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.

Wavefront-guided photorefractive keratectomy with and without iris registration: comparison of astigmatic correction

This study aimed to compare the visual outcomes after photorefractive keratectomy (PRK), with and without the iris registration (IR) technology. The retrospective cohort study was performed for wavefront-guided PRK using the Technolas 217z100 excimer laser system in patients with myopic astigmatism (cylinder error - 2 to - 4 diopter [D]). Eyes were divided into IR group (IRPRK) and non-IR group (non-IRPRK). Visual acuity (VA), cylindrical refraction, and the astigmatic vector components using the Alpins method were compared between the two groups preoperatively and 6 months postoperatively. Fifty IRPRK patients (66% female, mean age 30.56 ± 6.31 years) and 50 non-IRPRK (60% female, mean age 29.60 ± 5.63 years) were enrolled. The mean logMAR uncorrected VA improved from 0.89 ± 0.44 to 0.032 ± 0.05 in the IRPRK group (P < 0.001) and from 0.89 ± 0.46 to 0.042 ± 0.06 postoperatively while follow-up in the non-IRPRK group (P < 0.001). No statistically significant differences were observed between the two groups regarding mean uncorrected distance VA (P = 0.4), corrected distance VA (P = 0.5), spherical equivalent (P = 0.16), defocus equivalent (P = 0.18), and absolute cylinder (P = 0.94). More than 90% eyes were within ± 1.00 D of emmetropia in both groups. Moreover, Alpins vector analysis revealed that no significant differences were found in any astigmatic parameters between the two groups (P > 0.05). Wavefront-guided PRK independent of the IR status is effective, safe, and predictable in patients with myopic astigmatism. No statistical significance was observed supporting data for the better outcome of visual acuity and astigmatism correction using IR in comparison with a non-IR system.

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.].

Correlation between iris-registered static and dynamic cyclotorsions with preoperative refractive astigmatism in PRK candidates

Purpose

To evaluate static and dynamic cyclotorsions during photorefractive keratotomy (PRK) surgery in refractive surgery candidates and their correlations with preoperative factors.

Methods

This cross-sectional case series was performed in 138 eyes of 77 patients who underwent PRK surgery by Technolas 217z100. Iris registration was used to evaluate the degree of static and dynamic cyclotorsion. Wavefront measurements were performed in sitting position using Zywave (versions 3.1 and 3.2, Bausch & Lomb) Hartmann Shack aberrometer (Bausch & Lomb), and the cyclotorsion from upright to supine position was measured using iris image comparison. Dynamic cyclotorsions were measured by Advanced Cyclotorsional Eye Tracker (ACE) mounted on Excimer laser machine Technolas 217z100 during surgery.

Results

The mean absolute static cyclotorsion that was captured in surgery time was 3.37 ± 2.38° (range, 0.00 to 11.30), and the mean absolute dynamic cyclotorsion was 2.54 ± 2.50° (range, 0.00 to 13.60). There was a significant correlation between dynamic cyclotorsions and static cyclotorsions (P < 0.001 and R = 0.704). There was a strong association between preoperative refractive astigmatism and range dynamic cyclotorsion. Total pulses (P = 0.009), ablation depth (P = 0.012), gender (P = 0.008) had significant correlations with cyclotorsional movements.

Conclusion

The measurements of static and dynamic cyclotorsions are highly recommended for refractive surgery candidates with significant preoperative refractive astigmatism.

Effect of iris registration on outcomes of FEMTOLASIK for myopia and myopic astigmatism

PURPOSE

To compare the visual and refractive outcomes after FEMTOLASIK with and without iris registration.

METHODS

In this randomized, prospective, comparative, contralateral eye study, 118 eyes of 59 patients with myopia and myopic astigmatism underwent LASIK using the Femto LDV femtosecond laser (160 µm) and the MEL80 with or without iris registration. For each patient, iris registration FEMTOLASIK was performed on one eye and non-iris registration FEMTOLASIK was performed on the other eye, assigned at random. Patients were evaluated before and 12 months. Uncorrected visual acuity, best-corrected visual acuity, manifest refraction, contrast sensitivity, and higher-order aberrations (HOAs) were evaluated.

RESULTS

At 12 months, the mean UDVA was 0.002 ± 0.07 logMAR (20/19) in iris registration eyes and 0.00 ± 0.06 logMAR (20/24) in non-iris registration eyes (P = 0.9). 61% of iris registration eyes and 71.2% of non-iris registration eyes achieved a UDVA of 20/20 or better (P = 0.31); 98.3% of eyes with the iris registration FEMTOLASIK and 94.9% with the non-iris registration FEMTOLASIK were within ±0.50 D from emmetropia (P = 0.71). No statistically significant difference was found in postoperative contrast sensitivity between groups at 3, 6, 12, or 18 cycles/degree (P > 0.05). There was significant increase in total HOA root mean square in two groups. The mean error magnitude of surgically induced astigmatism 12 months postoperatively was -0.33 in iris registration eyes and -0.24 in the non-iris registration eyes (P = 0.36).

