GB2029225A - Method and materials for cleaning soft contact lenses. - Google Patents

Abstract

A cleaning solution for soft contact lenses is described. The solution differs from previously known solutions in that it includes a lipolytic enzyme in addition to Papain or Bromolain so that not only are Albumin deposits removed from the surface of the lens but also any Lipids present are also split into fatty acids and esters for removal by subsequent rinsing and boiling in physiological saline solution. A supplementary cleaning solution comprises a Lipase and phosphate buffer which is typically applied to the lens after the primary cleaning solution and before the rinsing and boiling stage. By utilising a stable enzyme containing solution, only relatively small volumes of the liquid are required to clean a lens and the solution is applied using a droplet technique.

Description

1

GB 2 029 225 A

1

SPECIFICATION

Method and materials for cleaning soft contact lenses

5

The present invention relates to methods and materials for removing from soft contact lenses, deposits that occur during use. Such deposits contain Albumin, Globulins and Lipids.

10 Deposits that occur during use of soft contact lenses generally result in an opaque film, yellow discoloration, white spots and thread-like configurations on the lenses. Investigations carried out have shown that these deposits can consist of Albumin, Ig 15 -y-Globulin, Lysozyme and lipoproteins.

The deposits are often largely composed of denatured Albumin, which is deposited on the lenses from the tear fluid as a result of the saline solution with which the lenses are impregnated being 20 exchanged forthetearfluid. The drying-out of a lens, for instance through its use in a dry environment and by air flowing past it, etc. causes some Albumin to be denatured and deposited on the lens. Even when contact lenses are sterilised by boiling. Albumin is 25 denatured which gives rise to apolar interior groups of Lipids. Other causes too, such as for example continuous use, cause Albumin and Lipids to be deposited on contact lenses in fairly large quantities.

One method of cleaning contact lenses is already 30 known which comprises the steps of dissolving in water a proteolytic enzyme in tablet form and then placing the lenses to be cleaned in the solution for a period of at least two hours. This process has been regarded as complicated by the wearers of contact 35 lenses so that cleaning has not always been carried out as regularly as is required and this has resulted in lenses finally acquiring such a coating that the lenses have become unusable.

An object of the present invention is to provide 40 cleaning solutions and methods for cleaning soft contact lenses which, on the one hand are simple for the contact lens wearer to use and which also provide an improved cleaning effect.

It is another object to provide cleaning liquids 45 which prevent a general build-up of proteins and lipids.

According to one aspect of the present invention an enzyme containing cleaning liquid for soft contact lenses consists of a solution containing Papain or 50 Bromelain (for reducing the Albumin deposits) and a Lipolytic Enzyme (for reducing the Lipids).

A pack for cleaning soft contact lenses comprises a volume of a solution containing Papain or Bromelain and a Lipolytic Enzyme, a device for forming drop-55 lets of the solution for depositing same on the surface of a soft contact lens and a volume of a sterile isotonic physiological saline solution in which the lens can be rinsed and subsequently boiled.

A method of cleaning a soft contact lens in accor-60 dance with the invention to remove deposits on the surface of the lens by enzymatic action comprises the steps of placing at least one drop of a solution containing Papain or Bromelain and in addition a Lipolytic Enzyme, on the contact lens which is to be 65 cleaned to reduce both Albumin and Lipids present to water soluble peptones, fatty acids and esters, and subsequently removing the resulting products by rinsing and boiling in a physiological saline solution.

70 Preferably the enzyme activity in the cleaning solution is of the order of 100 tyrosine units per /ig of protein.

The fluid activity is allowed to occur for a period of the order of 15 minutes.

75 Preferably the physiological saline solution has a particle size below 0.2 microns, and is isotonic, has a pH-value of 7.0 with a buffer capacity of 6-8 and is also sterile.

A preferred enzyme solution for cleaning the lens 80 consists of Bromelain, Mannitol, Sorbitol, Ethylenediaminetetraacetic acid, Sodium Metabisulphate, and a lipolytic enzyme.

An alternative cleaning solution (which comprises another aspect of the invention) which may be used 85 to clean a soft contact lens consists of a solution of Lipase and a phosphate buffer.

Example /

A soft contact lens cleaning fluid (known as PRO-LEN) is made up as follows:—

90 Purified fruit bromelain 100 g.

Sorbitol 500 g.

Mannitol 50 g.

Sodium hydrogen sulphite 10 g.

Ethylenediaminetetraacetic acid disodium salt 1 g. 95 Potassium sorbate 100 mg.

