Laser Direct Writing of Graphene Quantum Dots inside a Transparent Polymer

Graphene quantum dots (GQDs) have emerged as a promising new class of environmentally friendly quantum dots with unique properties. However, the limitations of synthesis and patterning methods have hindered GQDs from displaying their true potentials to date. Here, we demonstrate the simultaneous synthesis and patterning of GQDs for the first time inside a transparent polymer, polydimethylsiloxane (PDMS), using femtosecond laser pulses. By focusing and scanning femtosecond laser pulses, arbitrary fluorescent patterns such as a concealed fluorescent QR code can be readily patterned without pre- and/or post-treatment. In addition, the proposed method is applied to the fabrication of fluorescent three-dimensional structures inside a transparent polymer via multiphoton interactions. The proposed method realizes single-stepped and spatially selective patterning of GQDs directly inside polymer substrates and expands the possibilities of GQDs for applications in novel flexible three-dimensional optoelectrical devices.

'Cookies on a tray': Superselective hierarchical microstructured poly(l-lactide) surface as a decoy for cells

In this research we developed a micro-sized hierarchical structures on a poly(l-lactide) (PLLA) surface. The obtained structures consist of round-shaped protrusions with a diameter of ~20 μm, a height of ~3 μm, and the distance between them ~30 μm. We explored the effect of structuring PLLA to design a non-cytotoxic material with increased roughness to encourage cells to settle on the surface. The PLLA films were prepared using the casting melt extrusion technique and were modified using ultra-short pulse irradiation - a femtosecond laser operating at λ = 1030 nm. A hierarchical microstructure was obtained resembling 'cookies on a tray'. The cellular response of fibro- and osteoblasts cell lines was investigated. The conducted research has shown that the laser-modified surface is more conducive to cell adhesion and growth (compared to unmodified surface) to such an extent that allows the formation of highly-selectively patterns consisting of living cells. In contrast to eukaryotic cells, the pathogenic bacteria Staphylococcus aureus covered modified and unmodified structures in an even, non-preferential manner. In turn, adhesion pattern of eukaryotic fungus Saccharomyces boulardii resembled that of fibro- and osteoblast cells rather than that of Staphylococcus. The discovered effect can be used for fabrication of personalized and smart implants in regenerative medicine.

One year outcomes after small incision lenticule extraction ReLEX in the correction of myopia and myopic astigmatism

Purpose

To report the visual and refractive outcomes of small incision lenticule extraction ReLEX (SMILE) technique using VisuMax femtosecond laser in myopia and myopic astigmatism patients.

Material and methods

A non-randomized clinical study has been conducted on patients with myopia and myopic astigmatism who underwent ReLEX SMILE technique, using the Zeiss VisuMax Laser system (Carl Zeiss Meditec AG, Jena, Germany) at Oculens Clinic, Cluj-Napoca, Romania. Patients older than 18 years, with ocular astigmatism up to -5 diopters (D), spherical equivalent up to -10.00 D, corrected distance visual acuity (CDVA) of 0.3 or better before the surgery, stable refraction for one year, and with a minimum calculated post operator residual stromal bed of 250μ were included in the study.

Results

The study involved a total of 25 myopic eyes (median of sphere diopters equal with -4D) and 67 myopic astigmatic eyes (median of cylinder diopters equal with -1.5 D). The mean refractive spherical equivalent (MRSE) on patients with myopic eyes reduced from -4.25D (median) to -0.5D at one month follow-up, -0.25 D at 6 and 12 months. The mean refractive spherical equivalent (MRSE) on patients with astigmatic myopic eyes reduced from-6.25 D to -0.67 D at one month, -0.62 D at six and twelve months. The value of sphere decreased postoperatively on myopic eyes with a median of -0.25D at one, six and twelve months. The value of cylinder decreased postoperatively on myopic astigmatic eyes with a median of -0.50 D at one month, -0.25 D at six months and -0.50 D at 12 months. At 6 and 12 months, 20 (80.0%) of myopic eyes were maintained within ±0.5 D and 22 (88.0%) with ±1D. On both groups (myopic eyes and myopic astigmatic eyes), statistically significant differences were observed when the keratometric baseline values were compared to each follow-up (P-values < 0.0001), without any significant differences between follow-ups (P-values>0.15). At 1-month follow-up, uncorrected distance visual acuity (UDVA) was better than or equal to 0.5 in 88.0% of myopic eyes and 82.1% of myopic astigmatic eyes. UDVA remained stable in all cases of myopic eyes at six months and the percentage increased at 92.0% in myopic eyes. UDVA slightly increased at 6-months (85.1%) and remained at the same value at 12-months in myopic astigmatism eyes.

