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Contact Lens
Contact lenses are artificial lenses placed on the anterior surface of the cornea as an alternative to glasses for correcting the eye's refractive errors. In addition to their use for correcting refractive defects, they may also be preferred for cosmetic reasons or to treat certain corneal diseases. The fundamental principle of the working mechanism of contact lenses is to replace the curvature of the cornea with a contact lens surface according to the degree of myopia or hyperopia, thereby correcting the existing defect.
In the case of astigmatism, since it usually arises due to irregularities in the anterior surface of the cornea, the use of either rigid contact lenses or specially designed soft lenses (toric lenses) for correcting astigmatism is required. Contact lenses that are produced to address presbyopia, a near-vision problem that typically occurs after the age of 40, are also available.
The History of Contact Lenses
The use of small plastic lenses placed on the eye's transparent layer, the cornea, has become increasingly common and are referred to as contact lenses. Nowadays, many people with vision impairments prefer lenses over glasses. Contact lenses were first conceived by Leonardo da Vinci in 1508. He prepared a document called “Codex of the Eye,” which described basic optical principles through various drawings and explanations of a water-filled lens placed in contact with the eye. Contact lenses have significantly advanced today.
One hundred years after Leonardo da Vinci, Rene Descartes developed the concept of corneal lenses to correct vision problems. About 170 years later, Thomas Young succeeded in creating what is considered the first lens by refining Descartes' idea. However, the lenses developed until then could not yet be worn on the eye.
In Germany, in 1887, a glassmaker named August Muller announced that he had developed contact lenses that could be worn on the eye and accepted by the eye. He was awarded an honorary doctorate for this invention in the field of medical science. Following this, designs and developments related to lenses accelerated worldwide.
In America, in 1948, rigid contact lenses made of plastic that covered only a portion of the cornea were manufactured by Kevin Tuohy. This revolutionary step led to many changes in contact lenses. Sohnges (Germany), Neill (USA), and Dickinson (UK) became pioneers in micro-corneal lenses.
Lens production continued to grow with technology, and in the 1960s Otto Wichterle and Drahoslav Lim produced soft contact lenses that were water-absorbing. This development has inspired the production of contact lenses today. Until the 1970s, lenses for myopia and hyperopia were being produced.
In 1978, the first toric contact lenses for patients with astigmatism were produced in America. Permanent lenses were produced in 1975. In the 1980s, soft and colored lenses became available. Sequentially, GGS lenses and Bifocal lenses were launched. In the 1990s, the first multi-purpose lens care solution became available.
There are three types of lenses: rigid, soft, and semi-soft. Rigid lenses are made from polymethylmethacrylate, soft lenses from Hema (hydroxymethylmethacrylate) and Hydron, and semi-soft lenses from Cap (cellulose acetate butyrate). There are also lenses made from silicone.
Lenses have positive and negative aspects compared to glasses. A clearer image is obtained with lenses compared to glasses. The weight and pressure on the temples and nose from glasses is not present with contact lenses. The field of vision is wider. The drawbacks are that they require careful maintenance, there may be some discomfort until one gets used to them, and most importantly, they make it difficult for the cornea to receive oxygen, so they must be removed by the end of the day. Recently, soft lenses that can be worn continuously have also been produced.
What are the Criteria for Contact Lenses?
Not everyone has the suitable eye structure to wear contact lenses. Any inflammatory issues around the eye must be resolved beforehand as they can cause inflammation in the cornea due to lenses. The conjunctival structure covering our eye (which we see as white) also needs to be healthy. If this structure is compromised due to severe allergies or rheumatic diseases, wearing contact lenses will not be appropriate. All these criteria are determined and evaluated through a detailed examination by an eye doctor.
How Long Can Contact Lenses Be Used?
Contact lenses have specific usage durations, such as daily, monthly, etc., and can be used for their designated lifespan. However, if the comfort of lens use declines for the patient after a period, alternative treatments or more permanent surgical methods may be considered. Because the maintenance of lenses is just as important and meticulous as their use. The decision on whether to discontinue lens use is made collaboratively between the eye doctor and the patient.
After your examination by a doctor and the selection of the appropriate lens for you, initial trials will be conducted, and you will be provided with training regarding the use of lenses. This training will enable you to take care of and use your lenses independently during the time you wear them. Therefore, lens use is suitable for individuals who can perform their own self-care.
Is It Difficult to Use Contact Lenses?
