Journal of Refractive Surgery

Original Article Supplemental Data

Correction of Astigmatism With SMILE With Axis Alignment: 6-Month Results From 622 Eyes

Pei Chen, MD, PhD; Yiming Ye, MD, PhD; Na Yu, MD, MS; Xiaoying Zhang, MS; Jing Zhuang, PhD; Keming Yu, MD, PhD

Abstract

Click here to read a Letter to the Editor about this article.

PURPOSE:

To evaluate postoperative clinical outcomes in myopic eyes with astigmatism that underwent femtosecond laser small incision lenticule extraction (SMILE) surgery with axis alignment.

METHODS:

Overall, 622 eyes from 353 patients with myopia and astigmatism greater than −0.75 diopters (D) who had SMILE were included in this prospective study. Standard examinations were performed and visual acuity and vector astigmatism values were analyzed preoperatively and postoperatively.

RESULTS:

Preoperative manifest spherical equivalent (SE) was −6.11 ± 1.68 D (range: −0.50 to −11.25 D) and manifest refractive cylinder was −1.60 ± 0.65 D (range: −0.75 to −6.25 D). In 622 enrolled eyes with astigmatism, 29.9% did not require rotation modification during surgery, and the average rotation degree (absolute) was 2.82° ± 1.44° (range: 0° to 10°). By 6 months after SMILE, all eyes showed improved uncorrected distance visual acuity (UDVA); approximately 96.8% of eyes with astigmatism achieved the same or better UDVA postoperatively compared to the preoperative corrected distance visual acuity (CDVA). Moreover, the cylinder of all eyes was within ±1.00 D, and 97% of eyes were within ±0.50 D. Only 47 eyes exhibited a low degree of astigmatism (range: −0.75 to 0.50 D). In patients with high astigmatism (>−3.00 D), the preoperative CDVA was −0.02 ± 0.11 logMAR and the 6-month postoperative UDVA was −0.01 ± 0.16 logMAR (n = 24, P > .05), further implying the effectiveness of modified SMILE for refractive correction in patients with astigmatism.

CONCLUSIONS:

SMILE with axis alignment provides efficient, predictable, and safe refractive correction in patients with myopic astigmatism.

[J Refract Surg. 2019;35(3):138–145.]

Abstract

Click here to read a Letter to the Editor about this article.

PURPOSE:

To evaluate postoperative clinical outcomes in myopic eyes with astigmatism that underwent femtosecond laser small incision lenticule extraction (SMILE) surgery with axis alignment.

METHODS:

Overall, 622 eyes from 353 patients with myopia and astigmatism greater than −0.75 diopters (D) who had SMILE were included in this prospective study. Standard examinations were performed and visual acuity and vector astigmatism values were analyzed preoperatively and postoperatively.

RESULTS:

Preoperative manifest spherical equivalent (SE) was −6.11 ± 1.68 D (range: −0.50 to −11.25 D) and manifest refractive cylinder was −1.60 ± 0.65 D (range: −0.75 to −6.25 D). In 622 enrolled eyes with astigmatism, 29.9% did not require rotation modification during surgery, and the average rotation degree (absolute) was 2.82° ± 1.44° (range: 0° to 10°). By 6 months after SMILE, all eyes showed improved uncorrected distance visual acuity (UDVA); approximately 96.8% of eyes with astigmatism achieved the same or better UDVA postoperatively compared to the preoperative corrected distance visual acuity (CDVA). Moreover, the cylinder of all eyes was within ±1.00 D, and 97% of eyes were within ±0.50 D. Only 47 eyes exhibited a low degree of astigmatism (range: −0.75 to 0.50 D). In patients with high astigmatism (>−3.00 D), the preoperative CDVA was −0.02 ± 0.11 logMAR and the 6-month postoperative UDVA was −0.01 ± 0.16 logMAR (n = 24, P > .05), further implying the effectiveness of modified SMILE for refractive correction in patients with astigmatism.