Conclusions

SMILE proved an effective and safe refractive corneal procedure and provided a predictable and stable correction of myopia and myopic astigmatism. SMILE technique demonstrated very good outcomes in terms of keratometric, cylinder, spherical measurements.

Refractive outcomes of femtosecond laser-assisted cataract surgery with arcuate keratotomy and standard phacoemulsification with toric intraocular lens implantation

PURPOSE

Femtosecond laser arcuate keratotomy (FS-AK) and toric intraocular lens (IOL) implantation are effective for the correction of eyes with corneal astigmatism. In this study, the postoperative refractive outcomes of patients receiving femtosecond laser-assisted cataract surgery (FLACS) with FS-AK and patients receiving standard phacoemulsification with toric IOL implantation were evaluated.

METHODS

This retrospective study reviewed the postoperative outcomes of patients undergoing FLACS with FS-AK (the FS-AK group) and patients undergoing standard phacoemulsification with toric IOL implantation (the toric IOL group). The main outcome measures were uncorrected and corrected visual acuities, keratometric and refractive astigmatism, and vector analysis.

RESULTS

The FS-AK group included 41 eyes with preoperative keratometric astigmatism of - 1.64 ± 0.42 diopters (D), and the toric IOL group included 53 eyes with preoperative keratometric astigmatism of - 2.29 ± 0.91 D (P < 0.001). Postoperative refractive astigmatism was comparable between the two groups. Compared with the FS-AK group, postoperative uncorrected visual acuity was significantly better (P = 0.005) and corrected visual acuity was marginally better in the toric IOL group (P = 0.051). The absolute angles of error were 9.95° ± 9.57° and 5.08° ± 4.94° (P = 0.02) in the FS-AK and the toric IOL groups, respectively.

CONCLUSION

Both FLACS with FS-AK and standard phacoemulsification with toric IOL implantation are safe and effective methods for astigmatism correction during cataract surgery. Standard phacoemulsification with toric IOL implantation achieves better visual acuity than FLACS with FS-AK at the 6-month follow-up.

Femtosecond laser-assisted cataract surgery in small pupils using non-aligned iris expansion ring without viscoelastic and corneal suture

PURPOSE

To describe a technique for cataract surgery in eyes with small pupils that combines the use of the femtosecond laser and an iris expansion device, but without the use of corneal sutures and an ophthalmic viscosurgical device (OVD) at the time of laser application.

METHODS

A retrospective case series of three eyes with small pupils were operated by the same surgeon without a corneal suture and with removal of anterior chamber OVD prior to laser application.

RESULTS

Corrected distance visual acuity (CDVA) for 1 eye in a 70 year-old patient was 20/70 preoperatively and 20/20 thirty days postoperatively. CDVA for a second patient was 20/50 and 20/200 in the two eyes, which improved to 20/25 two months postoperatively in both eyes. There were no complications observed and the intraocular lens were well-centered.

CONCLUSION

The use of mechanical pupil expander rings is safe and practical in setting small pupils during femtosecond laser-assisted cataract surgery.

Esterification of perfluorinated carboxylic acids with bromomethyl aromatic compounds for gas chromatography combined with laser ionization mass spectrometry

Perfluorinated carboxylic acids (PFCAs) were derivatized with two types of aromatic compounds that contained a bromomethyl group, i.e., 2-(bromomethyl)naphthalene (BMN) and benzyl bromide (BB). The conditions for derivatization were optimized in terms of reaction temperature and time and the concentration of derivatizing reagent. Using these optimal conditions, the PFCAs-MN and PFCAs-B derivatives were measured by gas chromatography (GC) combined with mass spectrometry using an ultraviolet femtosecond laser (267 nm) as the ionization source. The efficiency of derivatization for PFCAs-B was higher than that for PFCAs-MN because of the smaller size of the chromophore (benzene). The ionization efficiency of PFCAs-MN, however, was better than PFCAs-B, since a larger sized chromophore (naphthalene) and then a larger molar absorptivity was preferable for resonance-enhanced two-photon ionization. Due to superior GC separation, BB was successfully used as the derivatizing agent for the trace analysis of PFCAs, with detection limits of 6.0, 8.4, and 9.5 ng/mL for perfluoroheptanoic, perfluorooctanoic, and perfluorononanoic acids, respectively. The other bromomethyl aromatic compounds were evaluated for use as a derivatization reagent in future studies.

