSES The invention relates to a method for disinfecting contact lenses and the like, and to a capsule for use in such a method.

It is a requirement that contact lenses are cleaned and disinfected regularly and various methods are already known. The most acceptable and effective disinfectant is hydrogen peroxide solution, which works well using a 3% solution and by submerging the lens in the solution for a period in excess of about three hours. It has been found, for example, that some cysts may survive if the sterilisation period is less than two hours. It is however imperative that the hydrogen peroxide solution is removed from the lens before the lens is used again.

It has already been proposed for this purpose to add a catalase that serves to accelerate breakdown of the hydrogen peroxide into its constituents of water and oxygen, or in other words, to neutralise the solution.

Such a catalase can be added initially but this weakens the solution and its disinfecting action from the start.

It has also been proposed to add a coated catalase having a water soluble coating that delays the exposure of the catalase to the solution and therefore the on-set of accelerated breakdown of the hydrogen peroxide. It has also been proposed to mix a colouring compound with the catalase to provide a visual indication that the catalase is present and to what extent it has been used up.

Coating material and/or colouring compound can build up on the lenses when these methods are used over a period of time and cause toxic or allergic reactions. Thus, although the disinfecting function is enhanced temporarily by delaying accelerated breakdown of the hydrogen peroxide solution, certain disadVantages can arise due to possible consequent contamination of the lenses.

It is an object of the invention to overcome or at least reduce these disadvantages.

According to one aspect of the invention there is provided a method of disinfecting a contact lens comprising submerging the lens in a solution of hydrogen peroxide in a container and exposing the solution to hydrogen peroxide catalase to neutralise the solution, in which the catalase is contained in a sealed capsule in the container which is opened automatically after a predetermined time.

The capsule may be sealed at its mouth by material which is acted upon by the solution to uncover the mouth of the capsule after the predetermined time.

The seal preferably comprises a layer of contact lens polymer.

According to another aspect of the invention there is provided a capsule containing hydrogen peroxide catalase for neutralising a quantity of hydrogen peroxide solution in a container, the capsule having a seal that responds to the solution to automatically expose the catalase to the solution after a predetermined time period.

The seal is preferably formed of contact lens polymer.

A method of disinfection of contact lenses and a capsule for use in the method will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 shows a cross-sectional view of the capsule; Figure 2 shows a sectional side view of a container for use in carrying out the method; and Figure 3 shows diagrammatically in time sequence the condition of the capsule when carrying out the method.

Referring to the drawings, in Figure 1 a transparent cylindrical rigid capsule 10 is formed with a solid base 11 and an open top 12 sealed by a layer 13 of contact lens polymer. A sealed cavity 14 contains a quantity of hydrogen peroxide catalase. Typically, the capsule is 5 4 mm in diameter and 5 mm long, the layer 13 is 0.5 mm thick and positioned about 0.5 mm inside the peripheral rim of the open top. The cavity 14 is 2 mm deep. The quantity of catalase is at least sufficient to neutralise (that is, breakdown into water and oxygen) 10 ccs of a 3% by weight hydrogen peroxide solution.

The layer 13 must be prepared and stored in an environment where the humidity is 30% or less. When the capsule is immersed in the hydrogen peroxide solution, the layer 13 absorbs water and swells up so as to at least partially spring away from the capsule even when the capsule is upside down. This takes place consistently and after approximately three hours, the layer becomes at least partially unsealed from the capsule. Thus, the catalase becomes exposed for the first time to the hydrogen peroxide solution and acts to neutralise the solution.

The thickness of the layer 13 can be increased up to say 1.0 or 1.5 mm to delay the unsealing of the capsule and, broadly stated, the delay will increase more or less linearly as the layer thickness is increased. A layer of 1 mm, for example, will provide a delay of approximately six hours. So far as the preferred dimensions are concerned, as described, a layer thickness of 0.5 mm is used which ensures for all practical purposes in a 3% solution that the capsule remains sealed and the 3% solution remains at full strength for three hours. This is normally a quite sufficient time period to provide comprehensive disinfection of a contact lens.