Initially, putting them on and taking them off may be somewhat challenging, but adhering to regular instructions will ensure no difficulties arise. However, the most important aspect to consider while using lenses is hygiene. The cleanliness and maintenance of lenses are very important and must be applied with care. One should not sleep with the lenses, swim in pools or the sea, or shower with them. Moreover, since lenses that remain in the eye for a long time can cause dryness, it is important to remove them as soon as you get home and relax your eyes.
Is Contact Lens Solution Necessary?
With the help of special contact lens solutions and tablets, the cleanliness of the lenses can be maintained. There is no need to clean daily disposable lenses when you take them out in the evening since daily lenses should not be used the next day.
Contact Lens Examination
In addition to a standard eye examination, assessments of the corneal measurements of the patient and a contact lens trial may be conducted. Because contact lenses, like eyeglass prescriptions, are specific to the individual and will be determined based on the measurements taken. Not every brand might be suitable for every eye, therefore multiple trials may be necessary.
Types of Contact Lenses
Currently, there are two main types of lenses in widespread use.
- Gas-Permeable Rigid Lenses: They are named this way because they allow the eye to access oxygen. This permeability inflicts less damage to the corneal epithelial metabolism compared to rigid lenses that are not in use today. Due to their rigid structures, they are preferred for treating high degrees of astigmatism and keratoconus cases.
- Soft Lenses: These lenses are categorized into several subcategories based on usage style and frequency: disposable daily lenses, monthly lenses for daily use, annual lenses for daily use, therapeutic lenses used to treat some corneal disorders, bifocal lenses that enable near vision, and colored lenses. Soft lenses are generally more comfortable to wear. Most contact lenses used for correcting refractive errors are colorless and do not alter the appearance of the eye when worn. As long as they are worn, they eliminate the defect and clarify the image.
Advantages of Using Contact Lenses
- People who use lenses see objects in their actual size. While the side view angle is weak with glasses, contact lenses offer a wider field of vision.
- While eyeglass users often complain about the discomfort caused by the frame and lens edges, similar obstacles are not encountered with contact lenses.
- Contact lenses are not uncomfortable as they do not add weight to the face like glasses do.
- Fogging that occurs when moving from a cold environment to a warm one with glasses does not happen with contact lenses.
- In active activities such as sports and dancing, there is a risk of glasses falling off the face. This disadvantage is absent with contact lenses.
- It can be challenging for glasses wearers to use sunglasses. However, this difficulty does not exist with contact lens use.
What to Pay Attention to When Buying Contact Lenses
Selecting lenses that are not suitable for the eye will likely lead to various problems. Therefore, regardless of the type of contact lens or the intended use, appropriate contact lenses with the specifications recommended by a specialist doctor should be obtained. During the specialist examination, the most suitable measurements and features of the contact lens for the individual are determined, and the compatibility of the lenses with the eye is evaluated using trial lenses. If everything is in order, a contact lens prescription is provided. Additionally, basic usage instructions for putting in, taking out, and cleaning lenses are given for guidance. Following regular check-ups as recommended by the eye doctor, contact lens use can continue if conditions are favorable. Contact lenses are practical and aesthetic objects for those who wish to live without glasses but are not suitable for refractive surgery or want to avoid invasive methods. However, if not chosen, maintained, and used correctly, they can cause eye dryness and redness, and sometimes lead to eye infections that can result in permanent vision loss.
Tips for Trouble-Free Lens Use
- Lenses should be worn for the duration recommended by the eye doctor and should not remain in the eye for longer periods.
- Even if there is no discomfort in the eyes, the maximum usage time for contact lenses should not be exceeded.
- Periodic contact lens examinations should not be neglected.
- Before applying or removing lenses, hands should be thoroughly cleaned with soap and water; for drying, paper towels are recommended to avoid residue.
- Lenses should be rinsed with special solution every time they are removed and stored in that solution.
- Different lens care methods should not be used simultaneously, or the method recommended by the eye doctor should be followed.
- Contact lenses are strictly personal and should not be shared with others.
- Avoid contact between aerosol and spray products with lenses.
- When applying makeup, attention should be paid to the inner parts of the eyelids, and contact between makeup materials and the lenses should be avoided. Contact lenses should be inserted first, followed by makeup application, and lenses should be removed before cleaning off the makeup.
- Any medication and drops not prescribed by the eye doctor should not be used.
- The tip of the solution bottle should not touch fingers or lenses.
- In the case of any discomfort in the eyes, contact lens use should be discontinued, and if the issue persists, an eye doctor should be consulted.