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.

Automated measurement of the disc-fovea angle based on DeepLabv3

Purpose

To assess the value of automatic disc-fovea angle (DFA) measurement using the DeepLabv3+ segmentation model.

Methods

A total of 682 normal fundus image datasets were collected from the Eye Hospital of Nanjing Medical University. The following parts of the images were labeled and subsequently reviewed by ophthalmologists: optic disc center, macular center, optic disc area, and virtual macular area. A total of 477 normal fundus images were used to train DeepLabv3+, U-Net, and PSPNet model, which were used to obtain the optic disc area and virtual macular area. Then, the coordinates of the optic disc center and macular center were obstained by using the minimum outer circle technique. Finally the DFA was calculated.

Results

In this study, 205 normal fundus images were used to test the model. The experimental results showed that the errors in automatic DFA measurement using DeepLabv3+, U-Net, and PSPNet segmentation models were 0.76°, 1.4°, and 2.12°, respectively. The mean intersection over union (MIoU), mean pixel accuracy (MPA), average error in the center of the optic disc, and average error in the center of the virtual macula obstained by using DeepLabv3+ model was 94.77%, 97.32%, 10.94 pixels, and 13.44 pixels, respectively. The automatic DFA measurement using DeepLabv3+ got the less error than the errors that using the other segmentation models. Therefore, the DeepLabv3+ segmentation model was finally chosen to measure DFA automatically.

Conclusions

The DeepLabv3+ segmentation model -based automatic segmentation techniques can produce accurate and rapid DFA measurements.

Toric intraocular lenses: Expanding indications and preoperative and surgical considerations to improve outcomes

Since the introduction of the first toric intraocular lens (IOLs) in the early 1990s, these lenses have become the preferred choice for surgeons across the globe to correct corneal astigmatism during cataract surgery. These lenses allow patients to enjoy distortion-free distance vision with excellent outcomes. They also have their own set of challenges. Inappropriate keratometry measurement, underestimating the posterior corneal astigmatism, intraoperative IOL misalignment, postoperative rotation of these lenses, and IOL decentration after YAG-laser capsulotomy may result in residual cylindrical errors and poor uncorrected visual acuity resulting in patient dissatisfaction. This review provides a broad overview of a few important considerations, which include appropriate patient selection, precise biometry, understanding the design and science behind these lenses, knowledge of intraoperative surgical technique with emphasis on how to achieve proper alignment manually and with image-recognition devices, and successful management of postoperative complications.

Three-month clinical outcomes with static and dynamic cyclotorsion correction using the SCHWIND AMARIS

PURPOSE

To evaluate intraoperative static and dynamic cyclotorsions and postoperative outcomes on astigmatism and high-order aberration in astigmatic or aberrated eyes that underwent laser in situ keratomileusis treatments with advanced cyclotorsion control using the SCHWIND AMARIS.

METHODS

Fifty eyes (30 for aberration neutral and 20 for corneal wavefront) were treated. Treatments were planned with Custom Ablation Manager and ablations were performed using the SCHWIND AMARIS. Laser in situ keratomileusis flaps were cut with an LDV femtosecond laser. Cyclotorsional movements were evaluated for static cyclotorsion component (SCC) for mean and repeatability, and for dynamic cyclotorsion component (DCC) for mean and amplitude. Clinical outcomes were evaluated for predictability, refractive outcome, safety, and wavefront aberration.

RESULTS

Registration rates were 90% for SCC and 98% for DCC. SCC was within ± 5 degrees in 64% of cases. Repeatability of SCC was ± 1 degree in 88% of cases. Mean DCC was within ± 1 degree in 98% of cases, partly compensating for SCC. DCC amplitude was within ± 2 degrees in 84% of cases. At 3-month follow-up, 88% of eyes were within ± 0.50 diopter (D) of astigmatism. Mean defocus was -0.06 ± 0.24 D and astigmatism was 0.27 ± 0.20 D. Best spectacle-corrected visual acuity improved in 42% of eyes versus 2% losing 1 line. In corneal wavefront-customized treatments, coma, trefoil, spherical aberration, and root mean square high-order magnitudes at 6-mm analysis diameter were reduced by -0.04, -0.13, -0.04, and -0.10 μm, respectively.

