Cleaning contact lenses

Surface action contact lens cleaners

The need for contact lens cleaners. Contact lenses begin to be covered with deposits from the first minutes of wearing. These deposits increase during the entire period of their use. If you do not use lens cleaners, the process of formation of deposits accelerates and can lead to a number of negative consequences. Effective cleaners reduce the amount of deposits and the possibility of negative consequences. Cleaners play the most important role in the safe and successful use of contact lenses. Contact lens cleaners reduce the accumulation of deposits and prevent the negative effects caused by them. However, cleaners cannot remove all deposits from the lens surface. In the process of wearing, non-removable deposits form on the lenses. The mass of such deposits depends on several factors, including the lens material, the nature of the deposit, the lens care regimen and the age of the lenses.

Classification of cleaners

Lens cleaners can be classified according to their mechanism of action, into surface cleaners and enzymatic cleaners.

Surface cleaners

All surface cleaners contain a surface reagent. A surface reagent is a chemical compound that moves and interacts with an external or internal surface. Surface-active reagents are also called detergents and are similar in their properties to soap, but different in chemical composition. Surface cleaners perform an important function in the care of contact lenses. Their use is especially effective in the fight against lipid deposits. Since many of them contain EDTA, they are also effective at fighting inorganic deposits such as calcium. Surface cleaners have different effectiveness in the fight against deposits, caused by environmental factors and cosmetics. Their effectiveness depends on the type and degree of development of these deposits. Surface cleaners remove loosely bound protein deposits. However, they have limited capabilities in the fight against tightly bound protein deposits. Removal of the protein, after denaturation associated with the surface of the lens, can be carried out by enzymatic cleaners.

Mechanism of action

Surface cleaners remove loosely bound deposits by moving across the surface of the lens, interacting with the deposits and removing them from the surface. Distant deposits are then finally removed during washing. Surface cleaners are used simultaneously with wiping the lens with a finger or with mechanical cleaning. The combination of this mechanical action with the action of a surface cleaner ensures the removal of weakly bonded deposits. For a better understanding of the mechanism of action of the surface cleaner, let's consider some basics of its chemical structure.

The surface cleaner molecule has two parts: a water-attracting "head" and a water-repellent "tail".

The effectiveness of surface cleaners depends on two important characteristics:

- head and tail are attracted by different environments;

- identical parts of surface cleaner molecules repel each other.

The water-attractive head is attracted to aqueous media, and the water-repellent tail is attracted to non-aqueous media (for example, oily media). Because these two parts of the surfactant molecules are attracted to different environments, they often accumulate at interfaces or surfaces. For this reason, surface cleaners are known as "surfactants".

The tendency of such cleaners to accumulate on the surface ensures their cleaning ability. Depending on the type of deposit, surface cleaners are cleaned by:

- formation of micelles;

- displacement of sediments.

Formation of micelles

If the concentration of the surface cleaner exceeds a certain level, the molecules form spherical groups called "micelles". The water-repellent tails line up in the direction of the inside of the micelle, and the water-attracting heads line up outside the micelle.

Each micelle forms a water-repellent environment inside the aqueous environment. Water-repellent deposits are attracted by the water-repellent environment inside the micelle and are pulled away from the surface of the lens by the micelles. As soon as they leave the surface of the lens, the micelles surround the deposit and immerse it in the solution. Micelles containing polluting substances are removed during washing.

Displacement

The water-repellent tail of the cleaner is attracted to the water-repellent environment inside the polluting substances. The water-attracting head is attracted by the water (water-attracting) medium.

Since identical parts of the cleaner molecule repel each other, the cleaner generates forces that break the polluting substance into small parts.

These forces lead to the formation of polluting substances in small drop-like formations that dissolve easily. This process is accelerated by mechanical influence. As soon as the polluting substance gets into the solution, it is easily removed by rinsing.

Surface cleaners

A chemical compound that, moving, interacts with the surface of the lens and the interface.

Interface

Contact points between two surfaces.

The second main type of cleaners are enzymatic cleaners

Many of them are used once a week to remove protein deposits. Enzymatic cleaners effectively remove protein deposits, but do not affect other types of deposits, such as calcium, cosmetics, etc. Enzymes can remove these types of deposits only when they are embedded in a layer of protein deposits. As the protein is removed, other sediments trapped in the protein layer are also removed. An enzyme is a protein with active sites. These active sites allow enzymes to enter into various chemical reactions. Examples of enzyme reactions can be the processes of food digestion and the delivery of nutrients to cells.

Mechanism of action

Most enzyme cleaners destroy the structural chemical bonds inside the protein deposits (chain of amino acids). By destroying these bonds, enzymes destroy protein deposits into smaller fragments.

These protein fragments largely lose their ability to bind to contact lenses, which facilitates their subsequent removal.

