Femtosecond laser-assisted cataract surgery with integrated optical coherence tomography

Evaluating the effect of pulse energy on femtosecond laser trabeculotomy (FLT) outflow channels for glaucoma treatment in human cadaver eyes

BACKGROUND AND OBJECTIVES

Femtosecond laser trabeculotomy (FLT) creates aqueous humor outflow channels through the trabecular meshwork (TM) and is an emerging noninvasive treatment for open-angle glaucoma. The purpose of this study is to investigate the effect of pulse energy on outflow channel creation during FLT.

MATERIALS AND METHODS

An FLT laser (ViaLase Inc.) was used to create outflow channels through the TM (500 μm wide by 200 μm high) in human cadaver eyes using pulse energies of 10, 15, and 20 μJ. Following treatment, tissues were fixed in 4% paraformaldehyde. The channels were imaged using optical coherence tomography (OCT) and assessed as full thickness, partial thickness, or not observable.

RESULTS

Pulse energies of 15 and 20 μJ had a 100% success rate in creating full-thickness FLT channels as imaged by OCT. A pulse energy of 10 μJ resulted in no channels (n = 6), a partial-thickness channel (n = 2), and a full-thickness FLT channel (n = 2). There was a statistically significant difference in cutting widths between the 10 and 15 μJ groups (p < 0.0001), as well as between the 10 and 20 μJ groups (p < 0.0001). However, there was no statistically significant difference between the 15 and 20 μJ groups (p = 0.416).

CONCLUSIONS

Fifteen microjoules is an adequate pulse energy to reliably create aqueous humor outflow channels during FLT in human cadaver eyes. OCT is a valuable tool when evaluating FLT.

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.

Ophthalmic surgeries on post mortem porcine eyes with picosecond ultrashort laser pulses

Purpose

This work demonstrates significant advantages in ophthalmic surgeries through the use of picosecond ultrashort laser pulses instead of state-of-the-art nanosecond laser pulses. These ultrashort lasers shall serve as universal tools more effectively combining advantages of high precision, low impact and economic advantages compared to existing instruments.

Methods

As samples, we used post-mortem porcine eyes on which we performed the experiments with both picosecond and nanosecond lasers. Performed surgeries were laser iridotomy, (post-) cataract treatment/capsulotomy and selective laser-trabeculoplasty. Pulse widths were between 12 ps and 220 ns with pulse energies between 30 μJ and 10 mJ at 532 nm and 1,064 nm. Additionally, we investigated accompanying shock waves, cavitation bubbles, and heat effects during the ablation processes.

Results

For all surgeries, significant differences were observed between picosecond and nanosecond pulses: It was possible to scale the pulse energy down to 10 of microjoules rather than requiring millijoules, and resulting tissue ablations are much more precise, more deterministic and less frayed. The shock wave and cavitation bubble investigation revealed major differences in pressure between picosecond pulses (0.25 MPa, 50 μJ) and nanosecond pulses (37 MPa, 5 mJ). The heat input during ablation could be lowered by two orders of magnitude.

Conclusion

Picosecond ultrashort laser pulses show substantial benefits for several ophthalmic surgeries, with regard to ablation precision, shock wave generation and heat input. They are better than state-of-the-art ophthalmic nanosecond lasers in all aspects tested.

Kerr-lens mode-locked femtosecond Yb:CALYO oscillator with more than 20-W average power

We report on the demonstration of a pure Kerr-lens mode-locked Yb:CALYO laser which can directly deliver sub-200 fs pulses with more than 20-W average power. With an incident pump power of 89 W, 153-fs pulses were generated with an average power of 21.5 W at a repetition rate of 77.9 MHz. The corresponding peak power and single pulse energy were 1.6 MW and 0.27 µJ, respectively. The stable operation of the mode-locking was confirmed by very small fluctuations in both spectrum and output power recorded over an hour. Second harmonic generation (SHG) was conducted with 59% conversion efficiency, which indicated that the high-power mode-locking pulses are of good quality. Stable Kerr-lens mode-locking (KLM) with 156-fs pulse duration and 27.2-W average power was also achieved with 109-W pump power. To the best of our knowledge, this is the highest average output power ever reported from a femtosecond mode-locked bulk oscillator.

Application of Femtosecond Laser in Challenging Cataract Cases

Femtosecond laser can provide precise and customized incision of ocular tissue with excellent accuracy and predictability. Thus, femtosecond laser-assisted cataract surgery (FLACS) can theoretically enhance the safety and efficacy of cataract surgery by providing reproducible and reliable clear corneal incision, limbal relaxing incision, anterior capsulotomy, and lens fragmentation. However, thus far, the superiority of the anatomical and visual outcomes of FLACS over those of conventional cataract surgery have been unclear. Nevertheless, studies have indicated that FLACS can potentially be helpful in improving the safety of cataract surgery in challenging situations, such as zonular weakness, preexisting capsular tear, white cataract, shallow anterior chamber, and pediatric cataracts, which may contribute to enhanced visual and anatomical outcomes. In this review, we provide a summary of the application of femtosecond laser in general cataract cases. In addition, we introduce the application of FLACS in the abovementioned challenging situations and discuss the results of studies regarding the safety and outcome of FLACS in these challenging cases.

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.

Characterization of Femtosecond Laser and Porcine Crystalline Lens Interactions by Optical Microscopy

The use of ultrafast laser pulses for eye anterior segment surgery has seen a tremendous growth of interest as the technique has revolutionized the field, from the treatment of myopia, hyperopia, and presbyopia in the cornea to laser-assisted cataract surgery of the crystalline lens. For the latter, a comprehensive understanding of the laser-tissue interaction has yet to be achieved, mainly because of the challenge of observing the interaction zone in situ with sufficient spatial and temporal resolution in the complex and multi-layered tissue of the crystalline lens. We report here on the dedicated characterization results of the laser-tissue interaction zone in the ex vivo porcine lens using three different methods: in situ and real-time microscopy, wide-field optical imaging, and phase-contrast microscopy of the histological cross sections. These complementary approaches together revealed new physical and biological consequences of laser irradiation: a low-energy interaction regime (pulse energy below ~1 µJ) with very limited cavitation effects and a stronger photo-disruption regime (pulse energy above 1 µJ) with a long cavitation duration from seconds to minutes, resulting in elongated spots. These advances in the understanding of the ultrafast laser's interactions with the lens are of the utmost importance for the preparation of the next-generation treatments that will be applied to the lens.

Intracameral bleeding during femtolaser assisted cataract surgery: A case report

Purpose

To report a case of anterior chamber bleeding that was noted post completion of laser during femtosecond laser assisted cataract surgery (FLACS).

Observations

A 54 yr old woman with no ocular and systemic morbidity underwent Right Eye FLACS.Vacum loss was noted due to patient's eye movements. Suction and Docking was achieved at the 2nd attempt, following which laser treatment was uneventful. An intracameral bleed was noted superiorly extending towards center of the anterior chamber. Cataract surgery with IOL implantation was uneventful. Post-operative course was uneventful.

Conclusions and importance

This is the first report in literature of intracameral bleeding during FLACS. It is essential to proceed with caution in patients with repeated vacuum loss due to a higher risk of developing intraocular bleeds.

