The need for vision correction is becoming increasingly popular in modern society. There are reasons for this - both completely objective (unhealthy diet, poor ecology, the need for constant eye strain at work, injuries and diseases), and subjective (unhealthy lifestyle, ignorance or unwillingness to follow preventive procedures, for example, therapeutic exercises for the eyes) .
Contact lenses are the most common method that successfully competes with glasses in terms of efficiency and has a number of advantages - comfortable wearing, attractive appearance, full viewing angle, etc. But lenses are not suitable for medical reasons for everyone, require painstaking care, and most importantly - careful choice.
Contact Lens Selection
Can I choose contact lenses myself?
It is more than risky to try and independently find the best option for yourself - especially without having the slightest experience in wearing corrective lenses. A prescription for glasses can in no way be the basis for a choice - they have fundamentally different parameters.
For the right choice, which does not entail further visual impairment or dry eye syndrome and can have a therapeutic effect, a special consultation with an ophthalmologist is required.
How is the selection of lenses
A number of criteria that are vital for the proper operation of the lenses, comfort and eye health can only be determined by a specialist:
- To select contact lenses, it is necessary to take into account an additional parameter - the basic curvature of the cornea. It can only be measured by an ophthalmologist with a special instrument - a keratometer.
- In some cases, even this study may not be enough and the data are refined by computer diagnostics: aberrometry or keratotopography. It is obviously impossible to independently determine the correct value - and lenses without it simply will not be sold to you (in any case, responsible and decent people);
- The size of the eye (respectively - the size of the lens) is calculated by a special measurement or based on the same analyzes;
- Correction of vision with lenses has a significant limitation - insufficient tear production, which is established by a separate analysis (Schirmer test). In this case, it is possible to use only silicone-hydrogel variants (with separate reservations);
- The glasses are located at some distance from the eyes (about 12 mm), while the lenses are practically on the surface. Therefore, discrepancies begin (a small correction of the optical power is required).
After all the necessary research and calculations, the ophthalmologist provides a trial model for fitting. All samples are taken again to make sure that the eye has acquired the required visual acuity, feels comfortable (if the pain is too strong or does not stop for more than 5 minutes, your eyes are too sensitive to this type). Only after this is a separate prescription for contact lenses written with updated and supplemented data.
Important: Keep recipes after purchase - this is a convenient and reliable way to track in dynamics all changes in the eye and objectively evaluate the effectiveness of treatment.
Which is better: lenses or glasses?
As a way to maintain visual acuity, glasses and lenses are not inferior to each other in effectiveness, read the differences in points:
- Wearing comfort: lenses in no way limit a person leading an active lifestyle - on the other hand, glasses are easy and quick to take off and put on;
- Aesthetics: lenses will be the best choice for people who tend to hide their vision from others. It should be borne in mind that well-chosen glasses will fit into a certain style and help to hide some flaws, for example, to correct the symmetry of the face;
- Cost and Care - glasses are cheaper, last longer and are easier to care for. If you forget to put the lens in time in a special storage solution, it can no longer be restored.
The obvious advantages of contact lenses are no fogging when the temperature drops, a full peripheral review (the ophthalmologists themselves believe that its absence stimulates atrophy of the eye muscles and further visual impairment), a certain psychological and practical comfort.
Attention: it is worth remembering that in no case should you use lenses for glaucoma, infectious inflammations of the eye (for example, conjunctivitis or bluffer) and diseases associated with a serious decrease in immunity (tuberculosis or AIDS), diabetes mellitus, acute sinusitis, severe allergic reactions.
Types of Contact Lenses
What affects the choice of lenses?
The market of vision correction is represented by many manufacturers offering a wide range of various lenses, the selection criteria of which can confuse not only a novice. According to its purpose, the material of manufacture and the processing method, the mode of wearing and the estimated frequency of replacement, several classifications of contact lenses can be distinguished at once. In each case, the service life, specific purpose, cost and conditions of wearing the tool are determined.
A more detailed article on the types of contact lenses.
