Synonyms in a broader sense
Sticky lenses, sticky cups, sticky glasses, glasses
engl .: contact lenses
Contact lenses are thin plastic lenses that rest on a tear film or directly on the cornea of the eye. Most contact lenses are visual aids that, like glasses, can be used for farsightedness or nearsightedness. Due to the close contact with the cornea of the eye, irregularities in the cornea such as astigmatism (corneal curvature) or after injuries can be compensated. However, there are also colored contact lenses that are worn for a purely cosmetic aspect.
Read also: Anatomy of the Lens
History of contact lenses
As early as the 17th century, the French philosopher and scientist "René Descartes" was the first to come up with the idea of a visual aid whose lens lies directly on the eye.
However, it was not until the end of the 19th century that the first contact lenses were developed, which at that time were still made of glass and were very uncomfortable to wear due to their large diameter. Only with the development of acrylic glass (PMMA) did it become possible to produce smaller, comfortable lenses that can be worn for several hours.
Important terms on the subject of contact lenses
- Dk value
The Oxygen permeability using a contact lens Dk / t specified. The higher the Dk / t, the better the oxygen supply to the cornea. There are various minimum values: For a lens that can only be worn during the day, the Dk / t must be at least 20 in order to guarantee a minimal supply of oxygen to the cornea. For contact lenses that can also be worn overnight, the minimum value is 87; wearing these lenses overnight does not cause any corneal swelling.
In the case of contact lenses that do not want to change the oxygen supply to the cornea, the Dk / t is at least 125.
With the unit diopters (dpt = 1 / m) denotes the refractive power of lenses. Lenses for correcting myopia have negative values when correcting Farsightedness the lenses have positive diopter values.
- BC value
De BC value gives the degree of curvature of contact lenses on. Every cornea has its own curvature and therefore needs suitable contact lenses so that it is not damaged. When fitting contact lenses, the optimal BC value is determined.
Contact lens types
It will two forms of contact lenses differentiated: the hard and the soft.
The hard contact lenses consist of dimensionally stable plastics and are slightly smaller than the switches. Since they retain their shape, they need a little more time to get used to the eye until they have adapted to the cornea. They are suitable for daily wear over longer periods of time than so-called. Semi-annual / all-year lenses. Especially special forms of ametropia, such as Astigmatism can be corrected well with the hard contact lenses. It is important to have the contact lenses adjusted by an ophthalmologist or optician, not to exceed the wearing time according to the manufacturer and to have a check-up carried out by a doctor once a year.
The classic - malleable ones soft contact lenses adapt flexibly to the cornea and allow the eye to get used to the new visual aid more quickly. You have one high spontaneous tolerance and a comfortable to wear, which is why they are especially suitable for contact lens beginners. Due to their slightly larger contact area, they slip less often than hard contact lenses. Because this type of contact lens something less permeable to oxygen is as a hard one, it is particularly suitable for alternating with glasses. The same applies here: The maximum wearing time must not be exceeded.
Put in contact lenses
Inserting their contact lenses should be hygienic and painless respectively. This requires the right technique and a little practice. You should wash your hands thoroughly before inserting.
At long fingernails or problems with inserting the Mission aids on. It is best to always start with the same eye, e.g. right. Beginners can use one Mirror, sufficient light and, if necessary, a cloth in the sink (if the contact lens falls). Take out the contact lens for her right eye with your right index finger out of its container and place it on the tip of your index finger. Make sure that the edge of the contact lens is rounded and lies like a bowl on your finger. If the edges curve downwards, the contact lens must be turned inside out. If it is used the wrong way round, a uncomfortable foreign body sensation in the eye. With the lens in place on your fingertip, pull the same with your middle finger (right) Hand down the lower eyelid of the right eye. With the middle finger of your left hand, pull the upper eyelid upwards. So you have enlarged your insert area, which helps you insert the contact lens more easily. Slowly bring the contact lens towards the eye, best looking at the center of the lens. Gently place the contact lens on your eye and close your eyelids. Looking down and blinking can help put the contact lens in position. After blinking several times, the contact lens should no longer be felt.
You should still have one Foreign body sensation feel it, it is better to carefully remove the lens. There can be several reasons for this: The lens may have been inserted the wrong way round or the smallest dirt particles may be on the contact lens. Clean them again or, if necessary, turn the contact lens over and insert it again. If you continue to feel uncomfortable wearing your contact lens, ask your optician or ophthalmologist for advice. Be careful when you take out your contact lenses dry fingersso that the lens can be removed more easily. Use your fingers to enlarge the gap between the eyelids by pulling the upper eyelid apart with the index finger of your left hand and the lower eyelid with the thumb of your left finger. The thumb and index finger of the right hand form a pair of pliers, carefully squeeze the contact lens and remove it from the eye. Both processes - inserting and removing - are repeated for the other eye.