CONCLUSIONS:

SMILE with axis alignment provides efficient, predictable, and safe refractive correction in patients with myopic astigmatism.

[J Refract Surg. 2019;35(3):138–145.]

Small incision lenticule extraction (SMILE), an allin-one invasive femtosecond laser procedure, has been proposed as a promising refractive correction surgery for patients with refractive errors.1 This advancing technology provides rapid and precise photodisruption for intrastromal lenticule without creating a cornea flap, and allows excellent refractive correction, stable corneal biomechanics, fewer complications, and fast nerve recovery in patients.2 However, surgical refractive correction for astigmatism is still a significant challenge for SMILE surgeons, because no acknowledged method of cyclotorsion compensation exists for the VisuMax femtosecond laser system (Carl Zeiss Meditec, Jena, Germany).3

Accurate alignment and correction are crucial factors for obtaining satisfactory SMILE surgical outcomes in patients with myopic astigmatism.4 However, a specific phenomenon called eye rotation or cyclotorsion, which occurs during the changing of position (sitting for examination and lying down for surgery), can induce misalignment of the treatment orientation.5–7 This is the main reason for suboptimal visual outcomes in patients with astigmatism undergoing SMILE surgery.8,9 Theoretically, an 8° misalignment causes a 25% undercorrection of astigmatism.10 A pupil-tracking system and an iris registration technique have been employed in wavefront-guided laser in situ keratomileusis (LASIK) or femtosecond laser–assisted LASIK by the AMARIS 750s system (SCHWIND eye-tech-solutions, Kleinostheim, Germany) to perform personalized refractive surgery in patients with refractive errors to optimize correction outcomes.11–13 Incorporation of this technique facilitates the correction of the optical axis deviation caused by eye rotation in patients with astigmatism, thus resulting in better clinical outcomes postoperatively.14,15 Clinical evidence has indicated that wavefront-guided LASIK with iris registration provides more efficient and predictable correction in patients with astigmatism compared to conventional LASIK.16,17 However, due to technical limitations, the SMILE femtosecond laser system cannot quantitatively track and label eye rotation, and the surgeon must adjust the astigmatic axis subjectively during surgery. Therefore, concerns have been raised regarding astigmatism correction after SMILE.

In the current study, we sought to evaluate SMILE combined with cyclotorsion error compensation, by using the corneal marking method, for patients with astigmatism and to explore its efficacy in alignment and correction.

Patients and Methods

Patient Recruitment

A total of 622 eyes from 353 patients (183 men and 170 women) diagnosed as having myopia (between −0.75 and −10.50 diopters [D]) with astigmatism greater than −0.75 D who requested surgical refractive correction with SMILE using the VisuMax femtosecond laser system were included in this prospective study done at the Zhongshan Ophthalmic Center between July and December 2017. All patients included in this study presented with no other ocular pathological illness or systemic diseases and had no history of any previous ophthalmic surgery. Approval was obtained from the national ethics committee (approval: #2017KYPJ087). All participants were informed about the study procedure before inclusion and signed the informed consent form. All procedures were performed in strict accordance with the tenets of the Declaration of Helsinki.

Patient Examinations

Standard ocular examinations were conducted, and clinical data were collected before surgery for each patient. The corneal topography was obtained with a scanning-slit topography system (Orbscan IIz; Bausch & Lomb, Rochester, NY), intraocular pressure was evaluated by an automatic tonometer, keratometric readings were obtained with an auto-refractometer (RM-8000B; Topcon Corporation, Tokyo, Japan), the average central corneal thickness was measured by an ultrasound pachymeter (SP-100; Tomey Corporation, Nagoya, Japan), and a thorough examination was performed by an experienced ophthalmologist using slit-lamp and funduscopic techniques. Moreover, the uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and manifest and cycloplegic refraction of each eye were evaluated by a trained optometrist with a phoropter preoperatively and 1 day and 1, 3, and 6 months postoperatively. The UDVA and CDVA were converted to logMAR units from decimal notation using the Holladay method for statistical analysis. Astigmatism was analyzed using the vector method of Alpins.