Degree of rigidity
The lens design can be soft or hard. The solid structure of the first has a more pronounced therapeutic and prophylactic effect, they are stronger and will last longer than soft ones. There is no need to constantly wet the surface with moisturizing drops. But adaptation to them occurs over a longer period of time (some more discomfort may be present for a week), the shape of the cornea (the so-called keratoconus) may change, and the price is slightly higher.
Soft lenses weaken vision defects more often and fail more often - fragile material easily tears and causes regular troubles during maintenance (mandatory exposure and storage in a disinfectant solution). Advantages - a simple and affordable replacement for a worn tool, a wide variety of colors and disguises for eye defects (for example, eyesore).
Corneal cells are not connected to the circulatory system and are supplied with oxygen directly from atmospheric air. Therefore, there arises such an important characteristic of the material as gas permeability - how well air is passed. Lack of oxygen leads to severe pathologies, swelling, ulcers and keratitis.
Another important property of the base for the future lens is that foreign organic components are better retained on some surfaces. These may be the vital products of microorganisms living in the eye cavity, fat and protein elements in the composition ofёh, metabolic results displayed through teardrops (this becomes especially noticeable in smokers - the lens turns yellow with nicotine over time). Materials with increased ionic potential are more prone to retaining such debris, which can cause mucosal irritation and impair visibility.
Any lenses are made from complex polymer composites with high biological compatibility. The two most common options are pure hydrogel (hydroxyethyl methacrylate, aka NEMA) or combined with silicone. The first method gives clear vision without side allergic effects and discomfort, but they practically do not let oxygen through. the minus lens dries quickly and is poorly prepared for prolonged wear - regular overexposure leads to serious consequences (hypoxia turning into severe eye swelling).
Silicone hydrogel lenses It is very popular because of its low moisture content (optionally regular wetting) and optimal oxygen access - it becomes possible to wear long-term lenses without side effects.
Separately, it is worth noting the American standard for the classification of contact lenses of the National Committee on Medicines and Food Additives (FDA), in which all materials are divided into their ability to adsorb water and foreign protein deposits into 4 groups:
- Group 1: non-ionic polymers with a low water content (up to 50%);
- Group 2: non-ionic polymers with high moisture content (over 50%);
- Group 3: ionic polymers with a low content;
- Group 4: ionic polymers with a high water content.
A more detailed article on the material and composition of contact lenses.
Size and shape
The lens can be located on the eye in completely different ways, as a result - have a different size. Three groups are distinguished depending on the diameter:
- Corneal (from 9 to 11 mm). Their distinguishing feature is that the lens does not rest against the mucous membrane surrounding the eye, but is held by the surface tension of a thin layer of tears directly on the cornea. This type is especially well tolerated for patients with hypersensitivity and allergies and can be prescribed even to children.
- Corneoscleral (12-15 mm). An extended version of the cornea, facing the sclera. The format is rapidly gaining popularity, as, along with all the advantages of a small size, it shows good effectiveness in correcting many visual impairments.
- Scleral (up to 21 mm). Historically, the first version of contact lenses, with two layers - the visual in the center and the haptic support part at the edges. It is held on the sclera, as a result of which there is a gap between the cornea and the material. Currently, the method is not widely used, although it shows impressive therapeutic results.
The form is completely determined by the tasks that the use of lenses should solve. So, spherical ones correct the consequences of myopia (myopia) and hyperopia (hyperopia), aspherical ones have a more advanced design (the front part is made in the form of an ellipse), which allows to further increase contrast and clarity of vision, toric ones are an effective tool in the fight against astigmatism.
Attention: Multifocal lenses stand apart - with alternating hard and soft layers, which gives an equally good and clear overview of objects at different distances. The number of layers proportionally determines the smoothness of the transition between the near and far planes - the most famous are bifocal lenses with two clearly defined zones.
