Clinical utility of femtosecond laser-assisted astigmatic keratotomy after cataract surgery

Predicting the impact of femtosecond-assisted arcuate keratotomy combined with tri-planar clear corneal incisions on astigmatism in implantable collamer lens surgery: one-year follow-up

PURPOSE

To investigate the factors associated with and impact on the femtosecond-assisted (FS-assisted) limbal relaxing incision (LRI) combined with the steep-meridian tri-planar clear corneal incision (TCCI) to reduce astigmatism in patients undergoing Implantable Collamer Lens (ICL) surgery.

METHODS

Retrospective case series. The study reviewed patients with ICL surgery combined with FS-assisted LRIs paired with steep-meridian TCCIs. Correlation analysis examined the relationship between independent variables, including preoperative characteristics (intraocular pressure, corneal thickness, axial length, et al.), TCCI, and LRI surgical parameters. The predictors of surgically induced astigmatism (SIA) were determined using individual-level analysis and accounting for inter-eye correlation with the generalized estimating equation (GEE).

RESULTS

The study enrolled 69 patients, with 114 eyes (55 right and 59 left). The mean spherical equivalent (SEQ) was - 10.29 ± 2.99D and - 9.99 ± 2.72D for the right and left eye, respectively, while the mean preoperative corneal astigmatism was - 1.54 ± 0.47D and - 1.54 ± 0.46D for the right and left eyes, respectively. After 12 months of follow-up, univariate analysis revealed significant correlations between SIA and intraocular pressure (IOP), astigmatism type, TCCI position (degree), peripheral corneal thickness (PCT), LRI arc incision diameter, post depth (%), and angle, respectively (P = 0.046, 0.016, 0.039, 0.040, 0.009, 0.000, 0.000). Multivariate analysis using GEE demonstrated that axial length (AL), astigmatism type, LRI arc diameter, and angle were independent predictors of SIA (P = 0.000, 0.005, 0.029, 0.000).

CONCLUSIONS

The type of astigmatism and axial length were independent factors that affected SIA when modifying the LRI arc diameter and angle through FS-assisted steep-meridian TCCI paired with LRI in ICL surgery.

Astigmatic correction of simultaneous femtosecond laser-assisted cataract surgery (FLACS) with intrastromal arcuate keratotomy (ISAK) versus Toric intraocular Lens Impantation with conventional phacoemulsification

Background

To compare the efficacies in astigmatic correction of simultaneous femtosecond laser-assisted cataract surgery (FLACS) with intrastromal arcuate keratotomy (ISAK) versus toric intraocular lens (IOL) implantation with conventional phacoemulsification in moderate astigmatism.

Methods

A retrospective chart review was conducted for patients who had undergone cataract surgery by one surgeon. We identified patients with preoperative corneal astigmatism from + 0.75 to + 2.00 diopters (D) who had undergone astigmatic correction with FLACS with ISAK or toric IOL implantation with conventional phacoemulsification. We measured the visual acuity, intraocular pressure, automated keratometer, manifest refraction, and topography preoperatively and 1-day, 1-month, 3-month, and 6-month postoperatively. The vector analysis of refractive astigmatism was performed.

Results

Of a total of 48 eyes of 48 patients, 27 eyes of 27 patients had FLACS with ISAK (AK group), and 21 eyes of 21 patients had conventional cataract surgery with toric IOL implantation (toric IOL group). Refractive astigmatism was significantly decreased in both groups. The mean preoperative and 6-month postoperative refractive astigmatism were 1.85 ± 1.07 and 0.99 ± 0.51 D, respectively, in the AK group (P = 0.028), and 1.84 ± 0.81 and 0.68 ± 0.21 D, respectively, in the toric IOL group (P < 0.001). There was no significant difference in refractive astigmatism between the two groups at 6-month postoperatively (0.99 ± 0.51 vs 0.68 ± 0.21 D, P = 0.057). At 6-month postoperatively, parameters for vector analysis of refractive astigmatism showed no statistical difference between the two groups. Corneal astigmatism was significantly decreased in the AK group. Corneal astigmatism from topography and the automated keratometer were significantly lower in the AK group 6-month postoperatively compared to toric IOL group (0.94 ± 0.40 vs. 1.53 ± 0.46 D, P = 0.018 for topography; and 0.98 ± 0.69 vs. 1.37 ± 0.41 D, P = 0.032 for the automated keratometer).

Conclusions

FLACS with ISAK could be an effective procedure for reducing astigmatism as well as toric IOL implantation in cataract surgery.