Subfoveal Choroidal Thickness After Femtosecond Laser-Assisted Cataract Surgery for Age-Related Cataracts

Purpose

To compare the effects of femtosecond laser-assisted cataract surgery (FLACS) and conventional phacoemulsification surgery (CPS) on subfoveal choroidal thickness (SFCT) in patients with age-related cataracts.

Methods

In this prospective consecutive study, 26 patients (26 eyes) with age-related cataracts without previous ocular surgery or other ocular diseases who had FLACS were included as the study group. Twenty-six age-matched patients (26 eyes) who underwent CPS in the same period were also included as the control group. The SFCT and the foveal retinal thickness (FRT) were measured at baseline and at 1 day (D1), 7 days (D7), 1 month (M1), and 3 months (M3) postoperatively by spectral-domain optical coherence tomography. Aqueous flare was also measured with a laser flare meter.

Results

The mean SFCTs of the FLACS group at baseline and at D1, D7, M1, and M3 were 185.2, 174.3, 184.2, 180.8, and 184.1 μm, respectively. A Bonferroni posttest showed that the choroid became thinner on postoperative D1 (P = 0.006). The measurements at 1 week, 1 month, and 3 months postoperatively showed no significant differences in the SFCTs compared with that at baseline (P = 0.66, P = 0.22, and P = 0.53, respectively). A different trend was observed in the CPS group. The choroid became thicker by the 3-month postoperative measurement, as follows: 1 day (P = 0.28), 1 week (P = 0.016), 1 month (P = 0.020), and 3 months (P < 0.001).

Conclusion

The mean SFCT significantly and temporarily decreased following FLACS. In contrast, an increased SFCT was observed following CPS.

Intraoperative Anterior Segment Optical Coherence Tomography in the Management of Cataract Surgery: State of the Art

Background: The introduction of non-invasive diagnostic tools in ophthalmology has significantly reshaped current clinical practice in different settings. Recently, different anterior segment (AS) intraoperative optical coherence tomography (i-OCT) systems have been employed for different interventional procedures including cataract surgery. Materials and Methods: A review on the use of AS i-OCT in the management of cataract surgery, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA). The level of evidence according to the Oxford Centre for Evidence-Based Medicine (OCEM) 2011 guidelines, and the quality of evidence according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system were assessed for all included articles. Results: Out of 6302 articles initially extracted, 6302 abstracts were identified for screening and 32 of these met the inclusion/exclusion criteria for full-text review; 19 articles were excluded. Conclusions: The use of AS i-OCT in cataract surgery, even if only a few studies have a high level or grade of evidence, may represent a useful tool for novel surgeons approaching phacoemulsification but also for expert ones for teaching purposes and to plan and manage complicated cases.

The Postvitrectomy Cataract

To review the recent literature regarding risk factors for cataract formation after vitrectomy, the challenges and management strategies for anterior segment surgeons when facing post-vitrectomy cataract surgery, and the visual outcomes of patients undergoing post-vitrectomy cataract surgery. Cataract surgery after vitrectomy can be safely performed to significantly improve the visual outcome in most post-vitrectomy patients, although final visual acuity is primarily limited by the patient’s underlying vitreoretinal pathology.

Study on the enlargement index of femtosecond laser-assisted capsulorhexis in 2-6-year-old patients with congenital cataract

Background

To identify the capsule enlargement index after femtosecond laser-assisted anterior capsulorhexis in 2–6-year-old children who underwent congenital cataract surgery.

Methods

In this prospective case series study, femtosecond laser-assisted anterior capsulorhexis was performed in patients with congenital cataract, aged 2–6 years. The actual achieved capsulorhexis diameters were measured with Digimizer version 4.2.6. Correlation coefficient (r) and multiple linear regression analysis were used to evaluate the variables that could potentially influence anterior capsulorhexis enlargement index (E).

Results

This prospective study enrolled 28 eyes of 22 patients with congenital cataract. The mean age of the patients at surgery was 4.67 years ±1.54 (standard deviation [SD]). “E” of the 28 cases was 1.211 ± 0.039 (SD). Correlation analysis showed that “E” correlated significantly with the anterior chamber depth (ACD) (r = − 0.469, p = 0.021) and axial length (AL) (r = 0.452, p = 0.027). The following formula was developed by using multivariable linear regression analysis: Predicted E = 1.177–0.052 × ACD + 0.009 × AL, R² = 0.346 (F = 4.396, p = 0.046).

Conclusions

The anterior capsulorhexis enlargement index and its calculation formula could help to set up an accurate programmed capsulorhexis diameter for femtosecond laser-assisted congenital cataract surgery in children aged 2–6 years. Thus, an appropriate actual capsulorhexis diameter could be achieved.

Quantitative investigation of laser ablation based on real-time temperature variations and OCT images for laser treatment applications

BACKGROUND AND OBJECTIVE

Lasers are widely employed in clinical applications. In vivo monitoring of real-time information about different-wavelength laser surgeries would provide important surgical feedback for surgeons or clinical therapy instruments. However, the quantitative effect of laser ablation or vaporization still needs to be further explored and investigated. Here, we investigate and quantitatively evaluate the ablation variations and morphological changes of two laser ablation models: point- and sweeping-based models.

METHODS

An infrared thermal imager was used to monitor the temperature variations, and curve fitting was used to build the relationship between the laser radiation duration/sweeping speed and quantitative parameters of the ablated areas. Optical coherence tomography (OCT) images were used to visualize the inner structure and evaluate the depth of the ablated craters. Optical attenuation coefficients (OACs) were computed to characterize the normal and ablated tissues.

RESULTS

The results demonstrated that there was a good linear relationship between radiation duration and temperature variation. Similarly, a linear relationship was observed between the sweeping speed and quantitative parameters of craters or scratches (width and depth). The mean OAC of normal tissues was significantly distinguished from the mean OACs of the ablated craters or scratches.

CONCLUSION

Laser ablation was investigated based on a quantitative parameter analysis, thermal detection, and OCT imaging, and the results successfully demonstrated that there is a linear relationship between the laser parameters and quantitative parameters of the ablated tissues under the current settings. Such technology could be used to provide quantitative solutions for exploring the laser-tissue biological effect and improve the performance of medical image-guided laser ablation in the future.

Damage Induced to DNA and Its Constituents by 0-3 eV UV Photoelectrons†

The complex physical and chemical interactions between DNA and 0-3 eV electrons released by UV photoionization can lead to the formation of various lesions such as base modifications and cleavage, crosslinks and single strand breaks. Furthermore, in the presence of platinum chemotherapeutic agents, these electrons can cause clustered lesions, including double strand breaks. We explain the mechanisms responsible for these damages via the production 0-3 eV electrons by UVC radiation, and by UV photons of any wavelengths, when they are produced by photoemission from nanoparticles lying within about 10 nm from DNA. We review experimental evidence showing that a single 0-3 eV electron can produce these damages. The foreseen benefits UV-irradiation of nanoparticles targeted to the cell nucleus are mentioned in the context of cancer therapy, as well as the potential hazards to human health when they are present in cells.

