Femtosecond-Laser Assisted Surgery of the Eye: Overview and Impact of the Low-Energy Concept

Comparison of low-energy FLACS and conventional cataract surgery: meta-analysis and systematic review

TOPIC

To systematically compare the effectiveness of conventional phacoemulsification surgery (CPS) and low-energy femtosecond laser-assisted cataract surgery (FLACS) in patients with cataract.

CLINICAL RELEVANCE

Cataract surgery is a common procedure, and comparing different techniques such as CPS and low-energy FLACS is crucial for optimizing patient outcomes.

METHODS

The PubMed, Web of Science, MEDLINE, EMBASE, and Cochrane library databases were searched for clinical trials. Outcomes of procedure time, effective phacoemulsification time, balanced salt solution usage, cumulative dissipated energy, mean change of corrected distance visual acuity, endothelial cells reduction, central corneal thickness (CCT), and aqueous cytokine level were evaluated. The effect measures were weighted mean differences with 95% CI. The protocol was registered at the Prospective Register for Systematic Reviews (registration number CRD42023420173).

RESULTS

11 studies were included in this meta-analysis, of which 1680 eyes were analyzed (637 eyes in the low-energy FLACS group and 1043 eyes in the CPS group). Low-energy FLACS demonstrated significantly fewer reductions in endothelial cell count at 6 months ( P < .001) compared with CPS. It also exhibited a shorter effective phacoemulsification time ( P < .001) and less balanced salt solution usage ( P < .001). However, there were no differences in cumulative dissipated energy, corrected distance visual acuity, CCT changes, or aqueous cytokine levels between the 2 groups.

CONCLUSIONS

Both low-energy FLACS and CPS are effective in treating cataracts, but low-energy FLACS may offer advantages such as reduced phacoemulsification time and less endothelial cell loss.

Femtosecond Laser-Assisted Autologous Glueless Simple Limbal Epithelial Transplantation in Unilateral Limbal Stem Cell Deficiency: 12-Month Outcome of the First Clinical Cases

PURPOSE

Surgical treatment of unilateral limbal stem cell deficiency (LSCD) is based on limbal stem cell transplantation. Glueless simple limbal epithelial transplantation (G-SLET) technique implements several limbal micrografts harvested from the healthy eye of the same patient into the peripheral corneal tunnels without the use of fibrin glue and human amniotic membrane.

METHODS

A novel customized algorithm and software for a low-energy femtosecond laser (FSL) were developed and tested using 5 pairs of isolated porcine eyes. FSL-assisted G-SLET modification was assessed in 3 clinical cases of unilateral LSCD caused by chemical burns. Corneal epithelization efficacy, best-corrected visual acuity, corneal epithelial mapping, central corneal thickness, and impression cytology with immunohistochemical examination were evaluated. All patients were followed up for 12 months postoperatively.

RESULTS

The FSL set for 100% energy and the pattern of 8 nonpenetrating vertical cuts with oblique tunnel portions having variable incision depths and diameter of 8.5 mm and higher were selected for further clinical evaluation. Clinically, stable corneal epithelialization was achieved 2 to 3 weeks after intervention. At the 6-month follow-up, all patients had a healthy corneal epithelium with limbal micrografts visible inside the corneal tunnels. Best-corrected visual acuity markedly improved in 2 cases, but not in the third case with severe corneal stromal scarring. In addition, all patients noted a full-scale reduction in subjective complaints and substantial improvement in their quality of life.

CONCLUSIONS

The FSL-assisted G-SLET is a new technique for autologous limbal stem cell transplantation in patients with unilateral LSCD. It allows the standardization of corneal tunnel localization and dimensions, thereby increasing the safety of the surgical procedure.

Pupil versus 1st Purkinje capsulotomy centration with femtosecond laser: Long term outcomes with a sinusoidal trifocal lens

PURPOSE

To assess the role of femtosecond laser-assisted capsulotomy centration in the long-term intraocular positioning of a multifocal intraocular lens.

DESIGN

Prospective comparative study.

