Journal of Refractive Surgery

Original Article Supplemental Data

Detection of and Compensation for Static Cyclotorsion With an Image-Guided System in SMILE

Bülent Köse, MD

Abstract

PURPOSE:

To evaluate the effect of cyclotorsion compensation with an image-guided system (Callisto eye; Carl Zeiss Meditec AG, Jena, Germany) on the visual and refractive outcomes of small incision lenticule extraction (SMILE) surgery for astigmatism.

METHODS:

The medical records of 124 right eyes of 124 patients with astigmatism of 0.75 diopters (D) or greater who underwent SMILE for myopic astigmatism were reviewed. Patients were treated with cyclotorsion compensated SMILE or standard SMILE. After the sitting position reference axis was registered with IOLMaster 700 (Carl Zeiss Meditec AG), these data were transferred to the Callisto eye system, which was connected to the operating VisuMax microscope (Carl Zeiss Meditec AG). Cyclotorsion was measured by activating the Z-align function and compensated for by repositioning the patient's body or tilting the head until the reference axis from the IOLMaster 700 (0–180) was parallel to a manually drawn reference axis on the screen (0–180) before docking. The visual and refractive results were studied preoperatively and postoperatively. Astigmatic changes were interpreted using the Alpins method.

RESULTS:

Six months after surgery, the results showed that the astigmatic eyes in the cyclotorsion compensated group had improved axial alignment, more precise astigmatic correction, and better postoperative uncorrected distance visual acuity (UDVA) compared with the standard group. The mean logMAR UDVA was 0.02 ± 0.10 (range: −0.15 to 0.30) and 0.06 ± 0.11 (range: −0.15 to 0.30) (P = .13) and the mean astigmatic error was −0.19 ± 0.17 D (range: −0.50 to 0.00 D) and −0.45 ± 0.38 D (range: −1.50 to 0.00 D) (P < .001) in the cyclotorsion compensated group and the standard group, respectively. In regard to vector analysis, the mean index of success was 0.00 ± 0.00 (range: 0.00 to 0.00) and 0.40 ± 0.48 (range: 0.00 to 2.72) (P < .001), and the mean absolute angle of error in degrees was 1.18 ± 2.23 (range: 0.00 to 13.00) and 3.76 ± 3.80 (range: 0.00 to 14.00) (P < .001) in the cyclotorsion compensated group and the standard group, respectively.

CONCLUSIONS:

The combination of the Callisto eye system with a VisuMax laser might be an efficacious and reliable approach to enhance astigmatism treatment with SMILE surgery.

[J Refract Surg. 2020;36(3):142–149.]

 

 

Abstract

PURPOSE:

To evaluate the effect of cyclotorsion compensation with an image-guided system (Callisto eye; Carl Zeiss Meditec AG, Jena, Germany) on the visual and refractive outcomes of small incision lenticule extraction (SMILE) surgery for astigmatism.

METHODS:

The medical records of 124 right eyes of 124 patients with astigmatism of 0.75 diopters (D) or greater who underwent SMILE for myopic astigmatism were reviewed. Patients were treated with cyclotorsion compensated SMILE or standard SMILE. After the sitting position reference axis was registered with IOLMaster 700 (Carl Zeiss Meditec AG), these data were transferred to the Callisto eye system, which was connected to the operating VisuMax microscope (Carl Zeiss Meditec AG). Cyclotorsion was measured by activating the Z-align function and compensated for by repositioning the patient's body or tilting the head until the reference axis from the IOLMaster 700 (0–180) was parallel to a manually drawn reference axis on the screen (0–180) before docking. The visual and refractive results were studied preoperatively and postoperatively. Astigmatic changes were interpreted using the Alpins method.