Femtosecond laser semi-assisted Descemet stripping endothelial keratoplasty: 2-year outcomes of endothelial cell loss and graft survival

Purpose

To assess 2-year endothelial cell loss and graft survival after femtosecond laser semi-assisted Descemet stripping endothelial keratoplasty (FLS-DSEK).

Methods

In this prospective and noncomparative study carried out at Eye Hospital of Shandong First Medical University, 85 eyes (84 patients) with endothelial dysfunction receiving FLS-DSEK (n=62, 75.9%) or FLS-DSEK combined with phacoemulsification cataract surgery and intraocular lens implantation (n=23, 27.1%) from 2013 through 2016 were included. The graft endothelial cell loss, endothelial graft thickness, visual acuity, and complications after surgery were evaluated.

Results

Thin endothelial grafts were all successfully prepared, with no occurrence of perforation. The rate of endothelial cell loss was 17.4%, 18.8%, 19.9%, and 26.7%, and the central graft thickness was 113±54 μm, 102±40 μm, 101±28 μm, and 96±23 μm at 3, 6, 12, and 24 months, respectively. The median best-corrected visual acuity was 0.4 logMAR (range, 0–2 logMAR) at 24 months, demonstrating a significant difference from that before surgery (2 logMAR; range, 0.2–3 logMAR) (T=187.5, P<.001). Partial graft dislocation was the most common postoperative complication, with an occurrence rate of 14% (n=12), and it was associated with an abnormal iris-lens diaphragm (r=.35, P<.001). The other complications included a high intraocular pressure (n=5, 6%), endothelial graft rejection (n=4, 5%), and pupillary block (n=1, 1%). Endothelial graft decompensation occurred in the two eyes, and 98% (n=83) of the grafts survived at 24 months.

Conclusions

Data of the study suggest that the treatment using FLS-DSEK seems to be promising and might be considered a feasible choice in patients with endothelial dysfunction.

Trial registration

1. Date of registration: 2021-02-18

2. Trial registration number: ChiCTR2100044091

3. Registration site: https://www.chictr.org.cn/

Supplementary Information

The online version contains supplementary material available at 10.1007/s00417-021-05383-x.

Femtosecond laser-induced periodic grooves and nanopore clusters make a synergistic effect on osteogenic differentiation

Polyether-ether-ketone (PEEK) materials have good biocompatibility, excellent corrosion resistance, chemical stability and an elastic modulus close to that of natural bone. However, due to its biological inertness, PEEK may affect osteogenic differentiation and leads to osseointegration failure, though PEEK is expected to improve osseointegration. In this work, by changing the power of femtosecond laser, micro-grooves are made on the PEEK surface. As observed by scanning electron microscopy, the trench has a periodic structure, the micro shape is neat, and the trench is also covered with nanometer-level pore clusters. In the in vitro culture experiments, through the proliferation experiment of mouse bone marrow mesenchymalstem cells (mBMSCs), cell viability analysis and alkaline phosphatase activity analysis, it is proven that after femtosecond laser treatment of the PEEK surface, the micro-grooves on the surface and the nanopore clusters due to laser energy ablation can produce a synergistic effect, enhancing the osteogenic differentiation ability of cells, and improving the bone integration ability of PEEK materials.

[Effects of femtosecond laser treatment on surface characteristics and flexural strength of zirconia]

OBJECTIVE

To evaluate the effects of femtosecond laser treated microgrooved surface on microscopic topography, phase transformation, and three-points flexural strength of zirconia, and to provide reference for surface microstructure optimization of zirconia implant.