Outcomes of Femtosecond Laser-Assisted Cataract and Refractive Lens Surgery in Patients with Prior Radial Keratotomy

PURPOSE

To investigate outcomes of femtosecond laser (FL-) assisted cataract surgery (FLACS) and refractive lens exchange (RLE) in patients with prior radial keratotomy (RK).

SETTING

Single clinical practice.

DESIGN

Retrospective observational case series.

METHODS

All patients with prior RK undergoing FLACS- or FL-assisted RLE surgeries over a 6-year period were reviewed. Inclusion criteria were diurnal stability and stable manifest refraction. Exclusion criteria included any other incisional corneal surgery, macular or glaucomatous pathology, or vision loss from any other cause. Data collected included demographics, visual acuity, laser settings, and complications. Main outcome measures were intra- and postoperative complications and visual outcomes. Safety and efficacy indices were evaluated.

RESULTS

Sixteen eyes of 9 patients were included. Average age and follow-up time were 59.9 ± 9.9 years (range 44-75 years) and 3.3 ± 2.5 months, respectively. Average number of RK cuts was 11.8 ± 5.3 (range 8-20). Mean preoperative UDVA and CDVA were 0.9 ± 0.4 logMAR (Snellen 20/160) and 0.2 ± 0.3 logMAR (Snellen 20/30), respectively. Two intraoperative anterior capsule (AC) tears were identified. One postoperative IOL dislocation occurred. Postoperatively, the mean UDVA and CDVA were 0.2 ± 0.2 logMAR (20/30) and 0.1 ± 0.1 logMAR (20/25), respectively. Safety index was 1.6 and efficacy index was 1.2.

CONCLUSIONS

FLACS- or FL-assisted RLE surgery in RK patients has a high risk of anterior capsule tear and should be avoided. Thickened incisional scars are potential sources of incomplete laser penetrance. Toric lens implantation in RK eyes provide unpredictable astigmatic correction and should also be avoided.

Low-Energy Electron Damage to Condensed-Phase DNA and Its Constituents

The complex physical and chemical reactions between the large number of low-energy (0-30 eV) electrons (LEEs) released by high energy radiation interacting with genetic material can lead to the formation of various DNA lesions such as crosslinks, single strand breaks, base modifications, and cleavage, as well as double strand breaks and other cluster damages. When crosslinks and cluster damages cannot be repaired by the cell, they can cause genetic loss of information, mutations, apoptosis, and promote genomic instability. Through the efforts of many research groups in the past two decades, the study of the interaction between LEEs and DNA under different experimental conditions has unveiled some of the main mechanisms responsible for these damages. In the present review, we focus on experimental investigations in the condensed phase that range from fundamental DNA constituents to oligonucleotides, synthetic duplex DNA, and bacterial (i.e., plasmid) DNA. These targets were irradiated either with LEEs from a monoenergetic-electron or photoelectron source, as sub-monolayer, monolayer, or multilayer films and within clusters or water solutions. Each type of experiment is briefly described, and the observed DNA damages are reported, along with the proposed mechanisms. Defining the role of LEEs within the sequence of events leading to radiobiological lesions contributes to our understanding of the action of radiation on living organisms, over a wide range of initial radiation energies. Applications of the interaction of LEEs with DNA to radiotherapy are briefly summarized.

Optimization of femtosecond laser-constructed clear corneal wound sealability for cataract surgery

PURPOSE

To compare the sealability of femtosecond laser (FSL)-assisted corneal incisions (CIs) with that of triplanar manual (M)-CIs and to determine FSL wound parameters minimizing leakage.

SETTING

Private practice.

DESIGN

Phase IV, single-surgeon, retrospective cohort study.

METHODS

One eye per patient was included. Two groups defined by the main wound (FSL-CI or M-CI) were compared for leakage, inferred by placement of a suture at the end of surgery. Leakage in FSL-CIs was analyzed as a function of customizable wound parameters: anterior plane depth (APD), posterior plane depth (PPD), anterior side-cut angle (ASCA), and posterior side-cut angle (PSCA). The risk of leakage of FSL-CIs with optimal and nonoptimal parameters was further compared with that of M-CIs.

RESULTS

A total of 1100 eyes (757 [68.8%] FSL-CI; 343 [31.2%] M-CI) were included. Wound leakage occurred in 133 FSL-CI (17.6%) and 30 M-CI eyes (8.7%) (P < .001). FSL wound parameters associated with the lowest risk of leakage were 60% APD, 70% PPD, 120 degrees ASCA, and 70 degrees PSCA. FSL-CIs constructed with at least 3 optimal parameters (60% APD, 70% PPD, and 120 degrees ASCA) had a similar risk of leakage to M-CIs (odds ratio [OR], 1.1; 95% CI, 0.5-2.3). FSL-CIs with suboptimal parameters had twice the risk of leakage of M-CIs (OR, 2.0; 95% CI, 1.1-3.8).

CONCLUSIONS

Overall, FSL-CIs leaked more than M-CIs. However, FSL-CIs with optimized wound profiles had an equivalent risk of leakage to M-CIs. Wound parameter customization is an asset of FSL technology that allows optimization of FSL-CI sealability.

Why Use Ultrashort Pulses in Ophthalmology and Which Factors Affect Cut Quality

The power density of femtosecond lasers and exposure time to the tissue are crucial for a successful procedure in terms of safety and precision. The reduction of the pulse duration allows reducing the quantity of the energy to be delivered to the tissue for disruption with strongly diminished mechanical and thermal collateral damage. The cutting effect of ultra-short pulses is very precise, minimally traumatic, safe, and predictable. Future developments will lead to further energy reductions to achieve optical breakdowns. However, the pulse length cannot be shortened arbitrarily because below 100 fs nonlinear effects can change the process in an unfavorable way. Compared to manual-conventional cataract surgery, femtosecond laser-assisted cataract surgery (FLACS) shows many advantages in clinical application, especially with regard to precision and tissue protection. The femtosecond laser has become particularly important and has made the overall procedure safer when we deal with complex cataract cases such as subluxated lenses. We provide an overview of the evolution of femtosecond laser technology for use in refractive and cataract surgeries. This article describes the advantages of available laser platforms with ultrashort pulses and mainly focuses on the technical and physical backgrounds of ophthalmic surgery technologies.

Bubble Forming Films for Spatial Selective Cell Killing

Photodynamic and photothermal cell killing at the surface of tissues finds applications in medicine. However, a lack of control over heat dissipation following a treatment with light might damage surrounding tissues. A new strategy to kill cells at the surface of tissues is reported. Polymeric films are designed in which iron oxide nanoparticles are embedded as photosensitizers. Irradiation of the films with pulsed laser light generates water vapor bubbles at the surface of the films. It is found that "bubble-films" can kill cells in close proximity to the films due to mechanical forces which arise when the bubbles collapse. Local irradiation of bubble-films allows for spatial selective single cell killing. As nanosurgery becomes attractive in ophthalmology to remove superficial tumors, bubble-films are applied on the cornea and it is found that irradiation of the bubble-films allows spatial and selective killing of corneal cells. As i) the photosensitizer is embedded in the films, which reduces its uptake by cells and spreading into tissues and ii) the bubble-films can be removed from the tissue after laser treatment, while iii) a low laser fluence is sufficient to generate vapor bubbles, it is foreseen that bubble-films might become promising for safe resection of superficial tumors.

