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CASE REPORT Suction loss during thin-flap femto-LASIK: Management and beneficial refractive effect of the epithelium David Smadja, MD, Marcony R. Santhiago, MD, Glauco Reggiani Mello, MD, Edgar M. Espana, MD, Ronald R. Krueger, MD, MSE We report the case of a 42-year-old man who experienced loss of suction during thin-flap femtolaser in situ keratomileusis, leading to a stromal step in the superior cornea where the cutting was stopped. The procedure was converted to photorefractive keratectomy 2 weeks later. Management of the loss of suction and the beneficial role played by the epithelium postoperatively on the refractive outcomes are discussed. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2012; 38:902–905 Q 2012 ASCRS and ESCRS Flap creation is one of the most important steps in the laser in situ keratomileusis (LASIK) procedure. Although the introduction of the femtosecond laser to create the flap has improved the safety and predictability of flap creation, complications still occur.1,2 Incomplete flap creation due to suction loss is a potentially vision-threatening complication, especially when it occurs in the central cornea. Recently, Haft et al.1 reported the complication rate of the femtoLASIK flap in 4472 eyes. The rate of suction loss was low, 0.06%. Binder3 also reported a small percentage of suction loss in 1000 eyes treated with femtosecond LASIK. Suction loss occurred in 8 eyes (0.8%); in 6 eyes, surgery was postponed and in 2 eyes, it was performed on the same day. We report a case in which suction loss occurred during femto-LASIK, resulting in a stromal step in the area where the cutting was stopped. The procedure was converted to photorefractive keratectomy (PRK) 2 weeks later. The stromal step corresponded to the area where the suction was lost and the laser cut was extended to a more anterior stromal plane. The Submitted: August 4, 2011. Final revision submitted: October 4, 2011. Accepted: October 5, 2011. From the Department of Refractive Surgery, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA. Corresponding author: David Smadja, MD, 1701 East 12th, W22Q– Cleveland, Ohio 44114, USA. E-mail: [email protected]. 902 Q 2012 ASCRS and ESCRS Published by Elsevier Inc. management of suction loss and the beneficial refractive effects of the epithelium, compensating for the stromal irregularity, are discussed. CASE REPORT A 42-year-old white man with no medical or ocular history was scheduled for myopic LASIK in his right eye, leaving the left eye with temporary monovision and possible correction later. The preoperative manifest refraction was 3.50 C1.25 2 in the right eye and 2.50 C0.75 174 in the left eye. The topography (Humphrey Atlas, Carl Zeiss Meditec AG) was normal (Figure 1). In the right eye, ultrasound pachymetry was 560 mm and the corneal diameter was 12.12 mm in the horizontal axis and 11.16 mm in the vertical axis. The wavefront measurement (Ladarwave, Alcon Laboratories, Inc.) through a 6.5 mm pupil in the right eye showed 0.42 mm root mean square (RMS) of higher-order aberrations, 0.26 mm RMS of coma, and 0.19 mm of spherical aberration. The LASIK procedure was performed in December 2010. The first step of the procedure used an Intralase 60 kHz femtosecond laser (Abbott Medical Optics, Inc.) to create the flap. The flap was 100 mm thick, 9.0 mm in diameter, and had a superior hinge and pocket. The laser parameters for the bed cut were 7 mm for the spot and line separations and 0.8 mJ for the laser pulse energy. After the center of the cornea was marked with a surgical marker, the suction ring was centered around the limbus before the suction was achieved. The laser’s cone was then docked into the suction ring and the cornea was found to be well centered (Figure 2, A). The laser cutting started from the upper part of the cornea; the lamellar dissection (raster pattern) extended to approximately the first third before suction loss occurred, before the cut reached the pupillary center (Figure 2, B). Because stopping the laser cut in this type of case is dependent on the surgeon’s reaction time in releasing 0886-3350/$ - see front matter doi:10.1016/j.jcrs.2012.02.004 CASE REPORT: MANAGEMENT OF SUCTION LOSS DURING THIN-FLAP FEMTO-LASIK 903 with the RTvue optical coherence tomography (OCT) (Optovue). It clearly showed how the epithelium had compensated for the stromal bed irregularity in this area, making the anterior surface smooth (Figure 3). DISCUSSION Management of Suction Loss Figure 1. Normal preoperative topography. the foot pedal, there is usually additional cutting in a more anterior stromal plane (Figure 2, C). After suction was unsuccessfully reapplied 3 times with instillation of a steroid drop before each attempt to reduce the inflammatory reaction and chemosis, the