Cyclotorsional and non-cyclotorsional components of eye rotation observed from sitting to supine position

Outcomes of astigmatic correction with and without two different cyclotorsion compensation methods in small incision lenticule extraction surgery

PURPOSE

To compare the astigmatic correction outcomes of small incision lenticule extraction (SMILE) surgery with or without two different cyclotorsion compensation methods.

METHODS

This is a prospective randomized clinical trial. Patients with myopic astigmatism that underwent SMILE surgery were randomly divided into static cyclotorsion compensated group (SCC group), slit-lamp group and control group. In the SCC and slit-lamp groups, the intraoperative cyclotorsion was manually compensated with different limbal marking methods. In the control group, the cyclotorsion was not compensated. Visual acuity and manifest refraction were measured preoperatively and postoperatively. Astigmatic outcomes were estimated with vector analysis.

RESULTS

A total of 94 eyes from 94 patients were analyzed postoperatively at the 3-month follow-up. Their mean preoperative cylinder was -1.56±0.86 D (range: -4.25 to -0.25 D). The mean preoperative spherical equivalent was -5.95±1.72 D (range: -10.50 to -2.75 D). All groups showed favorable results in the correction of myopic astigmatism. No statistically differences were found among three groups in postoperative visual acuity, refractive outcomes or vector parameters.

CONCLUSION

Cyclotorsion compensation with two different manual limbal marking methods was helpful in aligning the surgical position in SMILE, but it was not as effective as expected for the correction of myopic astigmatism under well controlled surgical positioning.

Impact of the preoperative cylinder on astigmatism correction in femtosecond lenticule extraction (FLEX): a prospective observational study

PURPOSE

To explore the impact of the preoperative manifest cylinder on astigmatism correction via femtosecond lenticule extraction (FLEX), or small incision lenticule extraction (SMILE).

METHODS

This was a prospective observational study. Eyes were categorized into mild (n = 88), moderate (n = 46), and severe (n = 53) astigmatism groups, based on the preoperative manifest cylinder. Vector analysis was conducted with the back vertex distance set at 12 mm. The primary outcome was the correction index (CI), with secondary outcomes including the safety, efficacy, predictability, and vectoral alterations related to FLEX.

RESULTS

The average target-induced astigmatism was 0.45 ± 0.20 D, 0.95 ± 0.17 D, and 1.99 ± 0.65 D in the three groups (P < 0.001), and the average CI was 1.12± 0.05, 1.01 ± 0.03, and 0.95 ± 0.02 (P = 0.020), with the severe astigmatism group displaying a notably lower CI. The efficacy, safety, predictability, or stability of FLEX did not demonstrate any significant differences among the three groups. The CIs exhibited a significant difference in eyes with with-the-rule (WTR) astigmatism and against-the-rule (ATR) astigmatism from the mild to severe astigmatism group. In eyes with oblique astigmatism, the average CI exceeded one.

CONCLUSION

Patients with manifest cylinder exceeding 1.25 D have a heightened risk of under-correction in WTR and ATR astigmatism compared to those with mild astigmatism, and mild over-correction may occur in cases of oblique astigmatism.

Vector analysis of astigmatism correction after PRK, FS-LASIK, and SMILE for myopic astigmatism

PURPOSE

To compare astigmatic correction among photorefractive keratectomy (PRK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and small-incision lenticule extraction (SMILE).

METHODS

This prospective study enrolled 157 eyes that underwent three procedures (59 PRK, 47 FS-LASIK, and 51 SMILE) for the treatment of myopia with low to high astigmatism (- 0.25 to - 4.50 D). Ocular residual astigmatism (ORA) was calculated by vector analysis using refractive (RA) and corneal astigmatism. Vector analysis results were compared in different procedures in the two RA groups (low ≤ 1.00 D and high > 1.00 D) at 3 and 12 months postoperatively.

RESULTS

There were no significant between-group differences in postoperative safety and efficacy outcomes (all P > 0.05). No significant differences were found in postoperative cylinders between all surgical groups (all p > 0.05), except for 3 months postoperative ORA in FS-LASIK (P = 0.004). At 12 months, 77%, 59.2%, and 50% of eyes attain emmetropia in the FS-LASIK, SMILE, and PRK groups, respectively. Vector analysis showed comparable values for surgical induced astigmatism, target induced astigmatism, mean error, and angle of error between groups at 12 months. Significant differences were observed only in the correction index and difference vector parameters in the astigmatic > 1.00 D group at 3 months (P < 0.001), and FS-LASIK was preferable.