Inspection of the lens thickness with preoperative biometric measurements prevents an erroneous interpretation of posterior capsule during FLACS

Optical opacity reduces quality of biometry images, making it potentially difficult to find the correct location for irradiation during femtosecond laser-assisted cataract surgery (FLACS). After experiencing a case of posterior capsule (PC) rupture because of optical opacity, we started lens thickness (LT) inspection, which indicates comparison of between intra- and pre-operatively measured LT. We retrospectively investigated the effectiveness of the LT inspection. One observer reviewed all FLACS treatment summaries for 3 years by CATALYS in the Jikei University Hospital, Tokyo. Based on the lines defining the PC on intraoperative OCT images, all cases were classified into three groups: undescribed, appropriate and inappropriate PC. Among the 1070 cases, 1047 cases had appropriate PC. In 19 cases, the PC line was undescribed because of dense cataract. Among 474 cases with no inspection, 4 cases had an inappropriate PC. Whereas, in 596 cases with the LT inspection, there was no case of an inappropriate PC. LT inspection significantly reduced the cases with inappropriate PC. The safety margins normally work to prevent severe complications. However, rare outlier cases had a high risk of severe complications. We propose LT inspection could be the most practical and convenient way for safety surgery.

Diagnostic imaging versus surgical procedure: intra- and postoperative OCT evaluation of sutureless scleral-fixated intraocular lens implantation and possible related complications

Because the popularity of corneal refractive surgery has been increasing throughout the last 25 years, many authors have thought to apply optical coherence tomography (OCT) to the anterior segment (AS-OCT); by revising the instrumentation needed and slightly improve the technique, it has become an element of vital importance in order to ensure a complete and exhaustive pre- and postsurgical evaluation. Many applications of OCT have been recently developed—mostly in cataract surgery due to the increasing numbers—such as chamber biometry, which is used in a preoperative stage to determine the details of IOL implantation, and lens evaluation. The aim of this review is to assess the applications of anterior segment OCT in dislocated IOL and/or capsular bag exchange surgery with scleral sutureless fixated intraocular lens and monitoring of possible postoperative complications.

The Emerging Role of Anterior Segment Optical Coherence Tomography in Cataract Surgery: Current Role and Future Perspectives

Modern-day cataract surgery has achieved equivalence with refractive surgery, thus requiring surgeons to perform all possible pre-emptive exercises to mitigate intraoperative complications. In this direction, we possess a tremendous amount of technology to understand the preoperative status of the lens. Anterior segment optical coherence tomography (ASOCT) is one such tool, which has played a distinctive role in imaging various forms of cataracts. In this review, we critically analyse the practical role of ASOCT in the preoperative and intraoperative periods from a cataract surgeon's perspective. After a thorough literature assessment, it was substantiated that the cross-sectional imaging ability of ASOCT can demonstrate delicate anatomical and pathological lenticular changes in a visually and clinically comprehensible way. The objective grading of immature cataracts to intralenticular and posterior capsular details in mature/white, posterior polar, traumatic and other forms of cataracts paves the way for various practical innovations as and when required. Hence, preoperative more than intraoperative ASOCT-derived lenticular knowledge is of immense help in careful surgical planning, with improved complication rates.

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

This article provides an overview of both established and innovative applications of femtosecond (fs)-laser-assisted surgical techniques in ophthalmology. Fs-laser technology is unique because it allows cutting tissue at very high precision inside the eye. Fs lasers are mainly used for surgery of the human cornea and lens. New areas of application in ophthalmology are on the horizon. The latest improvement is the high pulse frequency, low-energy concept; by enlarging the numerical aperture of the focusing optics, the pulse energy threshold for optical breakdown decreases, and cutting with practically no side effects is enabled.

Effects of Femtosecond Laser-Assisted Cataract Surgery on Macular and Choroidal Thickness in Diabetic Patients

Introduction

This study aimed to compare the short-term changes in retinal and choroid thickness in diabetic patients after femtosecond laser-assisted cataract surgery (FLACS) and phacoemulsification (PE) surgery.

Methods

A total of 47 eyes in the PE group and 44 eyes in the FLACS group were included. All patients underwent measurement of central macular thickness (CMT) and subfoveal choroidal thickness (SFCT) before and after surgery using optical coherence tomography (OCT).

Results

The effective phaco time (EPT) in the FLACS group was significantly reduced. The BCVA differed significantly between the two groups at 1 week and 1 month after surgery. The CMT in both groups increased at 1 week after the operation. It did not return to the preoperative level until month 12 in the PE group. In the FLACS group, the CMT began to decrease at month 3 and recovered to the preoperative level at month 12. The SFCT of the two groups increased at week 1; it began to decrease at month 6 in the PE group but did not recover to the preoperative level until month 12. The SFCT in the FLACS group recovered to preoperative levels at month 6. In the PE group, baseline CMT values predicted CMT change at week 1 and months 1, 3 and 12 after surgery. In the FLACS group, baseline CMT predicted CMT changes at week 1, month 1 and month 3. In the FLACS group, EPT predicted SFCT change at month 3.

Conclusion

FLACS is safe and effective in patients with no fundus change or mild diabetic retinopathy. It has advantages in effectively reducing EPT, achieving good vision earlier and promoting faster recovery of the retinal and choroidal thickness. Preoperative CMT is a significant predictor of CMT changes in the early period after FLACS.

Corneal complication after femtosecond laser-assisted cataract surgery: A case report

RATIONALE

The femtosecond laser LDV Z 8 is unique, and the only femtosecond laser used in ophthalmic microsurgery, which is characterized by low-energy near-infrared (1030 nm) femtosecond single pulses in the nano-Joule range and a very high repetition rate in the MHz range. To the best of our knowledge, this is the first description of unintentional partial corneal incision in the anterior part of a stroma by the femtosecond laser.

PATIENT CONCERNS

A 79-year-old patient was referred to our clinic for cataract surgery. On admission, we diagnosed mature cataract of the left eye and pseudophakic of the right eye. The patient was qualified for the Femtosecond Laser-Assisted Cataract Surgery (FLACS). Unexpectedly during FLACS procedure after lens fragmentation the surgeon observed unexpected paracentral incision in the cornea.

DIAGNOSIS

The corneal incision line between 4 to 8 o'clock was observed. In vivo confocal microscopy was performed to assess the morphology and depth of the corneal wound. The corneal incision covered the epithelium, Bowman's membrane and stroma of the cornea reached a depth of 336 um.

INTERVENTIONS

The patient was under increased ophthalmologic controls; follow up with typical ophthalmic examinations and confocal microscopy was performed.

OUTCOMES

In 2-year follow-up period, this complication had no effect on postoperative visual function, the patient had no visual problems and obtained the final BCVA 5/5. There is no dislocation of the lens in 2 years follow-up.

