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Comparing a new hydroexpression technique with conventional forceps method for SMILE lenticule removal
  1. Alex L K Ng1,
  2. George P M Cheng2,
  3. Victor C P Woo2,
  4. Vishal Jhanji3,4,
  5. Tommy C Y Chan4
  1. 1 Department of Ophthalmology, The University of Hong Kong, Cyberport, Hong Kong
  2. 2 Hong Kong Laser Eye Center, Hong Kong, Hong Kong
  3. 3 Department of Ophthalmology, University of Pittsburgh School of Medicine, Philadelphia, USA
  4. 4 Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong
  1. Correspondence to Dr George P M Cheng, Hong Kong Laser Eye Center, Queen’s Road Central, Central, Hong Long; drgeorgecheng{at}


Background We described a modified ‘hydroexpression’ technique for the lenticule removal during small-incision lenticule extraction (SMILE) surgery and compared the results with conventional forceps method.

Methods This was a retrospective, comparative study of 50 patients who underwent SMILE surgery by the same surgeon. We compared the 1-week and 3-months postoperative results after SMILE using the hydroexpression technique with the conventional forceps technique. Main outcome measures included uncorrected distance visual acuity, corrected distance visual acuity, refractive accuracy, safety index and efficacy index.

Results The baseline characteristics were comparable between both groups. At postoperative 1 week, the safety index in forceps and hydroexpression group was 0.93±0.11 and 0.97±0.10, respectively (P=0.246). At 3 months, they were 1.00±0.06 and 0.99±0.09 (P=0.850). For efficacy indices, at 1 week they were 0.84±0.17 and 0.91±0.17 (P=0.158). At 3 months, they were 0.92±0.13 and 0.94±0.19 (P=0.624). All eyes aimed for a plano target. 96% in forceps group and 90% in hydroexpression group were within ±0.50 dioptre (D) in spherical equivalent refraction (SEQ) correction at postoperative 3 months (P=0.567). The mean errors of SEQ correction were −0.10±0.21 D in forceps group and −0.08±0.30 D in hydroexpression group (P=0.705).

Conclusion Hydroexpression was simple and safe and had early results comparable to the conventional forceps technique. This technique was particularly useful for cases with more adhesions between lenticule and anterior cap, thin lenticule cases and for the inexperienced SMILE surgeons.

  • cornea
  • treatment lasers

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  • Contributors GPMC and VCPW were involved in the conception and design of the work. ALKN and GPMC were responsible for drafting the work. VCPW, VJ and TCYC were involved in the critical revision of the article. All authors substantially contributed to the acquisition, analysis and interpretation of data and the final approval of the manuscript.

  • Competing interests None declared.

  • Ethics approval Joint Chinese University of Hong Kong-New Territories East Cluster Clinical Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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