RESULTS:

Six months after surgery, the results showed that the astigmatic eyes in the cyclotorsion compensated group had improved axial alignment, more precise astigmatic correction, and better postoperative uncorrected distance visual acuity (UDVA) compared with the standard group. The mean logMAR UDVA was 0.02 ± 0.10 (range: −0.15 to 0.30) and 0.06 ± 0.11 (range: −0.15 to 0.30) (P = .13) and the mean astigmatic error was −0.19 ± 0.17 D (range: −0.50 to 0.00 D) and −0.45 ± 0.38 D (range: −1.50 to 0.00 D) (P < .001) in the cyclotorsion compensated group and the standard group, respectively. In regard to vector analysis, the mean index of success was 0.00 ± 0.00 (range: 0.00 to 0.00) and 0.40 ± 0.48 (range: 0.00 to 2.72) (P < .001), and the mean absolute angle of error in degrees was 1.18 ± 2.23 (range: 0.00 to 13.00) and 3.76 ± 3.80 (range: 0.00 to 14.00) (P < .001) in the cyclotorsion compensated group and the standard group, respectively.

CONCLUSIONS:

The combination of the Callisto eye system with a VisuMax laser might be an efficacious and reliable approach to enhance astigmatism treatment with SMILE surgery.

[J Refract Surg. 2020;36(3):142–149.]

 

 

Small incision lenticule extraction (SMILE) is becoming a popular surgery for correction of myopia and myopic astigmatism. This procedure can be performed only with the VisuMax femtosecond laser (Carl Zeiss Meditec AG, Jena, Germany) and is an alternative to excimer laser refractive surgery.1,2 The rotational movements that are detected when the patient switches from an upright position to a supine position are called static cyclotorsion. On the other hand, if they occur during excimer laser photoablation, they are called dynamic cyclotorsion.3,4 They are measured and compensated for by static and dynamic eye trackers during excimer laser surgery.3,4 In contrast to excimer laser platforms, the VisuMax femtosecond laser platform does not have a static or dynamic eye tracker system and cyclotorsional movements are not measured or compensated for in SMILE surgery. However, cyclotorsional misalignment may result in a clinically significant amount of residual astigmatism.5 Additionally, in SMILE surgery the eye is kept immobile by a suction cup during the creation of the refractive lenticule; thus, the lack of dynamic cyclotorsion compensation is not regarded as a disadvantage. However, the lack of a static cyclotorsion detection and compensation system is usually regarded as a major disadvantage of the VisuMax laser. Aslanides et al.5 found that the amount of residual astigmatism after an astigmatic excimer laser treatment was proportional to the amount of astigmatism and cyclotorsion. Chen et al.6 reported that manual cyclotorsion correction resulted in a significant improvement in refractive outcomes after SMILE. On the contrary, other authors reported that long-term results of SMILE (without cyclotorsion compensation) were comparable to laser in situ keratomileusis (LASIK) with static and dynamic cyclotorsion compensation.7,8 Xu et al.9 reported that no significant benefit was gained from manual cyclotorsion compensation, even in the high astigmatism subgroup.

A computer-assisted marker system named Callisto eye has been developed for toric intraocular lens positioning. According to one study, the Callisto eye system was found to be efficient and safe when compared to manual marking techniques.10 In our clinic, the author (BK) has developed a novel system for connection between the Callisto eye system and VisuMax femtosecond laser. In this way, static cyclotorsion was evaluated and compensated for before the docking phase. This study describes this method to visualize, evaluate, and compensate for static cyclotorsion on the VisuMax laser before docking and reports the results of cyclotorsion measurements performed by this system in eyes having SMILE surgery.

Patients and Methods

A total of 124 right eyes of 124 patients with astigmatism of 0.75 diopters (D) or greater were included in this retrospective study. There were two groups: patients treated with the static cyclotorsion compensated SMILE technique (cyclotorsion compensated group) and patients treated with the standard SMILE technique (standard group). Our clinic began performing SMILE surgery in April 2016. After incorporating the Callisto eye system with the VisuMax suite, we routinely started cyclotorsion compensated SMILE surgery in January 2017. Sixty-two patients in the standard group were patients before January 2017 and chosen according to their age, sex, and refractive error. The same surgeon (BK) performed all surgeries at the Department of Ophthalmology, Osmangazi Aritmi Hospital, Bursa, Turkey, between April 2016 and November 2017. All patients signed informed consent. The study was approved by the institutional review board of the Health Sciences University Bursa Higher Specialization Training and Research Hospital and adhered to the tenets of the Declaration of Helsinki.