CONCLUSIONS

Laser in situ keratomileusis with advanced cyclotorsion compensation using the SCHWIND AMARIS is safe and predictable and yields superior visual outcomes. Refractions and high-order aberrations were reduced to subclinical values without applying additional nomograms, showing the excellent performance of the system.

The effect of static cyclotorsion compensation on refractive and visual outcomes using the Schwind Amaris laser platform for the correction of high astigmatism

PURPOSE

To compare the refractive and visual outcomes using the Schwind Amaris excimer laser in patients with high astigmatism (>1D) with and without the static cyclotorsion compensation (SCC) algorithm available with this new laser platform.

METHODS

70 consecutive eyes with ≥1D astigmatism were randomized to treatment with compensation of static cyclotorsion (SCC group- 35 eyes) or not (control group- 35 eyes). A previously validated optimized aspheric ablation algorithm profile was used in every case. All patients underwent LASIK with a microkeratome cut flap.

RESULTS

The SCC and control group did not differ preoperatively, in terms of refractive error, magnitude of astigmatism or in terms of cardinal or oblique astigmatism. Following treatment, average deviation from target was SEq +0.16D, SD±0.52 D, range -0.98 D to +1.71 D in the SCC group compared to +0.46 D, SD±0.61 D, range -0.25 D to +2.35 D in the control group, which was statistically significant (p<0.05). Following treatment, average astigmatism was 0.24 D (SD±0.28 D, range -1.01 D to 0.00 D) in the SCC group compared to 0.46 D (SD±0.42 D, range -1.80 D to 0.00 D) in the control group, which was highly statistically significant (p<0.005). There was no statistical difference in the postoperative uncorrected vision when the aspheric algorithm was used although there was a trend to increased number of lines gained in the SCC group.

CONCLUSIONS

This study shows that static cyclotorsion is accurately compensated for by the Schwind Amaris laser platform. The compensation of static cyclotorsion in patients with moderate astigmatism produces a significant improvement in refractive and astigmatic outcomes than when not compensated.

Surgically induced astigmatism after phacoemulsification with and without correction for posture-related ocular cyclotorsion: randomized controlled study

PURPOSE

To report the impact of posture-related ocular cyclotorsion on one surgeon's surgically induced astigmatism (SIA) results and the variance in SIA.

SETTING

Institute of Eye Surgery, Whitfield Clinic, Waterford, Ireland.

METHODS

This prospective randomized controlled study included eyes that had phacoemulsification with intraocular lens implantation. Eyes were randomly assigned to have (intervention group) or not have (control group) correction for posture-related ocular cyclotorsion. In the intervention group, the clear corneal incision was placed precisely at the 120-degree meridian with instruments designed to correct posture-related ocular cyclotorsion. In the control group, the surgeon endeavored to place the incision at the 120-degree meridian, but without markings.

RESULTS

The intervention group comprised 41 eyes and the control group, 61 eyes. The mean absolute SIA was 0.74 diopters (D) in the intervention group and 0.78 D in the control group; the difference between groups was not statistically significant (P>.5, unpaired 2-tailed Student t test). The variance in SIA was 0.29 D(2) and 0.31 D(2), respectively; the difference between groups was not statistically significant (P>.5, unpaired F test).

CONCLUSIONS

Attempts to correct for posture-related ocular cyclotorsion did not influence SIA or its variance in a single-surgeon series. These results should be interpreted with full appreciation of the limitations of currently available techniques to correct for posture-related ocular cyclotorsion in the clinical setting.