METHODS

A total of 60 eyes of 30 patients underwent femtosecond laser-assisted Refractive Lens Exchange (RLE). For every patient, capsulotomy centration was randomly performed according to pupil centre (PC) in one eye and first Purkinje reflex (FPR) in the other. The intraocular lens (IOL) positioning, visual acuities, spherical equivalent, internal aberrometry and quality of vision were assessed and compared at 3 years' follow-up between groups (PC and FPR).

RESULTS

Intraocular lens positioning showed a statistically significant difference between groups, with a closer centration to the visual axis in the FPR patients (p < 0.001). Internal aberrometry showed higher values in the PC capsulotomy centration group (p < 0.01).

CONCLUSIONS

FPR centered capsulotomy is associated to a closer centration of the IOL to the visual axis.

Assessment of Changes in Cap and Residual Stromal Thickness Values during a 6-Month Observation after Refractive Lenticule Extraction Small Incision Lenticule Extraction

Background: In this study, the changes in corneal cap and residual stromal thickness (RST) values during a 180-day observation period after refractive lenticule extraction small incision lenticule extraction (ReLEx SMILE) were assessed. Methods: Fifty patients underwent ReLEx SMILE using the VisuMax 500 femtosecond laser, with corneal imaging conducted pre and post procedure via anterior segment optical coherence tomography (AS-OCT). Cap thickness in the center and 1.5 mm from the center in four meridians was measured at various intervals. Results: The results showed a significant decrease in cap thickness 180 days post procedure compared to earlier intervals (p < 0.05). Similarly, RST decreased gradually and significantly post procedure (p < 0.05). Notably, changes in cap thickness within the central 1.5 mm area were more dynamic than RST changes during the 6-month observation period following SMILE. Conclusions: The corneal cap thickness measured with swept-source AS-OCT within the central 1.5 mm area underwent more dynamic changes than the residual stromal thickness during the 6-month observation following SMILE.

Update on Femtosecond Laser-Assisted Cataract Surgery: A Review

The advent of femtosecond lasers has resulted in a new standard in cataract surgery, intended to overmatch the paradigm of conventional phacoemulsification. Femtosecond laser-assisted cataract surgery (FLACS) enables a higher level of reproducibility, precision, accuracy, and customization when performing several steps of cataract (or lens) surgery. Capsulotomy, corneal incisions, lens fragmentation, and arcuate incisions are the main procedures performed using FLACS. As the demand for better refractive outcomes and spectacle independence increases, the features of FLACS are highly relevant, especially when considering the implantation of premium intraocular lenses, such as toric, enhanced depth-of-focus, or multifocal lenses. The present article reviews the state of the art of femtosecond laser-assisted cataract (lens) surgery, contemplating the advantages and limitations of the two types of femtosecond laser pulses available (high and low energy) by evaluating their reported outcomes and complications.

Combined Femtosecond Laser-Assisted Keratotomy and Cataract Surgery for Enhancing Refractive Outcomes. An Indonesian Case Study

Purpose

We evaluate the reduction of corneal astigmatism and the improvement of visual outcomes of this surgical method in the Indonesian population. We also assess the accuracy and predictability of using femtosecond laser astigmatic keratotomy (FLAK) combined with cataract surgery.

Patients and Methods

In a retrospective study, a total of 275 subjects (78 with against-the-rule (ATR) astigmatism, 178 with with-the-rule (WTR) astigmatism, and 19 with oblique (OBL) astigmatism) with preexisting corneal astigmatism ranging from 0.75D to 3.00D underwent FLAK. All subjects completed a 3-month follow-up. The femtosecond laser used for creating paired AK 2.2 mm, primary incision, and paracentesis incision was the FEMTO Z8 NEO from Ziemer Ophthalmic System, Switzerland. The surgical approach was guided by the "NAPA" nomogram.

Results

The reduction in postoperative astigmatism was 56.90% for the WTR group, 49.46% for the ATR group, and 47.33% for the oblique group. A significant reduction in astigmatism was observed at the 1-week, 1-month, and 3-month follow-up intervals in both the WTR and ATR groups. The reduction in astigmatism was more favorable in cases of moderate astigmatism within the WTR group, as compared to the ATR and oblique groups. Postoperative astigmatism reduction was found to be more predictable in the right eye than in the left eye.