FOCUSED (Femtosecond Optimized Continuous Uncorrected Sight with EDOF and Diffractive Multifocal IOLs) - A Review

PURPOSE OF REVIEW

The aim of this article is to review techniques to maximize all-distance uncorrected visual acuity and minimize photic phenomena after the implantation of multifocal and extended-depth of focus (EDOF) intraocular lenses (IOLs). This review examines the role of femtosecond laser-assisted cataract surgery (FLACS) in postoperative minimization of astigmatism and optimization of outcomes with multifocal and EDOF lenses.

RECENT FINDINGS

By incorporating intraoperative and preoperative imaging, femtosecond platforms such as those that utilize iris or conjunctival vessel registration, can enable a precision of corneal incisions and toric IOL markings that enable the lowest possible postoperative levels of astigmatism. Current studies suggest that with increasing IOL complexity, that is, trifocal versus bifocal, image degradation with even low levels of postoperative astigmatism are increased. To this end, current data support the utility of femtosecond laser arcuate incisions to enable the achievement of 0.5 D or less postoperative astigmatism for best outcomes with multifocal lenses.

SUMMARY

The synergistic combination of multifocal/EDOF IOLs with FLACS is an extremely promising route in achieving postoperative spectacle independence for patients. The marriage of the precision of FLACS with the increasing complexity of multifocal/EDOF IOLs will fuel nomogram adjustment and systematic improvements, such as the Wörtz-Gupta formula. Such strategies provide an unprecedented precision to cataract surgery that makes FOCUSED (Femtosecond Optimized Continuous Uncorrected Sight with EDOF and Diffractive Multifocal IOLs) a reality.

Optimization of surgical parameters based on patient-specific models: Application to arcuate keratotomy

PURPOSE

To determine surgical parameters for arcuate keratotomy by simulating the intervention with a patient-specific model.

SETTING

University Eye Clinic Salzburg, Paracelsus Medical University, Austria, and Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland.

DESIGN

Computational modeling study.

METHODS

A new approach to plan arcuate keratotomy based on personalized finite element simulations was developed. Using this numeric tool, an optimization algorithm was implemented to determine the incision parameters that best met the surgeon's requirements while preserving the orientation of the astigmatism. Virtual surgeries were performed on patients to compare the performance of the simulation-based approach with results based on the Lindstrom and Donnenfeld nomograms and with intrastromal interventions.

RESULTS

Retrospective data on 28 patients showed that personalized simulation reproduced the surgically induced change in astigmatism (Pearson correlation = 0.8). Patient-specific simulation was used to examine strategies for arcuate interventions on 621 corneal topographies. The Lindstrom nomogram resulted in low postoperative astigmatism (mean 0.03 diopter [D] ± 0.3 [SD]) but frequent overcorrections (20%). The Donnenfeld nomogram and intrastromal incisions resulted in a small amount of overcorrection (1.5%) but a wider spread in astigmatism (mean 0.63 ± 0.35 D and 0.48 ± 0.50 D, respectively). In contrast, the new numeric parameter optimization approach led to postoperative astigmatism values (mean 0.40 ± 0.08 D, 0.20 ± 0.08 D, and 0.04 ± 0.13 D) that closely matched the target astigmatism (0.40 D, 0.20 D, and 0.00 D), respectively, while keeping the number of overcorrections low (<1.5%).

CONCLUSION

Using numeric modeling to optimize surgical parameters for arcuate keratotomy led to more reliable postoperative astigmatism, limiting the risk for overcorrection.

Corneal topography in keratoconus evaluated more than 30 years after penetrating keratoplasty: a Fourier harmonic analysis

The aim of this observational study was to examine the characteristics of anterior and posterior corneal topography in keratoconic eyes more than 30 years after penetrating keratoplasty (PK). Patients who maintained clear grafts for more than 30 years after PK were included and divided into the keratoconus (KC) group or other diseases (Others) group, based on the primary indication. Twenty-six eyes of 26 patients were included. The KC group and the Others group included 14 eyes and 12 eyes, respectively. The KC group participants were younger at the time of surgery (P = 0.03). No differences were found in best-spectacle-corrected visual acuity, keratometric power, and central-corneal-thickness. Based on corneal topography using Fourier harmonic analyses, regular astigmatism in the anterior cornea was significantly larger (P = 0.047) and the spherical component in the posterior cornea was significantly lower (P = 0.01) in the KC group. The area under the receiver operating characteristic curve of the spherical component, regular astigmatism, asymmetry component, and higher-order irregularity were 66.07%, 63.10%, 57.14%, and 59.23%, respectively, in the anterior cornea and 80.65%, 52.98%, 63.10%, and 63.99%, respectively, in the posterior cornea. Our results suggested that Fourier harmonic analysis of corneal topography could be useful for patients with KC long after PK.