decision was made to postpone the procedure. Two weeks later, PRK was performed with mitomycin-C (MMC) 0.02% applied for 30 seconds and then copiously washed away. After the epithelium was removed, a fine stromal step could be seen in the superior part of the cornea, corresponding to the area where the suction was lost in the first procedure and the laser cut extended into a different plane. An excimer laser ablation using an optimized profile was completed on the stromal bed, and a bandage contact lens was inserted for a week. Postoperatively, the patient received topical prednisolone acetate 1% and moxifloxacin 4 times daily for 1 week, along with artificial tears as needed. The steroid drops were gradually tapered over the next 3 weeks. After 1 month, the uncorrected distance visual acuity was 20/25 with a manifest refraction of 0.50 C0.5 105. No sign of the superior stromal step was seen in the slitlamp examination, and the topography and wavefront aberrometry showed no increased irregularity (especially with coma remaining at the preoperative magnitude of 0.26 mm RMS). In addition to the topography and aberrometry, a highresolution cross-sectional image of the cornea was made It is well known that suction loss can be attributed to factors such as small palpebral fissures, excessive eyelid squeezing, small corneal diameter, conjunctival chemosis, or epithelium breakthrough. When suction loss occurs, a different approach should be considered, depending on the circumstances. If suction is lost during the lamellar dissection and before creation of the side cuts, attention must be paid to the area where the cutting was suspended. Unless this occurs in the pupillary axis, we recommend that suction is reapplied at the same location, using the same flap parameters, same suction ring, and same applanation cone to increase the chance of having the new cut within the primary dissection plane. The timing to recut is also important because the conjunctival shape can change if too much time elapses before the suction is reapplied. Although not scientifically determined, a recut within 10 minutes is generally recommended.A If suction cannot be reapplied, postponing the procedure for at least a few days is recommended.A In this circumstance, we think performing PRK the same day could be detrimental to epithelial wound healing because the corneal nerves had been acutely severed and local inflammation induced by the primary laser dissection. If the suction is lost in the central cornea, a second pass on the same day is not recommended.4 The potential for an irregular interface or the creation of 2 dissection planes due to differences in applanation pressure, corneal hydration, or conjunctival chemosis can be Figure 2. Thin-flap femto-LASIK creation. A: Well-centered cornea after applanation. B: Stromal lamellar dissection (raster bed pattern) starting normally from the superior cornea. C: Loss of suction during the lamellar dissection. One can clearly see 2 edges of the raster pattern (black and red arrows); the outermost one (red arrow) is due to the laser pulse delivery after suction loss and before the foot pedal was released. J CATARACT REFRACT SURG - VOL 38, MAY 2012 904 CASE REPORT: MANAGEMENT OF SUCTION LOSS DURING THIN-FLAP FEMTO-LASIK Figure 3. The OCT image of epithelial hyperplasia and corneal surface smoothing 1 month after PRK. The epithelium thickens in the periphery to compensate for the stromal depression reaching up to 145 mm thickness. Figure 4. Histological section of a cornea to illustrate the trajectory of the laser dissection. Left: The black line shows the intended dissection plane of the 100 mm flap. Right: The black line shows the trajectory of the dissection plane achieved by the laser. prejudicial to the visual outcomes, as this area is critical for visual quality. If the suction is lost during side-cut creation, recutting with a smaller flap diameter, reduced from 0.5 mm to 1.0 mm, is recommended as this prevents the creation of tissue slivers from the inexact intersection of the primary side-cut plane with the new one.4,A In our case, the unsuccessful reapplication of suction was probably related to the patient’s small palpebral fissure and the chemosis, which had compromised the chance of maintaining suction. This led us to postpone the procedure and perform PRK with MMC 0.02% 2 weeks later rather than another LASIK flap at a deeper plane. At the time of epithelial removal during the PRK, using ethanol 20% to minimize mechanical trauma, we observed a fine superficial stromal step due to the externalization of the laser dissection plane after suction loss (Figure 4). Considering a mean epithelial thickness of 40 to 50 mm,5 the intended flap depth of 100 mm, and the unexpected more superficial dissection plane achieved during the suction loss, the