‘Infolded’ LASIK flap: an unusual variant of early postoperative flap dislocation
- 1 Cornea Service, The Cornea Institute, LV Prasad Eye Institute, Hyderabad, Telangana, India
- 2 Cataract and Refractive Services, LV Prasad Eye Institute, Hyderabad, Telangana, India
- 3 GPR ICARE, LV Prasad Eye Institute, Hyderabad, Telangana, India
- Correspondence to Dr Somasheila I Murthy; smurthy@lvpei.org
Abstract
Flap displacement is a rare but vision-threatening complication of laser-assisted in situ keratomileusis (LASIK). A young male patient underwent uneventful microkeratome-assisted LASIK. One-week postoperatively, flap displacement was noted in his right eye with its lower edge folded inwards, macrostria at the superior edge and the epithelium covering the bare stroma and into the interface. Anterior segment optical coherence tomography (AS-OCT) delineated the morphology of the displaced flap and the extent of epithelial ingrowth. The flap was repositioned by unrolling the fold and all the exposed surfaces were debrided to remove the epithelial ingrowth. Two months later, his corrected distance visual acuity improved to 20/30, and a smooth surface could be achieved. Infolded LASIK flap is a rare complication, which requires timely surgical intervention to achieve successful anatomical and functional outcomes. AS-OCT can be pivotal in determining the extent of infolding as well to delineate the extent of epithelial ingrowth within the interface.
Background
Laser-assisted in situ keratomileusis (LASIK) is the most common procedure to get rid of glasses.1 Its popularity over surface ablation lies in its advantages of minimal postoperative discomfort and faster visual recovery. However, creation of a flap has inherent risks such as incomplete flaps, buttonholing, free caps, flap slippage, dislocation, folds and microstria. Galvis et al have reported the rate of repositioning for flap folds or dislocations to range from 0% and 12.8% in a literature review of various published series.1 These flap dislocations or slippages most likely occur in the early postoperative period due to eye rubbing or tight squeezing of the eyes or even with normal blinking when there is either excessive lacrimation or a dry ocular surface.2 We present a case of non-traumatic LASIK flap displacement that had unusually folded inwards when the patient presented at 1 week postoperatively. With the help of imaging on optical coherence tomography, we were able to delineate the configuration of the folded flap and also the location and extent of the epithelial ingrowth. We also discuss the surgical technique used to manage this complication.
Case presentation
A male patient in his early 20s underwent routine screening for refractive surgery. The uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were 20/400 and 20/40+2 with −8.00–1.50D×40 in the right eye (oculus dexter (OD) and 20/80+2 and 20/20 with −3.25–0.75×125 in the left eye (oculus sinister OS), respectively. Anterior and posterior segment examination of both eyes was within normal limits except for scars of barrage laser photocoagulation in the peripheral retina. Corneal tomography using Pentacam HR (Allegro Oculyzer II, WaveLight GmbH, Wetzlar, Germany) showed keratometry (K) readings of 41.2/42.7 D×35.9 in the OD and 41.8/46.6×138 in OS. The thinnest pachymetry in OD and OS was 535 mm and 547 mm, respectively. No signs of suspicion of corneal ectasia were observed in the corneal topography. He chose to undergo microkeratome-assisted LASIK (Moria microkeratome, Moria, SA, Antony, France) was performed in both eyes with flap target depth of 90 micron and with ring diameter of 8 mm and a nasal hinge. The surgery was uneventful. Routine slit lamp examination 30 min postoperatively showed a well apposed flap in both eyes.
Postoperative treatment included moxifloxacin hydrochloride 0.5% eye drops four times a day for 1 week, fluorometholone acetate 0.1% suspension four times a day and sodium hyaluronate 0.1% eye drops four times a day. One week post-LASIK, he was asymptomatic. He did not recall any history of trauma or eye rubbing. UDVA was 20/60 in OD and 20/20 in OS. On slit lamp examination, the OD flap was noted to be folded inferiorly from 1600 to 1900 hours position and the stroma devoid of the flap was covered with epithelium. Nests of epithelial cells were also noted in the interface superior to the flap fold. A few flap macrostriae were noted superonasally (figure 1A,B). A diagnosis of LASIK flap displacement was made.
(A–D) Slit lamp image of the right eye in diffuse illumination (A) shows the inferior edge of the folded flap (yellow arrow) from 1600 to 1900 hour position, nests of epithelial cells in the interface superior to the flap fold (white asterisk) and flap macro striae noted supero-nasally (blue arrow). Slit-beam illumination under high magnification (B) shows the folded flap in the anterior stroma. Anterior segment optical coherence tomography (C) delineates the inferior edge of the folded flap (blue arrowhead) and the hyperreflective band of epithelial ingrowth (yellow arrow). The epithelial cells appear to be tailing off towards the superior edge of the fold (D) (yellow arrow).
Investigations
Anterior segment optical coherence tomography ((AS-OCT, RTVue, Optovue, Fremont, California) confirmed that the flap was folded inwards with a hyperreflective linear band of epithelium noted below the folded flap, tailing off as hyper-reflective dots towards the superior part of the interface (figure 1C,D).