CONCLUSIONS

One-year outcomes revealed that PRK, FS-LASIK, and SMILE were all equally effective in correcting myopic astigmatism. However, FS-LASIK demonstrated more favorable astigmatism correction in eyes with astigmatism > 1.00D in early postoperatively.

12-Month Outcomes of Small Incision Lenticule Extraction With Proper Head Positioning but No Reference Marking for the Correction of Astigmatism

PURPOSE

To investigate the 12-month outcomes of small incision lenticule extraction (SMILE) with proper head positioning but no reference marking for correcting astigmatism.

METHODS

This was a retrospective cohort study of 3,541 patients (5,953 eyes) who underwent SMILE between July 2010 and April 2021. Patient positioning on the treatment bed was meticulously done in every patient to avoid face turn, head tilt, and chin-up or chin-down posture. The corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), manifest refraction, astigmatic outcomes, and adverse events were evaluated at 1, 3, and 12 months postoperatively.

RESULTS

The mean preoperative manifest spherical equivalent and manifest cylinder were -5.15 ± 2.24 diopters (D) (range: -0.13 to -12.88 D) and -1.00 ± 0.77 D (range: -0.25 and -6.00 D), respectively. Of all eyes, 88.4% and 98.6% had the spherical equivalent within ±0.50 and ±1.00 D of emmetropia at 12 months. The percentage of eyes with UDVA of 20/20 or better was 92.5%. Six eyes (0.1%) lost two or more lines of CDVA at the 12-month visit. The predictability of cylinder correction was excellent, with 88.1% within ±0.50 D and 98.9% within ± 1.00 D of astigmatism correction at 12 months. The mean correction index (CI) at 12 months was 1.09 ± 0.45 (range: 0.17 to 4.99), indicating a slight astigmatism overcorrection. The high cylinder group tended to have undercorrection with greater residual astigmatism, whereas the low cylinder group was likely to have overcorrection with lesser residual astigmatism (P < .001). No serious adverse events were observed.

CONCLUSIONS

SMILE with proper head positioning but no reference marking produces safe, efficient, predictable, and stable outcomes for astigmatism correction over a 12-month period. [J Refract Surg. 2023;39(10):683-692.].

Vector analysis of high astigmatism (≥ 2.0 diopters) correction after small-incision lenticule extraction with stringent head positioning and femtosecond laser-assisted laser in situ keratomileusis with compensation of cyclotorsion

Background

The purpose of this study was to compare the astigmatic correction by vector analysis in patients with high myopic astigmatism after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) with cyclotorsion compensation or small-incision lenticule extraction (SMILE) with stringent head positioning.

Setting

Beijing Aier-Intech Eye Hospital, Beijing, China.

Design

A retrospective case series.

Methods

Patients who had correction of myopic astigmatism of 2 diopters (D) or more treated with either FS-LASIK with cyclotorsion compensation or SMILE with stringent head positioning were included. The results of vision and refraction were analyzed and compared between groups with the right eye.

Results

The study enrolled 94 patients (41eyes in an FS-LASIK with compensation of cyclotorsion group and 53 eyes in a SMILE with stringent head positioning control group. The mean preoperative manifest cylinder was -2.65 ± 0.77D in the FS-LASIK group and 2.51 ± 0.56D in the SMILE group (P = 0.302). At 12 months, there was no significant between-group difference in uncorrected distance visual acuity (UDVA, P = 0.274) and postoperative spherical equivalent (SEQ) (P = 0.107). 46.3% and 24.5% of eyes in the FS-LASIK and SMILE groups were within 0.25 D were within 0.25D postoperative cylinder, respectively, and 78% and 66% of eyes in these two groups were within 0.5 D postoperative cylinder (P = 0.027, P = 0.202). The vector analysis showed comparable between-group target-induced astigmatism (TIA) (P = 0.114), surgically induced astigmatism (SIA) (P = 0.057), difference vector (DV, P = 0.069), and the angle of error (AE) (P = 0 .213) values. The index of success (IOS) was 0.18 in the FS-LASIK group and 0.24 in the SMILE group (P = 0.024), with a significant difference between the two groups.

Conclusion

FS-LASIK with compensation of cyclotorsion showed a favorable correction of high myopic astigmatism (≥ 2.0 D) compared to SMILE with stringent head positioning at 12 months.

Comparative analysis of the clinical outcomes between wavefront-guided and conventional femtosecond LASIK in myopia and myopia astigmatism

AIM

To compare the clinical outcomes of wavefront guided femtosecond LASIK (WFG LASIK) and conventional femtosecond LASIK (NWFG LASIK) in eyes with myopia and myopia astigmatism.