LESSONS

Low pulse energy and high pulse frequency in the LDV Z8 causes a low traumatization of tissues. In a 2-year follow-up, the corneal incision line could be observed on the slit lamp examination without long-term visual consequences of this complication. In our opinion, the most likely cause of this complication was human error and lack of communication between medical personnel. The operation team should be alert and great caution must be exercised during the procedure and check the laser settings parameters carefully each time.

Evaluation of femtosecond laser-assisted anterior capsulotomy in the presence of ophthalmic viscoelastic devices (OVDs)

The introduction of femtosecond laser-assisted cataract surgery is an alternative approach to conventional cataract surgery. Our study aimed to determine the effectiveness of femtosecond laser-assisted capsulotomy in the presence of different ophthalmic viscoelastic devices (OVDs) in the anterior chamber. Fresh porcine eyes (n = 96) underwent LDV Z8-assisted anterior capsulotomy, either in the presence of an OVD (Viscoat, Provisc, Healon, Healon GV or HPMC) or without, using 90% and 150% energies respectively. Following that, the capsule circularity, tag’s arc-length, tag-length, tag-area and rupture strength (mN) of the residual capsular bag were evaluated. We found that increasing energy from 90 to 150% across the OVD sub-groups improved the studied capsulotomy parameters. Amongst the 90% energy sub-groups, the circularity and tag-parameters were worse with Viscoat and Healon GV, which have higher refractive index and viscosity compared to the aqueous humour. Using 150% energy, Healon GV showed a significantly worse total arc-length (p = 0.01), total tag-length (p = 0.03) and total tag-area (p = 0.05) compared to the control group. We concluded that; an OVD with a refractive index similar to aqueous humour and lower viscosity, such as Healon or Provisc, as well as a higher energy setting, are recommended, to enhance the efficacy of laser capsulotomy.

Efficacy of Femtosecond Laser-Assisted Capsulotomy: Experimental Evaluation Using the Zonular Dehiscence Model

Purpose

The purpose of this study was to evaluate experimentally the efficacy of femtosecond laser (FL)-assisted capsulotomy using an eye model with different degrees of zonular dehiscence (ZD).

Methods

An eye model with ZD was created by removing the total iris and including the planned range of the ZD in porcine and human cadaver eyes. FL-assisted capsulotomies (laser group) and manual capsulotomies (manual group) were created for the eye model with 0, 45, 135, 180, and 270 degrees of ZD. The continuity, mean diameter, ellipticity, and decentration of the capsulotomy were evaluated using the captured images. The same evaluation of FL-assisted capsulotomies was done for five human cadaver eyes with 180 degrees of ZD.

Results

In the laser group, no differences were seen in the mean diameter, ellipticity, and decentration, although the manual group resulted in significantly larger, ovalized, and decentered capsulotomies with different degrees of ZD (P < 0.001, P < 0.001, and P = 0.0317, respectively). Continuous capsulotomies or capsulotomies with microadhesions were obtained up to 180 degrees of ZD, and incomplete treatment areas were seen in eyes with 270 degrees of ZD. Capsulotomy of the human cadaver eyes with 180 degrees of ZD showed similar results to those of porcine eyes.

Conclusions

In this experimental study, FL-assisted capsulotomy showed favorable results in eyes with between 0 and 180 degrees of ZD compared to conventional manual capsulotomy.

Translational Relevance

Our experimental model can simulate the capsulotomy in cases with ZD, the results are useful when determining the indication for FL-assisted capsulotomies.

[What will cataract surgery look like in the future? Alternatives in the pipeline]

Phacoemulsification is the most frequently performed surgery in the world. Over the past few years, this surgery seems to have reached a plateau with no further innovative breakthroughs. In this paper, we focus on alternatives techniques, the latest innovations, and the research and development pipeline in this field.

Clinical and Surgical Outcomes of Femtosecond Laser-Assisted Cataract Surgery (FLACS) on Hard Cataracts in the Egyptian Population

Objective

To evaluate the clinical and surgical outcomes of femtosecond laser-assisted cataract surgery (FLACS) in hard cataract of Egyptian population.

Setting

ICare Center, Alexandria, Egypt.

Design

Retrospective observational.

Methods

The study included 50 FLACS cases of 40 patients who had cataract; NO4 NC4 or more according to Lens Opacities Classification System III (LOCS III), performed between October 2018 and May 2019. The cases underwent anterior capsulotomy, lens fragmentation, and corneal incisions with the femtosecond laser. Arcuate keratotomy was performed in selected cases. Phacoemulsification and implantation of an intraocular lens are then performed.

Results

Patients mean age was 63.06 ± 7.75 yr, mean femtosecond laser energy was 12.92 ± 0.72 mJ, mean docking time was 3.00 ± 0.83 min and overall mean laser treatment time was 92.00 ± 25.01 sec. Mean laser treatment time was lower in cases that did not get astigmatic keratectomy (87.7 ± 18.97 vs 89.47 ± 13.43 sec; p < 0.73). Attempted refraction was -0.09 ± 0.52 D and achieved 12 months postoperative manifest sphere equivalent refraction (SER) was -0.19 ± 1.11 D (r = 0.8 and P˂0.001). Mean error (ME) was -0.2 ± 1.11 (range: -2.5-1.5) while mean absolute error (MAE) was 0.97 ± 0.57 (range: 0-2.5). Eighty percent and 92% of cases had 1 month postoperative SER within 1.0 D and 1.5 D, respectively. One eye (2%) had incomplete capsulotomy, 7 eyes (14%) had incomplete corneal incision and lens fragmentation was complete in all cases except 1 eye (2%). Thirty-four eyes (68%) showed postdocking conjunctival ecchymosis and 35 eyes (70%) had intraoperative miosis.

Conclusion

FLACS has low complication rate with effective results. High cost of technology is still the main barrier against its popularity.

Stability of a non-applanating handheld liquid patient interface for femtosecond laser-assisted cataract surgery

PURPOSE

A stable and reliable vacuum is crucial for the correct planning and performance of femtosecond laser-assisted cataract surgery (FLACS) in order to avoid complications such as suction loss and cyclorotation. This study investigates, for the first time, the impact of different vacuum levels on the stability of the application of a liquid patient interface for FLACS in view of break-away forces.

METHODS

Break-away forces were measured using a multifunctional material testing machine with a mounted digital manometer. Sixteen porcine eyes were docked to the patient interface of a femtosecond laser platform (FEMTO LDV Z8), and the impact of different vacuum levels between 300 and 500 mbar investigated.

RESULTS

Mean break-away forces for each vacuum level were as follows: 1.78 N (± 0.58 N) for 300 mbar; 2.24 N (± 0.68 N) for 350 mbar; 2.66 N (± 0.68 N) for 400 mbar; 2.86 N (± 0.77 N) for 420 mbar; and 3.49 N (± 0.86 N) for 500 mbar.

CONCLUSION

The stability increases with the vacuum in a nearly linear manner. Vacuum levels higher than 500 mmHg and lower than 350 mmHg are not recommended for FLACS.

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.

Comparison of Perioperative Parameters in Femtosecond Laser-Assisted Cataract Surgery Using 3 Nuclear Fragmentation Patterns

PURPOSE

The purpose of this study was to compare the perioperative parameters of quadrant, sextant, and grid lens fragmentation patterns in femtosecond laser-assisted cataract surgery (FLACS).

