COMANAGEMENT

David Geffen, O.D. & Perry S. Binder, M.D.

A New Generation of LASIK

Many surgeons have opted for IntraLase, so its key you're familiar with this technique.

David Geffen, O.D. & Perry S. Binder, M.D. San Diego

The commercial introduction of the femtosecond second laser in 2002 triggered a change in how many refractive surgeons approached flap creation in laser in situ keratomileusis (LASIK). It became increasingly clear that the cut to create the corneal flap prior to excimer-laser ablation had a much greater affect on visual outcome than researchers had thought.

In the five years since its introduction, many refractive surgeons have adopted the IntraLase femtosecond laser, with the femtosecond laser creating approximately 36% of all LASIK flaps, according to the 2006 Marketscope report.

Because patients trust us to make the best recommendation for their eyes and because we're the primary entry point into eye care, it's essential we understand this technology.

IntraLase overview

The IntraLase femtosecond laser is a 1053nm infrared, scanning pulse laser. It is capable of cutting from inside corneal tissue using a process called photodisruption. The laser energy passes through the cornea without affecting the tissue until the surgeon focuses the beam. This means surgeons are able to cut without generating any heat or damaging surrounding tissue. Finally, the femtosecond laser cuts from within tissue, so it can move outward in either direction.

Ron Kurtz, M.D., developed the first laser in 1994, which had a speed of 6kHz. Today, the IntraLase laser operates at 60kHz and can create a corneal flap in under 20 seconds.

Clinical results

Since the arrival of the femtosecond laser, many refractive surgery centers have begun to offer a tiered approach to LASIK, offering patients a discount on procedures performed with a mechanical microkeratome and charging a premium price for IntraLase.

In our practice, patients have one choice: the femtosecond laser. We've found that IntraLase provides a safer more predictable and consistent method for flap creation than standard LASIK. In fact, studies have shown that epithelial defects occur in approximately 5% of microkeratome cases, while the second most commonly seen complication, an incomplete pass, occurs in 1.2% of surgeries.

In our experience, the most frequently seen complication with IntraLase, transient light sensitivity (TLS), occurs in 0.1% of cases and is seen even less frequently with the 60 kHz laser.¹

Further, we've found that flaps created via mechanical microkeratomes have a larger variation in the thickness and shape. Reported rates of the standard deviation seen with mechanical microkeratomes range from 12 to 14 microns in some studies to more than 19 to 20 microns in others.² The standard deviation with the 60kHz IntraLase Laser ranges from 4.1- to 9.8microns.^1,3,4

In addition, we've found that the IntraLase laser creates a consistent thickness across the entire flap surface. With a mechanical microkeratome, we've found the flaps are thinner in the center and thicker in the periphery than the flaps created by IntraLase due to the way the metal blade makes the cut. Studies have shown this can have an impact on visual outcomes, particularly when an M.D. carries out a customized ablation.⁵

One study demonstrated that IntraLase eyes had better contrast visual acuity, under both photopic and mesopic conditions, compared with eyes that underwent flap creation via mechanical microkeratome.¹ Another study compared changes in higher-order aberrations after LASIK in eyes that underwent IntraLase vs. a mechanically created microkeratome flap. Investigators found that mechanical flap creation alone could change the optical properties of the eye.⁵ They also found a statistically significant increase in higher-order aberrations in the mechanical microkeratome group. Finally, another study comparing outcomes with IntraLase and two mechanical microkeratomes revealed greater flap predictability and less induced astigmatism in the IntraLase group.⁶

Preoperative management

When it comes to explaining refractive surgery to patients, outline the pros and cons of both techniques. The biggest positive in favor of the IntraLase is safety. There is also less variability in the thickness of the flap than that of standard LASIK, which is important, particularly in patients with thinner corneas who may be at a greater risk for keratoectasia.

