The present study was a non-comparative case series, and was approved by the Ethics Committee of the Eye and ENT Hospital of Fudan University (Shanghai, China) and a written informed consent from each patient was obtained before surgery as a standard protocol preoperatively. All procedures were adhered to Declaration of Helsinki. Patients who underwent bilateral SMILE (performed by the same surgeon [ZX]) between January and July 2016, with available 1-year follow-up data, were reviewed. A total of 30 patients (10 male; mean age 45.53 ± 3.20 years [range, 41 to 52 years]) were enrolled. The cohort had a mean preoperative spherical diopter (D) of − 6.12 ± 2.39 D (− 1.5 to − 10 D), cylinder of − 0.79 ± 0.62 D (− 3.0 to 0 D), binocular uncorrected near visual acuity ranging from 20/32 to 20/20, and add 0.85 ± 0.56 D (0 to 2.25 D).
Inclusion criteria were as follows: ≥40 years of age; best corrected visual acuity ≥20/20 in either eye; spherical diopter ≤ − 10.0 D; add > 0 D; and cylinder ≤ − 3.0D. Exclusion criteria included severe eye comorbidities such as diabetic retinopathy, age-related macular degeneration, cataract causing visual impairment, or glaucoma with significant field loss, and a history of severe amblyopia or strabismus.
Regular preoperative examinations, including cycloplegic refraction, corrected visual acuity, slit-lamp examination, corneal topography (Pentacam, Oculus Optikgerate, Wetzlar, Germany), ocular aberration (WASCA wavefront analyzer, Carl Zeiss Meditec, Jena, Germany), and fundus examination were performed. The dominant eye was determined using the “hole test” . Patient was asked to align a dot 4 m away through a 1″ diameter hole in a A4 sheet of paper, held at arm length. Two eyes were covered in turn, and the eye with which the dot appeared most centered was regarded as the dominant eye. The procedures above repeated at least 3 times until the result was the same for at least 2 times consecutively.
The 1-year examinations typically included manifest refraction, assessments of monocular and binocular uncorrected distance visual acuity (UDVA) (at 4 m), uncorrected neat visual acuity (UNVA) (at 33 cm) and corrected distance visual acuity (CDVA) under the same illumination. In addition, we constructed a questionnaire considering patient satisfaction including spectacle dependence for daily activities, halo, glare, visual fatigue, dry eye, and overall satisfaction . Each question was graded on 4 levels: 0 indicated no discomfort whatsoever; 1 indicated discomfort occasionally occurred but did not influence life; 2 indicated discomfort, and usually influenced daily life; and 3 indicated discomfort that was too serious to tolerate. At the end of the questionnaire, patients were asked to grade overall satisfaction on a scale between 0 and 10, in which 0 indicated not satisfied at all and 10 indicated extremely satisfied.
The surgical procedure was similar to the standard SMILE treatments described by the authors in a previous study . The dominant eye was corrected for distance and the nondominant eye for near, with target ranging from − 0.5 D to − 1.75 D,. Preoperatively, we used glasses to simulate target refractive status, with binocular distance visual acuity ≥20/32(the residual myopia in the nondominant eye is –X for instance). If X ≥ adding power (A), then residual myopia is set to be –A; if X ≤ A, then residual myopia is set to be –X. The overall purpose of this design was to ensure good postoperative UDVA with increasing near visual acuity as much as possible. Thus, we considered preoperative presbyopia degree only and no preventive amount of residual myopia was added into design. This principle is derived from years of surgical l experience, though individual cases will be adjusted according to the needs of life.
Statistical analysis was performed using SPSS version 22.0 (IBM Corporation, Armonk, NY, USA), and all data are presented as mean ± SD. Visual acuity data are in LogMAR units. The paired t test was performed to compare root mean square (RMS) differences in ocular aberration, and the Wilcoxon signed-rank test was performed to compare safety indexes, which were nonlinear values between the dominant and nondominant eye. For satisfaction was subjectively graded on 4 ordered levels, orderly regression analysis was used to detect factors affecting satisfaction. Factors included in this analysis are age, sex, and preoperative spherical equivalent, which are independent variables.Spearman’s test was used to determine relationships between visual acuity and other parameters; P < 0.05 was considered to be statistically significant.