Inclusion criteria were age 20 to 40 years, central corneal thickness of more than 480 µm, corrected distance visual acuity (CDVA) of 20/32 Snellen or better, myopia between 0.50 and 10.00 D with refractive astigmatism between 0.75 and 5.00 D, and unchanged refraction for 1 year. The exclusion criteria were a history of ocular surgery, keratoconus, and slit-lamp signs of ocular diseases such as cataract or glaucoma.

Preoperative Assessment

A detailed, preoperative ophthalmological examination was made, measuring the following: subjective, manifest, and cycloplegic refraction, uncorrected distance visual acuity (UDVA), CDVA, automated refraction (Canon R-F10; Canon, Tokyo, Japan), slit-lamp biomicroscopy, corneal topography, corneal pachymetry with a Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany), reference and meridian registration with the IOLMaster 700, and corneal aberrations and dynamic pupil sizes with the WaveLight Topolyzer Vario (Alcon Laboratories, Inc., Fort Worth, TX). Soft contact lens use was discontinued 2 weeks and rigid contact lens use 4 weeks prior to the surgery. All patients were reexamined at 1 week and 1, 3, and 6 months postoperatively.

Treatment Planning

No nomogram was applied for spherical or cylindrical correction.

Surgical Technique

The surgeon (BK) used a novel system that enabled transferring the live images from the operating microscope of the VisuMax platform to the Callisto eye system in all operations. First, the sitting position images registered with the IOLMaster 700, stored in a USB drive, were transferred to the Callisto eye system. After a topical anesthetic drop was instilled into the inferior fornix and the eye was draped in a sterile fashion, a wire speculum was placed, the patient's bed was positioned under the surgical microscope of the VisuMax laser, and a live image was captured with the Callisto eye system, which uses limbal vessels as reference points. This captured image and the previously registered IOLMaster 700 images were overlapped in a translucent view (Figure A and Video 1, available in the online version of this article). After confirming the limbal vessels were overlapped exactly, the confirmation button was activated on the Callisto eye screen. Immediately after this activation, on a live stream, a yellow line appeared on the screen and represented the registered horizontal 0–180 axis of the patient in a sitting position. A black horizontal line was previously drawn with a marker pen on the center of the live stream window. This black line represented the 0–180 axis of the VisuMax laser treatment. The yellow line was positioned at the center of the live stream window by moving the joystick of the VisuMax laser's patient bed.

Cyclotorsion compensation with the Callisto eye system (Carl Zeiss Meditec AG, Jena, Germany). A black horizontal line was previously drawn with a marker pen on the center of the live stream window. (A) Captured image and the previously registered IOLMaster 700 (Carl Zeiss Meditec AG) image were overlapped in a translucent view and confirmation button was activated manually on the Callisto eye screen. (B) A yellow line appeared on the screen and represented the registered 0–180 axis of the patient. The black line represented the 0–180 axis of the VisuMax laser treatment (Carl Zeiss Meditec AG). Z-align function was activated and rotated to measure the amount of angle of cyclotorsion. (C) The Z-align was overlapped with black line and cyclotorsion angle was determined. (D) The patient's head was rotated until the black and yellow lines overlapped. The patient was instructed to remain still during the small incision lenticule extraction procedure.

Figure A.

Cyclotorsion compensation with the Callisto eye system (Carl Zeiss Meditec AG, Jena, Germany). A black horizontal line was previously drawn with a marker pen on the center of the live stream window. (A) Captured image and the previously registered IOLMaster 700 (Carl Zeiss Meditec AG) image were overlapped in a translucent view and confirmation button was activated manually on the Callisto eye screen. (B) A yellow line appeared on the screen and represented the registered 0–180 axis of the patient. The black line represented the 0–180 axis of the VisuMax laser treatment (Carl Zeiss Meditec AG). Z-align function was activated and rotated to measure the amount of angle of cyclotorsion. (C) The Z-align was overlapped with black line and cyclotorsion angle was determined. (D) The patient's head was rotated until the black and yellow lines overlapped. The patient was instructed to remain still during the small incision lenticule extraction procedure.

