For many patients, contact lenses are a constant companion and also promise a carefree feeling compared to wearing glasses. Unfortunately, however, these faithful companions also carry risks. It is not only inserting and removing the lenses that requires practice, as incorrect handling can lead to injuries to the cornea. However, hygiene is often the main problem. Contact lenses are often not cared for properly or are stored incorrectly. This can lead to germs entering the eye with the lens. However, intolerances and poor quality contact lenses can also pose risks.

Hygiene
Around half of all eye infections caused by bacteria are due to contact lenses. The frequency of infections depends on whether the contact lenses are soft or hard. With soft lenses, the risk of infection is approximately twice as high as with hard lenses. If you leave your contact lenses in overnight, the risk is even eight times higher. This is due to hygiene, as lenses are often only rinsed with saline solution and not cleaned properly. In addition, the container is often not cleaned properly and the storage fluid is changed too infrequently.

Intolerance
The reason for contact lens intolerance is often simply a foreign body under the lens or a surface injury to the cornea.

This is referred to as acute intolerance. If there is a longer-term intolerance, the reason is often that too little oxygen reaches the cornea through the lens. Other risks for intolerance include wearing the lens for too long or a contact lens that is not perfectly adapted to the shape of the eye. But even if the lens is perfectly adapted, incorrect care products can change a perfectly adapted shape.

Material
The material of the contact lens is also important when it comes to intolerance. Each eye has its own tear fluid, which in turn evaporates differently and thus keeps the eye moist or not moist. Just over 40 percent of contact lens wearers complain of dry eyes, often in combination with inflammation of the eyelid margins.

There are short and medium-term solutions for all side effects. However, to permanently eliminate all undesirable side effects, laser eye surgery is the only option, which has been shown in various studies to represent a significantly lower risk compared to contact lenses.

Refractive surgery (SMILE, LASIK, LASEK, PRK) can lead to superficial scarring of the cornea, but innovative laser technologies have made these complications extremely rare, occurring in less than 0.5 percent of patients operated on by an experienced surgeon.

Another risk of corneal refractive surgery is dry eye, which occurs in around 15 to 20 percent of patients. However, this side effect is only temporary and the condition usually recovers after around six months. Extremely rarely, in around 0.05 percent of patients, an infection or protrusion of the cornea can occur.

Depending on the type of procedure (SMILE, LASIK, LASEK, PRK), various other risks may occur, but these are discussed individually during the preliminary examinations.

In fact, corneal refractive surgery has never been as safe and effective as it is today. Nevertheless, patients should always be informed about any risks, however small they may be, and always seek out a surgeon with a great deal of experience for their procedure.

In the first few weeks after the operation, there may also be an accumulation of water in the yellow spot, the point of sharpest vision, which results in a reduction in visual performance.

Another typical side effect of refractive lens exchange is the development of a fibrotic or regenerative secondary cataract. This clouding behind the implanted artificial lens typically develops in the first few months after the operation, but can also occur years later. The secondary cataract can be treated with the YAG laser and does not require the eye to be reopened.

If multifocal lenses have been implanted, patients may have poorer vision at dusk and be more sensitive to glare. In most cases, the brain gets used to this new visual impression. This process is called neuroadaptation and can take up to 12 months. An experienced and well-informed surgeon will always explain the advantages and disadvantages of the various intraocular lenses to their patients in detail.

When phakic posterior chamber lenses are implanted, the temporary or permanent contact between the artificial IOL and the body's own lens can lead to an insufficient supply of nutrients to the latter. This in turn can promote cataract development around five years after the operation. This side effect affects around 5 to ten percent of patients who have been implanted with phakic posterior chamber lenses.

Very rarely, the implantation of phakic anterior chamber lenses can lead to a so-called endothelial cell loss of the cornea. This is caused by contact between the IOL and the innermost corneal layer. However, due to the continuous improvement of the lens design and regular check-ups after the operation, this side effect actually occurs extremely rarely in practice.

If complications occur during the implantation of phakic lenses and damage to the body's own lens occurs, it is possible that a complete refractive lens exchange may be necessary. This involves removing the body's own lens and replacing it with an artificial intraocular lens.