Chapter 22 – Management of LASIK Complications

Chapter 22 – Management of LASIK Complications


• The management of LASIK complications involves an appreciation of specific pathogenetic mechanisms, knowledge of appropriate interventional measures, and careful observation of surgical outcomes.

• Serious microkeratome-related complications often require repositioning of the flap and postponing laser ablation.
• Laser-related complications and other postoperative complications require flap.

• Intraoperative complications include incomplete cuts, free cap, buttonholing, corneal perforation, poor coupling to the globe, epithelial defects, wound dehiscence, slicing, bleeding, decentration, edema, irregular ablation, central islands, interface debris, and flap wrinkles.
• Postoperative complications include overcorrections, undercorrections, sliding, dislodged flap, flap loss, diffuse lamellar keratitis (DLK), infectious keratitis, epithelial ingrowth, flap melt, regression, corneal ectasia, glare, and night vision problems.

The majority of LASIK complications occur intraoperatively. Preoperative complications are related to the preparation for the procedure. Postoperative complications are almost always related to events that occurred during surgery. Many complications unique to LASIK are microkeratome related. With improvement in microkeratome technology, the incidence of LASIK complications has been substantially reduced and may decrease further as instrumentation becomes more sophisticated.[1] In one study,[2] the incidence of intraoperative complications decreased from 2.1% during the first 3 months to 0.7% during the last 9 months of the study, proving that the complication rates can be reduced as the surgical team gains experience. Most intra- and postoperative complications are common to myopic and hyperopic LASIK. Several complications may be prevented if the eye is examined on the slit lamp in the direct postoperative period.
This chapter summarizes the information obtained through an Advanced PubMed (National Library of Medicine) search for all articles reporting on LASIK complications as well as their management. The literature was searched using Medline (key word “LASIK” or “laser-assisted in situ keratomileusis”) and using citations from the articles obtained.

Figure 22-1 Attempting to extend the flap using a blade is not advisable because of the risk of flap perforation. (From Melki SA, Azar DT. Eight pearls in prevention and management of LASIK complications. In: Melki SA, Azar DT, eds. 101 Pearls in refractive, cataract, and corneal surgery. Thorofare, NJ: Slack; 2001:23–32.)
This search revealed that LASIK is not simply a blend of photorefractive keratectomy (PRK) and keratomileusis. [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] Although effective methods are available to deal with many LASIK complications, others are still subject to investigation. A comprehensive awareness of the potential complications of LASIK and the numerous strategies to handle them is fundamental for surgeons performing the procedure.
Microkeratome-Related Complications
These complications are related to the learning curve associated with microkeratome use. Experience with the Hansatome, Moria M-2, and new horizontal microkeratomes suggests that their use will significantly reduce the incidence of serious LASIK complications.
INCOMPLETE OR IRREGULAR CUT. [1] [5] [14] [15] [16] [17] [18] [19]
Incomplete flaps occur when the microkeratome blade comes to a halt before reaching the intended location of the hinge. Visual aberrations are most likely to occur when the new hinge results in scarring in proximity to the visual axis.
In cases in which the microkeratome head is jammed, the suction should be released, followed by careful removal of the suction-microkeratome complex from the eye.
If the exposed stromal bed is not large enough to allow adequate laser ablation, the flap should be repositioned and the laser procedure postponed. Irrigation of the flap-stromal interface is performed in a manner similar to that in uncomplicated LASIK. The flap is then flattened carefully and dried. Resuming