Outcomes of Femtosecond Laser Arcuate Incisions in the Treatment of Low Corneal Astigmatism

Purpose

To evaluate real-world outcomes of astigmatism management with femtosecond laser arcuate incisions in patients with low corneal astigmatism (<1.0 D) using a novel formula for arcuate incision calculation compared to outcomes after conventional cataract surgery without surgical management of astigmatism.

Patients and Methods

The Wörtz-Gupta™ Formula (available at www.lricalc.com) was used to calculate femtosecond laser arcuate parameters for 224 patients with <1 D of corneal astigmatism who underwent cataract surgery; lens power was determined with the Barrett Universal II formula. Uncorrected distance visual acuity (UCDVA) and refractive astigmatism measurements were obtained, with an average follow-up of 4 weeks.

Results

The average preoperative cylinder was similar (0.61 D in the femtosecond group [n=124] and 0.57 D in the conventional group [n=100] (P>0.05)). More patients had ≤0.5 D of postoperative corneal astigmatism in the femtosecond group (n=110/124, 89%) than in the conventional group (n=71/100, 71%), respectively (P=0.001). The mean absolute postoperative refractive astigmatism was higher in the conventional surgery group than in the femtosecond group (0.43 ± 0.4 D vs 0.26 ± 0.28 D); these differences were statistically significant (P<0.001). The percentage of patients with UCDVA of 20/20 or better vision was higher in the femtosecond group (62%) than the conventional group (48%) (P=0.025).

Conclusion

Using the femtosecond laser for arcuate incisions in combination with a novel nomogram can provide excellent anatomic and refractive outcomes in patients with lower levels of preoperative astigmatism at the time of cataract surgery.

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Femtosecond laser-assisted cataract surgery: A review

PURPOSE

Review scientific literature concerning femtosecond laser-assisted cataract surgery.

METHODS

Following databases were searched: CENTRAL (Cochrane Eyes and Vision Trials Register; Cochrane Library: Issue 2 of 12, June 2019), Ovid MEDLINE^® without Revisions (1996 to June 2019), Ovid MEDLINE^® (1946 to June 2019), Ovid MEDLINE^® Daily Update June 2019, MEDLINE and MEDLINE Non-Indexed Items, Embase (1980-2019), Embase (1974 to June 2019), Ovid MEDLINE^® and Epub Ahead of Print, in-Process & Other Non-Indexed Citations and Daily (1946 to June 2019), Web of Science (all years), the metaRegister of Controlled Trials ( www.controlled-trials.com ), ClinicalTrials.gov ( www.clinicaltrial.gov ) and World Health Organization International Clinical Trials Registry Platform ( www.who.int/ictrp/search/en ). Search terms/keywords included 'Femtosecond laser' combined with 'cataract', 'cataract surgery'.

RESULTS

Based on quality of their methodology and their originality, 121 articles were reviewed, including randomised controlled trials, cohort studies, case-controlled studies, case series, case reports and laboratory studies. Each step of the femtosecond laser-assisted cataract surgery procedure (corneal incisions, arcuate keratotomies, capsulotomy and lens fragmentation) has been discussed with relevance to published outcomes, as well as complication rates of femtosecond laser-assisted cataract surgery, and what we can learn from the larger studies/meta-analyses and the economics of femtosecond laser-assisted cataract surgery within different healthcare settings.

CONCLUSION

Studies suggest that the current clinical outcomes of femtosecond laser-assisted cataract surgery are not different to conventional phacoemulsification surgery and it is not cost effective when compared with conventional phacoemulsification surgery. In its current technological form, it is a useful surgical tool in specific complex cataract scenarios, but its usage has not been shown to translate into better clinical outcomes.

Toric intraocular lenses in eyes with with-the-rule, against-the-rule, and oblique astigmatism: One-year results

PURPOSE

To assess 1-year clinical results of toric intraocular lenses (IOLs) in eyes having with-the-rule (WTR), against-the-rule (ATR), or oblique corneal astigmatism.

SETTING

Four ophthalmic surgical sites, Japan.

DESIGN

Prospective case series.

METHODS

One of 3 toric IOLs or 1 nontoric IOL was implanted in eyes having phacoemulsification and IOL implantation.