DESIGN

Prospective randomized clinical trial.

METHODS

Setting: Eye Center of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.

STUDY POPULATION

A total of 894 eyes in 661 patients with cataracts were enrolled. Intervention or observation procedures: the nuclear density was graded according to the Emery-Little classification. Patients received lens fragmentation using a quadrant, sextant, or grid pattern after random allocation. Evaluations included intraoperative parameters, complications, and postoperative outcomes.

MAIN OUTCOME MEASUREMENTS

effective phacoemulsification time (EPT), intraoperative complications, visual acuity and intraocular pressure at one day postoperatively, as well as endothelial cell density, endothelial cell loss, and central corneal thickness at 1 week postoperatively.

RESULTS

In grade 1 nuclei, the mean EPT in the grid group was the shortest compared to those in the quadrant (P = 0.011) and sextant (P = 0.001) groups. In grade 2 nuclei, all 3 patterns showed no significant differences in the mean EPT (P > 0.05). In grade 3 nuclei, the sextant group revealed shorter mean EPT than the grid (P = 0.017) and quadrant (P > 0.05) groups. In grades 4 and 5 nuclei, the quadrant pattern had the shortest mean EPT among all 3 patterns (P < 0.05). The grid pattern is associated with higher intraocular pressure in hard nuclei (grades 4 and 5) than the other 2 patterns (P < 0.05).

CONCLUSIONS

The grid and quadrant patterns allow for shorter EPT in soft (grade 1) and hard (grades 4 and 5) nuclei, respectively. All 3 patterns can be selected for treating grade 2 nuclei. The sextant pattern may be the best option when treating grade 3 nuclei. The grid pattern should be avoided in hard nuclei combined with glaucoma or glaucoma suspect.

Combined Femtosecond Laser-Assisted Cataract Surgery and 27-Gauge Transconjunctival Sutureless Vitrectomy

Purpose

To report the outcomes of combined surgery using femtosecond laser-assisted cataract surgery (FLACS) and sutureless 27-gauge pars plana vitrectomy with intravitreal tamponade.

Methods

This retrospective clinical study involved 23 eyes of 23 patients on whom combined vitreoretinal surgery was performed. Patients were initially given the femtosecond laser treatment that was performed after selection of capsulotomy and lens fragmentation patterns. The capsulotomy diameter was chosen as 4.9 mm in all patients. After the femtosecond laser, the sutureless phacovitrectomy procedure was performed. At the end of surgery, perfluoropropane or sterile air tamponade was applied.

Results

The mean age of patients was 66.43 ± 7.61 (range, 54–83) years. Fifteen patients were females (65.2%). The mean follow-up was 16.09 ± 4.71 (range, 9–25) months. The most common surgical indication was epiretinal membrane (65.3%). The mean preoperative best-corrected visual acuity (BCVA) was 0.71 ± 0.44 (range, 1.7–0.3) logMAR, and the mean postoperative BCVA at 6 months was 0.16 ± 0.14 (range, 0.4–0) logMAR (p < 0.001). The mean target sphere refractive error was −0.24 ± 0.16 (range, −0.50–0.11) D, and the mean postoperative spherical equivalent refractive error was −0.14 ± 0.39 (range, −1.00–0.50) D at 6 months (p=0.196). All intraocular lenses (IOLs) remained well centered in the capsular bag during surgery and follow-up. There was no iris capture, posterior synechiae, capsular opacification, or pseudophakic cystoid macular edema. The only complication related to femtosecond laser was two cases of subconjunctival haemorrhage related with suction.

Conclusions

FLACS is a safe and effective technique providing the advantage of repeatable, precise capsulorhexis shape and size to achieve a well-centered and stable IOL postoperatively. These advantages can certainly improve the results of vitrectomy, especially in gas-filled eyes. FLACS and 27-gauge sutureless combined surgery may be a future trend in appropriate cases.

Application of Femtosecond Laser in Anterior Segment Surgery

Femtosecond laser (FSL) is a near-infrared laser that can create reliable and reproducible tissue cutting with minimal damage to adjacent tissue. As the laser can also create incisions with various orientations, depths, and shapes, it is expected to be a useful tool for anterior segment surgery, such as cornea, refractive, and cataract surgery. In this review, the authors will introduce the application of FSL in various anterior segment surgeries and discuss the results of studies regarding the efficacy and safety of FSL in cornea, refractive, and cataract surgery. Experimental studies regarding the potential use of FSL will also be introduced. The studies discussed in this review suggest that FSL may be a useful tool for improving the prognosis and safety of surgeries of the anterior segment.

CARS-imaging guidance for fs-laser ablation precision surgery

Due to ageing populations the number of tumors is increasing worldwide. Successful surgical treatment requires complete resection of tumors to reduce recurrence rates. To reach this goal, novel methods combining in vivo tumor and tumor margin detection with low invasive precision surgical tools are needed. Coherent anti-Stokes Raman scattering (CARS) imaging is a highly promising optical tool for visualizing tumors based on characteristic changes in tissue morphology and molecular composition, while fs-laser ablation is to date the most precise surgical tool established in ophthalmology. In this contribution, CARS imaging has been combined with fs-laser ablation as a new approach for image-guided precision surgery for the first time. CARS guided fs-ablation has been applied to ablate brain, liver, skin, muscular and vascular tissues with μm-precision using sub-100 fs pulses of μJ level. We demonstrate superior imaging performance and contrast as well as detection of tissue margins by coherent Raman microscopy in comparison to laser reflectance imaging. The combination of CARS-image-guided tissue ablation is a promising tool for minimally invasive surgeries particularly in the vicinity of functional structures in the future.

Comparison of the selected parameters of the anterior segment of the eye between femtosecond laser-assisted cataract surgery, microincision cataract surgery, and conventional phacoemulsification: A case-control study

The purpose of our study was to compare the selected parameters of the anterior segment of the eye in patients after femtosecond laser-assisted cataract surgery (FLACS) with the results of microincision cataract surgery (MICS) and conventional phacoemulsification surgery (CPS). This single-center prospective randomized comparative observational study included 87 patients. Patients were randomly selected into group A (FLACS), group B (MICS) and group C (control group). All the surgeries were performed by the same experienced surgeon. Preoperative and postoperative parameters were evaluated: best-corrected visual acuity (BCVA), endothelial cell density (ECD), endothelial cell loss percentage (ECL%), central corneal thickness (CCT), central anterior and posterior corneal astigmatism induction, posterior corneal elevation map were measured. Intraoperative parameters: effective phacoemulsification time (EPT), balanced salt solution use (BSS use), total surgical time and suction time were analyzed. Examination was performed preoperatively and on the first, seventh day, one and six months postoperatively. The follow up period was 6 months. There was no statistically significant difference in BCVA, central anterior and posterior astigmatism induction between studied groups. The ECL% was statistically significant lower in the group A on the 7th day, 1 month and 6-months postoperatively (P < .05). The CCT was statistically significant lower in the group A and in the group B than in the group C on the 7th postoperative day (P = .002). However, in the 6 months follow-up there was no statistically significant difference in the CCT between studied groups (P = .133). We observed statistically significant difference in change of the posterior corneal elevation map at the periphery assessed within the 90° to 120°meridian range between group A, group B and group C at every timepoint postoperatively (P < .05). The EPT and BSS use were statistically significant lower whilst total surgery time was statistically significant higher in the FLACS group (P < .05). To conclude in the 6 months follow-up there was statistically significant difference found between eyes undergoing FLACS, MICS and CPS with respect to the posterior corneal elevation map assessed within the studied range, ECL%, EPT, BSS use and total surgery time. Postoperative BCVA, central anterior and posterior astigmatism induction, CCT were comparable between studied groups.