Then, the Z-align function of the Callisto eye system was activated to measure the amount of angle of cyclotorsion. The Z-align function consisted of three parallel blue lines whose angles could be rotated manually. When the blue lines overlapped with the black line on the monitor, the angle between these lines and the yellow line noted the size of the cyclotorsion angle. The amount of angle between these lines and the yellow line provided the cyclotorsion angle. At the same time, the direction of cyclotorsion was also noted. To compensate for cyclotorsion, the head or body of the patient was rotated until the black and yellow lines overlapped. The patients were instructed not to move their body or head after this step.

The patient was moved to the laser treatment aperture and the docking was activated. SMILE surgery was completed as previously described.1,2 A small cup and the same laser parameters were applied in all patients. The spot distance was 3 µm and the spot energy was 140 nJ. The diameter was 6.5 mm for the optical zone and 6.6 mm for the lenticule. The diameter of the cap was 7.5 mm with a 2.5-mm side cut. The minimum lenticule side cut thickness was adjusted to 15 µm.

All patients were advised to use moxifloxacin (Vigamox; Alcon Laboratories, Inc.), dexamethasone (Maxidex; Alcon Laboratories, Inc.), and artificial tears (Artelac; Bausch and Lomb, Rochester, NY) four times a day for 2 weeks.

Vector Analysis of Astigmatism

Only the patient's right eye was included this study. Astigmatism results were presented in a standardized format. A vertex distance of 12 mm was used and astigmatism at the spectacle plane was transformed to the corneal plane. Alpins method vector analysis was done using Sait Egrilmez software.11,12 Target induced astigmatism vector (TIA) was designated as the astigmatic change the surgery was intended to induce, surgically induced astigmatism vector (SIA) was designated as the astigmatic change the surgery actually induced, and the difference vector was designated as the induced astigmatic change that would enable the initial surgery to achieve its intended target or as the postoperative astigmatism. Magnitude of error is the arithmetic difference between the SIA and TIA. Angle of error is the angle between the axis of the SIA and TIA.

Statistical Analysis

All statistical analyses were performed with SPSS software (version 22.0; SPSS, Inc., Chicago, IL). The Shapiro-Wilk test was used as a normality test. Continuous variables were compared using the Student's t test and Mann–Whitney U test when the data were not normally distributed. Categorical variables were compared using the Pearson's chi-square test, Fisher's exact test, and Fisher-Freeman-Halton test. Correlations between variables were tested using Pearson and Spearman correlation coefficients. A P value of less than .05 was considered significant.

Results

This study included 62 right eyes in the cyclotorsion compensated group and 62 right eyes in the standard group. Table 1 shows the baseline values of the two groups. There was no noteworthy disparity in mean preoperative spherical equivalent (−3.56 ± 1.84 vs −3.50 ± 2.09 D) or cylinder (−1.87 ± 0.90 vs −1.97 ± 1.02 D), central corneal thickness, CDVA, or UDVA between the cyclotorsion compensated and standard groups, respectively.

