Volume 38, Issue 1 , Pages 2-4, January 2012
Flaporhexis: Rapid and effective technique to limit epithelial ingrowth after LASIK enhancement
Article Outline
We describe a method of lifting and replacing the laser in situ keratomileusis (LASIK) flap to reduce the incidence of epithelial ingrowth beneath the flap after LASIK enhancement. In the rapid flaporhexis technique, the flap edge is opened by 1 clock hour with a Sinskey hook and the flap is peeled back after the exposed edge is grasped with a forceps. When necessary, further blunt retraction of the flap is performed with a triangular polyvinyl acetate sponge. After ablation and before the flap is replaced, a triangular sponge is used to clear epithelial remnants from the interface. This method consistently produces a smooth epithelial dissection and decreases the possibility that epithelium is retained beneath the flap.
Financial Disclosure
Neither author has a financial or proprietary interest in any material or method mentioned.
Optimal refractive surgery outcomes often necessitate that eyes treated with laser in situ keratomileusis (LASIK) have a reoperation (enhancement) to yield the best possible vision and maximum independence from glasses or contact lenses. Patient dissatisfaction is the primary indication for retreatment after primary refractive surgery. Techniques for lifting the LASIK flap for retreatment have been reported,1, 2 and the technique used for lifting the flap to perform enhancement varies substantially between surgeons and often entails inserting a spatula or other instrument through the epithelium at the flap edge and into the interface beneath the flap. Frequently, this instrument is used for blunt dissection of the epithelium circumferentially to further open the interface so the flap can be fully retracted. This approach often produces epithelial fragments and overhangs, which can be retained in the interface when the flap is replaced. Retention of epithelial tissue in the interface is likely a major risk factor for epithelial ingrowth into the interface after enhancement.
The incidence of epithelial ingrowth beneath the flap after LASIK enhancement is reported to be as high as 30%, depending on the author, and to be higher after enhancement than after primary LASIK procedures.3, 4, 5, 6 We hypothesized that this variation is related to the method used to lift and replace the LASIK flap during the enhancement procedure and developed a rapid and efficient method that does not damage the flap, produces a smooth epithelial edge, and includes a final check to ensure no epithelium is retained beneath the flap when it is replaced in its original position.
Surgical technique
The flaporhexis technique is shown in the Video (available at http://jcrsjournal.org). With this technique, LASIK retreatment is never performed earlier than 3 months after the primary LASIK procedure. Typically, it is performed between 3 and 6 months, when refractive and corneal topographic stability has been achieved on serial examinations.
Adhesive drapes are routinely used for the eyelids, along with an aspirating lid speculum to allow irrigated debris to be removed from the eye. The edge of the flap opposite the hinge is marked with gentian violet using a 2.0 mm diameter circular marker. Central corneal thickness is measured with ultrasonic pachymetry. At this point, a Sinskey hook is pressed into the epithelium at the limbus opposite the hinge and dragged with posterior pressure toward the center of the flap until the instrument tip falls into the potential space at the flap edge. The surgeon can feel this transition if the posterior pressure is maintained on the tip as it is dragged from the periphery to the center. The injury from dragging the tip of a Sinskey hook from the limbus to the flap edge is so small relative to the injury when the flap is lifted for more than 250 degrees that it contributes little, if any, additional discomfort. The Sinskey tip is then used to “crack open” the interface at that point and to extend the opening approximately 1 clock hour. The maneuver with the Sinskey hook is easiest to perform by right-handed surgeons if the entry point is made to the right of the point 180 degrees opposite the hinge center and by left-handed surgeons if the entry point is made to the left of this position. The flap edge is not marked at the slitlamp prior to using the Sinskey sweep to find the flap edge, although this could be incorporated if the surgeon so desires, especially when first using the technique. (In our experience, the procedure can be performed as easily at the operating microscope as at the slitlamp, without moving the patient from the slitlamp to the excimer laser after the flap is partially lifted.)
Forceps are then inserted into the opening in the flap interface, and the flap is peeled back toward the hinge. This maneuver results in a smooth epithelial tear with no fragments or tongues of epithelium to be caught within the interface. Our preference is to use a 0.12 mm forceps to gently grasp the flap edge for better flap fixation, which causes minimal damage to the flap edge. If the surgeon prefers, a toothless forceps can also be used for this maneuver. When necessary, further blunt reflection of the flap can be performed with a dry triangular fiber-free polyvinyl acetal sponge (Beaver-Visitec International, Inc.) pressed against the stromal surface of the reflected flap. If there is strong adhesion of the flap to the bed, the sponge can be used to safely reflect one-half or more of the flap.
Rarely, the surgeon will find the adhesion between the flap and the underlying stromal bed is so strong that too much force must be applied with the forceps to peel the flap; ie, there is a risk of tearing the flap. At this point, an iris spatula can be inserted into the opening in the flap edge and used for blunt dissection of most of the stromal interface, without disrupting the epithelium around the circumference of the flap, before peeling the flap back with the forceps and using a triangular sponge to further reflect the flap.
