The morphology of corneal cap and its relation to refractive outcomes in femtosecond laser small incision lenticule extraction (SMILE) with anterior segment optical coherence tomography observation.
OBJECTIVE
To investigate the morphology of corneal caps in femtosecond laser small incision lenticule extraction (SMILE) and its relation to the refractive outcomes.


METHODS
A prospective study of fifty-four corneal caps created with VisuMax femtosecond laser were examined using an Fourier-domain optical coherence tomography at 1 day, 1 week, 1 month and 6 months after SMILE. The cap thickness at nine points on each of the four meridians (0°, 45°, 90°, 135°) and the diameter were measured. Cap morphology, changes over time and its correlation with refractive outcomes were assessed.


RESULTS
The mean achieved central cap thickness were (108.74±5.06) µm at 6 months and (107.32±4.81 ) µm at 1 month postoperatively, significantly thinner than that at 1 day (110.81±7.95) µm and 1 week (109.58±7.48 ) µm (P<0.05). The mean diameter on 0° meridian was (7.61±0.07) mm, significantly larger than that on 90° meridian (7.57±0.06) mm (P = 0.001). Cap morphology showed good regularity, except that the differences of points in two pairs were significant at 1 day postoperatively. The uniformity was consistent over time and the central cap thickness was thinner than those in the paracentral and peripheral areas. The refractive outcomes stabilized within 1 month. Uncorrected distance visual acuity (UDVA) was correlated to the central cap thickness at 1 day and 1 week (both rs  = 0.33, p<0.05). The uniformity index was correlated with UDVA (rs  = 0.34, p<0.05) and corrected distance visual acuity (rs  = 0.32, p<0.05) at 1 week postoperatively.


CONCLUSIONS
Corneal caps of SMILE are predictable with good reproducibility, regularity and uniformity. Cap morphology might have a mild effect on refractive outcomes in the early stage. Further study should focus on the impact on the visual quality.
Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Myopia Key Laboratory of the Health Ministry, Shanghai, China.
Jing
J
Zhao
Peijun
P
Yao
Meiyan
M
Li
Zhi
Z
Chen
Yang
Y
Shen
Zhennan
Z
Zhao
Zimei
Z
Zhou
Xingtao
X
Zhou
D000328:Adult; D003315:Cornea / Q000473:pathology / Q000601:surgery*; D003319:Corneal Stroma / Q000473:pathology / Q000601:surgery*; D048988:Corneal Surgery, Laser; D005260:Female; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D055815:Young Adult