Characteristics of Eyes That Underwent Cyclotorsion Compensated SMILE and Standard SMILE

Table 1:

Characteristics of Eyes That Underwent Cyclotorsion Compensated SMILE and Standard SMILE

Visual Acuity, Efficacy, and Safety

Six months after the SMILE surgery, a significant increase was observed in mean UDVA in the cyclotorsion compensated group (0.96 ± 0.34 to 0.02 ± 0.10 logMAR, P < .001) and the standard group (0.93 ± 0.41 to 0.06 ± 0.11 logMAR, P < .001) (Tables 12); 47 eyes in the cyclotorsion compensated group (76%) and 36 eyes in the standard group (58%) showed UDVA of 20/20 or better (Figures 12). When compared to the preoperative CDVA, the UDVA increased, with 8 eyes (13%) in the cyclotorsion compensated group and 8 eyes (13%) in the standard group (Figures 12). Six months after the SMILE surgery, an important difference was observed in the mean efficacy index (ratio of postoperative UDVA to preoperative CDVA) between the cyclotorsion compensated group (1.02 ± 0.17) and the standard group (0.94 ± 0.12) (P = .003). There was no difference in the mean safety index (ratio of postoperative to preoperative CDVA) between the cyclotorsion compensated group (1.13 ± 0.19) and the standard group (1.07 ± 0.13) (P = .054).

Comparison of Postoperative Visual Acuity and Refractive Errors Between Patients Who Underwent Cyclotorsion Compensated SMILE and Standard SMILE

Table 2:

Comparison of Postoperative Visual Acuity and Refractive Errors Between Patients Who Underwent Cyclotorsion Compensated SMILE and Standard SMILE

Standard graphs for visual outcomes after cyclotorsion compensated small incision lenticule extraction. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters; SEQ = spherical equivalent refraction; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Figure 1.

Standard graphs for visual outcomes after cyclotorsion compensated small incision lenticule extraction. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters; SEQ = spherical equivalent refraction; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Standard graphs for visual outcomes after standard small incision lenticule extraction. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters; SEQ = spherical equivalent refraction; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Figure 2.

Standard graphs for visual outcomes after standard small incision lenticule extraction. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters; SEQ = spherical equivalent refraction; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Refraction

This study showed that postoperative mean UDVA, CDVA, sphere, cylinder, and spherical equivalent were significantly better in the cyclotorsion compensated group (Table 2). All treated eyes in the cyclotorsion compensated group and 55 eyes (89%) in the standard group achieved spherical equivalent within ±1.00 D of the intended value. The linear regression model of attempted versus achieved spherical equivalent in the cyclotorsion compensated group had a slope and coefficient (R2) of 0.9824 and 0.9963, respectively; the corresponding values in the standard group were 0.863 and 0.961, respectively (Figures 12).

Results of Astigmatism Correction and Vector Analysis

Cylinder value after surgery was 0.50 D or less in 62 (100%) and 44 (71%) eyes in the cyclotorsion compensated and standard groups, respectively (Figures 12). Linear regression models of TIA versus SIA vectors showed slopes and coefficients (R2) of 1.004 and 0.9999 in the cyclotorsion compensated group and 0.752 and 0.85 in the standard group, respectively.

Vector of astigmatism was analyzed by using Sait Egrilmez software, which is based on the Alpins method11,12 (Table 3). There was no significant difference in mean values of TIA, SIA, and arithmetic values of angle of error between the two groups. However, mean values of difference vector, correction index, index of success, absolute values of angle of error, and magnitude of error were significantly better in the cyclotorsion compensated group.

Comparison of Vector Parameters for Patients Who Underwent Cyclotorsion Compensated SMILE and Standard SMILE

Table 3:

Comparison of Vector Parameters for Patients Who Underwent Cyclotorsion Compensated SMILE and Standard SMILE

Discussion

Position-related cyclotorsion has been shown with various methods in patients with astigmatism.13–16 According to an iris recognition device–based study, cyclotorsion was found in 74.2% of patients and mean cyclotorsion degree was 2.86° (range: 0° to 9.2°).13 In other studies, in which an infrared camera was attached to a Visx Star S3 ActiveTrak excimer laser system, mean cyclotorsion was measured to be 2°.14 In our study, we measured cyclotorsion degree in the standard group with the Callisto eye system, which analyzed live stream images from a VisuMax surgical microscope. Similarly, we found that 25.2% of the eyes had no cyclotorsion, whereas 74.8% of the eyes had 3.52° ± 2.23° (range: 0° to 8°), with 11.3% eyes (n = 7) greater than 5°. If this cyclotorsion is not compensated for, undercorrection of astigmatism may occur.