Treatment
Flap repositioning was performed the same day, in the LASIK suite. The inferior loose epithelium on the bare stroma was removed with a Merocel sponge and the flap was carefully lifted to expose the fold, which was unrolled with the help of a cannula. A few drops of 20% alcohol were placed on the undersurface of the flap and on the bed for 20 s and washed off with balanced salt solution (BSS). A blunt-tipped hockey stick blade was used to ease out the fold on the undersurface of the flap and to debride the interface gently. The epithelium located beyond the flap edge inferiorly was debrided till the inferior limbus. The flap was repositioned and after it adhered to the bed, the epithelium of the flap starting from 2 mm within the superior edge till the inferior flap edge was debrided. After the flap appeared to be well adhered, and repositioned back with good orientation and alignment, the folds on the surface were massaged and stretched out repeatedly with the help of a moistened Merocel sponge with firm stokes directed downwards. After checking for firm adhesion, a bandage contact lens (Acuvue Oasys, Florida) was placed. Video 1 shows the surgical steps of management of flap repositioning. Postrepositioning, prednisolone acetate 1% ophthalmic suspension was started every 4 hours for 1 week and then tapered over 4 weeks, moxifloxacin hydrochloride 0.5% eye drops four times a day for 1 week and sodium hyaluronate 0.1% eye drops four times a day.
Outcome and follow-up
The UDVA improved to 20/40 and CDVA improved to 20/30 at the 2-month visit with refraction of +0.50–0.75D×90. The bandage contact lens was removed after 2 weeks. The flap was well apposed with intact epithelium and a nebular scar close to the inferior edge of the flap was present (figure 2A–C). AS-OCT (figure 2D) confirmed the proper alignment of the flap with a smooth anterior surface.
(A–D) Slit lamp images 2 months postoperatively shows a well-opposed flap in the slit-section (A). No striae are seen, but a small nebular opacity inferior to the flap is noted in the broad slit-beam illumination (B), diffuse illumination shows a smooth optical surface (C). Optical coherence tomography (D) shows restoration of the contour with a thinner flap evident nasally as compared with temporally.
Discussion
A survey presented at the Refractive Surgery Interest Group at the American Academy of Ophthalmology meeting found the mean percentage of occurrence of slipped flaps to be 0.1% and of flap striae to be 1.3%.3 Aetiologic factors include initial intraoperative misalignment, persistent interface fluid, excessive flap dehydration, trauma while removing the eyelid speculum, eye rubbing and early alteration of lubrication, which can cause adherence of the flap to the tarsal conjunctiva.4–6 AS-OCT has emerged as a useful imaging modality to assess the location, extent and morphology of the dislodged flaps.7 This new tool is also very useful in detecting other complications related to the LASIK flap, such as interface fluid syndrome also known as post-LASIK oedema-induced keratopathy.8 9 In the current case, it was invaluable not only in delineating the configuration of the fold but also the superior extent and the location of epithelial ingrowth, which was seen both as a dense hyperreflectivity below the area of the fold as well as extending above this zone. It is not clear how the patient had the dislocation, as he denied any history of eye rubbing; however, it is known that even excessive tearing or lid squeezing can cause this complication. The patient was asymptomatic for pain or watering as the bare stroma was covered by epithelium, leaving no epithelial defect and in terms of vision, being a high myope and amblyope, he did not note poor vision in his right eye. Contrary to what one would expect that a flap would fold or roll outwards due to the action of the lids, the folding inwards of the flap was the unusual feature in this case. We speculate that the thinner LASIK flap (90 microns), which could have been even thinner inferiorly, and flatter cornea may have been contributory factors associated with this complication and may have led to this unusual morphology of the fold, but we cannot be certain of the exact mechanism.
The principles of surgical management in such a situation involves four steps: 1: epithelial debridement: as the epithelium grows rapidly like a bridge over the pleat-like folds in the flap it freezes the flap, and these folds cannot be removed by simple smoothening unless the epithelium is debrided. In our experience, we have noted that this can happen as rapidly as 24 hours. The epithelium beyond the area of repositioning should also be debrided till the limbus in order to impede the growth of the epithelium upto flap edge, which could creep again into the interface. 2: Flap relifting and scraping of the flap undersurface and interface to get rid of epithelial cells lodged in the interface. 3: Hydration of the flap either with BSS or application of minimal heat or hypertonic saline and smoothening it with the help of either moistened surgical sponges or blunt tipped spatula. 4: Repositioning of the flap and ensuring complete adherence and alignment, enhanced if necessary, with the help of sutures or fibrin glue and placement of a bandage contact lens. Other manoeuvres such as a sandwich compression manoeuvre have been described, which involves using forceps to squeeze the flap and smoothen both surfaces.1 4 5 However, the chances of traumatising the flap are higher. Although the final result of the case was adequate, recognition of the LASIK flap displacement, which most likely occurred in the first 24 hours, would have been detected and managed earlier if the patient had been evaluated on the first postoperative day, in addition to performing the examination in the immediate postoperative period (30 min after the procedure), since at that time, as we described, the flap subluxation had not yet occurred. This schedule of repeated postoperative examinations in the early period after LASIK, suggested by Galvis et al, may increase the safety of the procedure.1
Learning points
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Flap displacements and flap striae are important complications of laser-assisted in situ keratomileusis (LASIK), which can lead to significant loss in uncorrected distance visual acuity postoperatively.
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Combination of focal de-epithelialisation, flap relifting, stretching and moderate hydration with hypotonic solution ensures good repositioning of the displaced flap.
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Infolded LASIK flap is a rare complication, which requires timely as well a tailored systematic surgical approach to achieve successful anatomical and functional outcomes.
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Anterior segment optical coherence tomography can be pivotal in determining the extent of infolding as well to delineate the extent of epithelial ingrowth within the interface to plan the management appropriately
Ethics statements
Patient consent for publication
Footnotes
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Contributors SIM contributed to the concept, and draft, final revision and managed the case. RPP wrote the initial draft, data acquisition, images and final draft preparation. VA and VMR contributed to interpretation of results and final draft.
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Funding This study was funded by Hyderabad Eye Research Foundation (LEC -BHR-R-10-21-759).
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Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
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Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.
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