forward cutting after stoppage may result in an irregular stromal bed and irregular astigmatism.
If the created hinge is beyond the visual axis, some surgeons may consider manually extending the dissection with a blade ( Fig. 22-1 ). Caution is advised when attempting such a maneuver because of the risks of uneven bed creation and flap buttonhole formation.[1] When the laser ablation is performed, the flap should be protected from laser exposure. Placement of a metallic plate or a surgical sponge over the flap may prevent inadvertent laser ablation on the hinge and flap.
With irregular cuts, the surgeon should not proceed with the ablation, but the flap or fragments thereof should be carefully replaced and realigned to their original position using the gutter width as a landmark. The pieces should fit together like a jigsaw puzzle. Additional waiting/drying time is used, and a bandage contact lens overnight may be considered if the epithelium is rough.
A LASIK flap may be fashioned 3 to 6 months later, assuming there was an uneventful postoperative course. It is advisable to attempt a deeper and more peripheral cut during the retreatment. Factors to consider in setting the depth for the second pass include corneal thickness and amount of tissue ablation contemplated.
In more serious situations, it may be necessary to perform a lamellar keratoplasty at least 6 months after the initial operation.
This may be due to inadvertent omission of the stopper or to the use of a thin suction ring on a flat cornea (Moria microkeratomes).[17] [18] [20] [21] [22] [23] [24] [25] In instances when a free cap is not visible on the surface of the cornea, the microkeratome head should be carefully inspected and, if need be, disassembled because the cap is probably inside the instrument.
Preplaced corneal marks with gentian violet used for proper orientation and careful attention during retrieval of the cap from the microkeratome head allow favorable management of a free cap.[26] If the diameter of the exposed stroma is equal to or larger than the intended laser ablation zone, laser treatment may proceed as planned. The cap is then retrieved from the antidesiccation chamber and repositioned using the preplaced marks. Proper orientation is important. The width of the gutter should be observed and a blunt atraumatic Merocel sponge sweep may be used for this purpose.
Chatter marks from vibration along the edges of the bed due to blade oscillation can often be of assistance; in order to highlight them better, the surgeon should use high magnification. It is important that the cap is replaced, epithelial side up, on the stromal bed. It has been suggested that the free cap be floated on a bed of balanced salt solution (BSS) and allowed to adhere spontaneously to the stroma assisted by careful placement of a Merocel sponge at different gutter positions. The bed of BSS will slowly disappear by capillary action toward the dry Merocel sponge, assuring even wrinkle-free adherence of the free cap to the corneal stroma. Care must be taken in aligning the preplaced corneal marks. Cap and stromal adhesion should be ensured by allowing adequate time of contact; 5 to 8 minutes should be sufficient for this purpose. Performing the striae test to check for adherence may be valuable. A dry Merocel sponge is used to exert light pressure on the outer section of the gutter of resection. Good adhesion is manifest as formation of striae that radiate from the point of pressure toward the center of the cornea. Sutures are seldom necessary but may be placed in an antitorque, external compression, or interrupted fashion.[26] A bandage contact lens may be placed in order to protect the cap, especially if the epithelium has been damaged. Some surgeons prefer to avoid the use of a bandage contact lens if the epithelium is intact because the lens may dislocate the cap.[27] Slit-lamp evaluation of the cap should be performed.
The potential for cap loss is real if the patient does not exercise caution in the early postoperative period. Wearing eye shields at night and special protective polycarbonate eyewear for sports activities is helpful. The patient should also be advised against eye rubbing because of the potential of cap dislocation.
If the suction is broken during passage of the microkeratome, the blade will surface; an irregular cap with a cut through the central cornea may result.
If the intraocular pressure is too low during passage of the head, a thin or “donut-shaped” flap or cap is likely to be created; it will probably be small in diameter.
Nonuniform cutting speed[28] in case of a manually advanced microkeratome may also predispose to this complication. [6] [14] [17] [25] [29] [30] [31] [32] [33] Buttonholed flaps can provide a channel for epithelial cells to infiltrate the flap-stroma interface. There is also an increased risk of subepithelial scar formation in flaps with buttonholes. Steep corneas (>46D) have been compared with tennis balls that buckle centrally under applanating pressure, resulting in a central dimple missed by the blade leading to a buttonhole. Another theory is that higher keratometric values offer increased resistance to cutting when applanated, leading to upward movement of the blade. The latter is probably more applicable to keratomes with lower blade oscillation rates. Blunted blades, poor oscillation, and microflaws of blades have also been described as mechanical microkeratome problems that may lead to buttonholes. [34] [35] [36] Inadequate coupling of the blade to the cornea is often due to poor suction.[37] [38] Another possible risk factor for flap buttonhole occurrence is previous ocular surgery. [2] A higher incidence of buttonholes with large flaps when using the Hansatome is reported. It is theorized that the larger area required for flattening may result in central dimpling if the intraocular pressure is not adequate.[39]
The safest way to proceed when a buttonholed flap is encountered is to avoid lifting the flap or immediately reposition the flap and abort the procedure. Epithelial debris should be gently irrigated out with BSS.
Although some advocate proceeding with scraping the epithelium and performing a PRK laser ablation within 2 weeks,[40] this approach may not be feasible in higher myopes because of the appearance of unexpected subepithelial haze.[41] A bandage contact lens should be used to protect the buttonholed flap from migration.
Most patients with buttonholes end up with no significant loss of vision after adequate healing has occurred, especially if uncomplicated by epithelial ingrowth ( Fig. 22-2 ). Epithelial ingrowth after a buttonhole can be central or in the periphery.[27] Management of epithelial ingrowth of this type can be very frustrating. Often the only viable option is discarding what remains of the flap. Reepithelialization is then allowed to occur with subsequent performance of phototherapeutic keratectomy (PTK) later.
The long-term approach to these eyes may be (1) soft contact lenses, (2) gas-permeable contact lenses, (3) retreatment with LASIK 3 to 6 months later if adequate thickness remains, (4) PRK (high risk of haze and irregular astigmatism), and (5) complete flap removal with PTK.
All LASIK surgeons should possess a good understanding of the mechanics, assembly, and calibration of the microkeratome being used.
This complication is almost always due to human error in placing the plate and controlling depth of cut in instruments such as the automated corneal shaper.
Anterior chamber penetration may occur during lamellar dissection [14] [42] [43] or through laser ablation.[44] [45] Globe perforation may range from a simple corneal perforation to perforation with damage to the iris and crystalline lens with or without vitreous loss. Corneal perforation may result from excessively thin corneas, for instance, following old corneal wounds, ulcers, or previous refractive surgery.[44]
Most modern microkeratomes have an integrated plate; thus, the risk of corneal perforation is avoided. With these newer microkeratomes,