METHODS

This was a retrospective, nonrandomized, comparative investigation enrolling 236 eyes of 122 patients (18-50y) with low & moderate and high myopia. The WFG group including 97 eyes (50 patients) undergone WFG LASIK and the NWFG group including 139 eyes (72 patients) undergone conventional LASIK. Mean efficacy index, high order aberrations (HOAs), pupil size and the quality of visual questionnaire were evaluated 6mo postoperatively.

RESULTS

There is no difference between WFG group (-0.054±0.049 in logMAR) and NWFG group (-0.040±0.056) in uncorrected distance visual acuity (UDVA) postoperatively. The myopia astigmatism is higher in WFG group than that in NWFG group (P<0.05). However, the mean efficacy index (MEI) in the WFG group (1.09±0.106) is better than that in the NWFG group (1.036±0.124; P<0.001). Increased HOAs were observed in NWFG group (0.30±0.196) than that in WFG group (0.146±0.188; P<0.001). The pupil size is larger in WFG group (5.15±0.76 mm) than that in NWFG group (4.32±0.52 mm). The patients are satisfied with the clinical surgery, yet WFG group showed better visual quality using the questionnaire survey. Meanwhile, high myopia would result in worse MEI, HOAs and visual quality than low & moderate myopia.

CONCLUSION

WFG and NWFG FS-LASIK are both effective and safe procedures to correct low & moderate and high myopia, but WFG FS-LASIK gives a better postoperative MEI, aberrometric control and predictable outcome. Meanwhile, WFG FS-LASIK is better than NWFG FS-LASIK in correction of myopia astigmatism. Low & moderate myopia allow better clinical outcomes than high myopia using any surgical method.

Early visual quality outcomes after small-incision lenticule extraction surgery for correcting high myopic astigmatism

Background

To evaluate early optical quality outcomes after small-incision lenticule extraction (SMILE) surgery for correcting high myopic astigmatism.

Methods

This retrospective study enrolled 55 eyes from 37 patients who had preoperative myopic astigmatism of ≥2.00 diopters (D) who had been treated with SMILE surgery. Preoperatively, the mean cylinder was − 2.41 ± 0.54 D (range, − 2.00 D to − 4.50 D). The preoperative and postoperative visual outcomes, refraction, and higher-order aberration (HOA) at 1 and 3 months were compared. Refractive astigmatism changes were analyzed by the Alpins vector method.

Results

Three months after SMILE surgery, the average cylinder was − 0.14 ± 0.31 D, and the average astigmatism vector was − 0.09 D × 6.34°. The angle of error (AofE) was limited to within ±10°, and the magnitude of error was limited to within ±1.0 D in all patients. The correction index (CI) was 0.98 ± 0.07, the index of success (IOS) was 0.08 ± 0.13, and the flattening index (FI) was 0.97 ± 0.07. Significant positive correlations were found between IOS and |AofE| (P = 0.000); negative correlations were found between FI and |AofE| (P = 0.000). The postoperative total HOA, spherical aberration, vertical coma aberration, and trefoil 30° were increased significantly compared with preoperative measurements, and the increase in HOA was closely related to preoperative astigmatism (P < 0.05).

Conclusions

SMILE has preferable outcomes for correcting high myopic astigmatism. Axis rotation during the surgery might influence the undercorrection of astigmatism. The increase of HOA after surgery is related to preoperative astigmatism.

Limbus-centered marking technique-assisted continuous circular capsulorhexis

To introduce a limbus-centered continuous circular capsulorhexis (CCC) marking technique.Compared with traditional capsulotomy diameter mark technique, a self-designed limbus-centered capsulotomy mark (LCM) was used to perform the routine cataract surgery in this observational study. Ten eyes were included in each group. The area outer/inner 5.5-mm CCC ring, the furthest/nearest distance from the capsule margin to the intraocular lens (IOL) margin, the CCC total coverage IOL area were measured and compared between this 2 groups.No significant differences were found for all the comparison parameters between the 2 groups (all P > .05). However, the capsule total coverage area, area inner 5.5-mm ring was lower in the LCM group, which demonstrated advantage of LCM.The limbus-centered capsulotomy diameter mark, as an inexpensive and convenient method, helps to perform limbus-centered capsulorhexis with not only a 360° overlapping capsular edge but also well-centered IOL optics.

