Late post-traumatic flap dislocation and macrostriae after laser in situ keratomileusis.

We report an unusual flap-related complication that occurred 4 years after uneventful laser in situ keratomileusis (LASIK) performed in the eye of a 20-year-old woman. She developed dislocation with partial infolding of the LASIK flap with macrostriae and epithelial ingrowth in her left eye after trauma by a wooden chip. The flap was refloated, stretched, smoothened, and hydrated on both under and outer surfaces after epithelial debridement. At 1 week, the uncorrected visual acuity was 20/20 with absence of flap striae. The present case highlights that flap adhesions are not very strong even months and years after LASIK. Flap refloatation and stretching with hydration on both sides of the flap are effective in removing flap striae.

Introdcution

Traumatic flap displacement is a known possible complication after laser in situ keratomileusis (LASIK).[1] It occurs most commonly in the first 24 h after surgery in approximately 1%-2% of cases.[2] However, late flap dislocations, defined as those occurring more than 1 week after the procedure, have been reported.[3] We present a case of traumatic flap displacement occurring 4 years after the initial LASIK surgery.

Case Report

A 26-year-old woman presented with pain and blurring of vision in the left eye following trauma with a wooden splinter 12 days back. She had a history of bilateral uncomplicated aspheric LASIK done 4 years back in both the eyes in a private refractive surgery clinic for a refractive error of -9.00DSph/-0.75DCyl@1250 in the right eye and -8.50DSph/-0.75DCyl@400 in the left eye. On examination, her uncorrected visual acuity (UCVA) was 20/20 in the right eye and 20/60 in the left eye. Slitlamp examination of the left eye revealed a superiorly displaced flap with prominent full-thickness dense macrostriae [Figure 1]. It was associated with epithelial ingrowth. The anterior chamber did not show any inflammatory reaction and the intraocular pressure was within normal limits. The right eye showed an evidence of previously performed LASIK in the form of a faint flap margin. The anterior segment was within normal limits and there was absence of any treatable lesion in the fundus.

Figure 1

Flap dislocation with macrostriae

Surgical repositioning of the flap was planned. With the help of a sinskey hook, the margin of the flap was demarcated. A LASIK spatula was insinuated in the pre-existing plane beneath the infolded flap. The dissection was continued circumferentially, freeing the temporal and nasal edges of the flap. After the central portion of the flap was freed, it was reflected on its superior hinge. The infolded portion of the flap was carefully dissected free with a moist merocel sponge and the spatula. The stromal surface of the reflected flap was thoroughly scraped to remove the epithelial ingrowth. The flap was repeatedly stretched and smoothened with forceps, and the undersurface of the flap was thoroughly hydrated. The epithelial ingrowth covering the inferior stromal bed was also removed with the spatula. The flap was reposited with a double cannula and the interface irrigated with balanced salt solution to remove any debris. The epithelium overlying the flap striae was scraped off and the underlying stroma hydrated and the flap smoothened with merocel sponge. A bandage contact lens was placed and one drop of moxifloxacin hydrochloride 0.5% eye drops was instilled. Postoperatively, the patient was prescribed moxifloxacin hydrochloride 0.5% TID, prednisolone acetate 1% eye drops TID, and carboxymethylcellulose 0.5% eye drops QID. On day 1 postoperatively, the bandage contact lens was removed and the UCVA was 20/25 with no evidence of epithelial defect, diffuse lamellar keratitis, or epithelial ingrowth. At 1 week, the patient's UCVA was 20/20 with absence of flap stria [Figure 2]. The patient maintained the same vision at the last follow-up of 2 years without any evidence of epithelial ingrowth.

Figure 2

Repositioned flap with absence of flap striae

Discussion

Late traumatic flap displacement from blunt or sharp trauma at various times after LASIK has been reported.[3] Studies of corneal wound healing after LASIK in rabbits[4] indicate that the wound-healing reaction occurs only at the periphery of the microkeratome wound, leaving the central optical zone clear. This healing response is beneficial to the patient, producing less visual axis scarring and allowing easy flap removal during enhancement surgery. However, it also predisposes the cornea to flap displacement due to trauma.

It is generally believed that the LASIK flap tends to fibrose progressively over time, making the flap resistant to dislocation. Analysis of human corneas after LASIK by Philipp et al.[5] showed only minimally increased staining of dermatan sulfate proteoglycan within the stroma adjacent to the lamellar flap, and only a few collagen lamellae were visible crossing between the residual stroma and the flap, accounting for the weak adhesion between the flap and stroma. This case illustrates that this weakening remains present even years after the initial procedure.

Visual prognosis is usually good in these cases, and loss of best-corrected visual acuity after flap repositioning is uncommon. However, optimal recovery may require management of complications including recurrence of striae, diffuse lamellar keratitis, and epithelial ingrowth. Epithelial ingrowth may begin as early as several hours after the dislocation and is typically treated with mechanical debridement, with careful attention to removing as much epithelium as possible from both the stromal and flap surfaces. Methods to prevent recurrence have included the use of absolute alcohol and flap suturing which is mostly required in late cases.[678] More recently, a method of sealing the flap edges with fibrin glue in recurrent epithelial ingrowth has been described, a method that may help prevent the invasion of epithelial cells while the flap adheres to the stromal bed.[9]

In the present case, as the patient presented at around 2 weeks of injury, we primarily planned flap lifting and refloatation with thorough scraping of the undersurface of the flap to remove the epithelial ingrowth. Intervention was planned in view of poor vision and risk of flap melt.[10] Stretching and smoothening of the flap were done followed by hydration of the stroma on both the under and outer surfaces of the flap. Since the superior two-thirds of the flap and the nasal hinge were not disturbed in our patient, the flap was not excessively distorted. The use of a bandage contact lens has been reported to reduce the chance of postoperative flap wrinkling,[11] and thus was used in our patient. The occurrence of repeated epithelial ingrowth after replacement of a detached lenticule after LASIK has been reported.[12] The reasons for this are not clear but could be the imprecise alignment of the flap edge with the corneal bed, greater irregularity of the two interface surfaces, and the presence of scarring along the flap edge. We carefully removed the epithelium in the inferior stromal bed, precisely along the margin of the original flap, to decrease the chances of misalignment. We did not use any suture as it may further induce astigmatism, and the suture track may act as a gateway for epithelial ingrowth. The use of fibrin glue as suggested by some authors[9] may be a good adjunct to prevent epithelial ingrowth. The glue forms a mechanical barrier and prevents the epithelial cells from growing underneath the flap, at least until the flap is healed. The glue typically dissolves gradually over a 2-week period and by then, the epithelial surface and stromal interface show complete healing with no cells in the interface. However, the major disadvantage of the use of fibrin glue for flap reattachment is that the glue is fairly opaque when it polymerizes and as a result it is difficult to see through it to determine if there are inflammatory cells in the interface. In addition, it is expensive and requires special equipment and preparation time.

Postoperatively, our patient had a vision of 20/20 without any discomfort, stria, or epithelial ingrowth which remained stable till last follow–up, i.e., around 2 years.

This case demonstrates the vulnerability of the LASIK flap to trauma even late after the procedure. Early recognition and management by refloating the flap along with stretching and smoothening and hydrating the flap on both sides may still be the best treatment option.