Figure 22-2 A, Corneal reflex showing irregular flap and stromal bed. (From Melki SA, Azar DT. Eight pearls in prevention and management of LASIK complications. In: Melki SA, Azar DT, eds. 101 Pearls in refractive, cataract, and corneal surgery. Thorofare, NJ: Slack; 2001:23–32.) B, Epithelial irregularity overlapping area of buttonholed flap without associated loss of visual acuity.
perforation occurs only if the surgeon performs the lamellar cut on a very thin or irregular cornea or a cornea with advanced keratoconus. It is therefore mandatory to perform accurate pachymetry at several points on the cornea.
Immediate closure of the corneal wound with 10-0 nylon sutures should be performed. Further management depends on the severity of the damage caused to the globe. An ocular protective shield should be placed, and the patient is asked to try to relax and minimize straining and coughing. The patient should be transferred to the major operating room and given general anesthesia after ensuring adequate closure of the corneal entry site. Administration of local periocular anesthesia increases the potential risks of ocular damage during surgical repair of an open globe. Repair may involve corneal repair, iris repair, lensectomy with or without intraocular lens implantation, and anterior and/or posterior vitrectomy.
A contact lens may be necessary postoperatively. Aphakic contact lenses with or without an artificial pupil may be required. There may be a need for a secondary intraocular lens implantation (posterior chamber, iris-sutured, or trans-scleral sutured). In some instances a rotational or penetrating keratoplasty (PK) may be required for visual rehabilitation.
Inadequate Suction.
Inadequate suction or total loss of suction is a potential source of serious problems during LASIK. The result maybe a thin or superficial flap, a buttonhole or interrupted flap, or an irregular flap.
If chemosis is induced from repeated suction ring placement, an incision in the conjunctiva may allow drainage of excess fluid; alternatively, blunt instruments such as a Merocel sponge, the handle of a swab, or a forceps can be used in an attempt to “milk” the fluid away from the limbus.
A better alternative is to wait 30 to 45 minutes and then try again. It is best to postpone the procedure for 1 to 2 days and allow the subconjunctival edema to reabsorb.
Inadequate Exposure.
Microkeratome placement is more difficult in sunken globes and in eyes with narrow palpebral fissures and small corneas.[14] The use of the newer generation microkeratomes with the down-up flap has overcome this obstacle. By turning the head of the patient slightly to the opposite side or by exerting a gentle pull and tilt on the eye through the suction ring handle, these cases can be operated on easily. Other authors advise using a manual dissection[16] of the corneal flap or another refractive procedure.