METHODS

According to different surface treatment methods, 57 computer aided design/computer aided manufacture (CAD/CAM) zirconia bars (20.0 mm×4.0 mm×1.4 mm) were evenly divided into three groups: sintered group, no treatment after sintering, taken as control; sandblasted group, sandblasted with 110 μm aluminium oxide (Al₂O₃) after sintering; microgrooved group, femtosecond laser fabricated microgrooves with 50 μm width, 30 μm depth, and 100 μm pitch. Surface microscopic topography was observed with scanning electron microscope (SEM) and 3D laser microscope. Further, surface roughness in each group and microgroove size were measured. Crystal phase was analyzed with X-ray diffraction. Specimens were subjected to three- points flexural strength test, and Weibull distribution was used to analyze their strength characteristics.

RESULTS

SEM showed that sintered surface was flat with clear grain structure; sandblasted surface exihibited bumps and holes with sharp margins and irregular shape; microgrooves were regularly aligned without evident defect, and nano-scale particles were observed on the surface inside of the microgrooves. Ra value of microgrooved group [(9.42±0.28)] μm was significantly higher than that of sandblasted group [(1.04±0.03) μm] and sintered group [(0.60±0.04) μm], and there was statistical difference between sandblasted group and sintered group (P < 0.001). The microgroove size was precise with (49.75±1.24) μm width, (30.85±1.02) μm depth, and (100.58±1.94) μm pitch. Crystal phase analysis showed that monoclinic volume fraction of sandblasted group (18.17%) was much higher than that of sintered group (1.55%), while microgrooved group (2.21%) was similar with sintered group. The flexural strength of sandblasted group (986.22±163.25) MPa had no statistical difference with that of sintered group (946.46±134.15) MPa (P=0.847), but the strength in microgrooved group (547.92±30.89) MPa dropped significantly compared with the other two groups (P < 0.001). Weibull modulus of sintered, sandblasted, microgrooved groups were 7.89, 6.98, and 23.46, respectively.

CONCLUSION

Femtosecond laser was able to form micro/nanostructured microgrooves on zirconia surface, which deleteriously affected the flexural strength of zirconia.

Evaluation of the change in retinal thickness after femtosecond laser-assisted laser in situ keratomileusis and photorefractive keratectomy

PURPOSE OF THE STUDY

To investigate the change in individual retinal layer thickness by spectral-domain optical coherence tomography (SD-OCT) in eyes underwent femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and photorefractive keratectomy (PRK).

METHODS

In patients who underwent PRK and FS-LASIK, changes in the thickness of all retinal layers in the foveal, parafoveal, and perifoveal regions were evaluated by SD-OCT automated segmentation analysis at pre-operatively and different time points post-operatively.

RESULTS

Seventy-one eyes of 71 patients (38 patients in PRK, 33 patients in LASIK) were included. In the pre-operative period, mean spherical equivalent (SE), mean keratometry, axial length, and segmentation values of the retinal layers were similar (P> .05). In the PRK group, the pre-operative measurements of individual retinal layers did not show a statistically significant difference compared to the post-operative measurements on the 1st day, 1st week, and 1st month. In the FS-LASIK group, the mean inner nuclear layer (INL) thickness one day after the surgery was significantly higher than that before surgery in the foveal (21.22 ± 4.66 µm vs 19.03 ± 4.50 µm, P= .013) and parafoveal regions (41.98 ± 3.70 µm vs 40.56 ± 3.49 µm, P= .044).

CONCLUSIONS

The findings of our study suggest that the increase of INL thickness may be due to temporary structural and circulatory changes of the retina that may occur in the suction phase in the FS-LASIK procedure.

Effects of frost formation on the ice adhesion of micro-nano structure metal surface by femtosecond laser