When the flap is fully reflected, the central posterior residual bed is measured with pachymetry to ensure sufficient stroma remains for the intended ablation and the excimer laser ablation is performed. (If the posterior residual bed after excimer ablation would be less than 250 μm, the procedure does not continue.) The stromal interface and posterior surface of the flap are irrigated to remove debris, and then a clean triangular sponge is used to examine the flap edge to ensure no fragments or overhangs of epithelium are retained within the interface. Special attention is given to the point where the interface was cracked open with the Sinskey hook because areas where the epithelium was breached are prone to having epithelial debris in the interface. Irrigation is then applied to the interface and an iris spatula used to reflect and smooth the flap into position, using the previously placed gentian violet marks for proper alignment. Sweeping with a wet sponge is always performed from hinge to flap edge, using the hinge as a pivot point, and can be used to move the flap and ensure striae are smoothed out of the flap. As a final step, a dry triangular sponge is used to dry and inspect the flap edge to verify that the flap is in the proper position.
The routine postoperative care after retreatment is prednisolone acetate 1.0% and antibiotic drops 4 times daily for 1 week. In addition, nonpreserved artificial tears are used 4 to 8 times a day for 1 week as needed. The patients are told to go directly home and take their first medication drops before taking a 3-hour nap. A prescription for oral narcotic analgesia for use if necessary is provided, although few patients report using this medication.
Discussion
The flaporhexis method for rapidly lifting the LASIK flap with minimal use of instruments to break through the epithelium at the flap edge is very rapid and less likely to yield epithelial debris or tongues of peripheral epithelium that can be caught within the interface when the flap is replaced after laser ablation. We have routinely used this method to lift microkeratome flaps more than 15 years after the primary LASIK procedure and femtosecond flaps out to at least a year after the primary procedure. During the past 6 years, in eyes with at least 1 year of follow-up, we have used this method in 214 eyes (54 microkeratome and 160 femtosecond laser) with no instances of clinically significant epithelial ingrowth. Occasionally, as noted with all primary and enhancement LASIK procedures, a few pearls of epithelium have been noted at the flap edge, but none of these pearls were progressive or required flap lifting to remove epithelium in this series. We have noted these pearls in 2.7% of flap lifts for retreatment and 2.9% of primary LASIK and did not note a difference between those using a femtosecond laser and those using a microkeratome in primary cases and retreatments. We believe the critical aspect of this method that limits epithelial ingrowth after retreatment is the smooth tearing of the epithelium overlying the flap edge over the entire periphery of the flap and limited passage of instruments through the epithelium to produce epithelial fragments and overhangs that could be caught in the interface when the flap is returned into position.
Very rarely, the wound healing at the flap edge and between the flap and underlying bed is so strong the surgeon cannot lift the flap even when an iris spatula is used to dissect the interface. In this case, photorefractive keratectomy with mitomycin-C can be used to safely perform the enhancement. In our experience, this is more likely to occur after primary LASIK using the femtosecond laser than primary LASIK using a microkeratome, especially with older model femtosecond lasers such as the 15 kHz and 30 kHz models, and is attributable to a greater overall wound-healing response, including more myofibroblast generation in the interface, at the flap edge with these earlier model femtosecond lasers.7
For several years after the technique was developed, a bandage contact lens was placed over the cornea for 1 day to improve patient comfort and protect the lifted flap edge from the blinking eyelid. For the past 7 years, the bandage contact lens has not been used and no difference in patient comfort, flap displacement, or epithelial ingrowth after retreatment has been noticed.
The principles of this technique, including the use of a triangular sponge to ensure no epithelium overlies the flap edge prior to replacing the flap, can be used in primary LASIK procedures performed with the microkeratome or the femtosecond laser to decrease the incidence of epithelial ingrowth. The technique can also be used in the early postoperative period to lift the flap to remove striae or repair flap displacements to limit subsequent epithelial ingrowth.
Supplementary data
Video. The flaporhexis technique for performing LASIK enhancement.
References
- . Laser in situ keratomileusis retreatment for residual myopia and astigmatism. J Refract Surg. 2000;16:170–176
- . Incidence and associations of retreatment after LASIK. Ophthalmology. 2003;110:748–754
- . Post-laser assisted in situ keratomileusis epithelial ingrowth and its relation to pretreatment refractive error. Cornea. 2011;30:550–552
- . Epithelial ingrowth after laser in situ keratomileusis. Am J Ophthalmol. 2000;129:746–751
- . Incidence and prevention of epithelial growth within the interface after laser in situ keratomileusis. Cornea. 2000;19:170–173
- . Incidence of epithelial ingrowth in primary and retreatment laser in situ keratomileusis. J Cataract Refract Surg. 2010;36:97–101
- . Femtosecond laser and microkeratome LASIK flaps: comparison of stromal wound healing and inflammation. J Refract Surg. 2007;23:667–676Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698458/pdf/nihms118773.pdfAccessed September 26, 2011
First author:
Steven E. Wilson, MD
Cole Eye Institute, The Cleveland Clinic, Cleveland, Ohio, USA
PII: S0886-3350(11)01571-9
doi:10.1016/j.jcrs.2011.10.015
© 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.
Volume 38, Issue 1 , Pages 2-4, January 2012