PRK or laser subepithelial keratomileusis (LASEK) should be considered if appropriate when suction cannot be obtained. A lateral canthotomy may be indicated. Alternatively, it may be possible to operate without using a speculum. If a speculum is not used, one must ensure that the eyelashes and the eyelids do not overlap and cover the ring, especially the track. In small eyes, an axial length measurement performed preoperatively allows the surgeon to select the correct ring diameter for the operation (under the circumstances, the standard 11?mm suction ring may not be suitable). A retrobulbar injection to cause proptosis of the globe has been suggested. This is a valid technique but may induce chemosis-related problems described previously, as can repeated attempts to place the ring. The patient with a prominent brow should be positioned with the chin raised slightly, as this will maximize exposure. [1]
This complication is usually caused by microkeratome head passage over a dry corneal surface. In the event of detachment, the epithelium is repositioned if possible. A loose-fitting bandage contact lens is used to protect the epithelium, with antibiotic coverage to avoid secondary infection. These measures help in pain control as well as improving flap adherence and preventing epithelial cell ingrowth. [47] [48] [49] Nonsteroidal anti-inflammatory drug [49] [50] [51] [52] [53] [54] drops may be used minimally (twice daily for 2 days maximum), as these will slow reepithelialization.
The bandage lens is removed as soon as epithelization is nearly complete. It should be thoroughly hydrated with artificial tears and a drop of anesthetic and floated on the corneal surface prior to gentle removal. Care should be taken to rule out an epithelial defect masquerade syndrome, a newly described, well-defined syndrome in which unrecognized epithelial ingrowth contributes to a persistent epithelial defect.[47]
Patients with a history of recurrent erosions[55] [56] and/or anterior basement membrane dystrophy (ABMD) are at higher risk of developing epithelial abrasions with LASIK and would probably be better PRK candidates. [57] [58] [59] [60] [61]
This complication may occur when a flap is being cut on a cornea-grafted eye. The high intraocular pressure exerted during the application of the suction ring is the cause. Several surgeons find LASIK a good treatment for the myopic and astigmatic refractive errors after a PK. Yet the time of surgery is still debatable. The consensus is to delay the LASIK procedure as much as possible after a PK. The presence of a good wound scar and the documentation of refractive and topographic stability for at least 3 months after removal of all keratoplasty sutures are good signs to do the surgery.[62] Surgeons should always warn their patient about this potential complication.

In these cases, the same treatment as for corneal penetration may apply.
This complication may occur when a flap is cut in an eye that had radial keratotomy (RK) with the incisions extending beyond the 8–9?mm central area. Inadequate healing of the RK incisions causes a part of the flap to separate in a triangular shape. An epithelial plug in the incision almost always precipitates this complication. As a rule, always check the RK incisions under the microscope before cutting the flap.
This usually occurs when the microkeratome blade hits limbal vessels in case of a decentered flap or corneal pannus in contact lens wearers. Bleeding can be minimized in the following ways:

Apply a dry sponge to the bleeding area (if bleeding is localized) and exert slight pressure (sufficient to arrest it) or wick away the blood and simultaneously perform the ablation.