Static and dynamic rotational eye tracking during LASIK treatment of myopic astigmatism with the Zyoptix laser platform and Advanced Control Eye Tracker

PURPOSE

To evaluate the amount of cyclotorsion and the effect of static and dynamic rotational eye tracking with the Advanced Control Eye Tracker (Bausch & Lomb) based on iris recognition in the treatment of myopic astigmatism with LASIK.

METHODS

All patients with myopic LASIK and attempted cylinder correction >0.75 diopters (D) on the Zyoptix 217z100 excimer laser platform between May 2005 and May 2007 were identified retrospectively through the existing databank. Pre- and postoperative refraction and the amount of cyclotorsion during treatment were extracted and analyzed in 828 eyes with >3-month follow-up.

RESULTS

Preoperative mean manifest refraction spherical equivalent (MRSE) was -4.31+/-1.84 D (range: -0.37 to -9.50 D), and mean cylinder was -1.27+/-0.87 D (range: -0.75 to -6.75 D). Mean static rotation was 3.96+/-2.96 degrees (maximum 14.8 degrees ). Median dynamic rotation was 1.32+/-1.85 degrees (maximum 24 degrees). At 3 months postoperatively, MRSE was -0.10+/-0.36 D (range: -2.25 to +1.25 D), and mean cylinder was -0.33+/-0.35 D (range: -2.00 to 0 D). Predictability was 90.2% within +/-0.50 D and 98.2% within +/-1.00 D (MRSE), and 82.5% within +/-0.50 D and 96.9% within +/-1.00 D (cylinder). The efficacy ratio was 0.99. Safety was 99.4% (5 dry eyes), reaching 100% at 12 months. Stability from 3 to 12 months (n=275) was 98.2% for sphere, 95.3% for cylinder, and 96.0% for MRSE.

CONCLUSIONS

Our study demonstrates that significant cyclotorsion occurs before and during treatment. By using the dynamic rotational eye tracker presented, the efficacy of cylinder correction can be improved compared to those studies not performing cyclotorsional correction.

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.

Zyklorotation des Auges bei wellenfrontgeführter LASIK mit statischem Iriserkennungstracker

PURPOSE

Centration of the ablation zone decisively influences the result of wavefront-guided LASIK. Cyclorotation of the eye occurs as the patient changes from the sitting position during aberrometry to the supine position during laser surgery and may lead to induction of lower and higher order aberrations.

METHODS

Twenty patients (40 eyes) underwent wavefront-guided LASIK (B&L 217z 100 excimer laser) with a static eyetracker driven by iris recognition (mean preoperative SE: -4.72+/-1.45 D; range: -1.63 to -7.00 D). The iris patterns of the patients' eyes were memorized during aberrometry and after flap creation.

RESULTS

The mean absolute value of the measured cyclorotation was -1.5+/-4.2 degrees (range: -11.0 to 6.9 degrees ). The mean cyclorotation was 3.5+/-2.7 masculine (range: 0.1 to 11.0 degrees ). In 65% of all eyes cyclorotation was >2 masculine.

CONCLUSIONS

A static eyetracker driven by iris recognition demonstrated that cyclorotation of up to 11 degrees may occur in myopic and myopic astigmatic eyes when changing from a sitting to a supine position. Use of static eyetrackers with iris recognition may provide a more precise positioning of the ablation profile as they detect and compensate cyclorotation.

Cyclotorsional eye motion occurring between wavefront measurement and refractive surgery

PURPOSE

To quantify the cyclorotation occurring between wavefront measurement and laser refractive surgery.

SETTING

LaserVue Eye Center Ophthalmic Clinic, Santa Rosa, California, USA.

METHODS

The pupil camera of the Visx WaveScan wavefront device was used to obtain images of 51 eyes (26 patients) from 5 to 20 minutes before refractive laser surgery. Additionally, an infrared camera was mounted on the Visx Star S3 ActiveTrak excimer laser system to obtain another image immediately before the laser was fired. After surgery, the 2 sets of images were compared to determine the amount of cyclotorsion between the measurement and surgery.

