The femtosecond laser (IntraLase; IntraLase Corp, Irvine, Calif) is a solid-state laser used to create corneal flaps in LASIK. The 1053-nm wavelength delivers 3-pm spots focused to a preset depth to photodisrupt corneal stroma. This laser may have potential advantages over blade-based microkeratomes, including predictable flap dimensions, use of low suction pressure, and decreased flap complications.1,2 During laser delivery, gas bubbles composed of carbon dioxide and water normally appear under the corneal flap thus creating a dissection plane.3 Gas bubble formation in the anterior chamber is a rare complication, and to our knowledge, has been reported only once previously.4 We present a case of gas bubble formation in the anterior chamber during myopic LASIK.
A 30-year-old man was referred for laser vision correction. Medical and ocular history was unremarkable. Best spectacle-corrected visual acuity was 20/20 in both eyes with a manifest refraction of ?4.75 in the right eye and -4.75 -0.25 × 15° in the left eye. Ocular examination, including intraocular pressure, was normal in both eyes. Preoperative corneal topography was normal with mean keratometric readings of 44.97 diopters (D) and 45.12 D in the right and left eyes, respectively. Preoperative ultrasound pachymetry was 583 pm in the right eye and 565 µm in the left eye.
Following informed consent, the patient underwent bilateral wavefront-guided (OPD; NIDEK Co Ltd, Gamagori, Japan) LASIK. The IntraLase was used to create a 100-pm flap in both eyes. Laser settings for flap creation were: 9.0-mm flap diameter, 50? superior hinge angle, 1.10-μ] raster energy, 9-µm spot separation, 9-µm line separation, and 1.10-sidecut energy. A superior pocket depth of 220 pm and width of 0.250 µm was created. The cornea was applanated with a disposable glass contact lens cone docked to the suction ring. During flap creation in the right eye, gas bubbles were noted to escape from the superior pocket and inferior margin of the flap. The IntraLase pass was successfully completed with no loss of suction. Following laser undocking, gas bubbles were observed in the flap plane and in the anterior chamber. Upon lifting the flap, multiple gas bubbles were seen over the pupillary area in the anterior chamber (Fig). Uneventful excimer ablation of the stromal bed was performed without using an eye tracking device. The LASIK procedure in the left eye was uneventful. On the first postoperative day, uncorrected visual acuity was 20/20 in both eyes with clear corneas bilaterally. No gas bubbles were noted in the anterior chamber.
Figure. Photograph showing multiple air bubbles in the anterior chamber following corneal flap creation with a femtosecond laser.
The femtosecond laser can be focused at any depth in the target tissue, where the energy can be raised to a threshold such that plasma is generated. This plasma expands with a shock wave, cavitation, and gas bubble formation, a process termed laser-induced optical breakdown.5 We believe pressure from the suction device and docking system forced bubbles under the flap to subsequently escape through the peripheral corneal stroma and trabecular mesh work into the anterior chamber. It is unlikely that these bubbles would have traversed the posterior stroma and the endothelium, as considerable stromal pressure induced by intracorneal air injection during deep anterior lamellar keratoplasty has been shown to retain the integrity of the posterior stroma and Descemets membrane.6
Gas bubbles can form in the anterior chamber during corneal flap creation with a femtosecond laser. Because these bubbles are over the pupillary area, they may interfere with an eye-tracking mechanism during excimer laser ablation.
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4. Lifshitz T, Levy J, Klemperer I, Levinger S. Anterior chamber gas bubbles after corneal flap creation with a femtosecond laser. J Cataract Refract Surg. 2005;31:2227-2229.
5. Vogel A, Schweiger P, Freiser A, et al. Intraocular Nd: YAG surgery: light-tissue interactions, damage range, and reduction of collateral effects. IEEE J Quantum Electron. 1990;26:22402260.
6. Anwar M, Teichmann KD. Big bubble technique to bare the Descemet' s membrane in anterior lamellar keratoplasty. J Cataract Refract Surg. 2002;28:398-403.