Vector analysis of small incision lenticule extraction and toric implantable collamer lens implantation for astigmatism correction

OBJECTIVES

To compare the efficacy of small incision lenticule extraction (SMILE) and toric implantable collamer lens (TICL) implantation for myopic astigmatism correction using vector analysis.

METHODS

In this retrospective study, 171 eyes of 171 patients with cylinder ⩾1.0 diopters (D) were recruited, with 97 eyes underwent SMILE and 74 eyes underwent TICL implantation. Preoperative and 3-months postoperative visual and refractive results were examined. The astigmatism correction, graded by the degree of preoperative cylinder was compared between two groups using vector analysis.

RESULTS

At 3-months postoperatively, the residual cylinder was -0.10 ± 0.21 D in the SMILE group and -0.30 ± 0.32 D in the TCL group (p < 0.05). Furthermore, 98% and 85% of eyes had the cylinder within ±0.5 D in the SMILE and TICL group, respectively. The vector analysis revealed similar target induced astigmatism vector in two groups. However, the difference vector, magnitude of error, angle of error, and index of success were significantly higher (0.30 ± 0.32 D, -0.19 ± 0.25, -2° ± 4.35°, and 0.16 ± 0.17 D, respectively) in the TICL group than the values in the SMILE group (0.10 ± 0.21 D, -0.05 ± 0.20, -0.03° ± 2.13°, and 0.05 ± 0.12, respectively), regardless of the degree of preoperative cylinder (all p < 0.05). For preoperative cylinder < 2.0 D, surgically induced astigmatism vector and correction index in the SMILE group were higher than those in the TICL group (p < 0.05).

CONCLUSION

Both SMILE and TICL implantation are effective techniques for myopic astigmatism correction. However, the accuracy of correction in the magnitude and axis of astigmatism with SMILE was better than that achieved with TICL implantation.

Posture-related ocular cyclotorsion during cataract surgery with an ocular registration system

Ocular cyclotorsion when a patient changes from seated to supine position in cataract surgery and factors predicting the amount of cyclotorsion were investigated using VERION system. Variables analyzed were age, gender, preoperative visual acuity, axial length, laterality of eyes, operative duration, and the direction and degree of cyclotorsion. The mean cyclotorsion of 107 eyes of 93 cataract patients was 0.98 ± 4.85 degrees (median, 1 degree; range, -11 to 12 degrees), and the median absolute value was 4 degrees (mean, 4.05 ± 2.82 degrees; range, 0 to 12 degrees). Cyclotorsion was ≥3 degrees in 68 (63.6%) eyes. Excyclotorsion occurred more frequently than incyclotorsion (50.5% vs. 43.0%). There was no cyclotorsion in seven (6.5%). Multiple regression analysis showed that gender was a significant predictive factor for the absolute value of cyclotorsion (β = 1.06, P = 0.041); however, the other variables had no effect on cyclotorsion. The absolute value of cyclotorsion was significantly larger in female than in male patients [median, 4 degrees and 3 degrees, respectively; mean, 4.66 ± 3.02 degrees and 3.44 ± 2.52 degrees, respectively (P = 0.039)]. In conclusion, cataract patients had significant posture-related ocular cyclotorsion. The amount of cyclotorsion was larger for female than male patients.

Astigmatism Correction Using SMILE

Small incision lenticule extraction (SMILE) was introduced in the recent decade for the treatment of myopia and myopic astigmatism. This flap-free technique has a high efficacy and safety profile and also carries potential advantages over laser in situ keratomileusis such as a better corneal biomechanical stability, reduction in dry eyes rate, and the avoidance of flap complications. However, there have been concerns regarding the precision of astigmatism correction that undercorrection has been reported to be apparent. Various factors that affect astigmatism correction have been identified in the literature. The purpose of this review is to discuss the factors that affect astigmatism correction in SMILE and several techniques to improve the refractive outcomes.

Comparison of Small Incision Lenticule Extraction Surgery With and Without Cyclotorsion Error Correction for Patients With Astigmatism

PURPOSE

To evaluate the add-on effect of manual cyclotorsion error correction by the cornea-marking method over standard small incision lenticule extraction (SMILE) surgery in astigmatic eyes.

METHODS

Consecutive patients (84) who had preoperative myopic astigmatism of -0.75 diopters (D) or more and were seeking surgical refractive correction by SMILE surgery during July 2017 to August 2017 were included in this study and randomized to treatment with standard SMILE surgery (S group: 30 eyes) or cyclotorsion compensated SMILE surgery (CC group: 54 eyes). The visual acuity and refractive outcomes were analyzed preoperatively and postoperatively. Refractive astigmatic changes were analyzed by the Alpins method.