Conclusion

The combination of FLAK can be considered as a potential method for reducing corneal astigmatism ranging from 1.00D to <3.00D. The highest reduction was observed in the WTR group, along with a higher rate of intended correction without astigmatism meridian shift in the right eye for the WTR group. However, factors such as cyclotorsion resulting from the surgical technique, alignment of docking, incision length, and preoperative astigmatism need to be taken into account for further enhancement and predictability of astigmatism reduction with this method.

Safety and efficacy of cataract surgery performed with a low-energy femtosecond laser compared with conventional phacoemulsification in Chinese patients: a randomized clinical trial

BACKGROUND

To compare the safety and efficacy of femtosecond laser-assisted cataract surgery (FLACS) performed with the low-energy FEMTO LDV Z8 (Ziemer Ophthalmic Systems AG, Port, Switzerland) laser compared with conventional phacoemulsification (CP) in Chinese patients.

METHODS

This prospective, multicenter, interventional study included 126 patients who were randomized (1:1) to undergo either FLACS or CP followed by intraocular lens (IOL) implantation between January 2019 and April 2020. The primary endpoint included the comparison of the endothelial cell loss (ECL) between the two groups at 3 months. Secondary endpoints included the comparison of cumulative dissipated energy (CDE), change in central corneal thickness (CCT) from baseline, and postoperative uncorrected and corrected distance visual acuities (UDVA and CDVA) in the two groups.

RESULTS

At all postoperative time points, the FLACS group was found to be non-inferior to CP for the mean ECL (- 409.3 versus - 436.9 cells/mm² at 3 months) and mean CDE (4.1 versus 4.5 percent-seconds). The increase in CCT was significantly lower in the FLACS group compared with the CP group at Day 7 (4.9 versus 9.2 µm; P = 0.04); however, the difference was not statistically significant at 1 and 3 months. Postoperatively, mean UDVA and CDVA were comparable between the two groups. No intraoperative complications occurred.

CONCLUSIONS

Cataract surgery performed with a low-energy femtosecond laser was non-inferior to CP; however, the FLACS group had a statistically significantly lower increase in CCT at Day 7 compared with CP. Trial registration This trial is registered at ClinicalTrials.gov on May 15, 2019, with trial registration number: NCT03953053.

Design and test of a rigid endomicroscopic system for multimodal imaging and femtosecond laser ablation

Significance

Conventional diagnosis of laryngeal cancer is normally made by a combination of endoscopic examination, a subsequent biopsy, and histopathology, but this requires several days and unnecessary biopsies can increase pathologist workload. Nonlinear imaging implemented through endoscopy can shorten this diagnosis time, and localize the margin of the cancerous area with high resolution.

Aim

Develop a rigid endomicroscope for the head and neck region, aiming for in-vivo multimodal imaging with a large field of view (FOV) and tissue ablation.

Approach

Three nonlinear imaging modalities, which are coherent anti-Stokes Raman scattering, two-photon excitation fluorescence, and second harmonic generation, as well as the single photon fluorescence of indocyanine green, are applied for multimodal endomicroscopic imaging. High-energy femtosecond laser pulses are transmitted for tissue ablation.

Results

This endomicroscopic system consists of two major parts, one is the rigid endomicroscopic tube 250 mm in length and 6 mm in diameter, and the other is the scan-head (10 × 12 × 6    cm 3 in size) for quasi-static scanning imaging. The final multimodal image accomplishes a maximum FOV up to 650    μ m , and a resolution of 1    μ m is achieved over 560    μ m FOV. The optics can easily guide sub-picosecond pulses for ablation.

Conclusions

The system exhibits large potential for helping real-time tissue diagnosis in surgery, by providing histological tissue information with a large FOV and high resolution, label-free. By guiding high-energy fs laser pulses, the system is even able to remove suspicious tissue areas, as has been shown for thin tissue sections in this study.