In Figure 2, a container 15 is shown containing 10 cc of hydrogen peroxide solution in which a cage 16 is suspended for holding a pair of contact lenses 17. An apertured lid 18 fits to the top of the container and supports the cage 16. The capsule 10 is shown at the bottom of container.

In Figure 3, the sequence of activity at the capsule is shown during the sterilisation method, with the capsule 10 shown in section. The layer 13 absorbs water and swells up progressively for approximately 24 hours, and swells significantly thereafter. At 3 hours (see bottom left hand drawing of Figure 3) the layer 13 springs away from the capsule so that the capsule becomes unsealed and the catalase is exposed to the hydrogen peroxide solution in the container 15. In about 5 to 10 minutes thereafter, the solution is completely neutralised while the capsule 10 tends to float towards the top of the solution. When oxygen bubbles disappear the capsule then sinks to the bottom of the container, and indicates that the neutralisation of the hydrogen peroxide is complete.

It will be appreciated that the capsule 10 is formed of inert material and the layer 13 is formed of contact lens polymer so that there can be no incipient or other transfers of any harmful or unidentified chemical compounds to the lens surfaces during disinfection of the lenses from the capsule. The layer 13 is preferably made of contact lens polymer as described because such material is generally and readily available from various suppliers, including Ciba Vision Incorporated. This material is not particularly expensive and, more important, the material is fully tested as inert or non-reactive in ophthalmic applications. Other suitable material may however be used that will respond predictably when exposed to hydrogen peroxide solution to automatically spring away from or unseal the capsule 10 in some other way after a reasonably long time period, say 2 or 3 hours at least.As stated earlier, embodiments of the invention must ensure in practice that the sterilisation period is sufficiently long so that the contact lenses are fully disinfected.

This is normally, as described, achieved by using a fullstrength 3% solution for at least three hours before any reduction of strength or neutralisation begins. After the three hours, the capsule automatically acts to expose the catalase and neutralise the solution in a matter of a few minutes. Neutralisation is clearly indicated to the user by the presence of the relatively empty capsule and partial or total unsealing of the layer 13.

It will be noted in Figure 3 that the capsule 10 cannot actually reach the top surface in the container 15 because the cage 16 arrests its upwards movement (see bottom right hand drawing of Figure 3). This and the solid base 11 of capsule generally causes the open top 12 to remain uppermost which ensures that the catalase in the capsule 10 remains exposed to react with the solution. As such if the used up quantity of catalase at which buoyancy occurs is not quite sufficient to neutralise the solution, the solution will never-the-less continue to be neutralised because the capsule is still below the surface of the solution. This overcomes any slight variations of the capsule dimensions and the actual operating conditions rendering when the capsule becomes buoyancy. In other words, the arrangement as described is "fail-safe" and makes sure that the solution is always fully neutralised.

Claims

1. A method of disinfecting a contact lens comprising submerging the lens in a solution of hydrogen peroxide in a container and exposing the solution to hydrogen peroxide catalase to neutralise the solution, in which the catalase is contained in a sealed capsule which is opened automatically after a predetermined time in the container.

2. A method according to claim 1, in which the capsule is sealed at its mouth by material which is acted upon by the solution to uncover the mouth of the capsule after the predetermined time.

3. A method according to claim 1 or 2, in which the seal comprises a layer of contact lens polymer.

4. A capsule containing hydrogen peroxide catalase for neutralising a quantity of hydrogen peroxide solution in a container, the capsule having a seal that responds to the solution to automatically expose the catalase to the solution after a predetermined time period.

5. A capsule according to claim 4, in which the seal is formed of contact lens polymer.

6. A method of disinfecting contact lens substantially as herein described with reference to the accompanying drawings.

7. A capsule substantially as herein described with reference to the accompanying drawings.