We noticed you’re blocking ads

Thanks for visiting CRSToday. Our advertisers are important supporters of this site, and content cannot be accessed if ad-blocking software is activated.

In order to avoid adverse performance issues with this site, please white list https://crstoday.com in your ad blocker then refresh this page.

Need help? Click here for instructions.

Up Front | Aug 2003

Using the Intralase FS Laser

CPredictability and a decrease in unwanted side effects are the reasons to switch from conventional microkeratomes.

My practice purchased the INTRALASE FS laser (IntraLase Corp., Irvine, CA) because it was capable of creating more predictable flap dimensions compared with our microkeratome systems. Additionally, it had the potential to decrease the incidence of unwanted side effects reported with conventional microkeratomes.

FLAP THICKNESS
The first flap created at my practice with the laser had an attempted thickness of 140 um. As my colleagues and I performed more procedures using the INTRALASE FS laser, we decreased the attempted flap thickness. With our current settings, we achieve an average flap thickness of 119 ±13 µm (Table 1). The standard deviation is less than half the amount that has been reported with conventional microkeratomes.1 As we gain experience with the laser, the standard deviation and range of flap thicknesses has continued to decrease. Also, we have learned that the original algorithms that were developed using in vitro models placed the spot energy 20 to 30 µm deeper than planned. Unlike other traditional microkeratomes, we can easily compensate for this offset by programming for a thinner flap.

HINGE LOCATION AND FLAP CREATION
The software for the INTRALASE FS laser allows us to choose any hinge location (temporal and inferior placement are permitted), a side cut angle from 30º to 90º, a hinge width from 30º to 120º, and various energy settings. We appreciate that the laser permits us to switch to a temporal hinge in the case of hyperopia. Most hyperopic eyes have a slightly nasal angle kappa, so this capability removes the chance of the laser beam's striking the hinge.

We have found the new technology easy to master. The major change we faced was using a joystick to connect (dock) the laser to the suction fixation ring (applanation cone) on the eye (Figure 1). Additionally, we had to become comfortable with the flap-lift technique, which involves placing a spatula into the interface and gently dissecting away from the hinge toward the periphery (Figure 2).

Once we mastered these steps, we found that the clinical appearance of the eye on the first postoperative day is indistinguishable from that of a standard microkeratome-created flap. In our first year using the laser, we have not experienced epithelial defects or ingrowth, nor have we encountered free, buttonhole, or decentered flaps. The system's new 15-kHz engine has decreased the time of flap creation from 90 seconds to between 43 and 59 seconds (Figure 3).

SUCTION LOSS
The INTRALASE FS laser has also been useful for treating previous cap perforations (eg, buttonholes or lacerations) created with conventional microkeratomes. In such a case, we attempt to create a flap 30 to 40 µm below the original flap depth; this decision is based on information from a conversation I had in March 2003 with Dan Tran, MD, of Long Beach, California. With a conventional microkeratome, the loss of suction most often leads to a cap perforation, whereas a loss of suction with the INTRALASE FS laser instantaneously moves the focus of the energy spots to the surface of the epithelium. When suction is lost, we reapply the applanation cone, restart the laser pattern, and produce a smooth interface without creating any adverse side effects. With this laser, a loss of suction does not damage the flap; if we stop the laser as soon as suction is lost, there will be no epithelial damage, either.

COMPLICATIONS
Initially, we used the laser energy settings supplied by the manufacturer and experienced a high incidence of grade I DLK in the interface periphery. By reducing the energy settings and spot separation for the side cut, we have all but eliminated this complication. IntraLase Corp. has updated its recommended settings to less than 4 µJ so that newcomers will not face this problem.

We experienced an increased rate of slipped flaps only when we used the LADARVision4000 excimer laser (Alcon Laboratories, Inc., Fort Worth, TX). In a conversation in April 2003, Brian Will, MD, of Battle Ground, Washington, suggested to me that the topical phenylephrine impacted the endothelium. Since stopping the use of this agent, we have not had any additional slipped flaps with the LADARVision4000 excimer laser.

CONCLUSION
We found that an increased premium for the procedure has offset the greater overhead of this new technology, and patients accept the higher fee in exchange for decreased side effects and are comfortable with a bladeless procedure.

Each INTRALASE FS laser has interacting laser variables under the surgeon's control (eg, spot separation and energy), so surgeons need to monitor their achieved flap dimensions and modify the laser settings to achieve their desired goals. It is also important to recognize that the technology adds between 5 and 10 minutes to a bilateral procedure. The increased safety of the laser combined with a high acceptance rate by patients prompted us to transition from our conventional microkeratome systems to the INTRALASE FS laser within 2 months of acquiring it.

Perry S. Binder, MS, MD, is an associate clinical professor, nonsalaried, for the Department of Ophthalmology, University of California, San Diego, and he practices at the Gordon Binder Vision Institute in San Diego. He is a paid consultant for IntraLase Corp. Dr. Binder may be reached at (858) 455-6800; garrett23@aol.com.
1. Binder PS. Flap dimensions created with the Intralase laser. J Cataract Refract Surg. In press.
Advertisement - Issue Continues Below
Publication Ad Publication Ad
End of Advertisement - Issue Continues Below

NEXT IN THIS ISSUE