Postoperative management

As with standard LASIK patients, we place IntraLase patients on a topical antibiotic and steroid q.i.d. for one week to reduce the swelling that accompanies both procedures. We also recommend our IntraLase patients use artificial tears up to six times per day for six weeks, and we prescribe a shield to be worn at night for the first week.

We've encountered two side effects with IntraLase: First, a very small percentage of patients will develop TLS about two weeks following surgery. You can easily treat this phenomenon, however, with topical corticosteroids for one to two weeks. Second, we've identified subconjunctival hemorrhages caused by the suction ring used to create the flap. This typically resolves, however, in a few days and has yet to affect visual outcomes. Otherwise, it's very easy to manage our IntraLase patients, and they're generally some of the happiest patients we have in our practice. This is because, in our experience, they have such quick visual recovery compared with mechanical microkeratome LASIK or Photo-Refractive Keratotomy (PRK) patients.

There is some anecdotal evidence that there is less dry eye in IntraLASIK eyes compared with those who have undergone standard LASIK. This may be due to the fact that most IntraLase flaps are thinner and smaller in diameter than what is created by a mechanical keratome thereby cutting fewer corneal nerves. However, we still see quite a bit of dry eye in our practice following laser refractive surgery.

The best way to manage dry eye: Deal with the problem preoperatively. Before surgery, it's important to ensure the patient's lid margins are free of blepharitis, and place a punctal plug into the lower eyelid punctum, if necessary. We also attempt to determine whether patients have exposure keratitis, either from sleeping with their lids slightly open or from plastic surgery on their eyelids, both of which cause symptoms of dryness upon waking.

Something else to keep in mind: Post laser-refractive-surgery dry-eye symptoms may occur in many patients who previously wore soft contact lenses, which would act as a bandage contact lens and hide the effects of drying.

In any of these circumstances, we prescribe a dry-eye ointment to use at night. In our experience, about 3% to 5% of LASIK patients suffer from dry-eye symptoms that aren't related to a decreased tear production, but rather a neurotrophic component caused by severing the corneal nerves. Rarely do we need to prescribe additional therapies to stabilize the tear film.

As optometrists, we have the opportunity to educate and direct our patients to receive the most effective treatment. By staying up to date on the latest technological advancements, we have the ability to create a loyal and happy patient. OM

Drs. Geffen and Binder are in group practice at Gordon Binder & Weiss Vision Institute in San Diego. Dr. Geffen specializes in family eye care, contact lenses, low vision and refractive surgery consultation. Dr. Binder is a board-certified ophthalmologist and founder of Gordon Binder Vision Institute in San Diego. He is the recipient of the Lifetime Achievement Award for Refractive Surgery, presented by the International Society of Refractive Surgeons.

1. Kezirian GM, Stonecipher KG. Comparison of the IntraLase femtosecond laser and mechanical keratomes for laser in situ keratomileusis. J Cataract Refract Surg. 2004 Apr;30(4):804-11.

2. Solomon KD, Donnenfeld E, Sandoval HP, et al. Flap thickness accuracy: comparison of 6 microkeratome models. J Cataract Refract Surg. 2004 May;30(5): 964-77.

3. Binder PS. One thousand consecutive IntraLase laser in situ keratomileusis flaps. J Cataract Refract Surg. 2006 Jun;32(6):962-9.

4. Nordan LT, Slade SG, Baker RN, et al. Femtosecond laser flap creation for laser in situ keratomileusis: six-month follow-up of initial U.S. clinical series. J Refract Surg. 2003 Jan-Feb;19(1):8-14.

5. Tran DB, Sarayba MA, Bor Z, et al. Randomized prospective clinical study comparing induced aberrations with IntraLase and Hansatome flap creation in fellow eyes: potential impact on wavefront-guided laser in situ keratomileusis. J Cataract Refract Surg. 2005 Jan;31 (1):97-105.

6. Talamo JH, Meltzer J, Gardner J. Reproducibility of flap thickness with IntraLase FS and Moria LSK-1 and M2 microkeratomes. J Refract Surg. 2006 Jun;22(6):556-61.