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Contact lens care
The Care of the contact lenses should be done daily and carefully. It is advisable to clean the contact lenses when they are put on and taken off, e.g. in the mornings and the evenings. They are kept in a special solution in the container provided for them, which is usually a small can. This Doses should be changed every four weeks become.
Caring for your contact lenses consists of the following steps cleaning and desinfection. Special Contact lens cleaners and disinfectants which you can get from your optician or eye doctor. You are allowed to clean never use tap water or drinking water! These often hide invisible microorganisms and bacteriacontaminating their contact lenses, making them a serious source of Eye infections can represent.
Before you start cleaning your contact lenses, wash your hands thoroughly with soap first and then dry them with a lint-free cloth. Then carefully place the contact lens on the palm of your hand to begin the first step - cleaning. Wet your contact lens with the cleaning agent and rub it gently with the little finger of your other hand. The little finger is ideal because it has the potentially smallest germinal area of all fingers. After rubbing, the contact lenses are rinsed once with the cleaning agent and placed in the container with the disinfectant provided for them.
The second step is the disinfection This should be done with a germ-reducing care product. In addition, the disinfectant solution in the containers should not be used a second time and thus changed daily become. Only fresh disinfectant solutions can develop their full effect. There are different preparations for disinfectants. It is essential to pay attention to the length of the contact lens insertion time according to the manufacturer. That works best Disinfect overnight. Before reinserting your contact lenses, the residues of the disinfectant must be rinsed off. This is also allowed no tap water be used. Rinsing is done with sterile sodium chloride solution (sterile saline solution) that you can obtain from your optician or eye doctor. This avoids irritation caused by the disinfectant remaining on the contact lens. Also before this step are yours Thoroughly clean hands! Saline solutions must not be prepared independently as they are not sterile.
Monthly / yearly lenses represent a special case: Due to their longer use they are more susceptible to Fat and protein deposits on the contact lens. The deposited fats and proteins can on the one hand worsen the view as well as irritation and Allergies trigger. These problems can be avoided by the additional use of a so-called Enzyme cleaner be avoided.
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One of the most common side effects of contact lenses is the risk of infection. The contact lens wearer brings infectious particles such as bacteria or microorganisms into the eye through dirt and residues on the lens, even while the lens is being used. You should therefore wash your hands thoroughly and work cleanly before handling your contact lenses. The germs can multiply particularly well between the eye and the contact lens, whereby the so-called soft contact lenses are more frequently affected than the hard contact lenses.
An infection usually manifests itself as an inflammation of the conjunctiva of the eye: the eye itches, burns, is reddened and watery. If this is the case, it is best to consult an ophthalmologist and avoid wearing the lens during this time. Use your glasses while doing this.
Another complication can be the inadequate supply of oxygen to the cornea of the eye caused by the contact lens. The contact lens rests directly on the tear film of the eye, which provides the eye with nutrients. When your contact lens is optimally fitted, it floats on the tear film and ensures that the eyes are adequately supplied with nutrients. If the contact lens is not washed sufficiently, e.g. wearing an improperly fitting contact lens will inadequately supply the eye with oxygen. The result is a possible swelling of the cornea due to the lack of removal of the metabolic products from the eye. Cornea clouding and vision impairment can occur.
Furthermore, a lack of oxygen in the eye can lead to the formation of new blood vessels on the cornea, which act as a protective mechanism to compensate for and restore the lack of oxygen supply. This also leads to a deterioration in vision.
Occasionally, allergies to the cleaning agents occur when wearing contact lenses. In general, when wearing contact lenses, working in dusty occupations and drying environments should be avoided. Contact lenses should not be worn if the eyes are very dry.
Also read our topic Contact lens side effects
Contact lenses are an alternative to glasses when correcting Farsightedness or myopia.
On the basis of the material, a distinction is made between soft and dimensionally stable contact lenses; daily lenses can be distinguished from monthly lenses and annual lenses based on the length of time they are worn.
The advantages of contact lenses are better comfort and a larger and unadulterated field of vision compared to glasses. The disadvantages include the greater risk of infection and injury to the eyes, the higher cost factor and that, unlike glasses, most contact lenses should not be worn continuously.
Contact lenses should always be like by qualified personnel Optician or ophthalmologists under a Eye tests adjusted to prevent damage to the cornea. Meticulous hygiene and care of the contact lenses is essential to prevent irritation and Infections of the eyes indispensable.