Journal of Refractive Surgery

Correspondence Free

Managing Suction Loss in SMILE

Sohini Mandal, MD; Manpreet Kaur, MD; Jeewan S. Titiyal, MD

Abstract

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Abstract

Click here to read the article.

We read with interest the study by Qin et al in the May 2020 issue highlighting the management of suction loss during small incision lenticule extraction (SMILE).1

The authors described a modified technique for the management of suction loss observed during lenticule cut. They advocated restarting a SMILE procedure after modifying the laser parameters by increasing the cap depth. Conventional protocols advocate abandoning the SMILE procedure if suction loss occurs after completion of more than 10% of the lenticule cut and converting to corneal ablative procedures in the same or a different session.2 The modified technique described by the authors results in the creation of multiple interfaces and may lead to an inadvertent dissection of the previous incomplete lenticule cut during lenticule dissection. Laser application during lenticule cut is in a spiral-in fashion from the periphery toward the center, and there is always a potential site for entry into the false plane with this technique. Long-term studies are required to validate the safety of the novel procedure. A hand-held intraoperative anterior segment optical coherence tomography device may be a useful adjunct to assess the relationship between the previous incomplete lenticule cut and the new lenticule cut, detect creation of inadvertent multiple lenticule fragments, and guide the surgeon to enter the correct posterior lenticular plane by avoiding the plane of the unfinished lenticule cut.3

The two lenticule cuts may not be exactly parallel to each other, because even a slight change in centration or cyclotorsion during docking may result in angulation or intersection of the two planes. Creation of multiple interfaces separated by 10 to 20 µm may result in interface irregularity and a decrease in contrast sensitivity. Their study population did not complain of any subjective dysphotic symptoms in the postoperative period; however, the higher order aberrations were not assessed. It would be interesting to objectively assess the visual quality, including higher order aberrations, modulation transfer function, and Strehl ratio, in the patients undergoing this novel rescue technique, and to compare the outcomes with an uneventful SMILE procedure.

Further, the authors advocate delaying the repeat procedure for 1 to 2 hours after the initial suction loss to ensure the disappearance of the gas bubbles and corneal edema. As per the authors, this will enable better centration during the repeat procedure. In addition, presence of bubble layer may adversely impact laser energy and surgical accuracy and result in significant undercorrection of up to −2.00 diopters.4 Good visual outcomes have been observed after immediate redocking with the use of the bubble layer as a guide to previous centration. The pupil center is unstable because it shifts with pupil size under different light settings5 and optical zone centration during immediate lenticule recutting seems to be of significance in patients with a larger mesopic pupil size, for which the initial gas bubble layer would act as a reference. This will further benefit the patient by minimizing higher order aberrations at night. Park and Koo4 compared the predictability and safety of immediate SMILE procedures following suction loss with uneventful SMILE procedures and observed that immediate redocking and completion of SMILE procedures was safe and had clinically predictable long-term outcomes.

Sohini Mandal, MD
Manpreet Kaur, MD
Jeewan S. Titiyal, MD
New Delhi, India

References

  1. Qin B, Li M, Shen Y, et al. Management of suction loss during SMILE in 12,057 eyes: incidence, outcomes, risk factors, and a novel method of same-day recutting of refractive lenticules. J Refract Surg. 2020;36(5):308–316. doi:10.3928/1081597X-20200323-01 [CrossRef]
  2. Titiyal JS, Kaur M, Rathi A, Falera R, Chaniyara M, Sharma N. Learning curve of small incision lenticule extraction: challenges and complications. Cornea. 2017;36(11):1377–1382. doi:10.1097/ICO.0000000000001323 [CrossRef]
  3. Titiyal JS, Rathi A, Kaur M, Falera R. AS-OCT as a rescue tool during difficult lenticule extraction in SMILE. J Refract Surg. 2017;33(5):352–354. doi:10.3928/1081597X-20170216-01 [CrossRef]
  4. Park JH, Koo HJ. Comparison of immediate small-incision lenticule extraction after suction loss with uneventful small-incision lenticule extraction. J Cataract Refract Surg. 2017;43(4):466–472. doi:10.1016/j.jcrs.2016.12.034 [CrossRef]
  5. Liu Q, Yang X, Lin L, et al. Review on centration, astigmatic axis alignment, pupil size and optical zone in SMILE. Asia Pac J Ophthalmol (Phila). 2019;8(5):385–390. doi:10.1097/01.APO.0000580144.22353.46 [CrossRef]

Reply

We would like to thank Mandal et al for their interest in our article1 and would like to respond to their letter.

First, they stated that the modified technique results in the creation of multiple interfaces and may lead to an inadvertent dissection of previous incomplete lenticule cut during lenticule dissection. We agree that the spatula could enter the false plane with the modified technique, but if the surgeon is experienced, the risk of this is low. In our experience, the surgeon would feel immense resistance if entering the false plane. We mentioned in our article that this modified technique is for highly experienced surgeons and 20 µm is a safer and better choice for cap thickness increase if the modified technique is applicable.

Mandal et al also recommended anterior segment optical coherence tomography for intraoperative guidance. We agree that anterior segment optical coherence tomography could be helpful to monitor whether the false plane is entered, and this could be an interesting topic for another study.

They also indicated that the two lenticule cuts may not be exactly parallel to each other. We recommend reviewing the intraoperative video to carefully analyze the suction loss. If there was an abrupt movement of the eye and the femtosecond laser was not cutting according to plan, the surgeon should make the decision to change to laser in situ keratomileusis or another type of surgery.

We agree that postoperative refractive quality (eg, higher order aberrations) should be assessed, but due to the limitations of our study, we were unable to gather such data. Also, the incidence of the suction loss is low in our center, so we were able to include only 27 eyes with suction loss from a total of 12,057 eyes undergoing surgery. The novel modified technique could only be applied to 8 of those 27 eyes.

Mandal et al suggested using the initial gas bubble layer as a centration reference during redocking and performing an immediate redocking when suction loss occurred. However, we would not recommend an immediate redocking but wait at least 1 hour. First, the patient could not see clearly and may not be able to fix on the green light, which may lead to decentration. Second, we agree with Mandal et al that the surgeon should always use the corneal vertex as the center instead of the pupil. Third, immediate redocking resulted in safe and clinically predictable long-term outcomes but could lead to overall lower predictability according to a study by Park and Koo2 or undercorrection up to −2.00 diopters in some cases, possibly due to corneal edema and/or opaque bubble layer.

Bing Qin, MD
Xingtao Zhou, MD
Shanghai, China

References

  1. Qin B, Li M, Shen Y, et al. Management of suction loss during SMILE in 12,057 eyes: incidence, outcomes, risk factors, and a novel method of same-day recutting of refractive lenticules. J Refract Surg. 2020;36(5):308–316. doi:10.3928/1081597X-20200323-01 [CrossRef]
  2. Park JH, Koo HJ. Comparison of immediate small-incision lenticule extraction after suction loss with uneventful small-incision lenticule extraction. J Cataract Refract Surg. 2017;43(4):466–472. doi:10.1016/j.jcrs.2016.12.034 [CrossRef]
Authors

The authors have no financial or proprietary interest in the materials presented herein.

10.3928/1081597X-20210114-01

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