CONCLUSIONS

FEMTOLASIK with and without iris registration provides similar results in myopic and myopic astigmatism patients.

Effect of Iris registration on visual outcome in wavefront-guided LASEK for myopic astigmatism

PURPOSE

This study aimed to investigate the effect of iris registration (IR) on visual outcomes in wavefront-guided LASEK for myopic astigmatism.

METHODS

The retrospective chart review was performed for wavefront-guided LASEK using VISX Star S4 in patients with myopic astigmatism (cylinder ≥ 1.00 diopter[D]). Eyes were divided into IR group (LASEK with IR at the time of surgery) and Non-IR group (LASEK without IR system + failed-IR engagement during LASEK). Visual acuity (VA), astigmatism, higher-order aberration (HOA), and contrast sensitivity were assessed preoperatively and 3 months postoperatively. The IR and Non-IR groups were subcategorized depending on the spherical equivalent (lower myopia ≤-5.00 D vs. higher myopia >-5.00 D) for the comparison of HOA changes.

RESULTS

Postoperative uncorrected VAs showed no differences between IR (n = 30) and Non-IR (n = 46). In astigmatic vector analyses, no differences were noted in the mean magnitude of error and the mean angle of error between two groups. There were no differences in postoperative total HOA, spherical aberration (SA), coma, and trefoil between the groups, either. The total HOA and SA increased in both groups, while coma increased only in Non-IR. In higher myopia, ΔRMS of coma was smaller in IR. Preoperative and postoperative total HOA were linearly correlated in Non-IR, but not for IR. Contrast sensitivity of 12 cycles per degree improved in both groups.

CONCLUSION

IR had similar outcomes to conventional trackers in wavefront-guided LASEK, with less tendency of inducing coma, especially in higher myopia.

Four-year visual, refractive, and contrast sensitivity outcomes after wavefront-guided myopic LASIK using an advanced excimer laser platform

PURPOSE

To evaluate the 4-year visual, refractive, and contrast sensitivity outcomes of wavefront-guided LASIK for the correction of low to moderate myopia using the VISX CustomVue technology (Abbott Medical Optics, Inc., Santa Ana, CA).

METHODS

This was a prospective study including 255 consecutive eyes of 145 patients (age range: 19 to 55 years) with low to moderate myopia (mean spherical equivalent: -3.36 ± 1.71 diopters [D]) undergoing laser refractive surgery. Wavefront-guided LASIK was performed in all eyes using the VISX STAR S4 IR excimer laser platform and the CustomVue procedure for the ablation profile design. Visual, refractive, and contrast sensitivity changes were evaluated during a 4-year follow-up period.

RESULTS

Postoperative logMAR uncorrected distance visual acuity was 0.1 or better (20/25 Snellen) in 98.0% and 100% of eyes at 1 and 4 years, respectively. At 4 years postoperatively, mean spherical equivalent was reduced significantly to a mean value of -0.22 ± 0.28 D (P < .01), with 97.3% of eyes with a spherical equivalent within ±0.50 D. The astigmatic power vector component J0 of manifest refraction was also reduced significantly (P < .01). Postoperative logMAR corrected distance visual acuity was 0.0 or better (20/20 Snellen) in 96.1% and 98.8% of eyes at 1 and 4 years, respectively. Improvement in contrast sensitivity was observed in some spatial frequencies between 1 and 4 years postoperatively. No significant correlations were found between 4-year contrast sensitivity and corrected distance visual acuity (0.024 ≤ r ≤ -0.120, P ≥ .06).

CONCLUSION

Wavefront-guided LASIK using the VISX CustomVue technology provides an effective and predictable correction of low to moderate myopia in the long term, preserving the patient's visual acuity and quality.

Effect of limbal marking prior to laser ablation on the magnitude of cyclotorsional error

PURPOSE

To evaluate the residual registration error after limbal-marking-based manual adjustment in cyclotorsional tracker-controlled laser refractive surgery.

METHODS

Two hundred eyes undergoing custom surface ablation with the iVIS Suite (iVIS Technologies) were divided into limbal marked (marked) and non-limbal marked (unmarked) groups. Iris registration information was acquired preoperatively from all eyes. Preoperatively, the horizontal axis was recorded in the marked group for use in manual cyclotorsional alignment prior to surgical iris registration. During iris registration, the preoperative iris information was compared to the eye-tracker captured image. The magnitudes of the registration error angle and cyclotorsional movement during the subsequent laser ablation were recorded and analyzed.

RESULTS

Mean magnitude of registration error angle (absolute value) was 1.82°±1.31° (range: 0.00° to 5.50°) and 2.90°±2.40° (range: 0.00° to 13.50°) for the marked and unmarked groups, respectively (P<.001). Mean magnitude of cyclotorsional movement during the laser ablation (absolute value) was 1.15°±1.34° (range: 0.00° to 7.00°) and 0.68°±0.97° (range: 0.00° to 6.00°) for the marked and unmarked groups, respectively (P=.005). Forty-six percent and 60% of eyes had registration error >2°, whereas 22% and 20% of eyes had cyclotorsional movement during ablation >2° in the marked and unmarked groups, respectively.