A Gimbel-Chayet sponge may be used to prevent the blood from oozing into the bed, as well as elevating the flap and keeping fat and debris in the tear film from coming into contact with the interface.

Leave the flap in position and wait until coagulation begins and bleeding diminishes.

Pressurized air can be used as a vasoconstrictor and to encourage coagulation.

In uncontrolled bleeding, the suction ring may be reapplied and pressure reactivated for the duration of the ablation; this will arrest bleeding until the end of treatment but should not be used longer than 30 seconds. A lower negative pressure would be better, which is available with some microkeratomes. A simple way of doing this is to perforate the suction tubing with a needle (the tubing will be discarded at the end of the surgery). Pressure can be instantly activated as needed by occluding the perforation.
Continuous oozing at the end of the procedure is stopped by flap replacement, irrigation, and smoothing, which closes the interface and tamponades the vessels.
If the flap is decentered and the area for ablation is adequate, the surgeon may proceed with laser treatment, possibly with a slight reduction in the optical zone. If this is not possible, the flap is repositioned and the operation repeated in 3 to 4 months. This is particularly important in hyperopic or astigmatic treatments and when a large ablation zone is planned.
The safest way to proceed when a thin or irregular flap is encountered is to reposition the flap and abort the procedure (see Fig. 22-2 ). It may be tempting to lift a thin flap and treat with the laser. If the thin flap has sufficient stromal tissue (i.e., sparing Bowman’s layer) and is of sufficient size, laser ablation may be possible.[27]
In cases of thin, irregular, or decentered flaps, a deeper flap may be recut (20–60?µm deeper) approximately 10–12 weeks later (after confirming a stable refraction) and the LASIK procedure completed. Three months seems to be the well-accepted time for reoperations. Although there have been reports of reoperations performed at earlier times, the risk of flap slippage during the reoperation may outweigh the benefits of early visual rehabilitation. A deeper properly placed flap during reoperation is essential, especially in hyperopic procedures requiring large ablation zones.[1]
Others advocate using a no-touch transepithelial PRK within 2 weeks of the initial irregular cut to prevent irregular astigmatism formation from the uneven ablation profile resulting from any late scar formation.[30] [64] This technique seems reasonable, especially in low myopes. During the reoperation, one can perform transepithelial PRK to eliminate the scar. This is best performed in cases with a very superficial cut and within the first few weeks after the initial procedure.
Having an edematous flap precludes the possibility of having a hassle-free adhesion of the flap to the

Figure 22-3 A, Temporal decentration after LASIK. B, Topographical pattern of pseudodecentration in a patient with lost LASIK cap. (From Johnson JD, Azar DT. Surgically induced topographical abnormalities after LASIK: management of central islands, corneal ectasia, decentration, and irregular astigmatism. Curr Opin Ophthalmol. 2001;12:309–17.)
stromal bed. Flap decentration or displacement may occur. This occurrence has been notorious enough to merit a name the “floating flap” phenomenon.[27]
Prolonged manipulation of the flap will traumatize the flap. Overzealous fluid irrigation under the flap is believed to be the culprit in producing an edematous flap.
Attempting to distend the flap gently with a nearly dry Merocel sponge or a blunt spatula to milk the flap may help. The use of the instruments such as the Pineda LASIK flap iron or the Caro island masher may be handy in flattening out these edematous corneas. In severe cases, suturing of the flap may be necessary in order to prevent flap migration. Aggressive use of topical steroids postoperatively may expedite the resolution of corneal edema.
Photoablation-Related Complications
DECENTRATION.[8] [15] [16] [20] [21] [24] [65] [66] [67] [68] [69]
Significant decentration is defined as ablation center displacement from the pupil center by 0.5?mm or more ( Fig. 22-3 ). Decentration may be precipitated by a decentered laser beam prior to ablation (shift) or to eye drift during ablation (drift).[65] [70] Decentration in LASIK may be

