scholarly journals New Possibilities of Refractive Modeling of the Cornea by the Radiation of an Argon-fluorine Excimer Laser

2021 ◽  
pp. 7-18
Author(s):  
I. M. Kornilovskiy
Keyword(s):  
Excimer Laser ◽  
Clinical Studies ◽  
Ablation Threshold ◽  
Objective Assessment ◽  
Corneal Stroma ◽  
Strength Properties ◽  
Secondary Radiation ◽  
Total Radiation Dose ◽  
Corneal Nerves ◽  
Negative Effect

Purpose: To consider new possibilities of refractive modeling of the cornea by the radiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin. Materials and Methods: Experimental (20 pork, 90 rabbit eyes) and clinical studies on photorefractive and phototherapeutic operations with saturation of the corneal stroma with riboflavin (610 operations) were analyzed. To activate riboflavin, secondary radiation induced by exposure to ablative and subablative energy densities was used. A quick transition to energy densities below the ablation threshold without additional calibrations was carried out using a “Microscan Visum-500” excimer laser (Optosystems, Russia). An objective assessment of the refractive keratomodelling effect and visual results was carried out according to the data of complex optometric studies. Results: Experimental and clinical studies have shown the advantages of refractive keratomodeling by theradiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin. Isotonic 0.25% riboflavin solution did not affect the accuracy of refractive ablation and blocked the negative effect of induced secondary radiation on keratocytes and corneal nerves. This reduced the aseptic inflammatory response and the risk of developing an irreversible form of fibroplasia. Ablation with riboflavin initiated a damped crosslinking effect, which increased the photoprotective and strength properties of the thinned cornea. A refractive keratomodelling effect was found when energy densities were applied below the stromal ablation threshold. The magnitude of this refractive effect depended on the total radiation dose and the topography of the affected area. This approach made it possible to implement laser-induced refractive keratomodeling without ablation of the corneal stroma. Conclusion: Refractive modeling of the cornea by the radiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin opens up new possibilities in laser correction of ametropia.

Corneal crosslinking by an argon-fluorine excimer laser

2021 ◽  
pp. 35-38
Author(s):  
I.M. Kornilovskiy ◽  
Keyword(s):  
Excimer Laser ◽  
Ablation Threshold ◽  
Objective Assessment ◽  
Corneal Stroma ◽  
Radiation Energy ◽  
Secondary Radiation ◽  
Cross Linking ◽  
Negative Effects ◽  
Corneal Crosslinking ◽  
Clinical Observations

Purpose. To substantiate the expediency of using ablative and subablative energy densities of an argon-fluorine excimer laser for corneal crosslinking. Material and methods. In the period from 1 month to 6 years, the results of more than 500 photorefractive and phototherapeutic operations with saturation of the cornea with riboflavin and the effect of crosslinking were analyzed. To activate riboflavin, secondary radiation was used, induced by the use of ablative and subablative energy densities of an argon-fluorine excimer laser. For an objective assessment of the effect of excimer laser crosslinking, we used the techniques of computed keratotopography, aberrometry, optical coherence tomography, and densitometry. Results. Clinical observations have shown that in most cases of photorefractive surgery of the cornea for the prevention of keratoectasias, it is sufficient to carry out ablation after saturation of the corneal stroma with 0.25% isotonic riboflavin solution for 3-10 minutes, depending on the degree of ametropia and the volume of tissue removed. This provided photoprotective protection of deeper stromal structures from the negative effects of ablation-induced secondary radiation. At the same time, upon completion of ablation, secondary radiation initiated the effect of crosslinking in the adjacent layers, which did not violate the elastic properties of the cornea. In a number of cases, the cross-linking effect was enhanced by additional exposure to energy densities below the ablation threshold and the formation of a Bowman-like membrane structure on the ablation surface. For keratoconus and corneal pathology, without and in combination with keratoectasia, the technology of therapeutic cross-linking was used. This technology provided for the saturation of the stroma with 0.1% or 0.25% isotonic riboflavin solution and its activation by subablative radiation energy densities of an argon-fluorine excimer laser. During therapeutic crosslinking, according to OCT and densitometry, all the classic signs of traditional corneal crosslinking were revealed. Conclusion. The radiation of an argon-fluorine excimer laser with the use of ablative pulse energy densities can be recommended for prophylactic crosslinking in all cases of corneal thinning during photorefractive surgeries, while the use of energy densities below the ablation threshold allows for therapeutic crosslinking in keratoconus and corneal ectasias of various etiology. Key words: excimer laser crosslinking, cornea, keratoconus, photorefractive ablation, riboflavin.

