What Is Thin-Flap LASIK?

Because it’s wonderful to live your life without relying on glasses or contact lenses, laser vision correction procedures such as LASIK have been developed to help many patients eliminate the need for visual aids.

LASIK eye surgery is one of the most commonly performed laser procedures to correct vision. However, not everyone is a good candidate for traditional LASIK. The development of thin‑flap LASIK has allowed more people to benefit from laser vision correction for nearsightedness, farsightedness, and astigmatism. Thin‑flap LASIK is considered an advanced form of laser vision correction.

SBK LASIK

Information About Standard LASIK

In conventional LASIK, the corneal flap is usually about half the thickness of the cornea, typically between 130 and 220 microns. In specialized thin‑flap LASIK, the flap is created just beneath the corneal surface at a depth of about 100 microns.

The outer layer above the corneal stroma is called Bowman’s layer. Because the flap is created just under Bowman’s layer, this technique is often referred to as Sub‑Bowman Keratomileusis (SBK). The flap lies directly beneath Bowman’s membrane, and although the flaps may differ in diameter, their thickness is usually more uniform and predictable.

Advantages of thin‑flap LASIK (SBK) include:

In general, SBK LASIK preserves more of the corneal tissue than traditional LASIK. The risk of developing corneal ectasia—a condition where the cornea becomes progressively thinner and bulges forward, leading to serious visual distortion—is significantly lower with SBK LASIK when performed on appropriately selected patients.

However, creating a thinner, smaller flap is technically more demanding than standard LASIK. For this reason, it is crucial that SBK LASIK be performed by an experienced ophthalmic surgeon, and the procedure often costs more than standard LASIK.

SBK LASIK surgery

The Standard LASIK Procedure

Preparation for SBK LASIK, or advanced thin‑flap LASIK, may include stopping contact lens wear for a period of time before the procedure. Since contact lenses can temporarily alter the shape of the cornea, it is important to allow the cornea to return to its natural shape beforehand. Your surgeon will tell you when to stop wearing your lenses and switch to glasses.

The actual LASIK procedure typically takes about 20 minutes for both eyes. Before the surgery, numbing eye drops are instilled so you should not feel pain during the procedure. A femtosecond laser is used in addition to the excimer laser used in standard LASIK. This combination provides a high level of precision and safety.

As in conventional LASIK, the laser creates a corneal flap, which the surgeon gently lifts to reshape the underlying corneal tissue with the excimer laser. This reshaping allows light entering the eye to focus properly on the retina.

In thin‑flap SBK LASIK, as the name suggests, the corneal flap is thinner and usually smaller in diameter than in standard LASIK. At the end of the procedure, the surgeon repositions the flap back into its original place, where it adheres naturally without the need for sutures.  

If you are considering this surgery, you should consult the best available refractive surgery center in your area to evaluate your options.

SBK LASIK Surgery

SBK LASIK is a procedure in which a thin corneal flap is created using a specialized SBK microkeratome (Sub‑Bowman Keratomileusis, such as the Moria SBK blade), followed by the application of a multi‑spot excimer laser (for example, the Carl Zeiss MEL 90 system) to precisely reshape the cornea.

The terminology used to describe corneal‑based refractive surgeries can sometimes be confusing, especially when multiple names are used for similar techniques.

For instance, Sub‑Bowman Keratomileusis (SBK) is sometimes referred to as “thin‑flap LASIK,” since the flap created during this procedure is about 90–110 microns thick, compared to approximately 120–180 microns in traditional or conventional LASIK.

The procedure usually takes about 15–20 minutes, and vision typically recovers quickly, allowing most patients to return to work or study within 24 hours. SBK LASIK is among the more cost‑effective refractive surgical options, giving you the opportunity to free yourself from glasses with relative ease.

There is usually little to no pain, thanks to the use of topical anesthetic eye drops before the surgery. SBK LASIK has demonstrated long‑term effectiveness over decades in patients worldwide. It is known for its safety and precision, due to highly controlled microkeratome technology and advanced multi‑spot excimer laser systems.  

If you experience significant discomfort or pain after the procedure, you should contact your doctor immediately.

SBK Eye Surgery

If you are considering SBK eye surgery, you may be wondering whether it is the right option for you.

This type of refractive surgery has become increasingly popular in recent years, with many patients achieving excellent results.

However, it is important to weigh the potential benefits and risks. SBK is a form of corneal refractive surgery used to correct vision problems.

The full name of the procedure is Sub‑Bowman Keratomileusis. It is performed using an excimer laser to reshape the cornea, the clear front surface of the eye.

SBK surgery is most commonly used to correct myopia (nearsightedness). Myopia occurs when the eye is too long or the cornea is too steeply curved.

This causes light rays to focus in front of the retina instead of directly on it, making distant objects appear blurry.

SBK eye surgery is generally considered safe. However, as with any surgical procedure, there are potential risks and side effects.

In very rare cases, patients have reported seeing halos, glare, or starbursts around lights, especially at night. If you are thinking about SBK surgery, it is essential to discuss all possible benefits and risks with your surgeon.

Only you and your eye doctor can determine whether the potential benefits of SBK surgery outweigh the risks in your particular case. The first step is a comprehensive eye examination by your ophthalmologist or another qualified eye‑care specialist to determine whether you are a suitable candidate. Typically, to be considered for SBK, you should have:

Advanced SBK LASIK

Am I a Candidate for Advanced LASIK?

Many people who have adequate corneal thickness are candidates for traditional LASIK. Because the flap in SBK/thin‑flap LASIK is thinner, more of the underlying corneal tissue is preserved, maintaining better corneal strength and stability.  

For this reason, patients who are not ideal candidates for standard LASIK due to relatively thin corneas may sometimes be eligible for SBK LASIK instead. Whether you are a candidate depends on several factors, including corneal thickness and shape, as well as the degree and type of refractive error.

All potential LASIK candidates must undergo a thorough preoperative evaluation, including detailed corneal mapping and measurement, to determine the safest and most appropriate treatment option.