Surgical Procedure

All patients received levofloxacin in both eyes (Cravit; Santen, Osaka, Japan) 3 days before surgery. Alcaine (Alcon Laboratories, Inc., Fort Worth, TX) was applied for topical anesthesia 30 minutes before the SMILE surgery.

All surgical designs and procedures were performed by the same surgeon (KY) using the VisuMax femtosecond laser system. The reference points were marked on the optical zone of the cornea (7 mm apart at the horizontal meridian) of each eye by the surgeon while the patient was seated upright to identify the axis crossing the pupil center; the rotational degree was determined with the patient in the supine position before laser treatment, and then the surgical design was modified accordingly.

First, the table board and the mandible support of the slit lamp were positioned horizontal to the floor. After preoperative preparation, the patient's head was adjusted in the mandible support of the slit lamp (Figure AA, available in the online version of this article), and the light beam was narrowed and set coaxially with the binoculars; then the patient was instructed to look straight ahead, the light band was moved to the cornea, crossing the pupil center, and the intersections were marked at the optical zone of the cornea of each eye at the 3- and 9-o'clock positions (Figure AB) with a sterilized skin marker (Medplus Inc., Guangzhou, China).

Surgical schematic of small incision lenticule extraction with cyclotorsion error correction. (A) Patient seated upright to identify the axis crossing the pupil center. (B) The intersections were marked at the optical zone of the cornea of each eye. (C) The patient was positioned supine on the operating table. (D) The surgeon manually rotated the pressure suction plate. (E) The axis misalignment between sitting and supine position. (F) The rotation degrees were modified during the surgery. White arrows point at the reference points. Red asterisks represent cyclorotation degree. The dotted line represent line drawn between the two cornea marks.

Figure A.

Surgical schematic of small incision lenticule extraction with cyclotorsion error correction. (A) Patient seated upright to identify the axis crossing the pupil center. (B) The intersections were marked at the optical zone of the cornea of each eye. (C) The patient was positioned supine on the operating table. (D) The surgeon manually rotated the pressure suction plate. (E) The axis misalignment between sitting and supine position. (F) The rotation degrees were modified during the surgery. White arrows point at the reference points. Red asterisks represent cyclorotation degree. The dotted line represent line drawn between the two cornea marks.

The patient was positioned supine on the operating table (Figure AC), after vacuum aspiration was performed, and the pressure suction plate was slightly rotated manually (Figure AD) so that the laser beam astigmatic meridian overlapped the reference points on the cornea (Figures AE–AF). The rotation degrees (red asterisks, Figure AE) were determined by the angle between the line drawn (dotted line, Figure AE) between the two cornea marks (white arrows, Figure AE) and the laser beam astigmatic meridian (white line, Figure AE). It was measured and compensated for by the surgeon (Figure AF). Clockwise rotation was recorded as a positive number, and counterclockwise rotation was recorded as a negative number.

The standard SMILE surgical procedure was performed using the VisuMax femtosecond laser system with a 500-kHz repetition rate. Laser centration on the cornea was guided by the input from the topographer. After vacuum aspiration was completed, the femtosecond laser incisions were performed using the following parameters: 110-µm flap thickness, 120-nJ power for lenticule and flap, a lenticule diameter of 6.5 to 7 mm and 1-mm larger cap diameter, and three side cut angles of 90° at a circumferential width of 2 mm. Suction was released and the lenticule was dissected with a thin spatula and removed with a serrated McPherson forceps. Postoperatively, TobraDex eye drops (Santen) were administered four times daily for 2 weeks.