Solving STODS-Surgical Temporary Ocular Discomfort Syndrome

The term STODS (Surgical Temporary Ocular Discomfort Syndrome) has been coined to describe the ocular surface perturbations induced by surgery. As one of the most important refractive elements of the eye, Guided Ocular Surface and Lid Disease (GOLD) optimization is fundamental to success in achieving refractive outcomes and mitigating STODS. Effective GOLD optimization and the prevention/treatment of STODS requires an understanding of the molecular, cellular, and anatomic factors that influence ocular surface microenvironment and the associated perturbations induced by surgical intervention. By reviewing the current understanding of STODS etiologies, we will attempt to outline a rationale for a tailored GOLD optimization depending on the ocular surgical insult. With a bench-to-bedside approach, we will highlight clinical examples of effective GOLD perioperative optimization that can mitigate STODS' deleterious effect on preoperative imaging and postoperative healing.

Intraoperative complications of cataract surgery using a low-energy femtosecond laser: Results from a real-world high-volume setting

In this study, we report data on intraoperative complications occurring after cataract surgery in a high-volume single-center setting using a low-energy, mobile femtosecond laser. We retrospectively reviewed the medical records of patients who underwent femtosecond laser-assisted cataract surgery (FLACS) in our hospital between August 2015 and December 2019. Among the sample of 1,806 eyes of 1,131 patients (903 left and 903 right eyes), the mean age was 75.8 years (range, 21-99 years). The overall intraoperative complication rate was 0.28% (n = 5), with three cases of anterior capsule tear (0.17%) and two cases of posterior capsule tear (0.11%). No further complications occurred. This study underlines the safety of low-energy femtosecond-assisted cataract surgery in a real-world setting with a very low rate of intraoperative complications.

Effectiveness of reducing corneal astigmatism after combined high-frequency LDV Z8 femtosecond laser-assisted phacoemulsification and arcuate keratotomy

Purpose: In this retrospective study, the efficacy of the FEMTO LDV Z8 Femtosecond Laser-Assisted Cataract Surgery (Femto Z8 FLACS) and the Femtosecond laser Arcuate Keratotomy (FSAK) in decreasing the corneal astigmatism was investigated.

Methods: During FLACS, FSAK was positioned with the help of the FEMTO LDV Z8 laser at a diameter of 8.5 mm and an 80% depth. Before and 3 months after surgery, the astigmatism of the cornea was measured with the aid of Pentacam. The variables influencing the efficacy of FSAK were assessed using the multiple regression analysis technique. Vector analyses were carried out. To determine the net corneal alterations, the with-the-wound and against-the-wound variations were computed along the FSAKs’ meridian.

Results: This study investigated 80 eyes from 62 participants. The average keratometric astigmatism value was 0.92 ± 0.44 diopters (D). The average keratometric astigmatism decreased to 0.61 ± 0.45 D 3 months following FSAK compared to preoperative corneal astigmatism (p &lt; 0.05). Additionally, there was a considerable decline in the percentage of eyes with ±0.5 D and ±1.0 D astigmatism, which reduced 3 months after surgery by 58% and 85%, respectively (p &lt; 0.05).

Conclusion: The FEMTO LDV Z8 laser can create an effective and precise arcuate keratotomy with an excellent safety profile, rapid recovery, and vision stability.

The creation of a corneal incision with a femtosecond laser

BACKGROUND: The cutting action of a femtosecond laser (FS-laser) on the corneal tissue is performed using a photodestructive effect. FS-laser technology is used in many different areas of corneal surgery, and studying this effect is an actual issue. AIM: To evaluate the surface of the corneal incision created by a FS-laser (experimental study). MATERIALS AND METHODS: 20 porcine eyes were divided into two groups (FS-laser and keratome). The corneal tissue surface in the area of contact between two lips of the incision was visualized by electron microscopy. RESULTS: In all cases, we received a full-thickness incisions through the cornea. Images obtained by electron microscopy showed regular surface, no signs of thermal or mechanical damage to the corneal structure. CONCLUSIONS: The FS-laser is used as a microscopic scalpel in surgery. The precision cutting process is performed by mechanical forces generated by photodestruction by expanding cavitation bubbles.