Enzyme activity

In the case of lens cleaners, enzyme activity is measured by the enzyme's ability to break down the chemical bonds that bind the enzyme together. Unlike surfactants, which interact with the entire mass of polluting substances, enzymes interact with some chemicals inside the protein. "Specific" enzymes are able to destroy the bonds of only certain types of chemical groups, while "non-specific" enzymes can destroy the bonds of a number of chemical compounds. Enzymes that are able to break down several types of chemical bonds are more effective in breaking down proteins. In general, the less specific the enzyme, the higher its cleaning properties.

Typical components of an enzyme cleaner. Most enzyme cleaners on the market come in solid form and contain a small amount of enzyme. Most of the substance that makes up this pill is necessary to make this pill.

The enzyme (active ingredient) removes protein deposits by breaking the structural bonds inside the protein, which leads to its destruction. Papain, pancreatin and subtilisin are usually used in industry, in the production of lenses.

Filler

Fillers are used to give tablets the right size. They do not affect the cleaning properties of the product. Typical examples of fillers are sodium chloride and lactose.

Solvents

Some products contain ingredients that promote their solubility. When exposed to moisture, they begin to emit carbon dioxide, which crushes the tablet and accelerates dissolution. Typical examples are tartaric acid and sodium carbonate.

Buffer system

Weak buffer systems are included in the composition in order to match the pH content and the range of action of the enzyme.

Lubricating material

A small amount of lubricant is included in the tablet. These additives prevent tablets from sticking in the mold during their manufacture. Polyethylene glycol is often used for this purpose.

Types of enzymatic cleaners

Most enzyme cleaners available on the market contain papain, pancreatin, or subtilisin.

Papain

Papain is a protease (an enzyme that affects proteins), which is extracted from the papaya plant. Papain combines with cysteine to facilitate protein stabilization and promote its removal. The unpleasant smell associated with papain is caused by the cysteine contained in it. Papain binds to soft lenses and causes hypersensitivity in many patients. In an attempt to reduce these phenomena, the company Allergan reduced the recommended time of saturation of their products with papain from two hours to fifteen minutes. Allergan successfully justified this by demonstrating improved cleaning properties and reduced sensitivity patient records. Although other companies have not conducted similar experiments with their products, they have followed the example of Allergan and also recommend a shorter saturation time. Papain is included in:

- Allergan soft lens cleaner Softlens;

- Allergan Extenzyme cleaner for protein removal;

- enzymatic cleaner Profree / GP by Allergan;

- IOM Tetraenzyme cleaner.

Pancreatin

Pancreatin is extracted from the pancreas of a pig, Pancreatin contains chemical compounds that exhibit three types of enzyme activity:

- protease that catalyzes protein cleavage;

- a lipase that catalyzes the splitting of some lipids;

- amylase, which catalyzes the splitting of carbohydrates (starches).

Based on these properties, Alcon claims that its pancreatin-containing products have a wide spectrum of action and are able to remove protein, lipids and mucin. However, there is no confirming information on this account yet. Pancreatin lipase and amylase are not effective against deposits that appear on contact lenses. Pancreatin lipase is very effective against di- and triglycerides, which are found in the tear film or in lipid deposits on contact lenses. Therefore, pancreatic lipase has little effect on lipid deposits on the surface of contact lenses. Pancreatin amylase removes mucin deposits due to its activity on carbohydrates. Mucin is a glycoprotein, the composition of which includes about 40% carbohydrates, and therefore pancreatin has little effectiveness in removing mucin deposits. Pancreatin is found in:

- Alcom Opti-Zyme;

- Alcon enzymatic cleaner, used for long-term wear.

Subtilisin

Subtilisin is a protease obtained from Bacillus bacteria. Subtilisin is produced by a fermentation process similar to the process used in brewing. Under certain conditions, Bacillus bacteria secrete the enzyme subtilisin. Special chemical technologies are used to separate it from bacteria. Subtilisin is approved as a safe enzyme by the US Food and Drug Administration (FDA). Since subtilisin is low-toxic, it is used in the manufacture of cookies, candies, crackers and washing powders. The effectiveness of subtilisin is higher than that of papain and pancreatin due to its lower binding characteristics. Subtilisin destroys more types of protein bonds and is therefore more effective in breaking down protein deposits. Subtilisin is included in:

- Enzymatic cleaner Fizz Clean by Bausch & Lomb;

- Enzymatic cleaner Therma Clean by Bausch & Lomb;

- Tablets for one-stage protein removal by Bausch & Lomb;

- Allergan Ultrazyme enzyme cleaner;

- Enzyme with cleaner Soft Mate by Barnes Hind.

Subtilisin is also included in most of the liquid enzyme cleaners that have recently appeared on the market.