Follow-up

The follow-up visits occurred 1 day and 1, 3, and 6 months postoperatively. At each postoperative visit, UDVA and CDVA, refraction, intraocular pressure, and slit-lamp examinations were performed in all patients. Efficiency was determined by the cumulative percentage of eyes with a postoperative UDVA between 20/16 and 20/20. Safety was assessed by using the difference between the preoperative and postoperative CDVA in each astigmatic eye. Predictability was evaluated by using the achieved spherical equivalent (SE) correction versus the attempted SE correction. The slope and intercept of the correlations were analyzed on scatter plots. Stability was determined by the change in manifest SE before and after SMILE surgery.

Statistical Analysis

The clinical data are presented as the mean ± standard deviation. Timely postoperative changes were evaluated using one-way analysis of variance, and the Dunnett test was used for multiple comparisons, which were performed with SPSS software (version 19; SPSS, Inc., Chicago, IL). A P value of less than .05 was considered statistically significant.

Results

Patients

The basic information of all patients included in this study is summarized in Table 1.

Preoperative Demographics of the Patients With Astigmatism

Table 1:

Preoperative Demographics of the Patients With Astigmatism

Cyclorotation During Surgery

As shown in Figure 1A, 186 of the 622 eyes with astigmatism (28.5%) did not experience position-related cyclotorsion; therefore, further modification during SMILE was not required. However, the other 466 eyes with astigmatism (71.5%) required manual axis compensation to avoid misaligned ablation caused by cyclotorsion during the position transition. The average rotation degree was 2.82° ± 1.44° (absolute) (range: 0° to 10°), with 53% of eyes showing clockwise misalignment and 47% showing counterclockwise misalignment. A few patients (57 eyes, 9.2%) required a high degree (> 5°) of axis compensation. No significant correlation was found between the manifest refractive cylinder and the required rotation degree (P > .05, data not shown). Moreover, 269 patients included in this study received surgery on both eyes, and no correlation between the rotation degrees of the right and left eyes was observed (Figure 1B).

Cyclorotation during the surgery. (A) Position-related cyclorotation degree during small incision lenticule extraction. (B) The rotation degree of the right and left eyes.

Figure 1.

Cyclorotation during the surgery. (A) Position-related cyclorotation degree during small incision lenticule extraction. (B) The rotation degree of the right and left eyes.

Visual Outcomes

Following SMILE, UDVA improved in all enrolled patients (Table 2). Most eyes with astigmatism (81.1%) had improved postoperative UDVA compared to preoperative CDVA. The other 118 eyes did not achieve ideal postoperative visual acuity, but 56 of these eyes recovered 1 week postoperatively and achieved the best corrected vision. Moreover, during the 6-month follow up, only 35 eyes (5.6%) did not achieve the desired UDVA (20/20), 22 of which only lost one line of visual acuity compared with the preoperative CDVA, which might be caused by the remaining refractive error.

Postoperative Visual Acuity

Table 2:

Postoperative Visual Acuity

Clinical Outcomes

Efficiency. At 1 day and 1, 3, and 6 months postoperatively, 81%, 93%, 95%, and 95% of the treated eyes had a UDVA of 20/20 or better, respectively. Figure 2A shows the distribution of preoperative CDVA and postoperative UDVA at 6 months.

Clinical outcomes. (A) Cumulative percentage of eyes that achieved definite cumulative levels of preoperative corrected distance visual acuity (CDVA) and 6-month postoperative uncorrected distance visual acuity (UDVA). (B) Percentage of eyes with astigmatism in gain/loss of lines of UDVA 3 months postoperatively compared with that of preoperative CDVA. (C) Percentage of eyes with astigmatism in gain/loss of lines of CDVA 6 months postoperatively compared with that of preoperative CDVA. (D) Scatter plot of the attempted against achieved manifest spherical equivalent (SE) correction at 6 months after small incision lenticule extraction (SMILE). (E) Accuracy of SE to intended target at 6 months postoperatively. (F) Stability of SE correction during follow-up in eyes with astigmatism with SMILE. (G) Amplitude of astigmatism preoperatively and 6 months postoperatively. (H) Target induced astigmatism vector versus surgically induced astigmatism vector 6 months after SMILE. (I) Refractive astigmatism angle of error at 6 months postoperatively.

