Stable vision before laser eye surgery
Quick answers
When is my vision stable enough for laser eye surgery?
Your prescription should not have changed by more than 0.50 diopters over a period of at least six months. Stability is assessed based on at least two vision measurements.
Why is stable vision important?
Laser treatment permanently corrects your current prescription. If your prescription continues to change after the operation, your vision may gradually become blurry again.
Can you have laser eye surgery if you are under 20 years old?
As a rule, no. Nearsightedness often continues to develop during the teenage years and into the early twenties. For that reason, it is usually recommended to wait until your vision has stabilised before undergoing surgery.
How long do I need to stop wearing contact lenses before a pre-examination?
Soft contact lenses should be avoided for at least 1 week, while hard (rigid) contact lenses should be avoided for at least 2 weeks before the examination.
Why do I need to take a break from contact lenses?
Contact lenses can temporarily change the shape of the cornea. A break ensures more accurate measurements and provides the best basis for planning the treatment.
Who is suitable for laser eye surgery?
People with stable vision, a healthy cornea, and a thorough pre-examination showing that the eyes are suitable for the treatment.
What happens during the pre-examination?
You will be examined by both an experienced clinical optometrist and a specialist ophthalmologist. Your vision, the shape of your cornea, and the overall health of your eyes are assessed before deciding on the most suitable treatment.
One of the most common questions we receive at Copenhagen Eye Institute is: “Can I have laser surgery now?” The answer often depends on one crucial factor: Is your prescription stable?
This is called refractive stability and is one of the most important prerequisites for achieving a long-lasting result with laser treatment.
Why stable vision is important
During laser surgery, the cornea is permanently reshaped to match your current prescription. If your prescription continues to change after surgery, the treatment will no longer match the eye’s needs, and vision may gradually become blurry again.
Therefore, we require that your prescription has not changed by more than 0.50 diopters over at least six months, documented through two separate vision measurements.
This threshold follows criteria used in international clinical studies on refractive surgery and is considered a fundamental requirement in global clinical guidelines.
Why we generally do not operate on people under 20
Nearsightedness often develops throughout the teenage years and may continue into the early twenties. Research shows that the eye can still be growing during this period, which may lead to further changes in vision.
For this reason, we generally do not offer laser surgery to people under the age of 20.
If you are in your early twenties, we assess your visual stability more carefully and may recommend a longer period of documented stability before planning surgery.
When do we use cycloplegic refraction?
In some cases, we measure your prescription after using cycloplegic eye drops, which temporarily relax the eye’s focusing muscles. This provides a more accurate measurement of your true refractive error without the eye’s natural focusing influence.
This examination is used, for example:
- if there is a discrepancy between your measured prescription and your vision,
- if we suspect hidden farsightedness,
- or when maximum precision is required before surgery.
The drops take effect after about 20–30 minutes and cause blurred near vision for a few hours, but they provide valuable information for treatment planning.
Taking a break from contact lenses before your pre-examination
Contact lenses can affect the shape of the cornea while being worn. In some cases, the cornea may remain slightly altered for a period after lens removal – a phenomenon called corneal warpage.
If the cornea has not yet returned to its natural shape, measurements become less accurate, which may affect treatment planning.
Therefore, we ask you to stop wearing contact lenses before your examination:
- Soft contact lenses (daily or monthly): at least 1 week
- Hard (rigid/gas-permeable) contact lenses: at least 2 weeks
Your pre-examination at Copenhagen Eye Institute
Your pre-examination is always performed in person by a senior clinical optometrist and a specialist ophthalmologist with extensive surgical experience.
The surgeon who assesses your eligibility is also the one who performs the procedure and follows you throughout the entire treatment journey.
If you are interested in finding out whether you are suitable for a vision correction procedure, you can book a free, non-binding pre-examination via our website.
Under 45 years
Free pre-examination for laser eye surgery
Over 45 years
Free pre-examination for lens replacement
Frequently Asked Questions (FAQ)
How do I know if my prescription is stable?
Compare at least two vision measurements taken at least six months apart. If the difference is no more than 0.50 diopters, it is a good sign that your prescription is stable. Your optician’s records are often the best starting point.
I am 19 years old – can I still have a pre-examination?
Yes. We are happy to offer an assessment and guidance. However, in most cases we recommend waiting until your vision has been stable for a longer period.
What if my cornea has not normalised after stopping contact lenses?
If we see signs of contact lens influence during your examination, we recommend that you continue without lenses for a period and return for new measurements before making a final decision.
Can a cycloplegic measurement change the surgical plan?
Yes. In people with strong focusing ability or hidden farsightedness, the cycloplegic measurement may show a different prescription than a standard eye test. In such cases, we use the most accurate measurement to plan your treatment.
Selected references (for further reading):
- Vega-Estrada A, et al. Update on contraindications in laser corneal refractive surgery. Arch Soc Esp Oftalmol. 2022. — Identifies absence of refractive stability and age under 18 as absolute contraindications to corneal laser surgery.
- WaveLight® EX500 FDA clinical trial (NCT04219891); Technolas® TENEO 317 FDA trial (NCT04111757). — Both define preoperative refractive stability as ≤0.50 D change in spherical equivalent between consecutive measurements.
- Gwiazda J, et al. COMET Study Group. Myopia progression in children. Invest Ophthalmol Vis Sci. 2003. — Documents continued axial elongation through adolescence and into the early twenties in a subset of myopic patients.
- Ng LT, Lee EM, Nguyen AL. Preoperative assessment of corneal and refractive stability in soft contact lens wearing photorefractive keratectomy patients. — Shows manifest refraction takes a mean of 10.7 ± 4 days to stabilise after soft lens removal.
- Shehadeh-Mashor R, et al. Duration of contact lens removal before myopic refractive surgery. Eur J Ophthalmol. 2021;31(4):1695–1699. — Large retrospective study (20,000 eyes) examining outcomes after varying soft lens cessation periods prior to corneal refractive surgery.