CONCLUSIONS

Limbal-marking-based manual alignment prior to laser ablation significantly reduced cyclotorsional registration error. However, residual registration misalignment and cyclotorsional movements remained during ablation.

Advanced corneal surface ablation efficacy in myopia: changes in higher order aberrations

OBJECTIVE

To evaluate the change of ocular and corneal higher order aberrations (HOAs) after wavefront-guided advanced surface ablation (WF-ASA) for myopia using 4 different epithelial management techniques (AA-PRK, LASEK, Epi-PRK, and Epi-LASIK).

DESIGN

Retrospective single centre excimer database analysis.

PARTICIPANTS

Two hundred and forty eyes equally divided between the 4 WF-ASA techniques, matched for mean and range of required spherical correction.

METHODS

Ocular wavefront aberrations were measured using the wavescan aberrometer and corneal aberrations were obtained from corneal topography elevation maps and calculated by ray-tracing. All data were collected preoperatively and 3 months following treatment. The aberrations were described as Zernike polynomials, and analysis focused on total HOAs and spherical aberration (SA).

RESULTS

Three months postoperatively, there was a statistically significant surgically induced increase in total HOAs and SA both for ocular and corneal analysis (p < 0.001). There was no statistically significant difference in the induced ocular SA and HOAs between the groups, but the differences in induced corneal SA and HOAs were significant (p < 0.010). Ocular changes in SA were weakly correlated to preoperative SA (20.30, p < 0.001) but strongly correlated to applied spherical correction (20.68, p < 0.001). Surgically induced corneal SA was weakly correlated to preoperative corneal SA (20.34, p < 0.001) and applied spherical correction (20.46, p < 0.001).

CONCLUSIONS

Three months postoperatively, all procedures resulted in an increase in ocular and cornealHOAs and SA. Induced aberrations were most strongly correlated to the applied spherical power correction. Modifying the existing ablation pattern to compensate for induced HOAs might improve the outcome.

Efficacy of laser in situ keratomileusis in correcting anterior and non-anterior corneal astigmatism: comparative study

PURPOSE

To compare the efficacy of conventional laser in situ keratomileusis (LASIK) in treating corneal astigmatism and in treating noncorneal ocular residual astigmatism.

SETTING

Private practice, Nashville, Tennessee, USA.

DESIGN

Retrospective case series.

METHODS

The records of dominant eyes of consecutive patients who had LASIK were retrospectively analyzed to compare the efficacy of LASIK in eyes with predominantly anterior corneal astigmatism with the efficacy in eyes with predominantly ocular residual astigmatism (ORA). The ORA was determined by vector analysis using refractive cylinder and topographic astigmatism. Preoperatively, the ratio of ORA to preoperative refractive cylinder (R) was used to divide the patients into 2 groups; that is, eyes with predominantly anterior corneal astigmatism (ORA/R ratio <1.0) and eyes with predominantly ORA (ORA/R ratio ≥1.0). Efficacy was determined by examining the magnitude of the remaining uncorrected astigmatism and comparing the index of success (proportion of preoperative refractive astigmatism that remained uncorrected by LASIK) between the 2 groups.

RESULTS

The study evaluated 61 eyes of 61 patients. Conventional LASIK was twice as efficacious in the low-ORA group as in the high-ORA group. The index of success was 0.24 and 0.50, respectively, and the difference between groups was statistically significant (P = .036).

CONCLUSION

The efficacy of astigmatic correction by LASIK was significantly higher in eyes in which the preoperative refractive astigmatism was located mainly on the anterior corneal surface than in eyes in which it was mainly located posterior to the anterior corneal surface.

Corneal limbal marking in the treatment of myopic astigmatism with the excimer laser

PURPOSE

To determine whether preoperative marking of the limbal cornea improves treatment of myopic astigmatism with the excimer laser.

METHODS

Retrospective study on 108 eyes with myopic astigmatism that underwent LASIK or laser epithelial keratomileusis (LASEK) with the Technolas 217 (Bausch & Lomb) excimer laser. Preoperative limbal marking was performed in 47 eyes (marked group). The 12-month results were used for refractive and visual analysis.

RESULTS

The achieved cylinder reduction, spherical reduction, and refractive predictability were similar for the marked and unmarked groups in the overall study collective, in the LASIK and LASEK subgroup analysis, and in a higher astigmatism (> 1.25 diopters) subgroup analysis. Limbal marking showed no influence on the refractive results, and vector analysis showed no significant difference in angle of error among groups.

CONCLUSIONS

Corneal limbal marking failed to improve the refractive outcome in LASIK and LASEK for myopic astigmatism.