Figure 2.

Clinical outcomes. (A) Cumulative percentage of eyes that achieved definite cumulative levels of preoperative corrected distance visual acuity (CDVA) and 6-month postoperative uncorrected distance visual acuity (UDVA). (B) Percentage of eyes with astigmatism in gain/loss of lines of UDVA 3 months postoperatively compared with that of preoperative CDVA. (C) Percentage of eyes with astigmatism in gain/loss of lines of CDVA 6 months postoperatively compared with that of preoperative CDVA. (D) Scatter plot of the attempted against achieved manifest spherical equivalent (SE) correction at 6 months after small incision lenticule extraction (SMILE). (E) Accuracy of SE to intended target at 6 months postoperatively. (F) Stability of SE correction during follow-up in eyes with astigmatism with SMILE. (G) Amplitude of astigmatism preoperatively and 6 months postoperatively. (H) Target induced astigmatism vector versus surgically induced astigmatism vector 6 months after SMILE. (I) Refractive astigmatism angle of error at 6 months postoperatively.

Visual Acuity. As shown in Figure 2B, by 6 months postoperatively, the UDVA of 96.8% of eyes with astigmatism was within one line of the preoperative CDVA, with no significant difference between the preoperative CDVA and the 6-month postoperative UDVA. Notably, most eyes that lost lines of UDVA postoperatively compared with preoperative CDVA decreased from 20/16 to 20/20.

Safety. The distribution of CDVA at 6 months postoperatively is presented in Figure 2C. In 622 enrolled eyes with astigmatism, 5.1% showed no change, 36% gained one or more lines, and only 1.9% (12 eyes) lost more than two lines of CDVA at 6 months postoperatively. Among these, 7 of 12 eyes had a UDVA of 20/20 and satisfactory postoperative visual acuity. At 6 months of follow-up, we did not observe any significant complications related to surgery. Therefore, we suspect that the vision loss might be caused by postoperative aberration.

Predictability. A scatter plot of achieved SE correction versus attempted correction at 6 months postoperatively is presented in Figure 2D, which demonstrates a significant correlation (P < .001). As shown in Figure 2E, by 6 months postoperatively, the SE of all eyes with astigmatism that underwent SMILE with axis alignment were within ±1.00 D, and 92% of eyes were within ±0.50 D (achieved vs intended target).

Stability.Figure 2F shows the changes in manifest SE. Only 3.37% of the treated eyes with astigmatism exhibited a change in SE greater than 0.50 D from 1 to 6 months after SMILE. The change in SE was 0.02 ± 0.20 D (range: −0.75 to 0.75 D).

Refractive Outcomes

The refractive astigmatism results are shown in Table 3. By day 1 postoperatively, 126 eyes exhibited uncorrected astigmatism ranging from −1.00 to +1.00 D. However, by 6 months postoperatively, the cylinder of all eyes was within ±1.00 D and 97% of eyes were within ±0.50 D (Figure 2G). The scatter plots of the surgically induced astigmatism vector versus the target induced astigmatism vector are presented in Figure 2H, demonstrating efficient astigmatic correction for patients with SMILE. The refractive cylinder was 0.10 ± 0.58, 0.08 ± 0.61, 0.06 ± 0.62, and 0.06 ± 0.50 D at 1 day and 1, 3, and 6 months postoperatively, respectively. Only 47 eyes showed a low degree of astigmatism 6 months postoperatively, ranging from −0.75 to 0.50 D. Most of these patients did not achieve the desired UDVA, losing one or two lines compared with preoperative CDVA. Moreover, the distribution of the refractive astigmatism angle of error at 6 months after SMILE is presented in Figure 2I. The angle of error in 579 eyes (93%) was within the −5° to +5° range.