scholarly journals Features of inflammatory and regenerative reaction to excimer laser refractive keratectomy with photoprotection

2017 ◽  
Vol 98 (1) ◽  
pp. 53-57
Author(s):  
I M Kornilovskiy ◽  
E M Kasimov ◽  
A I Sultanova
Keyword(s):  
Excimer Laser ◽  
Corneal Stroma ◽  
Corneal Tissue ◽  
Aseptic Inflammation ◽  
Excimer Laser Ablation ◽  
Regenerative Response ◽  
Negative Effect ◽  
Inflammatory Drugs ◽  
Myopic Astigmatism ◽  
Observation Period

Aim. To study the features of inflammatory and regenerative reaction to excimer laser refractive keratectomy with photoprotection.Methods. Clinical cases of 560 excimer laser refractive keratectomies with photoprotection in 280 patients with myopia and myopic astigmatism of different severity. The observation period varied from 1 month to 2.5 years.Results. The study showed that intensity of aseptic inflammation and the type of regenerative response are influenced by the amount of evaporated corneal tissue, which correlates with the severity of myopia. Moreover, in case of equal severity of myopia and amount of evaporated tissue inflammatory and regenerative response was less prominent if excimer laser ablation was performed under the superficial corneal flap. In this case epithelial stromal corneal flap allowed reducing the negative effect of ultraviolet exposure and interaction between proinflammatory epithelial and stromal cytokines. At photorefractive ablation of corneal stroma saturated with 0.25% isotonic riboflavin solution aseptic inflammatory and regenerative response, intensity and duration of corneal syndrome decreased. Due to such technique of photorefractive keratectomy stromal layers saturated with riboflavin absorbed the secondary ultraviolet induced by ablation. Clinical observation demonstrated the need for additional photoprotection by glasses from external unltraviolet in all types of photorefractive surgeries on cornea up to full recovery of visual and optometric parameters. Use of photoprotection during excimer laser refractive ablation allowed achieving early stabilization of vision and refraction, decreasing the duration of postoperative steroidal and nonsteroidal anti-inflammatory drugs intake by one third in average.Conclusion. Local photoprotection with riboflavin during excimer laser refractive keratectomy and photoprotection by glasses from external ultraviolet reduce the risk of oxidative stress in the cornea, postoperative aseptic inflammatory and regenerative reactions, promote stabilization of visual, optic refractive parameters and improve their predictability.

scholarly journals Severe Corneal Morphological Alterations after Excimer Laser Surface Ablation for a High Astigmatism

2021 ◽  
pp. 492-496
Author(s):  
Anna M. Roszkowska ◽  
Giovanni W. Oliverio ◽  
Giuseppe A. Signorino ◽  
Mario Urso ◽  
Pasquale Aragona
Keyword(s):  
Excimer Laser ◽  
Corneal Stroma ◽  
Corneal Topography ◽  
Laser Surface ◽  
Slit Lamp ◽  
Slit Lamp Examination ◽  
Morphological Alterations ◽  
Surface Ablation ◽  
Confocal Images

We report long-term alterations of anterior corneal stroma after excimer laser surface ablation for a high astigmatism. The patient claimed progressive visual loss in his right eye (RE) during the last 3 years after bilateral laser-assisted subepithelial keratectomy (LASEK) surgery. His examination comprised visual acuity (UDVA and CDVA), slit-lamp examination, corneal topography and tomography, AS-OCT, and confocal microscopy. The UDVA was 0.1 in his RE and 1.0 in the left eye. The CDVA in the RE was 0.8. The slit-lamp examination showed a stromal lesion in the inferior paracentral corneal zone, with multiple vertical tissue bridges and severe thinning. Corneal topography and tomography showed central flattening with inferior steepening and severe alteration in elevation maps. AS-OCT showed void areas in the anterior stroma with thinning of the underlying tissue, and confocal images were not specific. In this case, progressive corneal steepening and thinning that manifest topographically as inferior ectasia occurred in correspondence to the singular stromal alterations after LASEK.