RESULTS

The S and CC groups were comparable preoperatively regarding age, manifest spherical equivalent, and manifest refractive cylinder. The mean position-related cyclotorsion degree in the enrolled astigmatic eyes for the S and CC groups was 1.7 ± 2.2 degrees (ranging from 0 to 10 degrees) and 2.19 ± 1.74 degrees (ranging from 0 to 10 degrees), respectively. The mean cylinder was -1.67 ± 0.54 D versus -1.72 ± 0.71 D preoperatively. Six months after treatment, the surgical outcomes in the CC group were significantly better than those of the S group, with a postoperative corrected distance visual acuity of -0.07 ± 0.07 versus 0.016 ± 0.13. A vector analysis of astigmatism also yielded better outcomes in the CC group. However, these 2 groups were statistically similar in spherical equivalent.

CONCLUSIONS

SMILE surgery combined with cyclotorsion error compensation yielded a significant improvement in surgical outcomes regarding safety, efficiency, and predictability for patients with astigmatism.

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

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.].

Consistent comparison of angle Kappa adjustment between Oculyzer and Topolyzer Vario topography guided LASIK for myopia by EX500 excimer laser

AIM

To evaluate and compare the uniformity of angle Kappa adjustment between Oculyzer and Topolyzer Vario topography guided ablation of laser in situ keratomileusis (LASIK) by EX500 excimer laser for myopia.

METHODS

Totally 145 cases (290 consecutive eyes )with myopia received LASIK with a target of emmetropia. The ablation for 86 cases (172 eyes) was guided manually based on Oculyzer topography (study group), while the ablation for 59 cases (118 eyes) was guided automatically by Topolyzer Vario topography (control group). Measurement of adjustment values included data respectively in horizontal and vertical direction of cornea.

RESULTS

Horizontally, synclastic adjustment between manually actual values (dx_manu) and Oculyzer topography guided data (dx_ocu) accounts 35.5% in study group, with mean dx_manu/dx_ocu of 0.78±0.48; while in control group, synclastic adjustment between automatically actual values (dx_auto) and Oculyzer topography data (dx_ocu) accounts 54.2%, with mean dx_auto/dx_ocu of 0.79±0.66. Vertically, synclastic adjustment between dy_manu and dy_ocu accounts 55.2% in study group, with mean dy_manu/dy_ocu of 0.61±0.42; while in control group, synclastic adjustment between dy_auto and dy_ocu accounts 66.1%, with mean dy_auto/dy_ocu of 0.66±0.65. There was no statistically significant difference in ratio of actual values/Oculyzer topography guided data in horizontal and vertical direction between two groups (P=0.951, 0.621).

CONCLUSION

There is high consistency in angle Kappa adjustment guided manually by Oculyzer and guided automatically by Topolyzer Vario topography during corneal refractive surgery by WaveLight EX500 excimer laser.

Factors Influencing Cyclotorsion During Photorefractive Keratectomy

PURPOSE

To determine predictive factors for intra-operative cyclotorsion in photorefractive keratectomy (PRK).

METHODS

A retrospective statistical analysis of medical records pertaining to 3,996 eyes undergoing PRK was conducted. Outcome measures of this study were the likely existence of statistically significant relations between diverse and potentially influential factors and the occurrence of intraoperative cyclotorsion.

RESULTS

A total of 96% of examined medical records indicated some degree of cyclotorsion with the absolute mean intraoperative value of 1.38° ± 1.67° (range: 0° to 13.6°). Absolute mean cyclotorsion showed no significant correlation with age (r = 0.14, P = .37). Female patients had significantly higher degrees of cyclotorsion versus males (P < .001). Right and left eyes showed no significant difference in absolute mean torsion (P = .05). Higher diopters of refractive errors, hyperopia, more than 2.00 diopters of cylinder, high pulse numbers (r = 0.26), and use of the advanced personalized treatment ablation algorithm were all significantly related to higher degrees of torsion (P < .0001). Ablation depth (r = 0.13) and surgeon appeared to be dependent factors.

CONCLUSIONS

Incidence of intraoperative cyclotorsion is high in eyes undergoing PRK and most of them will experience some degree of torsion. Several diverse factors (sex, refractive error diopters, hyperopia, high cylinder, pulse numbers, and ablation algorithm) were significant predictors for higher degrees of the observed torsion. [J Refract Surg. 2018;34(2):106-112.].