Vector Analysis of Eyes With Astigmatism That Underwent SMILE With Cyclotorsion Correction

Table 3:

Vector Analysis of Eyes With Astigmatism That Underwent SMILE With Cyclotorsion Correction

Smile With Axis Alignment for High Astigmatism

Table 4 and Table A (available in the online version of this article) show the clinical information of the patients with high astigmatism (>−3.00 D, 24 eyes) who were included in this study. During SMILE, their mean rotation degree was 0.79° ± 2.1° (range: −30° to 50°). As shown in Table A, 9 of 24 eyes showed slightly uncorrected astigmatism (−0.07 ± 0.32 D; range: −0.75 to +0.50 D). In addition, patient 152 had amblyopia and a preoperative CDVA of 20/50. Amblyopia is a functional disease and will not affect the refractive surgical correction result, so we did not exclude this patient.

Manifest Refraction and Visual Acuity of Patients With High Astigmatism (>−3.00 D)

Table 4:

Manifest Refraction and Visual Acuity of Patients With High Astigmatism (>−3.00 D)

Patients With High Astigmatism (>−3.00 D)a

Table A:

Patients With High Astigmatism (>−3.00 D)

Discussion

In the current study, clinical observation of 622 eyes after SMILE showed that SMILE with alignment offers effective and predictable refractive correction in myopic patients with astigmatism. Various methods have been applied to determine the position-related cyclotorsional degree in patients with astigmatism.6,15,16,18 By using the pupil camera of the Visx WaveScan wavefront device, Chernyak showed that the average cyclotorsional degree was approximately 2° for each eye.6 Studies based on iris recognition devices have also demonstrated that cyclotorsion results in axis deviation in 74.2% of patients with astigmatism, with an average cyclotorsional degree of 2.86° (range: 0° to 9.2°).15 Consistently, in our study of 622 eyes analyzed using the corneal marking method, 28.5% of the eyes showed no cyclotorsion during the position transition; however, the other 71.5% of eyes experienced a change of 2.82° ± 1.44° in the astigmatic axis, with 9.2% (57 eyes) showing an axis change greater than 5°. If not compensated for, such an axis deviation can result in residual astigmatism and subsequent suboptimal postoperatively visual quality in patients with astigmatism who undergo SMILE.19

Before the implementation of the iris recognition technique, refractive surgery with corneal and laser astigmatic axis alignment was recommended for patients with an astigmatism of −0.75 D or greater.19 Accordingly, manual corneal markings have been shown to improve refractive outcomes for patients with astigmatism with photoastigmatic refractive keratectomy treatment of −1.25 D or greater.19 Our data demonstrated that no complications occurred during the cyclotorsion compensation procedure and all myopic eyes with astigmatism (622 eyes) achieved improved UDVA, 81.1% (504 eyes) of which achieved the intended UDVA on 1 day postoperatively. By 6 months postoperatively, only 5% (31 eyes) did not achieve the desired UDVA. Among these 31 eyes, none showed a postoperative loss of three or more lines of UDVA compared to preoperative CDVA. Moreover, no significant differences were observed between the obtained postoperative UDVA and the intended postoperative visual acuity at the follow-up time points. In addition, 84% of eyes were within ±0.25 D of the attempted astigmatic correction and 97% were within ±0.50 D. These observations are consistent with previous reports. Studies of LASIK with corneal axis alignment have shown improved accuracy for astigmatism correction. A small-sample study of 81 eyes also indicated that manual compensation is a safe, feasible, and effective approach for SMILE to refine astigmatism correction outcomes, especially in eyes with high astigmatism.20 Taken together, this evidence demonstrated that corneal marking may be a safe, efficient, and predictable approach to facilitate SMILE, but the latest version of the system still lacks an active eye tracker for better astigmatism correction outcomes.

