Many people dream of a life without glasses or contact lenses – and laser eye surgery often makes this possible. However, not everyone is automatically suitable for laser eye treatment: there are clear requirements that must be met for the procedure to be safe and successful. These include minimum age, stable vision, suitable diopter values and a healthy cornea.

In this blog, we explain which conditions are checked before laser treatment, for which visual defects itworks and when alternatives such as lens surgery make more sense. This way, you will know exactlywhat is important before the consultation– and whether the path to sharp vision without visual aids is an option for you.

Top 3 most important requirements for laser eye surgery at a glance

Anyone who would like to have their eyes lasered should be aware of this: Not everyone is automatically suitable for laser eye treatment. There are clear requirements for laser eye surgery in order to guarantee safety and the best possible results. The three most important are: minimum age, stable vision and treatable defective vision. These factors are checked during the preliminary examination to ensure that the procedure can reliably correct vision.

Minimum age: Why 18 is the lower limit

There is a clear rule for laser eye surgery in Austria and internationally: patients must be at least 18 years old. The reason: it is only from this age that vision has usually stabilized and the eye is no longer in the growth phase.

Although there is no fixed upper limit, from around the age of 45, when presbyopia sets in, laser procedures such as Femto-LASIK or ReLEx SMILE are sometimes no longer ideal. Alternative procedures such as lens replacement or the insertion of ICL lenses are possible here.

Stable visual acuity: Why fluctuating diopters are an exclusion criterion

For laser eye treatment to be successful in the long term, the diopter values must have been stablefor at least twelve months. Fluctuations in visual acuity – i.e. changing diopters – indicate that the eye is still changing. If treatment is carried out at this stage, there is a risk that the effect will not last and that visual aids (glasses or contact lenses) will be needed again. The following therefore applies: Before the procedure, have the refractive power of the cornea checked carefully to ensure that it is stable.

Treatable visual defects: Which visual impairments can be lasered

Not every visual defect can be treated with laser, but many can be corrected excellently:

• Short-sightedness (myopia) up to approx. -10 diopters
• Farsightedness (hyperopia) up to approx. +4 diopters
• Corneal curvature (astigmatism) up to approx. 4-6 diopters

Presbyopia, on the other hand, is not treated with traditional laser treatments, but usually with lens techniques or special laser eye surgery methods such as PresbyMAX. Important: In the case of certain eye diseases such as cataracts or a cornea that is too thin, laser eye surgery may not be possible or may not make sense. In this case, the ophthalmologist will check which individual requirements are met during the preliminary examination.

Preliminary examination: why it is crucial for the procedure

The preliminary examination is essential for laser eye surgery – it determines whether the individual requirements for laser eye surgery are met and which treatment method (e.g. Femto-LASIK, ReLEx SMILE) is suitable. The ophthalmologist not only checks the visual acuity and diopter values, but also the general health of the eyes. The aim is to optimally plan the procedure, minimize risks and ensure that laser treatment can permanently correct the visual impairment.

Which examinations are carried out in advance

A series of specialized tests are carried out before laser eye surgery:

• Measurement of corneal thickness: If the cornea is too thin, laser eye surgery may not be suitable.
• Analysis of the corneal surface (topography): It shows irregularities or a corneal curvature.
• Determination of the diopters: To ensure that the defective vision (e.g. short-sightedness, long-sightedness, astigmatism) is within the treatable range.
• Checking the stability of the visual values: Fluctuating values are an exclusion criterion.
• Intraocular pressure measurement and retinal check: To rule out eye diseases such as glaucoma or retinal damage.

Patients are also asked about previous illnesses, hormonal changes (e.g. pregnancy) and any contact lens use – all of which are taken into account in the treatment decision. Smartlaser carries out these preliminary examinations particularly thoroughly in order to find the best individual solution.

Corneal thickness as a decisive factor in laser eye surgery:

In addition to the diopter limits, corneal thickness plays a central role when it comes to suitability for laser eye treatment. The cornea must not only be thick enough to allow the desired correction by the laser, but also to remain stable after the treatment.

Typically applies:

• At least 500 micrometers corneal thickness for procedures such as Femto-LASIK
• Slightly thinner thicknesses are possible with superficial procedures such as Trans-PRK, because less tissue is removed here
• If the cornea is too thin (e.g. less than 480 micrometers), laser treatment is often not recommended – ICL lenses are often an alternative here

Precise measurements are taken during the preliminary examination using state-of-the-art equipment to avoid risks such as unwanted corneal curvature or instability.

When is laser eye surgery not possible?

As effective and safe as modern laser eye treatments such as Femto-LASIK or ReLEx SMILE are, they are not suitable for everyone. If certain requirements for laser eye surgery are not met, treatment is not recommended in order not to endanger the health and vision of the eye. This is why it is so important to have a thorough examination beforehand.

Typical reasons for refusal of laser eye surgery:

An ophthalmologist or specialist may advise against laser eye surgery if:

• The cornea is too thin or has scars
• The diopter values are outside the treatable range (e.g. more than -10 diopters for short-sightedness)
• The visual acuity has fluctuated considerably in the last 12 months (also recognizable by the need for new glasses and contact lenses)
• eye diseases such as cataracts, glaucoma or keratoconus are present
• You are pregnant or breastfeeding (hormonal fluctuations)
• Chronic diseases such as rheumatism increase the risk of recovery

Requirements not met? Alternatives to laser eye surgery: Lens surgery

If laser eye surgery is not possible, there are now excellent alternatives from lens surgery:

• ICL (phakic intraocular lenses): An artificial lens is used in addition to the natural lens, ideal for high myopia or thin corneas.
• Lens exchange (CLE): The natural lens is replaced by an artificial lens (e.g. monofocal, multifocal or EDOF lens) – often for presbyopia from around 45 years of age.

Smartlaser provides individual advice on which treatment method is best suited to your personal requirements – so that all options are discussed safely and transparently.

Laser eye treatment and its requirements: Femto LASIK, SmartSight, Trans-PRK, ReLEx SMILE

Each laser eye procedure has its own requirements and limits – especially when it comes to diopters. These values are important to ensure that the cornea remains sufficiently strong and that the treatment is safe. Here is a compact overview:

Procedure	Short-sightedness (myopia)	Farsightedness (hyperopia)	Astigmatism (curvature of the cornea)
Femto-LASIK	up to approx. -10 dpt	up to approx. +4 dpt	up to approx. 5 dpt
ReLEx SMILE	up to approx. -10 dpt	not suitable	up to approx. 5 dpt
Trans-PRK	up to approx. -6 dpt	up to approx. +3 dpt	up to approx. 3 dpt
SmartSight	up to approx. -10 dpt	not suitable	up to approx. 5 dpt

Important to know:

• Laser treatments are often not sufficient for presbyopia – lens surgery procedures such as CLE or multifocal lenses are an option here.
• The thickness of the cornea and the general condition of the eyes also play a decisive role.