RESULTS

The study comprised 218 eyes (155 patients). Based on the suggestion of an online toric calculator with anterior corneal curvature data, 63 eyes received the SN6AT3 IOL with a cylinder power of 1.50 diopters [D] at IOL plane (1.50 D cylinder IOL) 55 eyes the SN6AT4 IOL with a cylinder power of 2.25 D at IOL plane (2.25 D cylinder IOL), and 58 eyes the SN6AT5 IOL with a cylinder power of 3.00 D at IOL plane (3.00 D cylinder IOL) (all Acrysof IQ toric), and 42 eyes received the SN60WF IOL (nontoric IOL). One hundred ninety-four eyes (89.0%) completed 1-year of follow-up. The centroid error in predicted residual astigmatism calculated using vector analysis was close to the origin in eyes with WTR astigmatism (0.17 diopter [D] @ 174.9 ± 0.54 D), while those with ATR and oblique astigmatism were significantly shifted toward the ATR direction (P < .001). The distance from the origin was significantly smaller in the WTR group than in ATR and oblique groups (P < .05). The centroid errors were shifted toward ATR in all toric IOL groups (P < .001); however, the distance from the origin was not different between groups (P = .52). Postoperatively, the mean absolute misalignment of the IOLs was 5.92 degrees ± 5.59 (SD) at 1 day and 6.24 ± 5.87 degrees at 1 year. The results of other clinical parameters were excellent, with no significant differences between astigmatism categories or IOL models.

CONCLUSION

Based on anterior corneal curvature alone, toric IOLs undercorrected ATR and oblique astigmatism; however, 1-year clinical results of toric IOLs were highly stable and satisfactory.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Evaluation of the effectiveness of combined femtosecond laser-assisted cataract surgery and femtosecond laser astigmatic keratotomy in improving post-operative visual outcomes

Background

To determine postoperative refractive and visual outcomes and astigmatic changes after femtosecond laser astigmatic keratotomy in femtosecond laser-assisted cataract surgery (FLACS).

Methods

This was a prospective interventional case series. Patients with age-related cataract and corneal astigmatism (1.0–3.0D) were treated with FLACS and femtosecond laser astigmatic keratotomy (FSAK). All patients underwent examinations before and 3 months after surgery; visual acuity, subjective and objective refraction, and corneal astigmatism were evaluated and recorded for all patients by using an OPD-Scan III topographer. Vector analysis of astigmatic changes was performed by using the Alpins vector method.

Results

Twenty-five patients were included in the study. Postoperatively, refractive and corneal astigmatism were both reduced significantly (P < 0.05), concurrent with improved uncorrected distance visual acuity and corrected distance visual acuity. The rate of spectacle use was significantly reduced at 3 months postoperatively (P = 0.001). The mean magnitude of the target-induced astigmatism vector (1.40 ± 0.37D) was slightly higher than the mean magnitude of the surgically induced astigmatism vector (1.22 ± 0.46D). The magnitude of error (− 0.18 ± 0.36D), as well as the correction index (0.88 ± 0.29), demonstrated slight undercorrection. The angle of error was 0.85 ± 13.69°, which was close to zero.

Conclusions

Combined femtosecond laser-assisted cataract surgery and astigmatic keratotomy may be an effective approach to manage preoperative astigmatism in cataract surgery, although slight undercorrection may exist during short-term follow-up.

Trial registration

ChiCTR-TRC-14004977

Learning curve of femtosecond laser-assisted cataract surgery: Experience of surgeons new to femtosecond laser platform

PURPOSE

The purpose of this study is to assess the learning curve in the initial 100 cases of cataract surgery performed using femtosecond laser-assisted cataract surgery (FLACS) by experienced cataract surgeons without prior experience in femtosecond laser platform.

METHODS

This study was conducted at tertiary care eye hospital, South India. This was a prospective interventional study. The first 100 consecutive eyes undergoing FLACS were studied to understand docking time, number of docking attempts, problems encountered during docking, and complications attributable to docking. Phacoemulsification performed after femtosecond laser was also studied for complications, need for additional instrumentation, and total time required for surgery. Comparison was also made between two operating surgeons.

RESULTS

Successful docking was recorded in 70% eyes at the first attempt. Mean time taken for successful docking was 9.3 ± 6.4 min (median = 6 min, interquartile range (IQR) = 5-10 min, range = 4-35 min). When surgeries were divided into quartiles, docking time reduced significantly from 16.2 ± 7.9 min in the first quartile to 6.2 ± 2.7 min in the fourth quartile (P < 0.001). Phacoemulsification postdocking required 12.9 ± 6.2 min (median = 10 min, IQR = 9-17.5 min). Six eyes showed anterior capsular tags, one had radial extension of capsulorhexis, and two eyes showed pupillary miosis after femtosecond laser application. At 6 weeks, 79% eyes attained uncorrected vision of 20/20, and all eyes had best-corrected vision of 20/20.