Femtosecond Laser-Assisted Ophthalmic Surgery: From Laser Fundamentals to Clinical Applications

Femtosecond laser (FSL) technology has created an evolution in ophthalmic surgery in the last few decades. With the advantage of high precision, accuracy, and safety, FSLs have helped surgeons overcome surgical limits in refractive surgery, corneal surgery, and cataract surgery. They also open new avenues in ophthalmic areas that are not yet explored. This review focuses on the fundamentals of FSLs, the advantages in interaction between FSLs and tissues, and typical clinical applications of FSLs in ophthalmology. With the rapid progress that has been made in the state of the art research on FSL technologies, their applications in ophthalmic surgery may soon undergo a booming development.

Prostaglandin Release After Low-Energy Femtosecond Laser-Assisted Cataract Surgery Without Anti-Inflammatory Drug Premedication

PURPOSE

To compare prostaglandin E2 (PGE-2) levels in the aqueous and pupil diameter in patients undergoing low-pulse energy femtosecond laser-assisted cataract surgery (LCS) without non-steroidal anti-inflammatory (NSAID) pretreatment with either fragmentation or capsulotomy performed first.

DESIGN

Prospective, randomized, fellow-eye controlled comparison.

METHODS

This study was undertaken at the Department of Ophthalmology, Medical University of Vienna. The population consisted of 140 eyes of 70 patients with bilateral age-related cataract. Bilateral same-day LCS with either anterior capsulotomy before lens fragmentation (Caps-First) in one eye or vice versa (Frag-First) in a random sequence were performed. Aqueous was tapped 5 minutes after LCS and PGE-2 concentration was analyzed. Pupil diameters were recorded immediately before and after femtosecond laser pretreatment. The main outcome measure was PGE-2 concentrations in picograms/milliliter and pupil diameter in millimeters.

RESULTS

Mean PGE-2 concentrations were 42.0 ± 63.7 pg/mL in the Caps-First group versus 71.8 ± 160.7 pg/mL with the Frag-First group (P = .186). Mean pupil diameters before and after pretreatment were 7.6 ± 0.8 mm and 7.6 ± 0.8 mm, respectively (P = .871). Mean PGE-2 concentrations and pupil diameters did not show any significant difference between time points or groups.

CONCLUSIONS

Low-energy femtosecond laser pretreatment did not increase PGE-2 levels in the absence of NSAID pretreatment. This was independent of whether capsulotomy or fragmentation was performed first. Moreover, no pupillary miosis was observed.

Evaluation of the Optical Aspects of the Ophthalmic Viscosurgical Device During Femtosecond Laser-Assisted Cataract Surgery

Purpose

In femtosecond laser-assisted cataract surgery (FLACS), capsulorhexis can be performed with an ophthalmic viscosurgical device (OVD) filled in the anterior chamber. We aimed to investigate changes in the laser properties in various optical aspects, such as focal shifting, reflection, and absorption associated with OVD.

Methods

Simulation was achieved by calculating the laser power attenuation due to reflection and spot size change using the Gullstrand eye model. Additionally, we calculated the absorption coefficient by measuring the laser power passing through the OVD with a laser meter and evaluated the effect of absorption by the OVD.

Results

In our simulation, power attenuation due to reflection was a maximum of 0.07%, and power attenuation was 0.08% even when considering the change according to the incident angle. Power attenuation due to the change of the spot size at the focus was 0.005%. Owing to the absorption of the OVD, a power increase of up to 13.5% was required for an anterior chamber depth of 3.0 mm to obtain the same effect as the aqueous humor.

Conclusions

The main reason for laser power attenuation associated with OVD was laser absorption through the OVD, and could also be caused by laser cavitation bubbles. To complete a safe capsulotomy during FLACS, the laser power should be increased appropriately, considering the absorption by the OVD in the anterior chamber.

Translational Relevance

The study results can be applied to calculate the optimal femtosecond laser energy to achieve complete capsulotomy during FLACS in the presence of anterior chamber OVD.

Safety of femtosecond laser-assisted cataract surgery versus conventional phacoemulsification for cataract: A meta-analysis and systematic review

Purpose

To compare the complications of femtosecond laser-assisted cataract surgery (FLACS) with those of conventional phacoemulsification surgery (CPS) for age-related cataracts.

Methods

PubMed, Cochrane Library, and EMBASE were systematically searched for studies comparing FLACS and CPS. Outcomes were operative complications, including the intraoperative capsule tear, postoperative corneal edema, macular edema, uncontrolled IOP, etc. The effect measures were weighted with odds ratios with 95% CIs.