Uncompensated cyclotorsion was considered to be the main cause of axial misalignment and under-correction of astigmatism in refractive surgery.4 As a rule, a 4° astigmatic misalignment would produce 14% undercorrection, and as the degree increases, axial misalignment and undercorrection proportionally increases.17 Residual astigmatism (C) can be calculated by using this formula: C = 2F × sin a, where F is the cylinder to be treated and a is the degree of astigmatic error.18 It was shown that the manual marking method for cyclotorsion compensation was safe and effective in LASIK surgery.19 Currently, an integrated cyclotorsion compensation system is not available in the VisuMax laser suite. To overcome this shortcoming, several authors used the manual cornea-marking technique for treatment of astigmatism in SMILE surgery.6,20–22 Ganesh et al.20 were the first to report that the manual cornea-marking technique may be safe, feasible, and effective. Other investigators confirmed the efficacy of this technique.6,21,22 In our study, we used the Callisto eye system to compensate for cyclotorsion. Our data demonstrated that the astigmatic eyes in the cyclotorsion compensated group gained improved axial alignment, more precise astigmatic correction, and better postoperative UDVA compared with the control group, additionally proving the effectiveness of the Callisto eye system for the cyclotorsion compensation error. The applicability of this method was proved by safety and predictability analysis. Therefore, using the Callisto eye system might be an efficacious and reliable approach to enhance astigmatism treatment with SMILE surgery.

A major drawback of SMILE surgery is its lack of static cyclotorsion compensation in astigmatism correction. It is well known that if cyclotorsion is not compensated for, axial misalignment and undercorrection of astigmatism occurs in LASIK surgery.4,23 For this reason, most excimer laser systems currently contain eye tracker and registration systems to compensate for dynamic and static cyclotorsion. Conversely, Lee et al.24 reported that iris registration had no difference from the non-iris registration group in astigmatic patients treated with LASIK surgery. Similarly, Taneri et al.25 aimed to minimize cyclotorsion by carefully positioning a patient's head in SMILE surgery, and found that astigmatic correction was comparable to LASIK surgery performed with eye tracker systems. Xu et al.9 also compared results of SMILE surgery with or without cyclotorsion compensation for the treatment of myopia with astigmatism and found no difference. However, both investigators emphasized careful head positioning.

This study has some possible limitations. First, there were no data present about the amount of cyclotorsion in the standard group. We adopted the Callisto eye system with a VisuMax laser platform in January 2017. Since then, we have routinely used the Callisto eye system for cyclotorsion compensation in all SMILE surgeries for astigmatism correction. For this reason, we were able to retrospectively compare the results of the cyclotorsion compensated group with a control group. Because we observed the effectiveness of this technique, for ethical reasons we cannot design a prospective study. Second, we measured the angle of cyclotorsion manually, which was open to some personal errors. Third, after we compensated for the cyclotorsion by positioning both the head and the body of the patient, we did not remeasure cyclotorsion just before the docking. Although the patients were instructed not to move their head or body, during this short period there is always a possibility that the patient may move.

Studies on manual cyclotorsion compensation of astigmatism with SMILE were reported before. As far as we know, our study is the first preliminary report on cyclotorsion compensation for astigmatism with a registration software in SMILE surgery. An active eye tracker currently is not available in VisuMax femtosecond laser. Our technique seems to be a straightforward, effective, and safe method of astigmatism treatment with SMILE. Ideally, this technique should be incorporated with the VisuMax femtosecond laser by the manufacturer. It should also be improved to measure the amount of cyclotorsion. Prospective randomized controlled studies with a larger sample size of high astigmatism are needed to validate the effectiveness of our results. Effectiveness of this technique may be showed best in patients with high astigmatism with high cyclotorsion.

