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Up Front | Sep 2003

Buttonhole Flap After LASIK

CASE PRESENTATION
A 27-year-old white female with preoperative manifest refractions of -7.00 -0.75 X 10 = 20/20 OD and -6.75 -1.00 X 175 = 20/20 OS underwent bilateral LASIK with a mechanical microkeratome. The patient's preoperative keratometry readings were 45.25/46.00 D OD and 45.50/46.00 D OS, and her preoperative pachymetry measurements were 578 µm OD and 582 µm OS. Surgery on her right eye was uneventful, but the procedure on her left eye created a buttonhole flap and was aborted.

The patient presented to our office 1 week later. Her UCVA was 20/20 OD, and slit lamp examination revealed a well-healed cornea. Her manifest refraction was -6.75 -0.75 X 170 =20/20 OS, and a small paracentral buttonhole scar was visible. The flap was well positioned and without striae. Despite excellent UCVA in her right eye, the patient felt uncomfortable driving and working due to anisometropia. She had been contact lens intolerant in the past and was unwilling to wear a contact lens temporarily in her left eye.

HOW WOULD YOU PROCEED?
1. Would you instruct the patient to endure anisometropia for 3 months until a new flap may be created with a mechanical microkeratome?
2. Recommend PRK or LASEK?
3. Create a new flap 2 weeks after the initial procedure using an INTRALASE FS laser (IntraLase Corp., Irvine, CA)?

SURGICAL COURSE
The patient underwent LASIK with the INTRALASE FS laser 16 days after the occurrence of the buttonhole flap. The manifest refraction of her left eye was stable prior to surgery. The initial flap attempt appeared to be 8.5 mm in diameter, but information on the flap thickness (probably a maximum of 180 or 160 µm) was unavailable. We therefore planned to create a flap with a 9.3-mm diameter and a 200-µm depth in order to avoid the previous flap edge and interface.

Using a superior-to-inferior raster photodisruption method with a superior hinge and pocket and a 45º side-cut angle, we uneventfully created the flap in 81 seconds. After gently lifting the flap with a rounded LASIK spatula, we performed the originally intended ablation with the STAR S4 excimer laser (VISX, Inc., Santa Clara, CA). After replacing the flap, we irrigated the interface with BSS (Alcon Laboratories, Inc., Fort Worth, TX) and placed a Soflens 66 bandage contact lens (Bausch & Lomb, Rochester, NY) over the flap for extra protection overnight.

OUTCOME
On the first postoperative day, the patient's UCVA was 20/40 OS after the contact lens was removed, and her UCVA improved to 20/20 5 days later. Slit lamp examination revealed good corneal flap positioning without striae and a paracentral buttonhole scar.

DISCUSSION
Although LASIK with a mechanical microkeratome is safe, the device's malfunction can result in an imperfect flap.1 The incidence of flap complications can range from 0.3% for experienced surgeons2 to 2.2% for newer LASIK surgeons.3 The surgeon must then delay performing excimer ablation until he can create an optimal flap. We have generally found it prudent to wait at least 3 months after the creation of a poor flap before attempting a new pass with a mechanical microkeratome; high suction pressure and the sweeping path of the microkeratome head increase the risk of displacement or partial amputation of an inadequately healed, previously made flap.

The INTRALASE FS laser's ability to cut into corneal stroma without damaging anterior tissue makes it an effective alternative for LASIK flap creation.4,5 After applying topical anesthesia, the surgeon centers a suction ring onto the cornea and secures it at a pressure of 35 mm Hg (Figure 1). He docks the laser aperture to the suction ring with gradual downward applanation onto the corneal surface. Because the corneal surface is effectively flattened against the laser, laser energy can reach a uniform, desired depth within the stroma. Unlike with a traditional microkeratome, this flattening also eliminates corneal curvature as a variable that can affect flap diameter. Once the photodisruptive pulses have produced the flap interface, the surgeon positions side cuts at the outer edge of the flap, except in the area of the hinge. Next, he releases suction and lifts the flap for ablation of the stromal bed. Because it may change slightly with the occurrence of a buttonhole, surgeons should ensure that the patient's manifest refraction is stable before attempting a second procedure.

We have since used the INTRALASE FS laser in three additional cases of incomplete flaps 2 to 3 weeks after the complication with the mechanical keratome. All three patients achieved 20/20 UCVA postoperatively.

Howard S. Kornstein, MD, is a refractive surgeon at the Filatov Eye Institute in New York, New Jersey, and Connecticut. He holds no financial interest in the products or companies mentioned herein. Dr. Kornstein may be reached at (800) 984-2020; howard@diamondvision.org.
Vadim Filatov, MD, is a refractive surgeon at the Filatov Eye Institute in New York, New Jersey, and Connecticut. He holds no financial interest in the products or companies mentioned herein. Dr. Filatov may be reached at (800) 984-2020; vadim@diamondvision.org.
1. Leung AT, Rao SK, Yu EW, et al. Pathogenesis and management of laser in situ keratomileusis flap buttonhole. J Cataract Refract Surg. 2000;26:258-262.
2. Jacobs JM, Tarvella MJ. Incidence of intraoperative flap complications in laser in situ keratomileusis. J Cataract Refract Surg. 2002;28:23-28.
3. Yildirim R, Devranoglu K, Ozdamar A, et al. Flap complications in our learning curve of laser in situ keratomileusis using the Hansatome microkeratome. Eur J Ophthalmol. 2001;11:328-332.
4. Ratkab-Traub I, Juhasz T, Horvath C, et al. Ultrashort pulse (femtosecond) laser surgery: initial use in LASIK flap creation. Ophthalmol Clin North Am. 200;14:347-355.
5. Lubatschowski H, Maatz F, Heisterkamp A, et al. Application of ultrashort laser pulses for intrastromal refractive surgery. Graefes Arch Clin Exp Ophthalmol. 2000;238:33-39.
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