IntraLase: Creating a LASIK Flap with Precision

A newly developed technology called IntraLase appears to enhance the safety of LASIK vision correction by using laser energy instead of a microkeratome, a cutting tool with a metal blade used in traditional LASIK procedures.

In LASIK, the microkeratome is used to cut a hinged flap in the cornea. The flap gets folded back, and an excimer laser is used to remove (or "ablate") some tissue from the newly exposed surface. Then the flap is put back in place, resulting in a reshaped cornea that produces better vision.

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So in the IntraLase procedure, two different lasers are used, which is why LASIK surgeons sometimes call it "bladeless" or "all-laser" LASIK.

As in typical LASIK, the flap then is replaced to serve as a type of natural "bandage" for healing.

Advanced Medical Optics (AMO) in 2007 acquired IntraLase, which was integrated into the company's CustomVue excimer laser platform. The new system now is marketed as iLASIK.

While LASIK complications are relatively rare, they are sometimes associated with the oscillating blade used with traditional microkeratomes. Metal blades might create uneven flap edges, resulting in abnormal corneal surfaces and vision defects such as irregular astigmatism.

Metal blades also have been associated with formation of incomplete or improperly formed "buttonhole" flaps that can cause vision-threatening scars. Many eye surgeons report these types of complications are far less likely with laser-created flaps.

As a replacement for microkeratomes, IntraLase creates flaps through infrared laser energy that inserts a precise pattern of tiny, overlapping spaces just below the corneal surface. The IntraLase laser operates at extremely high speeds (pulses of one quadrillionth of a second), allowing tissue to be targeted and divided at a molecular level without heat or impact to surrounding tissue.

Studies indicate that IntraLase is associated with significantly fewer overall LASIK complication rates. Nevertheless, eye surgeons recently have reported one postoperative complication of unusual light sensitivity such as photophobia that appears unique to the use of the IntraLase in LASIK.

Published reports mention this complication has occurred in as few as 1 percent or as many as 20 percent of patients undergoing LASIK with IntraLase, according to an article in Review of Ophthalmology, October 2004. (The 20 percent figure was reported by one surgeon, whose IntraLase laser was replaced by the company because compared with other surgeons' experiences, the figure was abnormally high, according to the article.)

However, many eye surgeons report that the photophobia complication is temporary and can be resolved with steroid treatment (eye drops) lasting a few weeks. Eye surgeons favoring IntraLase emphasize that light sensitivity is a transient side effect that soon resolves, unlike more serious and potentially permanent vision-threatening complications that might result from defective flaps.

However, the tradeoff for potentially increased safety with the use of IntraLase is accompanying additional LASIK procedure costs of about $300 per eye, according to Review of Ophthalmology. [Read our LASIK cost article for other price estimates for IntraLase LASIK.]

Usually patients are given the choice of whether they prefer LASIK flaps to be cut with a blade or with the more expensive laser technology, but some surgeons may prefer to use only IntraLase and may bundle that cost into their overall LASIK fee. [Read a blade vs. bladeless LASIK debate.]

The LASIK surgeon uses computer software to guide the IntraLase laser beam, which applies a series of tiny (3-micron-diameter) bubbles within the central layer of the cornea. The resulting corneal flap is created at a precise depth and diameter pre-determined by the surgeon.

As occurs with a mechanical microkeratome, a small section of tissue at one edge of the flap is left uncut, forming a hinge that allows the surgeon to fold back the flap so that the cornea can be accessed and reshaped for vision correction. [See a slide show of how LASIK works.]

With IntraLase, people with thin corneas who once were unsuitable for LASIK may now be candidates. Most people have corneas that are between 500 and 600 microns thick, and most microkeratomes cut flaps ranging between 100 and 200 microns thick. Because of its precision, the IntraLase appears capable of more reliably and consistently producing corneal flaps as thin as 100 microns.

This means surgeons now have more options to perform LASIK in people with thinner and flatter corneas, according to Vance Thompson, MD, a Sioux Falls, S.D., refractive surgeon with experience using IntraLase. [Dr. Thompson is also an AllAboutVision.com Advisory Board member.]
 

IntraLase in some cases may present fewer LASIK complications. The IntraLase laser flap follows the curvature of the cornea and produces a flap with easily managed vertical edges, unlike thinner edges associated with microkeratomes that might tear more easily. This difference in flap structure may reduce the chance of cells growing underneath and pushing up the flap (epithelial ingrowth) to create an irregular corneal surface with accompanying vision defects.

Other complications such as "buttonholed" or partially formed flaps also might be avoided with the IntraLase. Because of its sterile system, IntraLase also may be associated with decreased chance of eye infection or contamination.

The IntraLase laser uses a low vacuum suction ring to hold the eye, compared with a higher vacuum used for microkeratomes. However, the time needed (up to a minute) for the suction ring to remain on the eye with the IntraLase may slightly increase chances of some superficial bleeding on the white part of the eye (subconjunctival hemorrhage). This type of temporary eye bleeding is not vision-threatening, and it resolves on its own.

People who have had previous corneal surgery often are candidates for LASIK with IntraLase. Dr. Thompson reports that he now uses laser-created flaps for most people who have undergone previous corneal surgeries such as radial keratotomy (RK), a now obsolete vision correction surgery that involved making cuts into the cornea.

Recovery is similar to that of traditional LASIK. Following surgery, some patients (as with traditional LASIK) have reported feeling eye irritation for up to two days.

While some studies indicate that more people achieve 20/20 or better vision with an IntraLase flap than with a microkeratome-made flap, other study results are inconclusive or show superior visual outcomes when microkeratomes are used (Review of Ophthalmology). Study results have shown that LASIK with IntraLase may produce a lower incidence of post-operative dry eye. Fewer enhancement ("touch-up") procedures appear to be required when LASIK is performed with IntraLase.

According to Dr. Thompson, laser-made flaps appear to adhere more tightly to the corneal bed at the end of the procedure and demonstrate a more aggressive healing response at the edges compared with microkeratome-made flaps. Dr. Thompson said that some microkeratome flaps, instead of adhering to the cornea, can still be lifted easily many years after surgery.

The "all-laser" LASIK approach, using the IntraLase laser and a standard excimer laser, may avoid some microkeratome-related complications such as corneal irregularities and scarring, which can degrade vision.

But plan on significantly increased procedure costs if IntraLase is used with LASIK. Also, IntraLase has been associated with a complication that causes light sensitivity, although eye surgeons report that steroid eye drops will resolve the condition.

More surgeon experience with computer-guided laser creation of LASIK flaps and further analysis of their results should confirm whether IntraLase is a significant advance.