The impact of axis misalignment caused by position-related cyclotorsion is especially obvious in patients with high astigmatism, resulting in unsatisfactory refractive correction and postoperative visual acuity.12,20 Here, our data showed that patients with astigmatism greater than −3.00 D could achieve optimal visual quality following SMILE with axis alignment, further indicating that the cyclotorsional degree can be accurately evaluated by manual corneal marking. However, 3.2% of the enrolled eyes with astigmatism showed loss of postoperative UDVA lines compared to preoperative CDVA. The main reason for poor postoperative vision in these eyes was caused by axis misalignment; manual corneal marking is subject to certain artificial errors, usually due to poor patient coordination. Therefore, to achieve satisfactory surgical correction in patients with astigmatism who have SMILE, the surgeon requires years of experience.

In addition, apart from cyclotorsion, possible causes of misalignment in patients with astigmatism undergoing SMILE include head movement, cyclophoria, and eyeball distortion caused by eyelid retractors. To obtain precise refractive correction and the best postoperative visual outcome, the surgeon should not only pay constant, meticulous attention to axis alignment, but also locate the visual center position precisely based on the kappa angle before and during surgery. Patients must also strictly comply with the surgeon's orders when they receive refractive surgery.

In the current study, the clinical evidence of 622 eyes demonstrated that SMILE with axis alignment provides an efficient, predictable, stable, and safe refractive correction in myopic patients with astigmatism. Longer follow-up observations are warranted to confirm the conclusions presented here and to standardize the surgical procedure.

References

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Preoperative Demographics of the Patients With Astigmatism

CharacteristicValue
No. of patients353
No. of eyes622
Sex (M/F)183/170
Age (y)25.27 ± 4.81 (range: 18 to 35)
Manifest spherical equivalent (D)−6.11 ± 1.68 (range: −1.38 to −11.25)
Manifest refractive cylinder (D)−1.60 ± 0.65 (range: −0.75 to −6.25)
UDVA (logMAR)1.22 ± 0.48
CDVA (logMAR)−0.08 ± 0.06
Central corneal thickness (µm)543.31 ± 39.8
Intraocular pressure (mm Hg)13.2 ± 1.7

Postoperative Visual Acuity

Visual AcuityPreoperativePostoperative

1 Day1 Month3 Months6 Months
UDVA
  logMAR1.21 ± 0.38−0.04 ± 0.09−0.07 ± 0.09−0.07 ± 0.08−0.07 ± 0.05
  > 20/200%81%92%93%95%
  > 20/160%65%67%72%73%
CDVA
  logMAR−0.08 ± 0.06−0.06 ± 0.07−0.08 ± 0.08−0.08 ± 0.08−0.09 ± 0.06
  > 20/2093%90%93%95%95%
  > 20/1673%65%70%73%76%

Vector Analysis of Eyes With Astigmatism That Underwent SMILE With Cyclotorsion Correction

ParameterPostoperative 1 MonthPostoperative 3 MonthsPostoperative 6 Months
TIA (D)1.60 ± 0.651.60 ± 0.651.60 ± 0.65
SIA (D)1.65 ± 0.701.62 ± 0.871.61 ± 0.68
AE (absolute)4.8 ± 8.13.8 ± 7.23.2 ± 6.9
ME−0.03 ± 0.57−0.01 ± 0.330.01 ± 0.4

Manifest Refraction and Visual Acuity of Patients With High Astigmatism (>−3.00 D)

ParameterPreoperativePostoperative

1 Day1 Month3 Months6 Months
UDVA (logMAR)1.23 ± 0.46−0.01 ± 0.21−0.01 ± 0.24−0.01 ± 0.17−0.01 ± 0.16
CDVA (logMAR)−0.02 ± 0.11−0.02 ± 0.16−0.05 ± 0.3−0.05 ± 0.3−0.05 ± 0.12
SE (D)−4.84 ± 2.100.04 ± 0.110.04 ± 0.100.02 ± 0.150.02 ± 0.17
Cylinder (D)−3.59 ± 0.75−0.21 ± 0.40−0.10 ± 0.43−0.08 ± 0.30−0.07 ± 0.32