RESULTS

Cyclorotation of individual eyes was as high as 9.5 degrees. The mean was approximately 2.0 degrees for each eye. Binocular excyclotorsion was the predominant trend, affecting 19 of 24 patients.

CONCLUSIONS

A low to moderate amount of cyclotorsion was observed in the transition from seated to supine position. Comparison of eye position at the time of measurement to eye position at the time of surgery can be used to adjust the laser ablation algorithm to compensate for this rotational displacement.

Very High Frequency Ultrasound Biometry of the Anterior and Posterior Chamber Diameter

PURPOSE

To measure the largest diameter of the anterior chamber (AC) and posterior chamber (PC) dimension and its orientation and determine the relationship with the principal keratometric meridians.

METHODS

Twenty-eight eyes of 14 subjects were scanned with high frequency (50 MHz) ultrasound in sequential meridional scan planes at 30 degrees increments. Observer identified angle and ciliary sulcus recess boundaries in each patient scan set were fit with an elliptical model to obtain the ellipse semi-major axis corresponding to the largest diameter and its meridional orientation. Anterior and posterior chamber diameters from raw data and model fit were compared using linear statistics. Circular statistics were used to compare the orientation of the largest diameter for raw ultrasound measurements, model estimations of largest diameter, and autorefractor determined keratometric axes.

RESULTS

The mean model diameters were anterior chamber OD 12.07 mm (0.32 SD); anterior chamber OS 12.06 mm (0.36 SD); posterior chamber OD 12.35 mm (0.42 SD); posterior chamber OS 12.33 mm (0.43 SD). The general trend for orientation of the meridian of largest diameter was in the horizontal meridian. In over 35% of eyes the difference between AC or PC meridian and the flat keratometric axis was greater than 20 degrees.

CONCLUSIONS

Accurate and reproducible anterior segment biometry depends on visualization of structures and minimization of eye and head movement error. The range and standard deviation of the diameter and orientation measures suggests anatomic variation is sufficient to require biometry for proper sizing and placement of intraocular devices that use angle or sulcus fixation.

Rotational malposition during laser in situ keratomileusis

PURPOSE

To investigate the degree of rotational malposition in eyes undergoing laser in situ keratomileusis.

DESIGN

Prospective observational study.

METHODS

We measured the rotational position of 240 eyes of 169 patients who underwent treatment for myopic or hyperopic astigmatism with the Alcon Summit Autonomous (Orlando, Florida) LADARVision excimer laser. Immediately preoperatively, each eye was marked while the patient was seated upright. Rotational position was measured on the supine patient immediately before beginning the laser exposure.

RESULTS

For all 240 eyes, mean +/- standard deviation (SD) torsional misalignment was 4.1 +/- 3.7 degrees (right eye 3.8 +/- 3.7 degrees, left eye 4.2 +/- 3.6 degrees). A total of 20 eyes (8%) had a deviation of greater than 10 degrees.

CONCLUSIONS

A 4 degree and 10 degree misalignment would theoretically result in a 14% and 35% undercorrection of astigmatism, respectively. Preoperative marking of the upright patient and subsequent rotational alignment of the supine patient before laser treatment may reduce the error in correction of astigmatism during excimer laser vision correction surgery.

Outcome of corneal and laser astigmatic axis alignment in photoastigmatic refractive keratectomy

PURPOSE

To compare the refractive results of laser astigmatic treatment in eyes in which the astigmatic axes of the eye and laser are aligned by limbal marking at the 6 o'clock position and in eyes that are not marked.

SETTING

University Hospital and Clinics, Madison, Wisconsin, USA.

METHODS

This retrospective study comprised 143 eyes that had photoastigmatic refractive keratectomy with the VISX Star excimer laser. The eyes were divided into marked (G1) and unmarked (G2) groups. Based on the preoperative astigmatism, each group was subdivided into low astigmatism (</=1.00 diopter [D]) and high astigmatism (>/=1.25 D). Early postoperative manifest refractions (1.0 to 2.5 months) were analyzed. The Alpins vector analysis method was used to calculate the target induced astigmatism, surgically induced astigmatism, difference vector (DV), magnitude of error (ME), angle of error (AE), and index of success (IS).

