Contact lenses

Contact lenses are available in a wide variety. Some are disposable, meaning you can only wear them for one day. There are contact lenses which are designed not to correct vision, but to provide an aesthetic role, changing eye color or the shape of the pupil, giving the cat-eye look.

Contact lenses must meet several criteria. First, they must correct the vision defect, but they must also be well fixed, they must not irritate the eyes and they must allow passage of oxygen to the cornea. Contact lenses are generally classified in hard (rigid) and soft. Hard contact lenses available today are actually quite flexible and are called rigid gas-permeable (RGP). Rigid lenses are recommended for correction of corneal astigmatism, and in some cases they can improve alacrimia as RGD lenses allow the exchange of fluid in the lens. The main reason is that RGP lenses are permeable to oxygen, not water. Soft lenses are made of plastic containing a liquid. The latest models of soft lenses are made from a mixture of silicone and hydrogel silicone. Silicone is a material with an optimum permeability for oxygen, but it erodes on contact with water, so it is mixed with the plastic containing liquid, so that the lens are functional when tears come up. Hydrogel silicone contact lenses allow oxygen filtering enough to be worn continuously for 24 hours. Contact lenses that do not correct vision can be used as protection lenses for the cornea. There are contact lenses with aesthetic function, for example those with cat-eye look. They provide the same risks and require the same maintenance as the medical ones. The latest innovation are bifocal and multifocal contact lenses used to correct long-sightedness due to age, instead of reading glasses. Contact lenses can be worn different periods of time. Currently there are contact lenses which can be worn for a year, six months, three months, one month, two weeks or one day. Disposable contact lenses require little effort, because they are thrown away at the end of the day. Every day other people start wearing contact lenses, however the overall percentage of contact lens wearers compared with the general population grows very slowly. This is because many people discontinue their use because of the price, because of eye irritations or alacrimia or because of the time you need maintenance.impului pe care îl necesită întreţinerea lor.

Contact lenses maintenance

Negligence or ignorance in handling contact lenses can lead to serious complications.

Cleaning contact lenses is mandatory to avoid complications. The cleaning process should remove residues and kill any virus, bacteria or fungi on the surface of the lens. Mechanical cleaning is often used. Rub the lens in your hands (after you washed your hands!) with a special soap solution (“cleaning solution for daily use”). It removes deposits and residues on the surface of the lens, which can irritate the eye. Cleaning also reduces the number of viable microbes. It is considered that mechanical cleaning process helps to reduce complications. Mechanical cleaning must always be supplemented with a disinfection process to remove bacteria, fungi and Acanthamoeba (unicellular micro-organisms). Currently there is a multi-purpose solution available that contains antibacterial chemicals, but non-irritant for the eye. But they are not as effective against fungi and amiba. There are also other solutions for disinfecting contact lenses, such as the solution with hydrogen peroxide. It is more effective against fungi and Acanthamoeba than the multipurpose solution. Hydrogen peroxide must be neutralized before fixing the lenses on the eyes. Inadequate care of contact lenses can lead to serious complications that can affect vision throughout life. Extremely serious is the microbial keratitis (a bacterial corneal infection). Lesions affecting vision install very quickly, and changes are not always discernible. Never wear contact lenses during a cold, because your eyes can become infected. Do not wear contact lenses if you have red eyes. Remove the lenses if eyes are irritated or if you get blurred vision. If the symptoms do not fade within 24 hours, consult your ophthalmology specialist. Regular checks are very important and they are recommended every six months, or at least once a year. This can prevent situations in which insufficient intake of oxygen to the cornea can affect vision.

Environment factors

Contact lenses can provide protection in an environment, but in another environment they may be dangerous for the eyes.
Contact lenses can protect the eyes from injury in some cases, but there are cases in which they can aggravate the injuries. Contact lenses should not be perceived as a means of eye protection, which explains why in toxic environments goggles are always worn. Contact lenses are not to be used in environments with high exposure to infrared radiation because they absorb radiation. Thus the temperature increases and dries the contact lenses, and they can stick to the cornea. This can happen in welding environments and in those where dryers with infrared radiation are used. Contact lenses provide protection against vapors of dissolved substances, but only for a short time. For longer periods, vapors can be absorbed by the lens. For example, contact lenses provide partial protection against tear gas or when cutting onions. When working with chemicals, they partly protect against acids, but not against alkaline substances. Soft contact lenses do not fall when you open your eyes underwater, but the rigid ones can easily fall. However, it is not advisable to swim wearing contact lenses of any kind, as water in pools contains many bacteria. Dry environments, like offices, can cause problems for contact lenses carriers because they become dry and can irritate the eyes. On the other side, cold is not a threat, because the lenses are heated by contact with eye and can not freeze.

Irritating residues

Residues accumulated on the surface of contact lenses can cause irritation or dry. The accumulated residues varies greatly from person to person.
Residues and tear film from the contact lens surface. The tear film is composed of many different substances, including water, salts, proteins and lipids (fat molecules), and acts for the damping and lubrication of the eyeball, as well as for leveling small irregularities to allow passage and good refraction of light. The tear film forms a layer on the surface of the cornea and evaporates on contact with air continuously. After a while, dry portions are formed on the surface of the eye, which causes us to blink to moisten the eye again. The time in which these dry parts appear is actually the tear film stability (a dry portion is not covered by the tear film), an important factor for contact lens carriers. Contact lenses are covered by the tear film, and if the film instability is high, it will irritate the eye.
Dry portions occurring on the surface of the contact lens will favor the accumulation of residues, which creates a vicious circle that will form even more dry portions. Residues or deposits formed on the surface of contact lenses contain proteins and lipids. Residues accumulation depends on the material from which contact lenses and tear film are made, whose characteristics vary from person to person. These deposits can cause irritation and dry-eye. In addition, they can cause allergic reactions. The easiest way to avoid accumulation of ressidues is to use disposable contact lenses that are discarded at the end of the day.

The risks of wearing contact lenses

Wearing contact lenses often creates problems, but in most cases they do not pose a threat to sight. However, there are complications that can cause permanent damage to vision.

The most common cause of complications due to wearing contact lenses is insufficient intake of oxygen in the cornea. The lack of oxygen can lead to fluid accumulation in the cornea, the so-called corneal edema. The result is blurred vision. Edema dissapears itself only if you quit wearing contact lenses. If, despite the shortage of oxygen, you continue to wear contact lenses, corneal neo-vascularisation can appear. If the newly formed blood vessels advance to the pupil, they affect the vision and make any surgery difficult (laser treatment or cataract surgery). It is important if the problem is detected as soon as possible, so that you can change the type of contact lenses or reduce the usage time. Edema may weaken the corneal epithelium and may increase the risk of bacterial or viral corneal infection.