The eye and sclera are extremely vulnerable parts of the body where pathogenic microorganisms develop rapidly, dirt, biological secretions and small debris are easily collected, and even a slight scratch is fraught with serious consequences for the health and well-being of the whole organism. It is possible to wear a lens continuously in the eye only for a strictly defined period specified by the manufacturer. Depending on the composition and form, these can be:
- Daily Wear (DW) Lenses - which must be removed at night and stored in a special disinfectant solution;
- Extended Wear Lenses (EW) - can remain in place for up to a week without taking off. After this period, it is necessary to give the eyes a rest, and the mucous membrane - the opportunity to clear.
- Flexible wear lenses (FW) - daytime, with enhanced performance and safety, allowing you to not remove them in case of a night or two. Sleep in this case does not harm the eye as a day lens would do;
- Continuous Wear Lenses (CW) - up to 30 days of continuous operation. As a starting material, exclusively thin silicone hydrogel polymers that allow good oxygen permeability can be used.
In addition, any contact lens has its own full service life, which is strictly limited by the properties of its material and production features. Using a super-acceptable norm is a big mistake, leading to new serious problems with vision and aggravation of existing ones.
The lifespan of traditional lenses (conventional) is up to a year. In reality, they are often worn until they become unusable or lost (similar to toothbrushes, the recommended period of possible use of which is also strictly limited).
Replacement Lenses (frequent replacement) mean an update in each new quarter of the year. Some species (disposable) Designed to be replaced once a month or more often - every 2 weeks. The idea of a planned replacement turned out to be so successful that today it is the most common method of production and most large ophthalmological companies have completely stopped producing traditional models.
Day Wear Lenses (one day) as safe as possible for health, perfectly suited for irregular wear and do not need maintenance at all - carrying them for less than a day, the patient discards the waste material. The downside is significant costs, even taking into account the absence of the need to purchase funds for care.
Rules for the care and wearing of contact lenses
Mandatory medical supervision
The task of the ophthalmologist is not only to conduct examinations and to appoint an adequate method of vision correction with fitting samples. Periodically, the patient's state of vision should be monitored, which will reveal the dynamics of the disease and allow it to respond adequately to it (for example, replace lenses with others with exact parameters).
Important: Doctors themselves strongly recommend a routine examination after 1.3 and 6 months after the start of wearing - so the degree of adaptation to vision correction is most correctly determined and possible problems are identified. Further, you should regularly visit an ophthalmologist at least once a year and monitor changes.
Recommendations for use
- Hygiene rules for contact lenses guarantee a healthy and safe wearing over the entire service life. The doctor who prescribed the lenses is required to brief the patient how to use and care for the lenses and tell the store. Some of them:
- Do not touch the lenses (dressed or removed) with dirty, greasy hands. Each time, you must first thoroughly wash your hands with a simple soap without smells;
- Women should remember that makeup is applied after putting on the lenses. It is recommended to take cosmetics not on a fat basis - this can damage the surface;
- The blister in which the new lens is stored must be hermetically sealed; damaged packaging automatically means defective. The same applies to wrinkled, wrinkled, and damaged lenses — you cannot use them;
- Rinsing and storage of the lens is carried out exclusively in a closed container with a special disinfectant solution for at least 4 hours. Tap water can lead to the most unexpected consequences.
A more detailed article on contact lens care.
Marking: legend on the packaging and the lens itself
The package contains symbolic information that tells the buyer about:
- Base lens curvature in mm (BC);
- Dimensions in mm (DIA);
- Optical power in diopters (D, as a variant of PWR);
- The thickness of the material in the center (CT);
- Shelf Life (Exp.);
- Sterility of goods (STERILE);
- Prescription-only sales in accordance with FDA (RXOnly) requirements.
Contact lenses are a rather sophisticated vision correction tool that requires a careful and caring attitude. Sloppy and sloppy people should seriously think before purchasing - after all, careless maintenance of the lenses will not only add trouble, but also dangerous to health.
The doctor should choose contact lenses for the patient. Too many factors measured only by special equipment in the laboratory must be considered. Subject to all the rules and careful selection of the tool, you can count on real improvement and optimization of vision. Today, good contact lenses are recognized as the most effective and popular therapeutic tool for solving vision problems.