Better Flaps = Better Results

Perfecting LASIK flap creation with the IntraLase femtosecond laser.

By UDAY DEVGAN, M.D. AND ROBERT MALONEY, M.D.

The IntraLase FS (femtosecond) laser (IntraLase Corp., Irvine, Calif.) has brought doctors a new level of precision and control in flap creation in corneal refractive surgery. At the Maloney Vision Institute in Los Angeles, we have optimized our techniques for use of the IntraLase in order to deliver the best quality results in the safest manner possible for our patients who undergo LASIK. For surgeons who are just starting to use this technology, we offer the following pearls for perfecting your femtosecond flaps.

Create Good Exposure and Positioning

Having proper exposure of the surgical site is one of the basic tenets of surgery, and it is particularly important in refractive surgery. After cleaning the eyelids and eyelashes with a povidone iodine solution, we instill additional anesthetic eye drops and then place a plastic surgical drape over both eyes. Both the IntraLase laser and the VISX Star S4 laser (for the LASIK procedure) controls are draped as well. This helps to maintain the sterility of the surgical field and aids in the prevention of postoperative infection. The IntraLase suction ring is designed to keep the eyelids and eyelashes away from the surgical field. For most cases, we do not use a separate speculum and we have found that the exposure and patient comfort level is quite good.

By having both lasers in close proximity to each other, the same surgical bed can be used for both by rotating the bed between the machines (Figure 1). Our current technique is to create both femtosecond laser flaps first, followed by stromal ablation of both eyes with the excimer laser. This technique of flap-flap-zap-zap requires less transferring between lasers and has given us consistent and accurate results.

Figure 1. Positioning the lasers together allows for maximum patient comfort and ease of use. The IntraLase and the VISX laser controls are covered with plastic drapes so the surgeon can maintain the sterility of his gloves during the procedure.

FIGURES COURTESY OF UDAY DEVGAN, M.D. AND ROBERT MALONEY, M.D.

The position of the head is of critical importance in order to properly position the patient under the laser and dock the suction ring to the applanation cone. In addition to angling the patient's head upward, the head may need to be rotated to the right or left to prevent the patient's nose from hitting the loading deck when the applanation cone is lowered. Sufficient clearance between the patient's nose and the laser is created by tilting the head (Figure 2).

Figure 2. The patient's head is tilted away from the applanation cone in order to avoid contact with the nose and to give the best exposure. The blue line indicates the axis of the laser.

Optimize Centration

Because laser ablation is centered on the pupil, the flap should be too. Optimal flap centration starts with applying the suction ring on the eye. The suction ring should be placed slightly nasal to the center of the pupil. A slight amount of posterior pressure during the placement of the ring allows fixation of the globe. The suction ring can be placed with or without the use of the IntraLase microscope. If the microscope is used, it should be done on the lowest magnification setting. Then turn the dial to the magnification level required for laser activation and tissue ablation.

Table 1. Instructions for using the nomogram:
1) Count horizontal and diagonal clicks. Ignore vertical clicks.
2) Round down in-between values (e.g., three clicks left reads the row for two clicks left)
Copyright Robert K. Maloney, 2007. Permission is hereby given to any surgeon to reproduce this for personal use (Table 1).

Once the eye is docked to the applanation cone, slight tilting of the suction ring optimizes applanation. Our preference is to have more cornea applanated nasally than temporally, because the optimal flap location is nasal to the pupil. We prefer more cornea applanated inferiorly than superiorly to allow the pocket to work optimally. Maneuvering the suction ring should be done with caution as it can cause a suction loss. If it is difficult to obtain the desired applanation, the cone is probably in contact with the nose or orbital rim — undock the applanation ring and reposition the patient's head.

When the surgeon has docked the eye to the IntraLase system, the standard approach is to use the control panel to center the femtosecond ablation over the pupil. We have found that this method does not yield optimal centration: It tends to leave the flap decentered slightly temporally. We have developed an IntraLase centration nomogram that compensates for this (Tables 1 and 2). In our plan, the technician counts the number of horizontal and diagonal clicks on the keyboard required to center the treatment on the pupil. The technician then moves the cursor an additional number of clicks as given by the nomogram. We find that this significantly improves the flap centration. Adjusting the flap position can decrease the flap diameter. We prefer a flap of 8.5 mm or more. If the flap diameter is too small, turning off the pocket increases the flap diameter.

Table 2. Instructions for using the nomogram:
1) Count horizontal and diagonal clicks. Ignore vertical clicks.
2) Round down in-between values (e.g., three clicks left reads the row for two clicks left)
Copyright Robert K. Maloney, 2007. Permission is hereby given to any surgeon to reproduce this for personal use (Table 2).

Avoid Losing Suction

We have found that suction loss is very rare with the IntraLase system. Its two primary causes are sudden patient head movement and contact of the cone with the nose or superior orbital rim. The former cause is avoided by constant verbal reassurance and good anesthesia. The latter problem is avoided through careful patient positioning. If suction is lost, the suction ring can be reapplied and the treatment redone, with additional suction accomplished by having the technician pull back on the plunger of the vacuum syringe.

Postoperative Course

In our experience with the new 60 KHz IntraLase platform, the postoperative course is very smooth. We use the same postoperative steroid regimen for the IntraLase as we did for the mechanical keratome: fluorometholone drops q.i.d. for 6 days. Diffuse lamellar keratitis is rare, and no more common than it is with a mechanical keratome. Transient light sensitivity has almost completely disappeared, occurring in less than 2% of patients. The safety, ease of use and outstanding results have made the femtosecond laser our preferred method of flap creation. OM

Uday Devgan, M.D., F.A.C.S., is in private practice at the Maloney Vision Institute in Los Angeles, and is Chief of Ophthalmology at Olive View-UCLA Medical Center. He is a consultant to AMO, but has no financial interests in the products mentioned. He can be reached at (310) 208-3937, email: drdevgan@maloneyvision.com, Web site: www.maloneyvision.com
Robert Maloney, M.D., M.A., (Oxon) is in private practice and director of the Maloney Vision Institute in Los Angeles. He is a consultant to AMO, but has no financial interests in the products mentioned. He can be reached at (310) 208-3937, email: erussell@maloneyvision.com.