Small-incision lenticule extraction (SMILE) is a femtosecond laser–based corneal refractive procedure for the correction of myopia and myopic astigmatism. Suction loss is an intraoperative complication that can affect visual outcomes. In this article, we report a case of an unusual passive incomplete suction loss and active suction loss during SMILE.
A 27-year-old woman presented for the correction of compound myopic astigmatism in both eyes. The preoperative assessment showed no ocular abnormalities. The uncorrected distance visual acuity was 20/200 in the right eye and 20/200 in the left eye. The corrected distance visual acuity (CDVA) was 20/20 with −5.25 −0.25 × 45 and 20/20 with −7.00 −0.75 × 135 in the right and left eyes, respectively. Corneal tomography was within normal limits with the thinnest pachymetry of 554 μm and 547 μm in the right and left eyes, respectively. A SMILE procedure was planned and performed using a femtosecond laser system (VisuMax, Carl Zeiss Meditec AG) with a targeted cap depth of 120 μm, a corneal cap diameter of 7.5 mm, and an optical zone of 6.5 mm (spot distance, 4.5 μm for lenticule cut and 2 μm for side cut; energy, 130 nJ); the incision was positioned at 120 degrees with a side-cut angle of 38 degrees.
During surgery in the right eye, the posterior lenticule cut and the lenticule side cut were completed successfully. During anterior lenticule cut, the eye suddenly moved to a state of incomplete suction and slipped from the interface (watch Video 1, available at http://links.lww.com/JC9/A4). Although off center, the laser continued to perform, which was identified as a passive incomplete suction loss. The surgeon immediately pressed the active suction loss button to prevent the transmission of femtosecond delivery, which was identified as an active suction loss. Although the process of anterior lenticule cut had reached 7.37 mm (the central roundness and the periphery circle anterior lenticule cut added up), the diameter of the central anterior lenticule layer showed the normal pattern after surgery. The anterior surface of the refractive lenticule was rescanned, and the incision cut was made subsequently. The lenticule was then separated and completely removed. An uncorrected distance visual acuity was 20/20 in the eye at the first postoperative visit and at the 6-month postoperative visit. The examination of corneal topography showed the normal pattern after surgery.
SMILE is an increasingly popular surgery to correct refractive error. Suction loss can occur at any stage during the SMILE procedure. It is more likely to occur during anterior lenticule cut because of the Bell phenomenon, patient anxiety, conjunctivochalasis, large-diameter corneal caps, and the small/large cone size.1–4 The femtosecond laser system stops automatically when passive suction loss occurs.3 However, in this case, a great slip occurred between the treatment pack and the cornea during anterior lenticule cut. The cornea was automatically suctioned again by the treatment pack when suction loss was about to occur. Although the eye was out of the center, the laser continued to scan without terminating automatically, showing a peculiar ring pattern (Figure 1). The surgeon immediately pressed the active suction loss button. This active suction loss prevented the incision cut that may be located in the lenticule and lead to irregular lenticule tear. Choosing the next step was challenging. According to the reports, several options are available: (1) performing femtosecond laser–assisted laser in situ keratomileusis (FS-LASIK), (2) performing photorefractive keratectomy, (3) performing SMILE with altered parameters, (4) performing SMILE with the same parameters, and (5) postponing the treatment.5–8 The rim of the anterior lenticule cut was not scanned to 6.5 mm because of the great slip. It was hard to remove the lenticule directly, increasing the risk for lenticule tear and residual (Figure 1). The bubbles of the complete posterior lenticule cut and the incomplete anterior lenticule cut might affect the accuracy of the excimer laser if the surgeon immediately switched to FS-LASIK. In addition, FS-LASIK creates a bigger incision cut compared with SMILE. We decided to perform SMILE with the same parameters for the next step. An immediate SMILE process may involve the following risks: (1) Bubble expansion may cause an opaque layer, resulting in difficulties in visualization of the green fixation light by the patient and redocking by the surgeon; (2) the increased anxiety of the patient and the surgeon is a risk factor for suction loss again; and (3) high risk for lenticule extraction. The edge of the temporal anterior lenticule was scanned 3 times (ie, before the suction loss, during the ring scan, and after restarting SMILE), which increased the risks for an uneven lamellar cut, 2 different dissection planes, and an irregular interface, resulting in difficulties in lenticule extraction.9,10 Moreover, the incomplete removal of the lenticule might lead to irregular astigmatism. We used a blunt spatula to carefully break any remaining tissue bridges and removed the lenticule completely. The success of the procedure was attested by the checkups on day 1, 1 month, and 6 months postoperatively. The uncorrected distance visual acuity was 20/20 in both eyes, and corneal tomography was normal (Figure 2). The anterior ring scan was healed as shown by corneal tomography and under slitlamp observation. The residual lenticule could have induced the local higher-order aberrations and irregular curvature found in the corneal tomographic map.10 However, the edge of the lenticule showed regular curvature in the patient's postoperative corneal tomographic map.
A consensus on the treatment of suction loss during SMILE is still lacking. Recent research indicates that the immediate SMILE procedure is safe and predictable for positive long-term outcomes.10,11 Our case study suggests that the surgeon could make a prompt decision when an unusual suction loss occurs and launch the active suction loss system to stop the scan to prevent further potential injury, making immediate SMILE possible to perform. In case of suction loss during anterior lenticule cut, an immediate SMILE procedure without changing any parameter is recommended. Future studies with large samples should be conducted to further test the validity and reliability of this treatment.
WHAT WAS KNOWN
- When suction loss occurs during small-incision lenticule extraction (SMILE), it is common to automatically stop the surgical step.
WHAT THIS PAPER ADDS
- Immediate SMILE without changing any parameters can be performed after suction loss to achieve positive visual acuity postoperatively.
- When incomplete suction loss occurs, the surgeon could promptly launch the active suction loss system to prevent further injury.
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