In vivo and in vitro results of an automated preloaded delivery system for IOL implantation in cataract surgery

PURPOSE

To compare the corneal tissue trauma after the use of an automated preloaded injector and a manual injector and assess scanning electron microscope (SEM) and atomic force microscope (AFM) features of both injector cartridges.

SETTING

Ophthalmology Clinic and Laboratory of Stem Cells and Regenerative Medicine University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy; DESIGN: Prospective randomized clinical study METHODS: Forty eyes of 40 patients for phacoemulsification were divided into two groups: implantation of intraocular lens was performed with AutonoMe automated delivery system (AutonoMe group: 20 eyes) and Monarch III injector system (Monarch group: 20 eyes). In vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT) were performed before surgery, at 1 h, 1 day and 1 month post-operatively. In addition, SEM and AFM were performed on cartridges of both injector systems after injection of the IOL.

RESULTS

A greater increase in central corneal thickness and corneal thickness at the incision site were observed in Monarch group versus AutonoMe group 1 h and 1 day post-operatively (p < 0.05). Endothelial cell count loss was significantly higher in Monarch group compared with AutonoMe group (p < 0.05) at 1 and 24 h. AS-OCT showed less endothelial misalignment at 30 days (p < 0.05), and IVCM showed less tunnel inflammation at all time points (p < 0.05) in AutonoMe group compared with Monarch group; roughness analysis at AFM of the AutonoMe cartridge was significantly lower compared to Monarch D cartridge (p < 0.05).

CONCLUSIONS

The AutonoMe injector provided less corneal tissue trauma compared with Monarch III injector. The AutonoMe cartridge showed lower roughness at AFM compared to the Monarch D cartridge.

Presbyopia and the aging eye: Existing refractive approaches and their potential impact on dry eye signs and symptoms

Every part of the human body is subject to aging, including the eye. An increased prevalence of dry eye disease with age is widely acknowledged. Aging threatens ocular surface homeostasis, altering the normal functioning of the lacrimal functional unit and potentially leading to signs and symptoms of dry eye. Additional age-related processes take place within the crystalline lens, leading to presbyopia and cataractogenesis. Correction strategies for presbyopia and cataracts may directly or indirectly challenge the ocular surface. Contact lenses disturb the normal structure of the tear film and can interact negatively with the ocular surface, further deteriorating an already unbalanced tear film in presbyopes, however, newer contact lens designs can overcome some of these issues. Moreover, cataract and corneal refractive surgeries sever corneal nerves and disrupt the corneal epithelium and ocular surface, which can influence surgical outcomes and aggravate dryness symptoms in older age groups. This review summarises the current understanding of how the invasive nature of contact lens wear and cataract and refractive surgery influence signs and symptoms of ocular dryness in an aging population.

Precision pulse capsulotomy in challenging cataract surgery cases

Purpose

To evaluate the use of the precision pulse capsulotomy (PPC) device for challenging cataract surgery cases.

Patients and methods

This single-center retrospective case series study comprised of 43 eyes (from 35 patients) that were challenging cataract surgery cases with poorly dilated pupils, anterior subcapsular opacity, white cataract, brunescent cataract, and corneal opacity. This was  conducted at the Busan Sungmo Eye Hospital (Busan, Republic of Korea) to assess the performance of the PPC device through a 2.2-mm clear corneal incision width, followed by the phacoemulsification technique and intracapsular intraocular lens fixation. The main outcome measurement was the anterior capsulotomy performance of the PPC device and the development of intraoperative complications. At postoperative 2 months, visual acuity, endothelial cell count, and refractive error were measured.

Results

No cases of anterior capsule tears or tags occurred. All 43 eyes received circular, 360-degree, free-floating, and appropriately sized anterior capsulotomies. During 2 months of follow up, no postoperative complications occurred in association with the PPC device.

Conclusion

The PPC device facilitated the creation of a precise, round, appropriately sized anterior capsulotomy in challenging cataract surgery cases. Further investigations are required to understand the long-term safety and efficacy of the PPC device.

Femtosecond laser-assisted capsulotomy with capsular marks for toric IOL alignment: Comparison of tensile strength with standard femtosecond laser capsulotomy

PURPOSE

To compare the capsulotomy rim strength with capsular marks (CMs) to the rim strength without CMs in porcine eyes, and to demonstrate the practicality of CMs for intraoperative toric intraocular lens (IOL) alignment.

SETTING

LENSAR facility, Orlando, Florida, USA.

DESIGN

Laboratory study.

METHODS

The biomechanical strength of the capsulotomy with CMs was tested under two different load orientations (orthogonal to or in-line with CMs). Thirty-six porcine eyes were randomly assigned to three treatment cohorts: (1) standard capsulotomy with no CMs, (2) capsulotomy with CMs for in-line tensile testing and (3) capsulotomy with CMs for orthogonal tensile testing. Study parameters were capsulotomy break force and maximum extensibility. The ease of using CMs for toric IOL alignment was also evaluated.

RESULTS

There was no significant difference between the mean break force for standard capsulotomy (180.57 mN ± 22 [SD]), capsulotomy with CMs with orthogonal load (178.04 ± 20 mN, P = 1.000), and with in-line load (181.05 ± 15 mN, P = 1.000). Likewise, the mean extensibility at the break point for standard capsulotomy (6.47 ± 0.33 mm) was equivalent to the mean extensibility with CMs with orthogonal load (6.49 ± 0.45 mm, P = 1.000) and with in-line load (6.3 ± 0.47 mm, P = .960). In the implanted eyes, toric IOLs were found to be easily aligned with the CMs.

CONCLUSION

The femtosecond laser capsulotomies with CMs were equivalent in tensile strength and extensibility to standard femtosecond laser capsulotomies and showed high potential for effective alignment of toric IOLs.

