Comparative study of functional optical zone:small incision lenticule extraction versus femtosecond laser assisted excimer laser keratomileusis

AIM:To investigate the size of functional optical zone(FOZ)after small incision lenticule extraction(SMILE)versus femtosecond laser assisted excimer laser keratomileusis(FS-LASIK)for myopia correction and potential associated factors for FOZ.METHODS:A total of 133 patients who received corneal refractive surgery in our hospital between November 2018 and July 2021 were retrospectively enrolled.There were 63 patients(123 eyes)in SMILE group and 70patients(139 eyes)in FS-LASIK group.The size of FOZ was measured using Pentacam 3-dementional anterior segment analyzer before and 3mo after surgery,so as to analyze postoperative achieved functional optical zone(AFOZ)and its contributing parameters.RESULTS:When planned functional optical zone(PFOZ)was 6.5 mm for both groups,AFOZ was 1.45±0.27 and 1.67±0.25 mm smaller than preoperative FOZ in SMILE group and FS-LASIK group 3mo after surgery.AFOZ in SMILE group was significantly larger than that in FS-LASIK group(P<0.001).Variation of FOZ was negatively correlated with preoperative spherical equivalent(SE)and positively correlated with variation of mean keratometry value(△Km),variation of spherical aberration(△SA),and variation of Q-value(△Q,all P<0.001)in both groups.Multiple variable linear regression equations were△FOZ=1.354-0.1×pre-SE+0.336×△Q+1.462×△SA in SMILE group and△FOZ=1.512+0.137×△Q+0.468×△SA in FS-LASIK group.CONCLUSION:AFOZ is significantly smaller than preoperative FOZ in both SMILE and FS-LASIK groups.With the same PFOZ,larger AFOZ is achieved in SMILE group than in FS-LASIK group.

Understanding the effects of excimer laser treatment on corrosion behavior of biodegradable Mg-1Ca alloy in simulated body fluid

In this study,a KrF excimer laser was used to modify the biodegradable Mg-1Ca alloy and the time-evolution degradation behavior of the alloy before and after laser treatment was investigated in simulated body fluid(SBF)solution using immersion tests and electrochemical impedance spectroscopy(EIS).A 5μm melted layer with a homogeneous microstructure and an MgO film on the surface were achieved by laser radiation.Corrosion observations(hydrogen evolution,morphology and corrosion products)and EIS results revealed an improvement of corrosion resistance after laser treatment for 48 h.It was found a two-layer structure developed after 2 h immersion on both the untreated and laser-treated alloys,but the sequence of forming the two layers was opposite and greatly influenced by the laser-treated layer.The time-evolution corrosion processes on the untreated and laser-treated alloys were discussed,providing a better understanding of corrosion behavior of biodegradable Mg alloys modified by excimer laser.

Phosphorus diffusion and activation in fluorine co-implanted germanium after excimer laser annealing

The diffusion and the activation of phosphorus in phosphorus and fluorine co-implanted Ge after being annealed by excimer laser are investigated.The results prove that the fluorine element plays an important role in suppressing phosphorus diffusion and enhancing phosphorus activation.Moreover,the rapid thermal annealing process is utilized to evaluate and verify the role of fluorine element.During the initial annealing of co-implanted Ge,it is easier to form high bonding energy FnVm clusters which can stabilize the excess vacancies,resulting in the reduced vacancy-assisted diffusion of phosphorus.The maximum activation concentration of about 4.4 ×10^(20) cm^(-3) with a reduced diffusion length and dopant loss is achieved in co-implanted Ge that is annealed at a tailored laser fluence of 175 mJ/cm^(2).The combination of excimer laser annealing and co-implantation technique provides a reference and guideline for high level n-type doping in Ge and is beneficial to its applications in the scaled Ge MOSFET technology and other devices.

Effect of open ultraviolet germicidal irradiation lamps on functionality of excimer lasers used in cornea surgery

We report on the impact of direct ultraviolet germicidal irradiation(UVGI) on reflective optics, used in the excimer laser system Allegretto Eye-Q. The aim of our work was to confirm our hypothesis based on long-rate observations of obtained anomalies in post-operative results that are attributed to degradation of reflective optics upon ultraviolet radiation. The presence of direct UVGI coupled with humidity in the operating environment caused merging anomalies and unwanted post-operative correction values. Ultraviolet-A radiation caused a similar effect on the reflective cover of the mirrors.