precipitated by the higher amount of correction attempted; the duration of the treatment becoming longer allows much more time for patient drift to occur. The poor unaided vision of the high myopes combined with the progressive decrease in visibility of the fixation target during ablation exacerbates the existing fixation difficulties. [65]
Correction of a decentered ablation is possible with ablation correlated to the topography (topolink treatment). In reality, it is not as simple. Frequently, two—one on the top of the other—do not integrate well; there is often excessive removal of the tissue and residual astigmatism persists.
An alternative method for recentering an ablation without topolink treatment is to use a recentering system, such as the one devised by Vinciguerra. This method is based on the concept that with a decentered ablation, recentering requires the ablation of a larger, deeper area that will include the decentered area. In this way, the surgeon can obtain a correction equal to that originally expected. A decentered ablation will cause an asymmetry of the optical zone through excessive ablation in some areas and insufficient ablation in others. The asymmetry is directly proportional to the amount of decentration. Moreover, the greater the decentration and the greater the visual defect to be corrected, the greater the visual reduction.
A secondary complementary ablation can be performed to produce an evenly ablated area. Using algorithms, the depth of the new ablation is calculated. By evaluating a tangential corneal topography, the center of the decentered zone, the axis for retreatment, or the axis of decentration must be calculated.
The Vinciguerra system consists of:

A suction mask with blocking positions at 45°, 90°, 135°, 180°, 225°, and 270°.

A cross-shaped reference point for centration.

7 to 10 diaphragms used for successive ablations.

PTK is then performed to smooth the newly ablated area.
Unfortunately, using the total algorithm results in decentration in the opposite direction. This may be due to the fact that the greater the degree of decentration, the less the validity of the topography. Therefore, it is more difficult to perform the calculations. In any case, it is easier to perform an additional treatment if 50% of the algorithm is used.
The combined treatment and retreatment create a well-centered ablation, the optical zone is wider, the ablation is deeper, and the final refraction outcome corresponds to the value originally expected. In order to do this, it is of the utmost importance to correlate the exact algorithm to the amount of decentration. All this produces a thinning of the cornea that is greater than the decentration of the initial error to be corrected and the initial optical zone used.
CENTRAL ISLANDS.[17] [71] [72] [73]
Central islands are diagnosed on corneal topography as central steep areas within the treatment zone and are defined by their width (=2?mm) and dioptric height (=3 keratometric diopters) ( Fig. 22-4 ). Central islands can cause irregular postoperative astigmatism, glare, ghosting and halo effect, loss of best-corrected visual acuity (BCVA), and monocular diplopia.
When faced with the diagnosis of a central island, always rule out iatrogenic keratectasia of the posterior corneal surface, especially in high myopia correction. Central islands should be treated conservatively as they may tend to resolve spontaneously, although not as successfully as with PRK, which forces the epithelium to undergo more extensive remodeling. Patient reassurance is needed pending possible laser retreatment. Statistics demonstrate that the incidence of central islands with broad-beam lasers is 80% in the first postoperative week, with a drop to 15% after 3 months and 5% after 6 months. When it persists for 6 months and more, one should consider treatment by laser ablation. Central islands are not seen with the flying spot laser. The amount of correction and diameter of the optical zone to be corrected depend

Figure 22-4 Central island after LASIK represented by axial topography (A) and profile map (B) showing approximately 5D island power. (From Johnson JD, Azar DT. Surgically induced topographical abnormalities after LASIK: management of central islands, corneal ectasia, decentration, and irregular astigmatism. Curr Opin Ophthalmol. 2001;12:309–17.)
on the corneal topography, according to Munnerlyn’s formula. In order to avoid a hyperopic shift, the conservative approach is recommended. It is better to undercorrect slightly ( Fig. 22-5 ). Treatment involves raising the original flap and then using laser ablation; treat with PRK or PTK mode centrally where the islands are found (see Fig. 22-5 ).
Two types of flap wrinkles are described. Those that occur intraoperatively are due to malpositioning of a thin flap (undetectable intraoperative misalignment of the corneal flap on the stromal bed). These wrinkles may not be detected with the operating laser microscope. Surgeons should inspect the flap at the slit lamp immediately after surgery to ensure that flap wrinkles are not present.
The second type occurs in the early postoperative period and might be caused by eye rubbing or by the eyelid pressure during