Patients With High Astigmatism (>−3.00 D)a

Patient No.Preop RefractionPreop CDVARotation DegreePostop 6-Month UDVAPostop RefractionPostop 6-Month CDVA
61−1.75 −6.25 × 18020/25 (0.05)−220/20 (0)plano20/20 (0)
76−4.50 −3.50 × 18020/16 (−0.08)220/25 (0.05)−0.50 × 30 DC20/20 (0)
76−5.75 −4.25 × 18020/25 (0.04)120/25 (0.05)−0.25 DS20/16 (−0.08)
77−6.00 −3.00 × 18020/20 (0)320/20 (0)−0.25 DS20/16 (−0.08)
89−2.25 −3.50 × 2020/20 (0)020/16 (−0.08)+0.50 × 50 DC20/16 (−0.08)
121−8.50 −3.75 × 18020/16 (−0.08)420/12.5 (−0.18)plano20/12.5 (−0.18)
121−8.25 −3.75 × 17520/16 (−0.08)420/12.5 (−0.18)plano20/12.5 (−0.18)
134−1.00 −3.50 × 16520/16 (−0.08)−220/20 (0)+0.50 × 60 DC20/20 (0)
137−4.25 −3.50 × 17520/16 (−0.08)020/16 (−0.08)plano20/16 (−0.08)
149−6.75 −3.50 × 520/16 (−0.08)320/20 (0)−0.75 × 65 DC20/16 (−0.08)
149−4.50 −3.50 × 17020/16 (−0.08)120/12.5 (−0.18)plano20/12.5 (−0.18)
152−6.00 −4.50 × 9520/50 (0.5)220/50 (0.5)−0.25 −0.50 × 14020/40 (0.3)
175−2.75 −3.50 × 520/20 (0)020/25 (0.05)+0.25 DS20/16 (−0.08)
176−4.00 −3.00 × 17520/16 (−0.08)020/20 (0)+0.25 DS20/20 (0)
189−3.00 −3.00 × 18020/20 (0)−120/16 (−0.08)+0.25 DS20/16 (−0.08)
214−4.25 −3.00 × 17020/16 (−0.08)−320/25 (0.05)0.50 × 165 DC20/16 (−0.08)
228−5.50 −4.50 × 8020/16 (−0.08)020/16 (−0.08)plano20/16 (−0.08)
239−5.75 −4.00 × 17020/16 (−0.08)520/20 (0)+0.25 DS20/16 (−0.08)
239−5.25 −3.00 × 18020/16 (−0.08)120/12.5 (−0.18)+0.25 DS20/12.5 (−0.18)
271−3.00 −3.75 × 17020/16 (−0.08)220/12.5 (−0.18)−0.50 × 110 DC20/12.5 (−0.18)
309−3.50 −3.25 × 18020/16 (−0.08)220/16 (−0.08)plano20/16 (−0.08)
313−4.25 −3.25 × 1020/16 (−0.08)020/12.5 (−0.18)+0.25 DS20/12.5 (−0.18)
319−9.50 −3.50 × 17520/16 (−0.08)−320/40 (0.3)−0.25 −0.50 × 5020/25 (0.05)
326−6.00 −3.00 × 18020/16 (−0.08)020/25 (0.05)−0.50 × 85 DC20/20 (0)
Authors

From State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong, People's Republic of China.

Supported by the National Natural Science Foundation of China (Grant Nos. 81470626 and 81670848).

The authors have no financial or proprietary interest in the materials presented within.

AUTHOR CONTRIBUTIONS

Study concept and design (PC, JZ, KY); data collection (PC, YY, NY, XZ); analysis and interpretation of data (PC, KY); writing the manuscript (PC, YY, NY, XZ, JZ, KY); critical revision of the manuscript (KY); supervision (JZ, KY)

Correspondence: Keming Yu, MD, PhD ( yukeming@mail.sysu.edu.cn), and Jing Zhuang, PhD ( zhuangj@mail.sysu.edu.cn), State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, People's Republic of China.

Received: September 07, 2018
Accepted: January 14, 2019

10.3928/1081597X-20190124-02

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