In this work, we study the effect and evolution of frost condensation on the ice adhered micro-nano structured Ni metal surface. By measuring the ice adhesion strength to the porous-structured surface under different frosting coverage, it is found that the ice adhesion on the surface changes not only with the morphology but also with the different evolution stages of the frosting coverage. Combining the changes in surface morphology and low-temperature wettability, the reasons for the changes in the ice adhesion strength are attributed to the change of wettability of the porous-structured surface under different frosting coverage, which affects the infiltration state of the surface and results in different mechanical interlocking, air-pockets and cracks states at the ice-solid interface. Moreover, it is found that the ice adhesion strength of the hydrophobic and hydrophilic porous-structured surface tends to be the same when the surface is heavily frosted. In addition, we demonstrate that both the hydrophobic and hydrophilic columnar-structured surfaces have smaller ice adhesion strength than the original surface without any micro-nano structures regardless of whether the surface is frosted or not, and the measured lowest ice adhesion strength of the hydrophobic columnar-structured surface can be down to 30 kPa in all frosted evolution stages, which is less than one tenth of the original surface. The findings in this work suggest that the influence of frosting should be fully considered when designing the icephobic micro-nano structured metal structure, and it can further serve as an important guidance for the design of passive icephobic surfaces expected to be free from the frosting effect.

Femtosecond laser-induced nanoporous layer for enhanced osteogenesis of titanium implants

The osteogenic activity of medical metal can be improved by lowering its surface stiffness and elastic modulus. However, it is very difficult to directly reduce the elastic modulus of medical metal surfaces. In this paper, with selected parameters, the titanium surface was treated via femtosecond laser irradiation. Micro indentation revealed that the femtosecond laser ablation can effectively reduce the surface Young's modulus and Vickers hardness of titanium. Besides, In order to explain the mechanical properties of degradation of titanium surface, Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) was used to simulate the process of laser ablation process of titanium surface, and it was found that after the ablation of titanium surface, voids were produced in the subsurface layer. The simulation showed that the voids are formed by the cavitation of metastable liquid induced by high tensile stress and high temperature during femtosecond laser irradiation. Subsurface voids with a thickness of about 40 nm were observed under the oxide layer in the experiment. Cell experiments showed that the surface with low Young's modulus was more conducive to cell proliferation and osteogenic differentiation.

The effect of femtosecond laser irradiation on the growth kinetics of Staphylococcus aureus: An in vitro study

We investigated the effect of femtosecond laser irradiation on the growth kinetics of Staphylococcus aureus. In order to improve laser-based antimicrobial therapy and develop a clinically viable modality, various laser parameters such as laser light wavelength, laser power, exposure time, and energy density were studied. The INSPIRE HF100 laser system (Spectra Physics) provided the femtosecond laser light, which was pumped by a mode-locked femtosecond Ti: sapphire laser MAI TAI HP (Spectra Physics). The survival of the bacterial cells was monitored after irradiation by determination of growth rate using optical density, which is a rapid, simple, and reliable method. The growth rate of laser-exposed cultures was compared to control cultures. Fifteen minutes of exposure to femtosecond laser radiation with a wavelength of 390 nm and 400 nm at an average power of 50 mW was enough to significantly reduce bacterial viability, with a lag in the growth phase of 5 h longer than the control culture (P < 0.0001 by ANOVA and Tukey test).

Femtosecond Laser Assisted Cataract Surgery: A Review

Femtosecond laser assisted cataract surgery (FLACS) offers a level of precision, accuracy and customization that is not possible with manual phacoemulsification (MP). With the increase of patient expectations and premium intraocular lens utilization in the era of refractive cataract surgery, predictability and accuracy has become of utmost importance. FLACS has four main functions: creation of a consistently sized round capsulotomy, treatment of keratometric astigmatism with arcuate incisions, construction of clear corneal incisions, and fragmentation and/or softening of the lens. However, FLACS may have limitations due to suction loss, incomplete capsulotomy or poor pupillary dilation. Patient selection and surgeon experience is critical. This review article will focus on the various platforms available for FLACS, the steps in cataract surgery it can perform, and overall advantages and limitations of the technology.

Robust Hierarchical Porous PTFE Film Fabricated via Femtosecond Laser for Self-Cleaning Passive Cooling

Passive cooling materials that spontaneously cool an object are promising choices for mitigating the global energy crisis. However, these cooling effects are usually weakened or lost when dust contaminates the surface structure, greatly restricting their applications. In this work, a robust hierarchical porous polytetrafluoroethylene (PTFE) film with coral-like micro/nanostructures is generated by a facile and efficient femtosecond laser ablation technique. Owing to its unique micro/nanostructures, the as-prepared surface exhibits an outstanding self-cleaning function for various liquids with ultralow adhesion. This self-cleaning characteristic enhances the durability of its passive cooling effect. It is demonstrated that the titanium (Ti) sheet covered with laser-ablated PTFE film can realize a maximum temperature decrease of 4 and 10 °C compared to the Ti sheet covered with pristine PTFE film and uncovered, respectively. This study reveals that femtosecond laser micromachining is a facile and feasible avenue to produce robust self-cleaning passive cooling devices.