Excimer laser coronary atherectomy for a severe calcified coronary ostium lesion:A case report

BACKGROUND Percutaneous coronary intervention can be challenging for ostial coronary artery lesions due to calcium burden and elastic fiber content.Excimer laser coronary atherectomy(ELCA)is a less common treatment for severe calcified coronary ostium lesions.CASE SUMMARY An 81-year-old male presented to the Cardiology Department of Qingdao Municipal Hospital with a 1-year history of chest pain.Coronary angiography showed severe calcific stenosis(approximately 90%)in the right coronary artery ostium.The right coronary artery ostium was unable to be advanced using a 2.5 mm×12.0 mm balloon(NC Sprinter,Medtronic,United States)or dilated using a 2.0 mm×12.0 mm balloon(Sprinter,Medtronic,United States).The patient underwent successful ELCA and balloon dilation of the calcified coronary ostium lesion.CONCLUSION ELCA appears to be a safe and effective treatment for the management of severe calcified coronary ostium lesions.

Surface Modification of Ceramic Materials Using Excimer Laser

Changes of surface morphology following XeCl excimer laser irradiation were investigated for three engineering ceramic materials （Al2O3, Al2O3-SiC nanocomposite and Si3N4）. Al2O3 and Al2O3-SiC nanocomposite samples exhibit a smooth rapid melt layer on the surface, and the formation of the metastable γ-Al2O3 was observed. A silicon-rich layer on the surface was formed after laser irradiation of Si3N4. The toughness K1c of the materials was measured by the indentation fracture method. After laser irradiation, the toughness of Al2O3, Al2O3-SiC nanocomposite and Si3N4 was improved to various degrees:Al2O3-SiC nanocomposite, 60% （max）, Al2O3, 40% （max）, Si3N4, 12% （max）.

A HISTOPATHOLOGIC IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL STUDY OF RABBIT CORNEA AFTER EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY

Objective To evaluate the corneal healing of non-epuality diopter response histopathologically, immunohistochemically and ultrastructurally after excimer laser photorefractive keratectomy(PRK) with SVS APEX PLUS(Summit Technology Inc. USA) excimer laser, and the effects of corticosteroid on the healing. Methods PRK on 6 white rabbits(12 eyes) was performed on right eye or the rabbit for an attampted correction or -4.00 diopter and on left eye for an attempted correction of -8.00 diopter. The rabbits were divided into 2 groups randomly and each group included 6 eyes: Group FLM (3 rabbits, 6 eyes) and group CM (3 rabbits, 6 eyes). Fluoromethalone was given to group FLM,and chloromycetin to group CM. On 10d, 30d and 100d,the eyes of one rabbit in each group were enucleated randomly. Half of each cornea was prepared for electron microscope observation (SEM and TEM) and the rest embedded in OCT compound for immunohistochemical study to examine Ⅲ-C and FN. Results All eyes were reepithelialized within 3d after PRK. Subepithelial corneal haze was observed on 15d,which was dominant on 30 or 60d. On 100d postoperatively,corneal hazes of 11 eyes were grades 0 or 0.5,only 1 eye(the left eye or group CM) was denser haze (grade 1). On 3d postoperatively, one or two layers of corneal epithelial cell covered the ablation zone. On 30d after PRK,the epithelial cells showed hyperplastic changes. The cells were larger and increased from normal 5 or 6 layers to 7 or 8 layers of cells on l00d after PRK,epithelium was clear with more bright epithelium. Mi- croplicae and microvilli were less than before. The expression of Ⅲ-C and FN in group CM was significantly more evi- dent than that in group FLM. Conclusion The study show that despite recovery of a continuous and smooth epithelial layer and nearly normal corneal tissues on 100d after PRK,abnormalities of both epithelium and superficial stroma can be detected in the area of ablation. The ablation depth of stroma can influence the appearance of corneal haze af- ter PRK. The microplicae and microvilli of rabbit cornea epithelium become less after PRK,which can be one of cause leading to ocular dry sensation in some patients.

