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Vector analysis of astigmatic correction after small-incision lenticule extraction and femtosecond-assisted LASIK for low to moderate myopic astigmatism
  1. Tommy C Y Chan1,2,
  2. Alex L K Ng3,
  3. George P M Cheng4,
  4. Zheng Wang5,
  5. Cong Ye2,
  6. Victor C P Woo4,
  7. Clement C Y Tham1,2,
  8. Vishal Jhanji1,2,6
  1. 1Department of Ophthalmology, Hong Kong Eye Hospital, Kowloon, Hong Kong
  2. 2Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong
  3. 3Department of Ophthalmology, The University of Hong Kong, Hong Kong, Hong Kong
  4. 4Hong Kong Laser Eye Center, Hong Kong, Hong Kong
  5. 5Department of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
  6. 6Centre for Eye Research Australia, University of Melbourne, Victoria, Australia
  1. Correspondence to Dr Vishal Jhanji, Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, Hong Kong; vishaljhanji{at}


Aim To compare astigmatic correction between femtosecond-assisted laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE).

Methods A total of 111 patients were included in this prospective study. Fifty-seven eyes were treated with LASIK and 54 eyes were treated with SMILE for myopia with low to moderate (−0.25 to −4.0 D) astigmatism. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity and manifest refraction were measured preoperatively and at 1 and 3 months postoperatively. Visual and refractive outcomes were reported. Changes in refractive astigmatism were evaluated using vector analysis.

Results Preoperative characteristics were similar between both groups. The UDVA at 1 and 3 months was better in the LASIK group compared with the SMILE group (p<0.009). Postoperative cylinder was higher in the SMILE group (p<0.001). Fewer eyes attained the attempted cylindrical correction in the SMILE group (p<0.029). Vector analysis showed no significant difference in target-induced astigmatism (p=0.091) and angle of error (p>0.596) between the two groups. Surgically induced astigmatism was significantly lower in the SMILE group (p<0.023), while the difference vector (p<0.001) and absolute angle of error (p<0.016) were significantly higher in the SMILE group. No significant difference was found in these parameters between 1 and 3 months in both groups (p>0.122).

Conclusions Our results showed that SMILE offered a less favourable astigmatic correction comparable to femtosecond-assisted LASIK in eyes with low to moderate myopic astigmatism. The alignment of treatment was more variable in SMILE, leading to a lower efficacy compared with LASIK by 3 months postoperatively.

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