Analysis of factors associated with unintended initial dissection of the posterior plane during small incision lenticule extraction

Background

To investigate potential risk factors for unintended initial dissection of the posterior plane in the initial learning curve of small incision lenticule extraction (SMILE).

Methods

Data were derived from consecutive 263 eyes of 136 patients who underwent SMILE at the beginning of the surgeon's learning curve. Probabilities of unintended initial dissection of the posterior plane in left and right eyes were analyzed. Preoperative sphere, cylinder, spherical equivalent (SE), J0, J45, lenticular diameter, lenticular thickness, corneal thickness, and axial length were assessed between eyes in which posterior plane dissection was unintended and those in which it was not.

Results

Unintended initial dissection of the posterior plane occurred in 29 eyes, corresponding to an incidence rate of 11.03%. The probability of difficulty in plane dissection in the left eye was significantly higher than that in the right eye (P=0.003). Significant differences were found in sphere (T =2.8, P=0.006), SE (T =2.37, P=0.019), J0 (T =2.05, P=0.043) and axial length (T =-2.79, P=0.006) between eyes with and without unintended initial dissection of the posterior plane.

Conclusions

In the present study, difficulty in plane dissection during SMILE was encountered significantly more often in left eyes for a right-hand doctor, and in eyes with low SE or high J0 values. Special attention should be paid to prevent unintended initial dissection of the posterior plane in such situations.

Significantly enhanced electrocatalytic activity of copper for hydrogen evolution reaction through femtosecond laser blackening

In this work, we report on the creation of a black copper via femtosecond laser processing and its application as a novel electrode material. We show that the black copper exhibits an excellent electrocatalytic activity for hydrogen evolution reaction (HER) in alkaline solution. The laser processing results in a unique microstructure: microparticles covered by finer nanoparticles on top. Electrochemical measurements demonstrate that the kinetics of the HER is significantly accelerated after bare copper is treated and turned black. At -0.325 V (v.s. RHE) in 1 M KOH aqueous solution, the calculated area-specific charge transfer resistance of the electrode decreases sharply from 159 Ω cm2 for the untreated copper to 1 Ω cm2 for the black copper. The electrochemical surface area of the black copper is measured to be only 2.4 times that of the untreated copper and therefore, the significantly enhanced electrocatalytic activity of the black copper for HER is mostly a result of its unique microstructure that favors the formation and enrichment of protons on the surface of copper. This work provides a new strategy for developing high-efficient electrodes for hydrogen generation.

Cosmetic outcome of femtosecond laser-assisted pterygium surgery

Background

To examine the cosmetic outcome of femtosecond laser-assisted pterygium surgery (FLAPS) with conjunctival autograft (CAG) and its potential predictive factors.

Methods

This was a prospective interventional case series (NCT02866968). We included 29 patients (29 eyes) with primary pterygium who underwent FLAPS. Cosmetic outcome was graded by two graders (an ophthalmology resident and an experienced ophthalmologist) using Hirst classification system (1–4 = excellent–poor). Weighted Cohen’s kappa analysis was performed to examine the intra- and inter-rater reliability. The relationship between cosmetic outcome and various factors were determined by Spearman’s correlation coefficients (r).

Results

The preoperative severity of pterygium (Tan grading system) was mild/atrophic (7%), moderate/intermediate (62%), and severe/fleshy (31%). An ultrathin CAG (mean thickness of 74.5 ± 9.8 μm) was fashioned intraoperatively. An excellent cosmetic outcome of FLAPS (median ± IQR) was observed at 3 months (1.0 ± 1.0) and remained similar at 6 months (1.0 ± 0.0) and 12 months (1.0 ± 0.0) postoperatively. At final follow-up, 27 (93%) patients achieved good-to-excellent cosmetic outcome, with 1 (3%) patient having a poor outcome due to incomplete pterygium removal. Weighted kappa analysis of Hirst grading system showed excellent intra-rater (κ = 0.86–0.95) and inter-rater reliability (κ = 0.84–0.88). There was a weak and borderline significant correlation between good cosmetic outcome and reduced postoperative CAG thickness (r = 0.38, P = 0.06) but not with age, gender, preoperative pterygium severity, or intraoperative CAG thickness.

