LASIK is a vision correction surgery that precisely reshapes the cornea, the clear, dome-shaped front surface of the eye. Preparation is a fundamental step for ensuring a successful procedure, and the most common requirement is the temporary cessation of contact lens use. This necessary break allows the cornea to return to its natural, stable shape before any pre-surgical measurements are taken. Following this instruction is a prerequisite for achieving the best possible outcome from the laser treatment.
Contact Lenses Alter Corneal Shape
Contact lenses sit directly on the corneal surface, and over time, they exert physical pressure that can temporarily distort or mold the tissue. This reshaping is sometimes called corneal molding and is a temporary alteration that affects the curvature of the eye. The cornea’s shape determines its refractive power, and any alteration from contact lenses will make the measurement of this power inaccurate.
Rigid gas permeable (RGP) lenses and hard lenses typically cause a more significant physical change compared to soft lenses. Beyond the direct mechanical pressure, contact lenses can also limit the amount of oxygen reaching the cornea. This reduced oxygen flow can lead to a condition called corneal swelling, which further changes the tissue’s topography.
Accurate pre-surgical planning relies on precise measurements of the cornea’s curvature and thickness, which is often done through a process called topography. If the cornea is still influenced by contact lenses during this mapping, the resulting data will reflect a distorted surface rather than the eye’s natural, stable state. This means the surgeon would be planning the laser ablation based on a temporary shape, compromising the final vision correction.
Required Cessation Periods
The necessary duration for abstaining from contact lens wear is determined by the type of lens and the surgeon’s assessment of corneal stability. Soft contact lenses generally require the shortest cessation period, typically ranging from one to two weeks before the pre-operative evaluation and surgery. Soft toric lenses, which are used to correct astigmatism, may require a slightly longer break of two to three weeks because they are often thicker.
Patients who wear RGP or hard contact lenses need a significantly longer period without them, often a minimum of three to four weeks, but sometimes extending up to 12 weeks. The longer duration for RGP lenses is necessary because they mold the cornea more profoundly than soft lenses. For these patients, the surgeon may perform serial topography mapping, taking measurements at set intervals, until the corneal shape is confirmed to be stable. During this transition period, patients must switch to wearing glasses to maintain functional vision.
Risks of Inaccurate Pre-Surgical Measurements
Proceeding with LASIK while the cornea is distorted introduces a high risk of an imperfect visual outcome. The success of the procedure depends entirely on the laser removing the correct amount of tissue from precise locations. If the initial measurements are inaccurate due to corneal molding, the surgical plan will be flawed.
An incorrect surgical plan can lead to several complications, including under-correction or over-correction of the refractive error. This means the patient may still require glasses or contacts after the procedure, negating the purpose of the surgery. Other potential issues include induced astigmatism, which creates blurred vision, or higher-order aberrations that cause visual disturbances like glare, halos, or starbursts, particularly at night. Inaccurate measurements can also result in the need for expensive enhancement procedures later, or disqualify the patient from having the surgery until the cornea stabilizes.