Over the past several years, I have refined my LASIK technique to minimize flap-related complications. My philosophy has been to manipulate the stromal bed and flap as little as possible while maintaining a consistent technique in order to obtain a pristine postoperative appearance with high-quality visual results. This article presents several surgical strategies that have enabled me to reduce the complication rate of my LASIK cases to far less than 1%. In your approach to LASIK, be conscious of how each tissue and layer is manipulated (epithelium, flap, stromal interface, and stromal bed). Also, be aware of your timing throughout the procedure; variations in timing from one step to the next will lead to changes in corneal hydration, which will impact patient outcomes.
ANESTHETIC
If the surgeon notices epithelial defects, he or she is most likely using an excessive amount of anesthesia. Proper administration produces the desired anesthetic effect without creating unwanted side effects. Anesthetic drops should not be administered until the patient is in the laser chair, and the proper timing of this step is key in minimizing trauma and keeping the epithelium intact, as it will be manipulated when the flap is created by the microkeratome and again when the flap is replaced after the laser treatment. I routinely use one drop of tetracaine 0.5% followed by another drop just seconds before positioning the microkeratome. This technique results in adequate anesthesia, which minimizes the chance of creating epithelial defects.
MICROKERATOME PASS
The microkeratome I prefer is the MK-2000 system (Nidek, Inc., Fremont, CA). I find that this microkeratome consistently produces smooth cuts with few chatter marks. I prefer to cut large-diameter, thinner flaps to enhance safety through greater residual bed depth. These flaps tend to measure 130 µm or less in thickness, with a 9.75- to 10-mm diameter and an average 5-mm hinge length. I like the larger flap sizes for both myopic and hyperopic cases because even myopic eyes may need a hyperopic enhancement in the future. I suggest following the microkeratome manufacturer's instructions, and I especially recommend administering lubrication drops prior to the pass in order to protect the epithelium and obtain consistent quality cuts. I prefer BSS (Alcon Laboratories, Fort Worth, TX) to other lubricants due to the inevitable introduction of this material into the flap interface prior to the laser treatment. Maintaining consistent stromal hydration is a priority for obtaining reliable outcomes, which is why I use BSS. I feel that it has the least likely chance of affecting the ablation.
LIFTING THE FLAP
After creating the flap, I wipe the cornea and cul-de-sacs with a dry surgical sponge to eliminate excess fluid introduced prior to the pass of the microkeratome. My goal is to reduce the chance of BSS, tear film, mucus, or heme being introduced onto the stromal bed as the flap is lifted. These fluids will absorb laser energy, resulting in an inconsistent ablation, and require the surgeon to wipe the stromal bed, which influences uniform hydration. Prior to reflecting the flap, I align the laser with the patient's eye, which ensures that the timing is more consistent and minimizes the chance of changing stromal hydration as it is exposed to room air. I then reflect the flap back with a straight spatula or the long portion of a Sinskey Hook (Katena Products, Inc., Denville, NJ), and begin the laser treatment almost immediately following refinement of alignment. I do not wipe the stromal bed. My goal is to maintain the cornea in its naturally hydrated state through efficient techniques and reproducible timing from eye to eye.
LASER ABLATION
I use a Nidek EC-5000 Excimer Laser for LASIK. At 40 Hz, this scanning-slit laser produces very smooth ablations at a fairly fast rate. Because the laser is continually scanning and rotating, there is no central pooling of liquid that may be seen with a broad beam laser. For this reason, there is no need to wipe the cornea during the ablation. Depending on the laser used, wiping the ablation area may be necessary.
REPLACING THE FLAP/IRRIGATION
After performing the laser portion of the treatment, I use a cannula attached to a bottle of sterile BSS to replace the LASIK flap. Then, with the cannula placed in the interface, I vigorously irrigate with BSS to ensure that no debris settles in the interface. With my free hand, I will hold a surgical sponge in the cul-de-sac and irrigate until the sponge is saturated. I am very conscious of maintaining the flow of fluid away from the stromal interface—I do not want to create flow back toward the stroma allowing meibomian secretions, epithelial cells, or any debris to become trapped in the interface under the flap. I repeat this process until I am confident the interface is pristine, and I use sponges to dry any excess BSS on or near the cornea.
DRYING
The old standard of waiting 3 to 5 minutes for flap adhesion has been replaced in my clinic by drying with oxygen (Figure 1). I use two liters of oxygen per minute to dry the flap once it has been replaced, and when the interface is sufficiently irrigated. Not only does this decrease the flap drying time, it allows me to control the drying in a uniform manner. I dry until the epithelium is barely dry, and before the flap shrivels from dehydration. My goal is to dry just enough to allow an instrument to adhere to the epithelium.
SQUEEGEE TECHNIQUE
This final step of my LASIK technique may be the most important in terms of preventing striae. Once the flap has been dried with oxygen and the epithelium is slightly tacky, I take the long portion of a Sinskey Hook and “squeegee” the flap (Figure 2).The tackiness of the dried epithelium allows the instrument to adhere, which allows the surgeon to stretch the flap back into its original, precut position. I start in the center of the cornea and stretch the flap to the gutter in each direction away from the hinge several times. This method of smoothing the flap not only reduces the amount of striae in my LASIK patients, but I feel it contributes to the high percentage (98+%) of patients seeing 20/40 or better prior to leaving the office. Before removing the speculum, I place an antibiotic drop and 1% carboxymethylcellulose. This lubricates a dried corneal surface and prevents the lid from dislodging the flap.
LESS IS MORE
When it comes to preventing striae in LASIK surgery, I feel that the combination of minimal flap and stromal manipulation, and adequate drying, along with the squeegee technique of flap smoothing, has been the key for my successful LASIK outcomes and high patient satisfaction. n
Jan Schumer is a Management Consultant in Central Ohio. She does not hold a financial interest in any of the materials mentioned herein. Jan may be reached at 614.880.9257; janschumer@earthlink.net