Conclusions

FLAPS can result in an excellent cosmetic outcome, which may be attributed to the beneficial effect of an ultrathin CAG.

Trial registration

ClinicalTrials.gov, NCT02866968. Registered in July 2016,

Supplementary Information

The online version contains supplementary material available at 10.1186/s40662-021-00230-w.

Femtosecond ionization mass spectrometry for chromatographic detection

Mass spectrometry is now in widespread use for the detection of the analytes separated by chromatography. Electron ionization is the most frequently used method in mass spectrometry. However, this ionization technique sometimes suffers from extensive fragmentation of analytes, which makes identification difficult. A photoionization technique has been developed for suppressing this fragmentation and for subsequently observing a molecular ion. A variety of lasers have been employed for the sensitive and selective ionization of organic compounds. A femtosecond laser has a high peak power and is preferential for efficient ionization as well as for suppressing fragmentation, providing valuable information concerning molecular weight and chemical structure as well. In this review, we report on applications of femtosecond ionization mass spectrometry combined with gas chromatography.

Femtosecond laser-assisted implantation of corneal stroma lenticule for keratoconus

Purpose

To review recent progress, challenges, and future perspectives of stromal keratophakia for the treatment of advanced keratoconus.

Methods

We systematically reviewed the literature in the PubMed database, last update June 30, 2020. No language restriction was applied. The authors checked the reference lists of the retrieved articles to identify any additional study of interest.

Results

Several techniques have been proposed for the treatment of keratoconus in order to avoid or delay keratoplasty. This was primarily due to the lack of accessibility to donor corneas in many countries. The ease and predictability of the more advanced femtosecond lasers used to correct ametropias by stromal lenticule extraction lead to hypothesize that generated refractive lenticules could be implanted into corneal stromal layers to restore volume and alter the refractive properties of the cornea in patients with corneal ectasias. At the same time, new techniques for preservation, customization, and cellular therapy of the corneal stromal have been developed, directing to the valorization of otherwise discarded byproducts such as donor corneas unsuitable for either lamellar of penetrating keratoplasty.

Conclusions

Femtosecond laser-assisted stromal keratophakia could be a suitable therapeutic option for the treatment of corneal ectasias, especially in patients with advanced keratoconus, providing biomechanical support recovering the pachimetry to nearly normal value at the same time. The accuracy and predictability of the refractive outcome are yet a critical issue and the patient eligible for the procedure still has to be characterized.

Femtosecond laser-assisted stromal keratophakia for keratoconus: A systemic review and meta-analysis

PURPOSE

Femtosecond lasers have revived the possibility of stromal keratophakia or tissue additive keratoplasty, a technique originally introduced by Prof. Jose Ignacio Barraquer in the 1960s. The surgical technique offers a unique solution to treat keratoconus. In the current study, we reviewed and performed a meta-analysis of the clinical outcomes of the femtosecond laser-assisted stromal keratophakia in the treatment of keratoconus.

METHODS

This is a systematic review and meta-analysis of the estimated outcome difference between pre- and post-lenticule implantations.

RESULTS

A total of related 10 studies were found in the literature. No studies reported adverse events, such as persistent haze or graft rejection, at last patients' visits. We further narrowed down the article selection in accordance to our inclusion criteria to report the composite outcomes (9 studies) and meta-analysis (4 studies). In the composite analysis, we demonstrated that lenticule implantation in keratoconus and post-LASIK ectasia patients appeared to expand the stromal volume of the thin corneas, flattened the cones, and significantly improved uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and spherical equivalent (SE). The meta-analysis showed that the random estimated UCVA, BCVA, SE and mean keratometry (K_m) differences following the lenticule implantation was -0.214 (95% CI: -0.367 to 0.060; p = 0.006), -0.169 (-0.246 to 0.091; p < 0.001), -2.294 D (-3.750 to -0.839 D; p = 0.002), and 2.909 D (0.805 to 5.012 D; p = 0.007), respectively.