Figure 22-5 LASIK-induced central island power profile prior to (A) and after (B) surgical management, showing a decrease in central island curvature. (From Johnson JD, Azar DT. Surgically induced topographical abnormalities after LASIK: management of central islands, corneal ectasia, decentration, and irregular astigmatism. Curr Opin Ophthalmol. 2001;12:309–17.)
blinking. Slight sliding or dislodgment of the flap almost always accompanies this type. After instillation of fluorescein dye in the eye, an uneven pattern of pooling in the tear film may be detected.[74]
The intraoperative management of flap wrinkles, striae, and folds is gentle replacement of the flap to its original neutral position. Gentle refloating of the flap may be attempted. This is followed by systematic sweeps of a moistened Merocel sponge to smooth to flap from the hinge out. A single-parallel-direction technique may be used in attempting to smooth out the flap, or a central-to-peripheral radial technique may be undertaken. Fluid in the flap-stroma interface should be eliminated. Air drying time should be at least 4 minutes to increase the likelihood of good adhesion. Mechanical hot air dryers may prove useful in this situation. Occasionally the Pineda or Caro LASIK flap irons

Figure 22-6 Flap folds following LASIK causing topographical abnormalities that improved upon surgical ironing and smoothing of the flap. (From Johnson JD, Azar DT. Surgically induced topographical abnormalities after LASIK: management of central islands, corneal ectasia, decentration, and irregular astigmatism. Curr Opin Ophthalmol. 2001;12:309–17.)
may be used to flatten the corneal irregularities. Usually epithelial wrinkling, striae, or folds disappear spontaneously within a few days.
Flap folds can induce irregular astigmatism with optical aberrations and loss of BCVA, especially if they involve the visual axis. [75] [76] [77] They are easily visualized as negative-staining lines with sodium fluorescein[74] [78] or with retroillumination ( Fig. 22-6 ).
A higher incidence of flap folds is usually found in higher myopes and is sometimes unavoidable. This is due to the reduced central convexity and stromal support resulting in flap redundancy that may be quite difficult to flatten. The latter is referred to as the “tenting” effect.[79] Folds and striae that have been neglected by the surgeon may be treated weeks or even months after the surgery, although the success rate declines with passing time. [80] [81] [82] [83] [84] The technique is the same except that after the flap has been lifted and refloated, folds typically appear much more prominent than they previously did at the slit lamp. The principle of flap centration and peripheral smoothing is the same, except that much more vigorous “ironing” with the smooth side of a spatula or forceps (Pineda iron) is required. The epithelial surface should be allowed to dry so that adequate traction with the smoothing instrument is achieved. Similarly, dry Merocel sponges on a dry corneal surface may be used. After this 8- to 12-minute process, the epithelium is usually in poor condition and a bandage contact lens is required.
The postoperative management of flap folds ranges from simple lifting and refloating of the flap to placement of sutures to stretch the flap in position. It is likely that the earlier a flap is attended to, the higher the chances of quick resolution.[79] Fixed folds probably occur when epithelial hyperplasia has time to form in the crevices formed by the folds. Flattening should aim at an even distribution of forces applied to the flap.[77] [79] [80] [81] Instruments such as the Pineda or Caro LASIK flap iron can also be used to flatten isolated flaps at the slit lamp or under the operating microscope by gently pressing on them. Recalcitrant folds may respond well to placement of running antitorque sutures at the flap edge.[40] However, this may result in significant astigmatism. Another strategy is to make superficial


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