RESULTS

There was no significant difference between the groups in DV, ME, and IS. When the subgroups were analyzed, the DV and ME were comparable; the IS in the G1 high astigmatism subgroup was significantly better than that in the G2 high astigmatism subgroup (0.22 +/- 0.08 and 0.29 +/- 0.04, respectively; P <.0001). There was comparable scatter of AE values; 30% and 36% in G1 and G2, respectively, had an AE of 0. Similar scatter was observed in the subgroups. Of the eyes that had an AE of 0, 90% and 43% in the high astigmatism subgroups of G1 and G2, respectively (P <.05), had full correction of astigmatism.

CONCLUSION

Limbal marking and subsequent eye and laser astigmatic axis alignment improved the refractive outcome of laser astigmatic treatment of >/=1.25 D. A preliminary report of an ongoing prospective randomized study of eyes that had laser in situ keratomileusis is included.

Limbal relaxing incisions with cataract surgery

PURPOSE

To evaluate the effectiveness of limbal relaxing incisions (LRIs) for correcting corneal astigmatism during cataract surgery.

SETTING

Cullen Eye Institute, Houston, Texas, USA.

METHODS

In 12 eyes of 11 patients, cataract surgery was combined with LRIs. The LRIs were made according to a modified Gills nomogram and were based on preoperative corneal astigmatism determined with standard keratometry and computerized videokeratography (EyeSys Corneal Analysis System Version 3.2).

RESULTS

The mean preoperative keratometric cylinder was 2.46 +/- 0.81 diopters (D). At 1 month postoperatively, mean arithmetic reduction in keratometric cylinder was 1.12 +/- 0.74 D, and the with-the-wound (WTW) change (calculated by Holladay, Cravy, Koch vector analysis formula) was -0.70 +/- 0.44. From 1 day to 1 month postoperatively, there was 0.55 D of WTW regression with minimal change in the mean cylindrical axis. There were no overcorrections.

CONCLUSION

Limbal relaxing incisions are a practical, simple, and forgiving approach to the correction of astigmatism during cataract surgery.

Using a reference point and videokeratography for intraoperative identification of astigmatism axis

PURPOSE

To estimate the misalignment of the astigmatism axis caused by intraoperative identification of the axis without using reference points.

SETTINGS

Osaka University Medical School, Suita, Japan.

METHODS

This study included 38 eyes of 19 patients with no ocular pathology except refractive error and 32 eyes of 16 patients with cataract. A point was marked on the nasal conjunctiva, on the "intraoperative" horizontal axis as estimated by the examiner using a surgical microscope while the patient lay on the operating table in the supine position. Videokeratography was performed with the patient seated, and the degree of axial misalignment was determined by measuring the angle between the conjunctival mark and the horizontal axis identified on the video image.

RESULTS

Mean axial misalignment for all patients was 4.4 degrees +/- 2.8 (SD), which could theoretically cause about a 15% loss of surgical effect. The maximal misalignment was 14 degrees, which would correspond to a 48% loss of astigmatic correction.

CONCLUSION

The results of this study suggest that intraoperative identification of the astigmatism axis without using reference points may reduce the surgical effect because of axis misalignment. The use of a reference point and preoperative videokeratography may increase the accuracy of identification of the astigmatism axis.

Cyclotorsion in the seated and supine patient

We used Maddox double-rod measurements to determine if positionally induced ocular cyclotorsion occurs when a patient moves from the seated to supine position. Maddox double-rod measurements were determined twice while patients (N = 30) viewed a fixation light at a distance of 7 feet in both the seated and supine positions. The difference between axis measurements made in seated and supine positions was not statistically significant. There was also no significant difference between the two measurements made in the seated and in the supine positions. These data show that the eyes do not undergo positionally induced ocular cyclotorsion when a patient moves from a seated to a supine position.