stromal step was unavoidable, even with careful epithelial dissection. Figure 5. Left: Topography 1 week after PRK showing lack of data in the superior cornea (arrow) due to the relative stromal depression. Right: Topography 1 month after PRK showing normal curvature from epithelial compensation for the stromal depression. J CATARACT REFRACT SURG - VOL 38, MAY 2012 CASE REPORT: MANAGEMENT OF SUCTION LOSS DURING THIN-FLAP FEMTO-LASIK Beneficial Refractive Effect of the Epithelium The ability of the epithelium to compensate for stromal abnormalities after irregular stromal ablation is well-established.6 In 2003, Huang et al.7 developed a mathematical model supporting the idea that the epithelium smoothes the corneal anterior surface by thinning over bumps or islands and thickening to fill relative depression areas. In our case, the topography after 1 week clearly showed an absence of data in the superior area where the stromal step was created (Figure 5, left) and a return to normal contour of curvature after 1 month (Figure 5, right). The lack of data in the superior area is likely due to poor imaging of the relative stromal depression, still present after 1 week. In support of our findings, Serrao et al.8 reported slower epithelial migration in the superior quadrant, leading to a thinner epithelial thickness during initial wound healing after PRK. They reasoned this was due to an increase in the epithelial sloughing rate superiorly, related to the mechanical action of the lid. After 1 month, high-resolution OCT imaging of our patient’s cornea showed not only the area of stromal depression but also a thickened epithelium, compensating for the stromal irregularity (Figure 3). This led to a normal post-refractive surgery topography (Figure 5, right), which is consistent with the finding of Gatinel et al.,9 showing that the epithelium has the ability to significantly modify the curvature, elevation, and asphericity of corneal topography maps. The uniformity in aberrometry can also be explained by the surface-smoothing effect of the epithelium, as well as the lower sampling resolution compared with topography. In summary, the epithelium plays an active role in determining the final surface power of the cornea, aiding in corneal surface smoothing after laser surface ablation procedures. Performing a later PRK after a primary thin-flap femto-LASIK complication such as 905 suction loss with an altered laser dissection plane appears to provide a good refractive outcome and an effective management strategy. REFERENCES 1. Haft P, Yoo SH, Kymionis GD, Ide T, O’Brien TP, Culbertson WW. Complications of LASIK flaps made by the IntraLase 15- and 30-kHz femtosecond lasers. J Refract Surg 2009; 25:979–984 2. Moshirfar M, Gardiner JP, Schliesser JA, Espandar L, Feiz V, Mifflin MD, Chang JC. Laser in situ keratomileusis flap complications using mechanical microkeratome versus femtosecond laser: retrospective comparison. J Cataract Refract Surg 2010; 36:1925–1933 3. Binder PS. One thousand consecutive IntraLase laser in situ keratomileusis flaps. J Cataract Refract Surg 2006; 32:962–969 4. Ide T, Yoo SH, Kymionis GD, Haft P, O’Brien TP. Second femtosecond laser pass for incomplete laser in situ keratomileusis flaps caused by suction loss. J Cataract Refract Surg 2009; 35: 153–157 5. Ringvold A, Anderssen E, Kjønniksen I. Impact of the environment on the mammalian corneal epithelium. Invest Ophthalmol Vis Sci 2003; 44:10–15. Available at: http://www.iovs.org/cgi/ reprint/44/1/10.pdf. Accessed October 6, 2011 6. Wilson SE, Mohan RR, Hong J-W, Lee J-S, Choi R, Mohan RR. The wound healing response after laser in situ keratomileusis and photorefractive keratectomy; elusive control of biological variability and effect on custom laser vision correction. Arch Ophthalmol 2001; 119:889–896. Available at: http://archopht.amaassn.org/cgi/reprint/119/6/889.pdf. Accessed October 6, 2011 7. Huang D, Tang M, Shekhar R. Mathematical model of corneal surface smoothing after laser refractive surgery. Am J Ophthalmol 2003; 135:267–278 8. Serrao S, Lombardo M, Mondini F. Photorefractive keratectomy with and without smoothing: a bilateral study. J Refract Surg 2003; 19:58–64. Available at: http://www.visioeng.it/documents/ PRKCsmoothingBilateralstudy.pdf. Accessed October 6, 2011 9. Gatinel D, Racine L, Hoang-Xuan T. Contribution of the corneal epithelium to anterior corneal topography in patients having myopic photorefractive keratectomy. J Cataract Refract Surg 2007; 33:1860–1865 OTHER CITED MATERIAL A. Jankov MR II, Jovanovic V, Coskunseven E, “How to Proceed After Suction Loss in LASIK.” Cataract & Refractive Surgery Today Europe, June 2010, pages 44–46. Available at: http://bmctoday. net/crstodayeurope/pdfs/0610CRSTEuro_feature_jankov.pdf. Accessed October 6, 2011 J CATARACT REFRACT SURG - VOL 38, MAY 2012