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Characteristics of Eyes That Underwent Cyclotorsion Compensated SMILE and Standard SMILE

CharacteristicCyclotorsion Compensated SMILEaStandard SMILEaP
No. of eyes (right)6262
Sex (M/F)28/3426/36.380
Age (y)26.74 ± 3.60 (20 to 34)24.83 ± 3.80 (21 to 38).260
Refractive errors (D)
  Sphere−3.56 ± 1.84 (−0.50 to −8.75)−3.50 ± 2.09 (−0.75 to −8.50).075
  Cylinder−1.87 ± 0.90 (−0.75 to −4.50)−1.97 ± 1.02 (−0.75 to −5.00).362
Spherical equivalent (D)−4.49 ± 1.79 (−1.25 to −9.63)−4.48 ± 2.11 (−1.5 to −10.00).064
logMAR CDVA0.02 ± 0.07 (−0.15 to 0.22)0.03 ± 0.09 (−0.15 to 0.22).073
logMAR UDVA0.96 ± 0.34 (0.01 to 1.50)0.93 ± 0.41 (0.01 to 1.52).660
CCT (µm)544.42 ± 30.12 (488 to 611)550.65 ± 33.64 (494 to 638).289

Comparison of Postoperative Visual Acuity and Refractive Errors Between Patients Who Underwent Cyclotorsion Compensated SMILE and Standard SMILE

ParameterCyclotorsion Compensated SMILEaStandard SMILEaP
logMAR UDVA0.02 ± 0.10 (−0.15 to 0.30)0.06 ± 0.11 (−0.15 to 0.30).013
logMAR CDVA−0.04 ± 0.61 (−0.15 to 0.15)0.01 ± 0.59 (−0.15 to 0.15)< .001
Sphere (D)0.00 ± 0.26 (−0.75 to 0.50)−0.14 ± 0.46 (−1.50 to 0.75).037
Cylinder (D)−0.19 ± 0.17 (−0.50 to 0.00)−0.45 ± 0.38 (−1.50 to 0.00)< .001
Spherical equivalent (D)−0.09 ± 0.26 (−0.87 to 0.50)−0.36 ± 0.47 (−1.88 to 0.50)< .001

Comparison of Vector Parameters for Patients Who Underwent Cyclotorsion Compensated SMILE and Standard SMILE

ParameterCyclotorsion Compensated SMILEaStandard SMILEaP
TIA (D)1.69 ± 0.81 (0.65 to 3.98)1.77 ± 0.91 (0.65 to 4.56).567
SIA (D)1.52 ± 0.74 (0.43 to 3.52)1.41 ± 0.74 (0.36 to 3.54).401
Difference vector (D)0.18 ± 0.18 (0.00 to 0.50)0.44 ± 0.37 (0.00 to 1.50)< .001
Correction index0.91 ± 0.11 (0.47 to 1.00)0.81 ± 0.19 (0.28 to 1.46)< .001
Index of success0.00 ± 0.00 (0.00 to 0.00)0.40 ± 0.48 (0.00 to 2.72)< .001
Angle of error (degrees)0.00 ± 2.63 (−7.00 to 13.00)0.06 ± 6.37 (−13.00 to 14.00).960
|Angle of error| (degrees)1.18 ± 2.23 (0.00 to 13.00)3.76 ± 3.80 (0.00 to 14.00)< .001
Magnitude of error (degrees)0.18 ± 0.17 (−0.50 to 0.00)0.37 ± 0.37 (−1.31 to 0.43)< .001
Authors

From the Department of Ophthalmology, Osmangazi Aritmi Hospital, Bursa, Turkey.

The author has no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (BK); data collection (BK); analysis and interpretation of data (BK); writing the manuscript (BK); critical revision of the manuscript (BK)

Correspondence: Bülent Köse, MD, Department of Ophthalmology, Osmangazi Aritmi Hospital, Ulubatli Hasan Bulv., No. 48, Osmangazi, Bursa, Turkey. E-mail: drbulentkose@gmail.com

Received: October 16, 2019
Accepted: January 02, 2020

10.3928/1081597X-20200210-01

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