[Clinical Edge] Can You Wear Contact Lenses Before an IOLMaster Test?

 In most cases, you should not wear contact lenses immediately before an IOLMaster examination, especially when the measurements will be used to calculate the intraocular lens power for cataract surgery.

Contact lenses can temporarily alter the shape of the cornea. Because corneal curvature is an important part of intraocular lens calculation, even a small contact lens–related change may affect the accuracy of the surgical plan.

The safest approach is to follow the specific lens-discontinuation instructions provided by your cataract surgeon or eye clinic.

What Is an IOLMaster Test?

The IOLMaster is an optical biometry device used primarily before cataract surgery.

Depending on the model, it may measure:

• Axial length, or the length of the eye
• Corneal curvature, also called keratometry
• Anterior chamber depth
• Corneal diameter
• Lens thickness
• Total keratometry, including information about the posterior corneal surface
• Parameters used to calculate intraocular lens power

These measurements help the surgeon choose the intraocular lens, or IOL, intended to produce the desired postoperative vision.

Axial length and corneal measurements are among the most important inputs used in IOL power calculations.

Why Can Contact Lenses Affect the Results?

Contact lenses rest directly on the cornea and can temporarily change its curvature.

The effect depends on factors such as:

• Whether the lens is soft or rigid
• Whether it corrects astigmatism
• How tightly it fits
• How many hours a day it is worn
• How many years the patient has worn contact lenses
• Whether the lens is designed to reshape the cornea

The IOLMaster can still measure axial length after the contact lens has been removed, but inaccurate corneal curvature measurements may lead to an inaccurate IOL power calculation.

This matters because cataract surgery permanently replaces the natural lens of the eye. Unlike changing glasses, correcting a refractive surprise after surgery may require additional treatment.

Should Soft Contact Lenses Be Removed?

Yes. Standard soft contact lenses should generally be removed before the examination.

Many clinics ask patients to stop wearing ordinary soft lenses for several days before preoperative cataract measurements. Some may allow a shorter interval, while others prefer a week or longer when highly precise measurements are needed.

Toric soft contact lenses, extended-wear lenses, and high-powered lenses may require a longer break because they may produce more persistent changes in corneal shape.

There is no universal number of days that applies to every patient. Your surgeon’s instructions should take priority.

What About Rigid Gas-Permeable Lenses?

Rigid gas-permeable lenses, also known as RGP or GP lenses, can alter the corneal surface for a longer period than soft lenses.

Patients who wear RGP lenses may be asked to discontinue them for several weeks before the final IOLMaster measurements.

Long-term wearers may need additional time. In some cases, the surgeon will repeat keratometry, corneal topography, or optical biometry to confirm that the measurements have stabilized.

The goal is not simply to remain out of the lenses for a fixed period. The goal is to obtain repeatable and stable corneal measurements.

What About Ortho-K Lenses?

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

Because the corneal reshaping is intentional, patients may need to stop Ortho-K wear for several weeks or even months before accurate cataract surgery planning.

The required interval depends on:

• How long the lenses have been used
• The degree of myopia being corrected
• The stability of the corneal shape
• The urgency of cataract surgery
• Whether older measurements from before Ortho-K are available

Patients should tell their surgeon about any current or previous Ortho-K use, even if they stopped wearing the lenses some time ago.

What If You Forgot and Arrived Wearing Contact Lenses?

Remove the lenses and tell the technician or surgeon before the examination.

The clinic may decide to:

• Perform preliminary measurements that day
• Repeat only the corneal measurements later
• Reschedule the full examination
• Compare the results with corneal topography
• Wait until the measurements become stable

Do not hide recent contact lens wear. A technically successful scan can still produce clinically misleading measurements if the cornea has not returned to its usual shape.

Can the IOLMaster Measure Through a Contact Lens?

The device may sometimes obtain measurements while a lens is present, but that does not mean the results are appropriate for cataract surgery planning.

A contact lens can interfere particularly with keratometry and corneal measurements. Therefore, being able to complete the scan is not the same as obtaining reliable data for IOL selection.

The contact lens should usually be removed, followed by the recommended lens-free period.

How Long Should You Stay Out of Contact Lenses?

The following ranges are general examples rather than universal rules:

• Standard soft lenses: commonly several days
• Toric or extended-wear soft lenses: often several days to one or two weeks
• RGP or hard lenses: commonly several weeks
• Ortho-K lenses: several weeks to several months

Your eye clinic may recommend a different interval based on your lens type and whether the measurements are stable.

Why Might the Measurements Be Repeated?

Even after the recommended lens-free period, some patients show changing corneal measurements.

The surgeon may repeat optical biometry when:

• Keratometry differs substantially between visits
• The two eyes show unexpected asymmetry
• Corneal topography suggests contact lens warpage
• Astigmatism measurements are inconsistent
• A toric intraocular lens is being considered
• A premium or presbyopia-correcting IOL is planned
• Previous refractive surgery complicates the calculation

Repeatability is especially important when choosing a toric, multifocal, extended-depth-of-focus, or other premium IOL.

Bottom Line

You should generally undergo IOLMaster testing without contact lenses.

Because contact lenses can temporarily change corneal curvature, they may reduce the accuracy of the intraocular lens calculation used for cataract surgery. Soft lenses may need to be discontinued for several days, while rigid and Ortho-K lenses may require a much longer break.

Tell your cataract surgeon exactly what type of lenses you wear and follow the clinic’s specific instructions before the final measurements.

Note for international readers: IOLMaster is not a South Korea–only product. It is a ZEISS optical biometry platform used internationally for cataract surgery planning. Other clinics may use different biometers, such as the Lenstar or ARGOS, but the same general principle applies: contact lenses should be discontinued long enough for the corneal measurements to become stable.