CONCLUSION

Approximately 25-30 cases were required before obtaining reproducible results with FLACS, irrespective of cataract surgical experience, suggesting that training programs must offer a minimum 25 surgeries. Very few complications occurred during the learning curve, making it patient friendly.

A novel nomogram for the treatment of astigmatism with femtosecond-laser arcuate incisions at the time of cataract surgery

Purpose

The purpose of this study was to determine an arcuate incision (AI) nomogram to treat astigmatism during femtosecond laser-assisted cataract surgery.

Methods

This is a retrospective, cohort study. Femtosecond laser (FSL)-assisted transepithelial AIs were created at a 9.0 mm optical zone, 80% depth, centered on the limbus. We modified the manual Donnenfeld limbal relaxing incision nomogram to 70% for with-the-rule (WTR), 80% for oblique (OBL), and 100% for against-the-rule (ATR) astigmatism. The correction index (CI) equaled AI-induced astigmatism/target-induced astigmatism. Measures included preoperative keratometric corneal cylinder (Pre Kcyl), postoperative Kcyl (Post Kcyl), and postoperative residual refractive astigmatism (Post RRA).

Results

Mean Pre Kcyl and 1–2 months Post RRA in 161 eyes of 116 patients were 0.626±0.417 diopters (D) (range 0.5–2 D), and 0.495±0.400 D (range 0–1.5 D), respectively. Mean absolute astigmatic changes (Pre Kcyl–Post Kcyl) without accounting for axis change in the WTR, ATR, and OBL groups were 0.165±0.383 D (P<0.001), 0.374±0.536 D (P<0.001), and 0.253±0.416 D (P=0.02), respectively. Mean absolute astigmatic changes using RRA as the postoperative measurement (Pre Kcyl–Post RRA) without accounting for axis change were 0.440±0.461 D (P<0.001), 0.238±0.571 D (P<0.05), 0.154±0.450 (P=0.111) in WTR, ATR, and OBL groups, respectively. CIs for WTR, ATR, and OBL were 0.53, 1.01, and 0.95, respectively. There were no intraoperative or postoperative complications related to the AIs.

Conclusion

Transepithelial FSL-AIs using the modified Donnenfeld nomogram show potential for management of mild to moderate corneal astigmatism. An increase in the magnitude or reduction of the optical zone size for the treatment of WTR and ATR astigmatism for this nomogram may further improve refractive accuracy.

Evaluation of Femtosecond Laser Intrastromal Incision Location Using Optical Coherence Tomography

PURPOSE

To use optical coherence tomography (OCT) to evaluate the femtosecond laser intrastromal incisions made during cataract surgery to reduce corneal astigmatism.

DESIGN

Retrospective case series.

PARTICIPANTS

Seventy-seven eyes of 77 patients.

METHODS

Paired intrastromal incisions were created using the Catalys femtosecond laser (Abbott Medical Optics, Inc., Santa Ana, CA). The planned intrastromal incision parameters were 20% uncut anterior, 20% uncut posterior, midpoint depth of 50%, and 90° side cut angle. Optical coherence tomography scans were obtained 3 weeks or more after surgery to assess these 4 parameters, and actual values were compared with intended values.

MAIN OUTCOME MEASURES

Percentages of uncut anterior and posterior tissue, midpoint depth, and degrees of side cut angle.

RESULTS

The mean values were 17.2±5.8% (range, 7.2%-36.9%) for uncut anterior, 32.5±8.8% (range, 6.0%-57.9%) for uncut posterior, and 42.3±6.6% (range, 25.5%-65.4%) for midpoint depth, which all were significantly different from the planned parameters (all P < 0.05). The mean side cut angle was 88.5°±5.6° (range, 71°-114°) and was significantly different from the planned side cut angle of 90° (P < 0.05). In 50 eyes that had paired intrastromal incisions scanned by the OCT, there was no correlation between the paired incisions for midpoint depth and side cut angle (correlation coefficient, r = -0.063 and -0.067, respectively; P > 0.05).

CONCLUSIONS

The intrastromal incision midpoint depth was significantly more anterior than the planned depth of 50%. The locations of paired intrastromal incisions in each eye were not correlated. Further improvements are needed to ensure the precise location of the intrastromal incisions made with this device.