Dilute to 1 litre aqua dest.

Then add:—

Lipase from cand. cylindracae 50.000 units in 1000 ml.

100 0.1 M Phosphate buffer in an aqueous polymer complex.

Example II

A second soft contact lens cleaning fluid (known as LIPREN) is made up as follows:—

105 Lipase derived from cand. cylindracae, lyophil-

ised 100 units

0.1 m phosphate buffer 10 ml.

Methods of use 110 PROLEN

A few drops (0.3 ml) of the fluid are placed on a lens and left on the lens for 15 minutes. The lens is then rinsed in a saline solution and thereafter boiled in the saline solution for 20 minutes. Finally the lens 115 is rinsed once more in the saline solution before reinserting.

LIPREN

(a) For regular periodic cleaning A freeze dried lipase is reconstituted with a phos-120 phate buffer (0.1 m). The lenses are placed in this

The date of filing shown above is that provisionally accorded to the Application in accordance with the provisions of

Section

15(4) of the Patents Act 1977, and is subject to ratification or amendment at a later stage of the application proceedings.

2

GB 2 029 225 A

2

solution and allowed to remain in the solution for 30 minutes.

Afterthis time the lenses are removed and rinsed in a saline solution and then boiled in the saline solu-5 tion for 20 minutes. After boiling the lenses they are once again rinsed in saline solution before reinserting.

(b) For lenses that have not previously been treated with Lipren and have visual deposits or are discol-10 oured.

A freeze dried Lipase is reconstituted with a phosphate buffer (0.1 m). The lenses are placed in the fluid and allowed to remain in the fluid for 8-10 hours.

15 The lenses are removed and rinsed in dest. water.

The lenses are then heated in a saline solution to 40°C for 30 minutes.

The lenses are then rinsed in dest. water and boiled in saline solution for 30 minutes.

20 Finally the lenses are rinsed in saline solution before reinserting.

The cleaning of soft contact lenses using cleaning liquids of the invention

After use a lens is usually coated with deposits of 25 protein, lipoproteins and lipids. In accordance with one aspect of the invention the lens is treated with a preparation having a high enzymatic effect which contains a stabilised protease and a high activity lipase. Drops of the preparation are placed on the lens 30 in accordance with the invention and it is left for the preparation to take effect, for 15 minutes.

This cleaning preparation is, as described above, preferably formed from Bromelain, Mannitol, Sorbitol, Ethylenediaminetetraacetic acid. Sodium 35 Metabisulphate and lipolytic enzyme.

Complete removal of lipids from the lens is achieved by using a stabilised enzyme in fluid form and this may be applied either separately or as a second step. This is typically dripped onto the con-40 tact lens so as to remove any lipid deposits.

The stabilised enzyme in fluid form is, as described above, preferably a lipase with a phosphate buffer.

A further step in the cleaning operation involves 45 rinsing the contact lens in a physiological saline solution and then boiling the lens in the same or a similar solution.

The saline solution should be particle-free (i.e.

have a particle size below 0.2 micron), should be 50 isotonic, should have a pH-value of 7.0 and a buffer capacity of 6-8 and should also be sterile. The pH-value which is indicated is that value which will avoid smarting when the lens is subsequently inserted. An incorrect pH-value will cause smarting 55 to occur. An incorrect pH-value will also cause the protein in the tear fluid to become denatured spontaneously which is not, of course, desirable.

In orderto fulfil the conditions imposed as to purity and sterility, the solution is preferably packed in a 60 disposable pack and is sterilised by means of Gamma radiation.

Report of experiments to determine effectiveness of invention

With a view to determining the cleansing effect of 65 the solutions and methods proposed by the invention, investigations were carried out as follows. For protein determination, the method according to Lowry as modified by Wedler was used. For determining the lipid quantity present, the method according to Boyer et al was used.

Analysis of tear fluid according to several different sources shows that the fluid consists of Lysozyme, Igy-globulin, 1-lipo-protein, small amounts of carbohydrates and phospholipids. A similar solution was therefore prepared from the following:— ■y-chymotrypsin, serum albumin, lysozyme, bovine mucin, globulin II, jS-globulin III, globulin and /3-lipoprotein in 0.9% NaCI solution. Lenses were placed in this prepared solution and left over night. Control lenses were kept in a sterile saline solution instead of the prepared solution. At the end of the period of storage the lenses were divided into four groups:—

Group 1. The lenses in this first group were rinsed and then boiled in a sterile saline solution.

Group 2. The lenses in the second group were rinsed in a "cleaning solution" and then stored in a saline solution containing preservatives.