Corrosion behaviors of the copper alloy electrodes in Ar F excimer laser operation process

The corrosion behaviors of the Ar F excimer laser copper alloy electrodes were studied. The morphology, composition and impurities were characterized by optical microscope, scanning electron microscopy, electron microprobe and glow discharge mass spectrometer methods. The anode produces the reef, the corrosion pits, the hole layer and the 1–10 μm level flake impurity. The cathode produces the particles, the sputtering pits, the element reduce layer and the 1 μm level particle impurity. Besides the Cu element, other elements in the alloy participate in the corrosion: Al element in the reef is over 1.5 times of the anode, Zn element in the particles is 1.3 times of the cathode, many trace elements congregate on the copper surface several and even hundreds of times. These elements are responsible to a great degree for the impurities and the rapid energy decline of the long-time idled laser.

Excimer laser 6^(th)generation:state of the art and refractive surgical outcomes

After nearly three decades of innovation in excimer laser,today we are presented with a state of the art generation targeting minimally invasive refractive surgery with high speed laser,faster trackers,pupil monitoring systems and better customization profiles.These systems are capable of delivering better treatments with less induced postoperative high order aberrations.The results reported by many authors had confirmed the superiority in efficiency and safety profiles of this generation compared to previous generations.Still,current technology is facing major challenges in the correction of high hyperopic errors and in presbyopic treatments,with upgrades in ablation centration and thermal control needed,which will ensure better biomechanical results,as a step closer to perfection in refractive surgery.

The Computer Analysis of the Excimer Laser Beam Intensity Uniformization by Rotational Lens Array

The excimer laser has important applications in many fields. Because of its non-uniform intensity distribution there are some limits in applications. This paper introduces rotational lens array to improve intensity distributions. The intensity variation is reduced to 1 percent by computer simulation.

Current review of Excimer laser Trabeculostomy

Background:Excimer laser trabeculostomy(ELT)is a microinvasive glaucoma surgery(MIGS)that creates multiple laser channels through the trabecular meshwork using a cold laser system,which minimizes tissue fibrosis and aids in bypassing the main area of resistance to aqueous outflow.The purpose of this review is to evaluate the current body of evidence surrounding ELT in terms of efficacy and review the safety profile of the procedure.Main text:Studies screened had to show clear inclusion and exclusion criteria as well as well-defined outcome measures.PubMed,MEDLINE,EMBASE and the Cochrane Controlled Trial Database were searched.Preferred Reporting Items of Systematic Reviews(PRISMA)guidelines were used to assess for study quality and for any bias.Sixty-four articles were initially identified with 18 meeting preliminary screening criteria.Ultimately,8 studies met inclusion criteria and 2 additional non-referenced publications were also included:1 randomized control trial,4 prospective case series and 5 retrospective studies.Overall studies showed moderate intraocular pressure(IOP)lowering of between 20%and 40%from baseline without medication washout and mostly a decrease in glaucoma medications with few complications.Conclusion:Current literature shows a significant IOP-lowering effect of ELT with a favorable safety-profile in standalone cases or combined with cataract surgery.Limitations to these studies are the lack of controls and washout IOP.Overall,ELT is an attractive MIGS option that does not require any residual device remaining in the angle.

Improved performance of Ge n^+/p diode by combining laser annealing and epitaxial Si passivation

A method to improve Ge n^+/p junction diode performance by excimer laser annealing(ELA) and epitaxial Si passivation under a low ion implantation dose is demonstrated. The epitaxial Si passivation layer can unpin the Fermi level of the contact of Al/n-Ge to some extent and reduce the contact resistance. In addition, the fabricated Ge n^+/p junction diode by ELA plus epitaxial Si passivation exhibits a decreased reverse current density and an increased forward current density,resulting in a rectification ratio of about 6.5×10~6 beyond two orders magnitude larger than that by ELA alone. The reduced specific contact resistivity of metal on n-doped germanium and well-behaved germanium n^+/p diode are beneficial for the performance improvement of Ge n-MOSFETs and other opto-electronic devices.