The Development and the Study of the Properties of Hydrosorption Material Based on a Blended Thermoplastic Vulcanisate

2017 ◽  
Vol 44 (8) ◽  
pp. 9-14
Author(s):  
M.F. Galikhanov ◽  
D.M. Akhmedzyanova ◽  
N.R. Nikitin
Keyword(s):  
Diffusion Processes ◽  
Testing Machine ◽  
Strength Properties ◽  
Water Soluble ◽  
Butadiene Rubber ◽  
Tensile Testing Machine ◽  
Water Soluble Polymer ◽  
Electret State ◽  
Swelling Rate ◽  
Negative Effect

Hydrosorption thermoplastic vulcanisates (TPVs) with a controllable swelling rate have been developed. They contain low-density polyethylene (LDPE), nitrile butadiene rubber (NBR), and sodium carboxymethyl cellulose (Na-CMC) – a water-soluble polymer (WSP). They were mixed on a laboratory mill in two stages and vulcanised at a temperature of 170°C. At the first stage, the NBR with a vulcanising system and carbon black were mixed with the WSP at 50°C, and at the second stage this composite was mixed with the polyethylene (PE) at 140°C. The hydrosorption, deformation and strength, and electret properties of the obtained TPVs were studied. The study of the sorption properties under conditions of limited and unlimited access of water showed that composites consisting of 25% polyethylene and 75% WSP swell in water by ∼28%, and here processes of migration of the WSP out of the composites are absent. The deformation and strength properties were determined on an Inspekt Mini TR-3 kN tensile testing machine. The level of deformation and strength characteristics of the obtained TPVs is not high, which is due to the low adhesion between the PE and the polar NBR, and also between the NBR and the WSP. However, for seals and gaskets, the achievable level of strength properties is quite adequate. An electret state of the TPVs was obtained in a negative corona discharge as they cooled down after heating to 90°C. Washers were manufactured from the developed TPVs, and they were tested for their sealing capacity. It was shown that the electret state inhibits the process of swelling of the TPVs in water, which is due to the negative effect of the electric field on the rate at which wetting, dissolution, and diffusion processes take place. However, during service, the electret state of articles manufactured from the developed TPVs rapidly relaxes, after which the swelling process occurs at a steady rate. This makes it possible to carry out assembly work involving the fitting or replacement of seals made of the hydrosorption TPVs.

Fabrication of High Density Silicon Nano-Dots by Excimer Laser Irradiation on Block Copolymer Masks

2007 ◽  
Author(s):  
Dae Up Ahn ◽  
Erol Sancaktar
Keyword(s):  
Laser Ablation ◽  
Block Copolymer ◽  
Laser Irradiation ◽  
Excimer Laser ◽  
Ablation Threshold ◽  
Laser Intensity ◽  
Selective Etching ◽  
Time Duration ◽  
Excimer Laser Ablation ◽  
Excimer Laser Irradiation

We report easy and fast fabrication methods to prepare densely packed polystyrene (PS) and silicon nano-dots using one-step excimer laser irradiation on cylindrically nanopatterned block copolymer materials, without any additional selective etching steps before a non-selective etching. Preferential etching in more ultraviolet (UV)-sensitive block component, and non-selective removal of all block components allowed transferring nanopatterns in block copolymer masks to inorganic silicon substrates, when an appropriate laser intensity was used. Surface melt flows of block components, which severely undermine the initial orders of nanopatterns in a block copolymer mask, were observed at the laser intensity near the ablation threshold of the less UV-sensitive component. Thus, in order to obtain mask-image-like topographic nanopatterns on the target material surfaces, the intensity of excimer laser radiation should be sufficiently lower than the ablation threshold of the less UV-sensitive component as long as the intensity is higher than that of the more UV-sensitive component. Numerical analyses on the photothermal excimer laser ablation in binary mixture systems predicted the presence of a matrix-assisted excimer laser ablation in the less UV-sensitive component at the laser intensity lower than its ablation threshold, owing to the heat conduction from the more UV-sensitive component during the nanoscopic level of time duration.

The influence of temperature on selected strength properties of furniture particleboard

2019 ◽  
Vol 108 ◽  
pp. 128-134
Author(s):  
PIOTR BORYSIUK ◽  
ANNA TETELEWSKA ◽  
AURIGA RADOSŁAW ◽  
IZABELLA JENCZYK-TOŁŁOCZKO
Keyword(s):  
Strength Properties ◽  
Large Decrease ◽  
Influence Of Temperature ◽  
Temperature Range ◽  
Influence Of Temperature On ◽  
Negative Effect

The influence of temperature on selected strength properties of furniture particleboard. As a part of the study, the influence of temperature on selected properties of furniture particleboard was tested. P2 type industrial particleboards in three finishing options: raw boards (1), boards covered with melamine film in white (2) and black (3) (10 samples per variant) have been subjected to temperatures from -20oC to +120oC, at 10oC intervals. The Time of exposure for individual temperatures was 7 days. MOR, MOE and IB were determined for tested boards. It has been shown that temperatures above 50oC have a negative effect on strength properties of boards. A large decrease in all tested parameters was observed in the temperature range from +60oC to +120oC. It was also noted that finishing boards with melamine film did not improve their durability.

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