Results

Nineteen RCTs and 18 cohort studies, including 24,806 eyes (11,375 of the FLACS group and 13,431 of the CPS group), were identified. There were no significant differences between the two groups in anterior capsule tear, corneal edema, macular edema, uncontrolled IOP, vitreous loss, posterior vitreous detachment, etc. Posterior capsule tear rate showed a significantly lower in RCT subgroups (P ​= ​0.04) and without differences in total (P ​= ​0.63). Significant differences were observed in the incidence of descemet membrane tear/trauma (P ​= ​0.02) and IFIS/iris trauma (P ​= ​0.04. Additionally, The FLACS specific complications showed a significantly higher rate of miosis (P ​< ​0.0001), corneal epithelial defect (P ​= ​0.001), corneal haze (P ​= ​0.002), and subconjunctival hemorrhage (P ​= ​0.01).

Conclusions

FLACS maintains the same safety compared with CPS in terms of all intraoperative and postoperative complications. Although FLACS did show a statistically significant difference for several FLACS specific complications, it would not influence the visual outcome and heal itself.

Ultrafast Laser Material Damage Simulation—A New Look at an Old Problem

The chirped pulse amplification technique has enabled the generation of pulses of a few femtosecond duration with peak powers multi-Tera and Peta–Watt in the near infrared. Its implementation to realize even shorter pulse duration, higher energy, and higher repetition rate laser systems relies on overcoming the limitations imposed by laser damage of critical components. In particular, the laser damage of coatings in the amplifiers and in post-compression optics have become a bottleneck. The robustness of optical coatings is typically evaluated numerically through steady-state simulations of electric field enhancement in multilayer stacks. However, this approach cannot capture crucial characteristics of femtosecond laser induced damage (LID), as it only considers the geometry of the multilayer stack and the optical properties of the materials composing the stack. This approach neglects that in the interaction of an ultrashort pulse and the materials there is plasma generation and associated material modifications. Here, we present a numerical approach to estimate the LID threshold of dielectric multilayer coatings based on strong field electronic dynamics. In this dynamic scheme, the electric field propagation, photoionization, impact ionization, and electron heating are incorporated through a finite-difference time-domain algorithm. We applied our method to simulate the LID threshold of bulk fused silica, and of multilayer dielectric mirrors and gratings. The results are then compared with experimental measurements. The salient aspects of our model, such as the implementation of the Keldysh photoionization model, the impact ionization model, the electron collision model for ‘low’-temperature, dense plasma, and the LID threshold criterion for few-cycle pulses are discussed.

Femtosecond laser-assisted cataract surgery after corneal refractive surgery

Cataract is the leading cause of blindness worldwide, and advanced cataract techniques such as femtosecond laser-assisted cataract surgery (FLACS) have been commercially available. Corneal refractive surgery (CRS) is one of the most popular surgeries for the correction of refractive errors. CRS changes the cornea not only anatomically but also pathophysiologically. However, there has been no clinical research analyzing the refractive and safety outcomes of FLACS after CRS. The aim of this retrospective chart review and comparative study is to evaluate the effect and safety of FLACS after CRS comparing with conventional PCS. Participants with a previous CRS history who underwent FLACS or conventional PCS were included in this study. The visual outcomes and the refractive outcomes including refractive, corneal, and ocular residual astigmatism were compared. The safety outcomes were then studied intraoperatively and postoperatively. A total of 102 patients with age-related cataract were enrolled. At 3 months postoperatively, UCVA, BCVA, and predictive error were not significantly different between the FLACS and conventional PCS groups. Reduction of refractive astigmatism was higher in FLACS. Postoperative ORA was significant lower in FLACS. Reduction of ORA was higher in FLACS. The intraoperative and postoperative complications were also not significantly different between the two groups. FLACS could effectively change refractive astigmatism and ORA; without more complications than conventional PCS. FLACS’ competitive edge in postoperative ORA may provide better visual quality than conventional PCS in patients with a previous history of CRS.