ONE YEAR RESULTS OF LASER IN SITU KERATOMILEUSIS FOR CORRECTION OF HYPEROPIA

Objective: To evaluate the effectiveness, predictability and city of laser in situ keratomileusis (LASIK) for correction of hyperopia. Methods 54 eyes of 35 patients with hyperopia ranging from+1.00 to + 6. 00 diopter(D) received a one-pass, multizone scanning excimer laser ablations using the Chiron Technolas Keracor 11 7C excimer laser and System ALK automated corneal shaper H-230.Data on uncorrected and hot corrected visual acuity, predictability, stability of refraction, and complications were analyzed. The average follow-up was 12 months. Results At 12 months, the average residual refraction was(+ 0. 29 ±0. 78)D. 45 eyes (83.3% ) were in the range of ±1. OD and 33 eyes(61. 1% ) were within the range of ± 0. 5D. 50 eyes (92. 6% ) had uncorrected visual acuity of 20/40 or better and 34 eyes (63. 0% ) had 20/20 or better. 1 eyes (1. 9% ) lost 2 line of the best-corrected visual acuity and 2 eyes (3. 7% ) gained 2 lines or more. 2 eyes (3. 7%) had complaint of halos and 1 eyes (1. 9% ) had glare at 12 months. Conclusion LASIK can he used to treat hyperopia from + 1. 0D to + 6. 0D with good predictability and city. Primary and second hyperopia should he treated with different nomogram. some modification of the surgical algorithms and laser nomogram will help to improve predictability and stability of outcome.

A recognition survey of granular corneal dystrophy type 2 genetic detection in China

AIM:To evaluate the feasibility of promoting genetic detection for granular corneal dystrophy type 2(GCD2)by a questionnaire conducted among citizens in five cities in China.METHODS:The data were collected by questionnaire,and analyzed by Chi-square test and one-tailed t test in IBM SPSS statistics.RESULTS:Based on the survey data on the awareness of GCD2 genetic detection in this study and the positive predictive analysis report of the citizens in five cities in China,the vast majority(84.2%)of respondents had never heard of it and did not know that GCD2 patients have been prohibited from performing excimer surgery that can deteriorate GCD2 patients’condition even leading to blindness.Though 3.4%of patients understood GCD2 very much,they have no idea that GCD2 could not be 100%accuracy diagnosed by the conventional inspection methods.CONCLUSION:It is feasible and necessary to use GCD2 genetic detection as an excimer preoperative examination project.In order to promote the development of detection project,a few improvements should be carried out in terms of the promoting efforts,costs,and research progress.

Navigation technology/eye-tracking in ophthalmology:principles,applications and benefits-a narrative review

Navigation technology in ophthalmology,colloquially called“eye-tracking”,has been applied to various areas of eye care.This approach encompasses motion-based navigation technology in both ophthalmic imaging and treatment.For instance,modern imaging instruments use a real-time eye-tracking system,which helps to reduce motion artefacts and increase signal-to-noise ratio in imaging acquisition such as optical coherence tomography(OCT),microperimetry,and fluorescence and color imaging.Navigation in ophthalmic surgery has been firstly applied in laser vision corrective surgery and spread to involve navigated retinal photocoagulation,and positioning guidance of intraocular lenses(IOL)during cataract surgery.It has emerged as one of the most reliable representatives of technology as it continues to transform surgical interventions into safer,more standardized,and more predictable procedures with better outcomes.Eye-tracking is essential in refractive surgery with excimer laser ablation.Using this technology for cataract surgery in patients with high preoperative astigmatism has produced better therapeutic outcomes.Navigated retinal laser has proven to be safer and more accurate compared to the use of conventional slit lamp lasers.Eye-tracking has also been used in imaging diagnostics,where it is essential for proper alignment of captured zones of interest and accurate follow-up imaging.This technology is not routinely discussed in the ophthalmic literature even though it has been truly impactful in our clinical practice and represents a small revolution in ophthalmology.

Modeling of three-dimensional exciplex pumped fluid Cs vapor laser with transverse and longitudinal gas flow

Considering the thermodynamical fluid mechanics in the gain medium and laser kinetic processes,a three-dimensional theoretical model of an exciplex-pumped Cs vapor laser with longitudinal and transverse gas flow is established.The slope efficiency of laser calculated by the model shows good agreement with the experimental data.The comprehensive three-dimensional distribution of temperature and particle density of Cs is depicted.The influence of pump intensity,wall temperature,and fluid velocity on the laser output performance is also simulated and analyzed in detail,suggesting that a higher wall temperature can guarantee a higher output laser power while causing a more significant heat accumulation in the cell.Compared with longitudinal gas flow,the transverse flow can improve the output laser power by effectively removing the generated heat accumulation and alleviating the temperature gradient in the cell.

