Grading for suction loss in small incision lenticule extraction

Introduction: To observe the characteristics of suction loss in small-incision lenticule extraction (SMILE) and analyze the factors affecting the stability of the suction ring, classify and grade suction loss, and determine the principles for its prevention and control.

Methods: This study enrolled patients who underwent SMILE between June 2014 and June 2017. The relationship between the stability of the suction ring and suction loss was ascertained using surgical records and video recordings. The suction loss was classified and graded according to its characteristics and relationship with eye or head movement. The effect of target intervention on suction loss was observed.

Results: Suction loss can be divided into sudden and progressive types. According to the severity, the latter was divided into three grades (grade 1A or 1B, 2 and 3). Of the 1200 eyes (608 patients), two (0.17%) had sudden suction loss, and 132 (11%) had progressive suction loss. The superior part, inferior part, and other parts accounted for 63.4%, 19.3%, and 17.3% of progressive suction loss, respectively. The proportion of grades 1A, 1B, 2, and 3 suction loss was 53%, 34%, 12%, and 1%, respectively. The location of the threatened suction loss was opposite to the direction of the patient's head movement. After the intraoperative intervention, grades 1 and 2 did not develop into "actual" suction loss.

Conclusions: Progressive suction loss was the most frequently observed suction loss during SMILE procedure. Grading suction loss can elucidate its underlying mechanism, which can guide targeted intervention measures to effectively control and reduce suction loss-induced damage, and further improve the safety and efficacy of SMILE.