Group 3. The lenses in Group 3 were treated with an enzyme solution and subsequently rinsed and boiled.

Group 4. The lenses from the saline solution were treated in the same way.

After treatment the protein and lipid content of each of the four groups was found to be as follows:—

Group 1 - Protein content 3-8 fig per lens. Total lipid content 100-250 fig per lens.

Group 2-Protein content 1-4ju.g per lens. Lipid content 60-120 fig per lens.

Group 3 - Protein content 0-0.5 fig per lens. Lipid content 0-30 fig per lens.

Group 4-Protein content 0.02 fig per lens. Lipid content 0 fig per lens.

The invention allows soft contact lenses to be cleaned rapidly and effectively and in general the cleaning operation should be carried out daily. However where lenses are worn day and night, the interval between cleanings may be extended to every other or even every third day.

The invention therefore provides for a simpler cleaning process than the known technique which requires the dissolving of tablets in water and also provides for a shorter cleaning period than hitherto. What is more important however is that the invention allows a more complete cleaning of the contact lens on account of the higher enzymatic activity. Unlike previously known cleaning preparations, the method according to the present invention is also designed to be used daily on the one hand for cleaning the lenses and on the other hand as a preventative measure to present the build-up of larger deposits of protein and lipids which after a time are difficult to remove and affect the properties of the lens.

The types of enzymes which can be utilised may be Papain or Bromelain in each case together with a lipolytic enzyme. Cysteine and Polysaccharides may be used as substrate materials.

Enzymatic activity should be of the order of 100

70

75

80

85

90

95

100

105

110

115

120

125

130

3

GB 2 029 225 A

3

tyrosine units per /xg of protein (substrate).

By splitting the albumin into water-soluble peptones by enzymatic action, the latter can be rinsed or boiled away using a physiological saline isotonic 5 solution.

The invention provides a stable liquid cleaning agent for cleaning soft contact lenses which can be stored under normal environmental conditions without loss of enzymatic activity thereby obviating 10 the need to dissolve a tablet or quantity of powder in water so as to produce the cleaning solution for the lens. In this way just sufficient quantity of the cleaning liquid need be used to cover the surface of the lens and it is with this in mind that the invention 15 provides forthe application of the cleaning liquid by means of droplet applicator or the like.

Typically the PROLEN solution described above is used as a regular daily cleaning agent. This will remove most of the deposits normally found on the 20 lens but will not completely remove the Lipid deposits. The steady build-up of Lipids is conveniently removed by periodically (e.g. monthly) cleaning the lens in LIPREN as described above. The Lipase in a phosphate buffer forming the LIPREN effec-25 tively removes the Lipid build-up.

Claims (8)

1. An enzyme containing cleaning liquid for soft contact lenses consisting of a Lipase and a phosphate buffer.

30

2. A cleaning liquid as claimed in claim 1 in which the Lipase is derived from cand. Cylindracae, lyophilised.

3. A cleaning liquid as claimed in claim 2 in which there are 100 units of the Lipase in 10 ml of

35 0.1M phosphate buffer.

4. A method of cleaning a soft contact lens comprising the steps of placing at least one drop of a solution as claimed in claim 1 onto the surface of the lens for a specified period of time, rinsing the lens in

40 a physiological saline solution, boiling the lens in the saline solution for a second period of time and lastly rinsing the lens in the saline solution.

5. A method of cleaning a soft contact lens comprising the steps of placing the lens in contact with a

45 solution as claimed in claim 1 for a first specified period of time, rinsing it in a saline solution removing it and boiling it for a second specified period of time in a saline solution thereafter rinsing it again in a saline solution.

50

6. A method as claimed in claim 5 in which the first specified period of time is 30 minutes and the second specified period of time is 20 minutes.

7. A method of cleaning a soft contact lens comprising the steps of placing the lens in contact with

55 the solution as claimed in claim 1 for a specified period of time, removing it from the solution and rinsing it in dest water, heating it in a saline solution to a given temperature for a second specified period of time, subsequently rinsing it in dest. water and 60 thereafter boiling it in saline solution for a third specified period of time and rinsing it in saline solution.

8. A method as claimed in claim 7 in which the first specified period of time is 8-10 hours, the sec-

65 ond specified period of time 30 minutes the given temperature is40°C and the third specified period of time is also 30 minutes.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd., Berwick-upon-Tweed, 1980.

Published at the Patent Office, 25 Southampton Buildings, London, WC2A1AY, from which copies may be obtained.