[Clinical Edge] How Long Should You Stop Wearing Contact Lenses Before a Pentacam Scan?

 You may need to stop wearing contact lenses before a Pentacam scan because contact lenses can temporarily alter the shape of the cornea.

If the cornea has not returned to its natural shape, measurements such as corneal curvature, thickness, and astigmatism may be inaccurate. This is especially important when the scan is being performed for LASIK, PRK, SMILE, keratoconus evaluation, or another procedure that requires highly precise corneal measurements.

There is no single discontinuation period that is correct for everyone. The appropriate interval depends on the type of lens you wear, how long you have worn it, and why the scan is being performed.

What Does a Pentacam Scan Measure?

The Pentacam is a noncontact imaging device that evaluates the cornea and the anterior segment of the eye.

Depending on the examination and software used, it can provide information about:

• Corneal curvature
• Corneal thickness
• The shape of the front and back surfaces of the cornea
• Corneal astigmatism
• Signs of keratoconus or corneal ectasia
• Anterior chamber measurements
• Suitability for refractive surgery

Because these measurements depend on the shape of the cornea, temporary changes caused by contact lenses may affect the results.

How Long Should You Stop Wearing Soft Contact Lenses?

For a routine examination, some clinics may ask patients to stop wearing standard soft contact lenses for approximately three days before the scan.

However, a longer break may be recommended if you wear:

• Toric soft lenses for astigmatism
• Extended-wear lenses
• High-powered contact lenses
• Lenses for many hours every day
• Lenses that appear to have altered the corneal shape

For refractive surgery screening, some centers use longer discontinuation periods to obtain the most stable measurements. For example, one major U.S. refractive surgery center instructs patients to stop ordinary contact lens wear for at least three days and uses longer intervals for toric, extended-wear, and hard lenses.

The instructions from the clinic performing your scan should take priority over a general rule.

How Long Should You Stop Wearing Rigid Gas-Permeable Lenses?

Rigid gas-permeable lenses, also called RGP or GP lenses, may change corneal shape for longer than soft lenses.

Patients may be asked to stop wearing them for several weeks or longer before a highly precise corneal evaluation. People who have worn hard lenses for many years may need an even longer period before their measurements stabilize.

In some cases, the eye doctor may repeat corneal topography or tomography on different dates. The goal is to confirm that the corneal shape is no longer changing before making a surgical or diagnostic decision.

What About Ortho-K Lenses?

Orthokeratology lenses, or Ortho-K lenses, are specifically designed to reshape the cornea overnight.

Because of this intended reshaping effect, the cornea may take much longer to return toward its untreated shape after Ortho-K is discontinued.

Depending on the duration of use and the purpose of the examination, your doctor may recommend stopping Ortho-K lenses for:

• Several weeks
• One or more months
• Occasionally longer when highly stable baseline measurements are required

This is particularly important before:

• LASIK, PRK, or SMILE evaluation
• Keratoconus assessment
• Corneal cross-linking evaluation
• Prescription of a new vision-correction strategy

Do not stop Ortho-K on your own without planning an alternative method of vision correction. Contact the clinic in advance so that you know how long to discontinue the lenses and what glasses you may need during the transition.

Why Do Different Clinics Give Different Instructions?

Different instructions do not necessarily mean that one clinic is wrong.

The required accuracy depends on the reason for the scan.

A shorter lens-free period may be acceptable for:

• A general corneal assessment
• Routine follow-up
• Comparison with previous scans performed under similar conditions

A longer period may be necessary for:

• Refractive surgery planning
• Suspected keratoconus
• Unexplained irregular astigmatism
• Confirming that the cornea is stable
• Decisions involving permanent corneal treatment

Lens material, fit, prescription, wearing schedule, and duration of use can also influence how quickly the cornea returns to its baseline shape.

What If You Forgot and Wore Your Contacts?

Tell the technician or eye doctor before the scan.

The scan can sometimes still be performed, but the results may need to be interpreted cautiously. If the measurements appear distorted or inconsistent, the clinic may ask you to remain out of contact lenses and repeat the examination later.

It is better to disclose recent lens wear than to rely on potentially inaccurate measurements.

A Practical Guide

The following ranges are general examples rather than universal rules:

• Standard soft lenses: often at least 3 days
• Toric or extended-wear soft lenses: sometimes 1–2 weeks
• RGP or hard lenses: often several weeks or longer
• Ortho-K lenses: commonly several weeks to several months

Your own clinic may recommend a different schedule based on your eyes and the purpose of the examination.

Bottom Line

Contact lenses should usually be removed for a period before a Pentacam scan because they can temporarily alter corneal shape.

Standard soft lenses may require only a few days away from wear, while toric lenses, rigid gas-permeable lenses, and Ortho-K lenses may require substantially longer. For refractive surgery or keratoconus evaluation, stable repeat measurements may be more important than following a fixed number of days.

Contact the clinic performing the Pentacam scan and follow its specific instructions.

Note for international readers: Pentacam is not a South Korea–only device. It is manufactured by OCULUS in Germany and is used internationally, including in the United States. The term “Dream Lens,” commonly used in South Korea, usually refers to orthokeratology or Ortho-K lenses. Contact lens discontinuation policies vary among countries, clinics, and individual surgeons.