CONCLUSIONS

Femtosecond laser-assisted stromal keratophakia is a feasible technique to correct the refractive aberrations, expand corneal volume and regularize corneal curvature in patients with keratoconus. However, there is a need to standardize the technique (e.g., whether to crosslink or not or to use convex or concave lenticules) and to formulate a mathematical model that accounts for the long-term epithelial thickness changes and stromal remodeling to determine the shape or profile of the lenticules, in order to improve the efficacy of the keratophakia further.

Transepithelial or intrastromal femtosecond laser arcuate keratotomy to manage corneal astigmatism at the time of cataract surgery

PURPOSE

The aim of this study was to compare the results of intrastromal arcuate incisions (AIs) and transepithelial AIs to treat corneal astigmatism during femtosecond laser-assisted cataract surgery (FLACS).

METHODS

This retrospective study included 20 patients with corneal astigmatism between 0.70 and 2.00 diopters (D) who underwent FLACS with concurrent intrastromal AIs in one eye and transepithelial AIs in the fellow eye. The main outcomes measures at 2-3 months of follow-up were the difference between pre-operative and postoperative keratometric corneal cylinder (Kcyl), the correction index (CI) and the percentage of overcorrection.

RESULTS

The mean difference between preoperative and postoperative Kcyl revealed a mean value of 0.36 ± 0.37 D in the transepithelial group and 0.53 ± 0.42 D in the intrastromal group (p < 0.001). The mean CI was 0.83 ± 0.71 in the transepithelial group and 0.68 ± 0.29 in intrastromal group (p = 0.17). Five eyes (25 %) had an astigmatism overcorrection in the transepithelial group and 1 eye (5%) in the intrastromal group.

CONCLUSIONS

Both intrastromal and transepithelial AIs showed potential for mild to moderate astigmatism correction and appeared to be a safe procedure. Despite transepithelial AIs presented a higher CI, the intrastromal AIs results were more predictable.

Laser-assisted corneal transplantation surgery

Corneal transplant surgeries have a broad range of indications with outcomes largely dependent on surgeon experience. Traditional manual techniques have certain limitations pertaining to the preparation of donor tissue and the recipient bed that might affect the predictability of visual outcomes. Use of lasers for keratoplasty procedures not only improves the repeatability and consistency of the technique, but also enables the surgeon to control the thickness and shape of the transplant tissue tailored to the specific condition. Despite the advantages, cost-effectiveness and technical know-how remain the major challenges. We discuss the various techniques of laser-assisted keratoplasties with respect to their methods, precision, and efficacy in various corneal indications.

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.

Comparison of the effects of femtosecond laser energy on corneal endothelium at two different dissection levels in femtosecond laser-assisted deep anterior lamellar keratoplasty for keratoconus

PURPOSE

The objective of this study is to compare the endothelial safety of femtosecond laser (FSL) energy at two different dissection depths in FSL-assisted deep anterior lamellar keratoplasty (FSDALK) for keratoconus.

METHODS

This prospective double-armed interventional study included 25 eyes from 21 patients with advanced keratoconus who underwent FSDALK (big bubble technique) at a trephination depth of 110 µm in group I (11 eyes) and 80 µm in group II (14 eyes)-all of which were anterior to the Descemet's membrane (DM). Visual acuity measurement, anterior and posterior segment examination, corneal tomography, and specular microscopy were performed preoperatively and at 3, 6, and 12 months, postoperatively. Endothelial cell density, coefficient of variation, percentage of cell hexagonality, and pachymetry were used to evaluate endothelial safety.

RESULTS

No statistically significant difference in any of the endothelial safety parameters was found between the two groups. The mean 12-month postoperative endothelial cell loss rate was 17.46% and 12.91% in group I and II, respectively (P = 0.345). Most of the endothelial cell loss occurred during the first 3 months after surgery. Group II showed statistically greater improvement in the mean keratometry values at all follow-up visits.

CONCLUSION

The endothelial safety profiles of lamellar FSL cuts at 110 µm and 80 µm anterior to the DM are comparable. Cuts as deep as 80 µm anterior to the DM can be safely applied without causing significant injury to the endothelium. Further studies are needed to compare the endothelial safety profiles of different FSL platforms available in the market. Trial registration PACTR201901615323963. Registered 24 November 2018-retrospectively registered.