Electron microscopy analysis of femtosecond laser-assisted capsulotomy before and after lens fragmentation

Studying anterior lens capsule cutting edge profiles from femtosecond laser-assisted capsulotomy procedures performed before and after lens fragmentation. Twenty eyes (10 patients) with age-related cataract underwent femtosecond laser-assisted surgery (FLACS) using the Ziemer Z8 platform. First step of laser surgery was either capsulotomy (group first) or fragmentation (group second). One eye of each patient was assigned randomly, the second eye treated with the different sequence of procedures. After anterior capsule removal, tissue was fixed in cacodylate-buffered solution and cutting-edge profiles were analysed using scanning electron microscopy (SEM). All cases had cataract grade 2 and 3 based on LOCS III grading. SEM analysis showed more smooth edges in the first group, especially in cases with pseudoexfoliation (P = 0.037); more tags and bridges and a significant number of staggered cutting patterns (7 out of 10 cases) in the second group. All cases evolved the same microgroves with "valleys and mountains " as signs of the photodisruption process. Femtosecond laser capsulotomy should be performed before lens fragmentation minimizing the rate of cutting errors. Especially in eyes with advanced cataract, as intracapsular pressure may increase due to lens fragmentation without anterior capsular opening.

Electron microscopy analysis of femtosecond laser-assisted capsulotomy before and after lens fragmentation

Studying anterior lens capsule cutting edge profiles from femtosecond laser-assisted capsulotomy procedures performed before and after lens fragmentation. Twenty eyes (10 patients) with age-related cataract underwent femtosecond laser-assisted surgery (FLACS) using the Ziemer Z8 platform. First step of laser surgery was either capsulotomy (group first) or fragmentation (group second). One eye of each patient was assigned randomly, the second eye treated with the different sequence of procedures. After anterior capsule removal, tissue was fixed in cacodylate-buffered solution and cutting-edge profiles were analysed using scanning electron microscopy (SEM). All cases had cataract grade 2 and 3 based on LOCS III grading. SEM analysis showed more smooth edges in the first group, especially in cases with pseudoexfoliation (P = 0.037); more tags and bridges and a significant number of staggered cutting patterns (7 out of 10 cases) in the second group. All cases evolved the same microgroves with "valleys and mountains " as signs of the photodisruption process. Femtosecond laser capsulotomy should be performed before lens fragmentation minimizing the rate of cutting errors. Especially in eyes with advanced cataract, as intracapsular pressure may increase due to lens fragmentation without anterior capsular opening.

Surgical outcomes with high and low pulse energy femtosecond laser systems for cataract surgery

Currently, there is no clear consensus in cataract surgery if low compared to high energy femto-lasers may enable better capsulotomy quality and induce lower inflammatory response. Therefore, the aim of this study was to compare the intra-operative outcomes achieved with high and low pulse energy femtosecond laser systems for cataract surgery. The charts of 200 eyes of 200 patients aged 68.3 ± 10.3 years who had undergone femtosecond laser-assisted cataract surgery using either group 1 high pulse energy: LenSx (Alcon Laboratories) (N = 100) or group 2 low pulse energy: FEMTO LDV Z8 (Ziemer) (N = 100) laser were reviewed retrospectively. Integrity of anterior capsulotomy, classified as (1) complete (free-floating or with minor microadhesions), (2) incomplete and (3) with capsular tears, intraoperative completeness of the clear corneal incisions (CCI, main incision and side port), incidences of intraoperative miosis and incidence of subconjunctival hemorrhage were evaluated and compared between the two groups. The proportion of complete capsulotomies was significantly higher in the group 2 than the group 1 (100% vs 94%; p = 0.03). The incidences of intraoperative miosis (0% vs 19%) and subconjunctival hemorrhage (1% vs 63%) were significantly lower in the group 2 than the group 1 (p < 0.001). Completeness of the main incision was comparable (97% vs 95%; p = 0.721) between the two groups. Although not statistically significant, the completeness of side-port incision was slightly better in the group 2 than the group 1 (91% vs 86%). Low energy laser system performed significantly better in terms of completeness of capsulotomy, intraoperative miosis and sub-conjunctival hemorrhage, compared with high energy laser; the CCI outcomes were comparable.