Comparative Analysis of Double and Trifocal IOL Implantation in Femtosecond Laser-Assisted Cataract Surgery

Purpose: to compare the clinical results of implantations of bi-and trifocal intraocular lenses (IOL) in femtosecond laser-assisted cataract surgery. Patients and methods. The article presents the results of the Acrysof IQ Panoptix trifocal lens implantations in 84 patients (112 eyes) — the main group and Acrysof IQ Restor bifocal IOL implantations in 52 patients (98 eyes) — the control group. All patients underwent femtosecond laser-assisted cataract surgery (FLACS). The following data were evaluated: uncorrected distance visual acuity (UCDVA) , uncorrected near visual acuity (30–45 cm) and at an average distance (50–70 cm) at discharge, after 14 days, 1 and 3 months after the surgery under photopic and mesopic lighting conditions. Postoperative refractometry data; the defocusing curve was performed in patients with a high UCDVA (0.9–1.0) monocularly under photopic conditions using standard optotypes 14 days after surgery; aberrometry indicators. Results. It was shown that both lenses provided high uncorrected distance and near visual acuity in photopic lighting conditions. At the same time, the Acrysof IQ Panoptix lens provided significantly better visual acuity at an intermediate distance and was more resistant to defocusing conditions. Refraction data: after 1 month, emmetropia was observed in 87 % of patients in the main group and in 85 % of control group, after 6 months — 92 and 89 % respectively. There were no significant differences in high order aberrations and total aberrations between patients of the compared groups. Conclusion. The use of the PanOptix trifocal lens made it possible to obtain maximum visual acuity at different distances, regardless of the level of illumination.

Multi-rate-equation modeling of the energy spectrum of laser-induced conduction band electrons in water

We study the energy spectrum of laser-induced conduction band (CB) electrons in water by multi-rate equations (MRE) with different impact ionization schemes. Rethfeld's MRE model [Phys. Rev. Lett.92, 187401(2004)Phys. Rev.B 79, 155424(2009)], but the corresponding rate equations are computationally very expensive. We introduce a simplified splitting scheme and corresponding rate equations that still agree with energy conservation but enable the derivation of an asymptotic SRE. This approach is well suited for the calculation of energy spectra at long pulse durations and high irradiance, and for combination with spatiotemporal beam propagation/plasma formation models. Using the energy-conserving MREs, we present the time-evolution of CB electron density and energy spectrum during femtosecond breakdown as well as the irradiance dependence of free-electron density, energy spectrum, volumetric energy density, and plasma temperature. These data are relevant for understanding photodamage pathways in nonlinear microscopy, free-electron-mediated modifications of biomolecules in laser surgery, and laser processing of transparent dielectrics in general.

[Comparison of clinical and functional results of conventional and femtosecond laser-assisted cataract phacoemulsification]

PURPOSE

To perform a comparative analysis of ultrasound and hydrodynamic parameters, and the outcomes of femtosecond laser-assisted cataract surgery (FLACS) and conventional phacoemulsification cataract surgery (CPCS).

MATERIAL AND METHODS

This prospective cohort study included 246 eyes. The first group consisted of 138 patients who underwent FLACS, second group - 108 patients after CPCS.

RESULTS

Total ultrasound time was 95.36±47.93 and 113.3±97.71 seconds (p=0.04) in the 1^st and the 2^nd groups, respectively. The duration of torsional ultrasound was 84.72±50.03 seconds in 1^st group (p=0.04) and 113.3±97.71 seconds in the 2^nd group (p=0.04). Aspiration time was 208.3±95.86 seconds in the 1^st group (p=0.04) and 258.43±158.81 seconds in the 2nd group (p=0.04). On the 3-4^th day after the surgery, uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were significantly better in the 1^st group - 0.62±0.21 (LogMAR 0.20±0.19) and 0.53±0.15 (LogMAR 0.30±0.21) (p=0.01), respectively, compared to the 2^nd group with UDVA of 0.75±0.18 (LogMAR 0.10±0.16) and CDVA of 0.69±0.19 (LogMAR 0.20±0.15) (p=0.04). Central corneal thickness (CCT) was 573.41±33.12 and 632.43±58.30 μm in the 1^st and 2^nd groups, respectively (p=0.020). At 1 month post-op there were no statistically significant differences in UDVA (p=0.17), CDVA (p=0.40) or CCT (p=0.50) between the groups.

CONCLUSION

Compared with CPCS, total ultrasound time (p=0.04), torsional ultrasound time (p=0.04) and aspiration time (p=0.04) were significantly lower in the FLACS group. CCT was significantly lower (p=0.02), while UDVA (p=0.04) and CDVA (p=0.01) were significantly higher in the FLACS group in the early post-operative period (3-4 days after surgery). There were no statistically significant differences in the parameters between the groups 1 month after the surgery.

Comparison of refractive outcomes between femtosecond laser-assisted cataract surgery and conventional cataract surgery

The purpose of our study is to compare the predictive accuracy of femtosecond laser-assisted cataract surgery with the results of conventional cataract surgery. This prospective study included 83 eyes from 83 patients who underwent femtosecond laser-assisted cataract surgery and 83 eyes from 83 patients who underwent conventional cataract surgery. Preoperative IOL power calculations were performed with the partical coherence interferometry. Femtosecond laser-assisted capsulotomy was based on 5.2 mm scanned capsule center. Following phacoemulsification, 1-piece IOL was inserted into the capsular bag. Refractive outcome was measured 3 months postoperatively with manual refraction. Predicted refraction was assessed by the Barret-Universal II, Haigis, Hoffer Q, SRK/T, and T2 formulas. We applied optimized IOL constants and retrospectively personalized IOL constants. There was no difference in preoperative demographic data. When the optimized IOL constants were used, the femtosecond laser-assisted group produced significantly lower MAEs in the Barret-Universal II, Hoffer Q, SRK/T, and T2 formulas (P < .05). After the personalization of IOL constants, there were statistical differences in the Barret-Universal II, Hoffer Q (P < .05). The standard deviation of ME and MedAE were also relatively lower with femtosecond laser-assisted group. In conclusion, femtosecond laser-assisted cataract surgery with Catalys femtosecond laser system produced better refractive outcomes than conventional cataract surgery.

Long-term intraocular pressure changes after femtosecond laser-assisted cataract surgery in healthy eyes and glaucomatous eyes

PURPOSE

To examine the long-term effect of femtosecond laser-assisted cataract surgery on intraocular pressure (IOP) in healthy (control) and glaucomatous eyes.

SETTING

University of Colorado, Aurora, Colorado, and Vanderbilt University, Nashville, Tennessee, USA.

DESIGN

Retrospective case series.

METHODS

The study comprised patients aged 18 to 89 years meeting the inclusion criteria. Combination procedures were excluded. The main outcome measure was the change in the mean IOP from baseline to postoperatively.

RESULTS

Of the 504 eyes meeting the criteria, 278 were in the glaucoma/glaucoma suspect group and 226 in the control group. Both groups had an initial mean increase in IOP 1 day postoperatively (control: +2.0 mm Hg; 95% confidence interval [CI], 1.4-2.6; glaucoma/glaucoma suspect: +3.4 mm Hg; 95% CI, 2.5-4.2) (both P < .001). The increase was significantly higher in the glaucoma/glaucoma suspect group. The IOP returned to baseline levels at 1 week. At 1 month, both groups had a significant decrease in IOP that persisted until year 1 in the control group and through 3 years in the glaucoma group. The number of IOP medications was unchanged in the glaucoma group during follow-up. The glaucoma/glaucoma suspect group achieved significantly greater IOP lowering than the control group after 6 months.

CONCLUSIONS

Control eyes and eyes with glaucoma had an initial mean IOP rise 1 day after femtosecond laser-assisted cataract surgery. This was followed by a significant decrease starting at 1 month. The reduction was sustained through 3 years in the glaucoma group.