The path to electrical energy using laser fusion

Direct-drive laser fusion has one potential advantage over all other approaches to fusion energy.The hot plasma can be kept near or below the various plasma instability thresholds,if one uses purely spherical targets,with a short wavelength,large bandwidth and optically smoothed excimer laser.Instead of trying to manage laser–plasma instabilities,one avoids them.There is a path to complete the evaluation and development of this energy option,with moderate costs and a moderate time scale.Glass lasers,with their longer wavelength and narrower bandwidth,are no longer useful to evaluate fusion targets.

Intraocular lens power calculation in eyes with previous corneal refractive surgery

Background:This review aims to explain the reasons why intraocular lens(IOL)power calculation is challenging in eyes with previous corneal refractive surgery and what solutions are currently available to obtain more accurate results.Review:After IOL implantation in eyes with previous LASIK,PRK or RK,a refractive surprise can occur because (i)the altered ratio between the anterior and posterior corneal surface makes the keratometric index invalid;(ii)the corneal curvature radius is measured out of the optical zone;and (iii)the effective lens position is erroneously predicted if such a prediction is based on the post-refractive surgery corneal curvature.Different methods are currently available to obtain the best refractive outcomes in these eyes,even when the perioperative data(i.e.preoperative corneal power and surgically induced refractive change)are not known.In this review,we describe the most accurate methods based on our clinical studies.Conclusions:IOL power calculation after myopic corneal refractive surgery can be calculated with a variety of methods that lead to relatively accurate outcomes,with 60 to 70%of eyes showing a prediction error within 0.50 diopters.

Surgical options for correction of refractive error following cataract surgery

Refractive errors are frequently found following cataract surgery and refractive lens exchange.Accurate biometric analysis,selection and calculation of the adequate intraocular lens(IOL)and modern techniques for cataract surgery all contribute to achieving the goal of cataract surgery as a refractive procedure with no refractive error.However,in spite of all these advances,residual refractive error still occasionally occurs after cataract surgery and laser in situ keratomileusis(LASIK)can be considered the most accurate method for its correction.Lens-based procedures,such as IOL exchange or piggyback lens implantation are also possible alternatives especially in cases with extreme ametropia,corneal abnormalities,or in situations where excimer laser is unavailable.In our review,we have found that piggyback IOL is safer and more accurate than IOL exchange.Our aim is to provide a review of the recent literature regarding target refraction and residual refractive error in cataract surgery.

Central corneal regularization (CCR): an alternative approach in keratoconus treatment

Background:To evaluate the safety and efficacy of an approach that combines corneal customized transepithelial therapeutic ablation to treat irregular corneal optics and accelerated corneal collagen cross-linking(CXL)to strengthen the corneal tissue and stop the progression of keratoconus.The transepithelial therapeutic ablation applied a novel concept named central corneal regularization(CCR)which could correct the corneal morphological irregularities and the eye’s spherocylindrical refractive error with minimal stromal tissue removal.Methods:Retrospective study.Eyes that underwent CCR combined with CXL were evaluated preoperatively and up to 12 months postoperatively for visual acuity,subjective refraction,corneal haze,pachymetry and maximum keratometry(Kmax).Results:Twenty four eyes of 24 patients with a mean age of 28.92±9.88 years were treated.The mean spherical equivalent(SE)refractive error changed from−0.74±1.17 D preoperatively to−1.05±1.52 D at 12 months postoperatively.The mean uncorrected distance visual acuity(UDVA)and corrected distance visual acuity(CDVA)improved.No eye lost lines of CDVA,21 had a mean improvement of 3.21 lines.The mean cylinder error and Kmax value dropped from−3.06±1.83 D and 51.38±3.29 D to−1.04±0.80 D and 48.70±2.58 D,respectively.The mean haze score at 3,6 and 12 months was 0.56,0.19 and 0.06,respectively.Conclusions:CCR combined with CXL offers promising results as a safe and effective treatment in keratoconic patients.