Surface Tear Research Articles

Evaluation the Effect of Nano Yttrium Oxide Addition on the Mechanical Properties of Room Temperature-Vulcanized Maxillofacial Silicone Elastomers

Objective: This study aims to investigate the effects of yttrium oxide (Y2O3) nanopowder inclusion on the mechanical properties, including tear strength, tensile strength, elongation percentage, hardness, and surface roughness, of room temperature-vulcanized maxillofacial silicone elastomers. Materials and Method: Y2O3 nanoparticles (30–45 nm) were added to VST50F platinum silicone elastomers in two weight percentages (1 and 1.5 wt%) as tested by the pilot study that showed superior results. A total of 120 specimens were qualified and divided into the control group and experimental groups (1 and 1.5 wt% Y2O3). Each group was subdivided into four identical subgroups in accordance with intentionally performed tests (tear strength, tensile strength and elongation percentage, shore A hardness, and surface roughness). For each subgroup, 10 specimens were used for each test. Data were statistically analyzed with significance level considered at p < 0.05. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were also conducted. Results and Discussion: SEM showed that NPs were distributed well within the silicon matrix. FTIR spectra proved no chemical reaction occurred between the Y2O3 NPs and VST50F silicone. Tear strength and hardness values significantly increased in the experimental groups compared with the control group. Tensile strength and surface roughness values increased non significantly. Elongation percentage values decreased non significantly. Conclusion: Incorporating Y2O3 NPs into VST50F maxillofacial silicone improved the tear strength with slight increase in tensile strength. Hardness and surface roughness increased but within accepted clinical levels. Elongation percentage slightly decreased.

Lipid polarity gradient formed by ω-hydroxy lipids in tear film prevents dry eye disease.

Meibum lipids form a lipid layer on the outermost side of the tear film and function to prevent water evaporation and reduce surface tension. (O-Acyl)-ω-hydroxy fatty acids (OAHFAs), a subclass of these lipids, are thought to be involved in connecting the lipid and aqueous layers in tears, although their actual function and synthesis pathway have to date remained unclear. Here, we reveal that the fatty acid ω-hydroxylase Cyp4f39 is involved in OAHFA production. Cyp4f39-deficient mice exhibited damaged corneal epithelium and shortening of tear film break-up time, both indicative of dry eye disease. In addition, tears accumulated on the lower eyelid side, indicating increased tear surface tension. In Cyp4f39-deficient mice, the production of wax diesters (type 1ω and 2ω) and cholesteryl OAHFAs was also impaired. These OAHFA derivatives show intermediate polarity among meibum lipids, suggesting that OAHFAs and their derivatives contribute to lipid polarity gradient formation for tear film stabilization.

The effect of sodium fluorescein on anterior eye surface measurements

PurposeDuring image acquisition, certain topographers require the addition of sodium fluorescein (NaFl) dye to the tear film. This study investigates the effect of NaFl dye on corneal topography and tear surface quality. MethodThe E300 corneal topographer (Medmont International Pty Ltd., Victoria, Australia) was used to measure ocular surface topography and quality of 57 eyes of 57 healthy individuals without dry eye symptoms, age 35.1 ± 15.2 years (mean ± standard deviation) ranging between 19 and 65 years. The mean of three simulated keratometry values, a variety of corneal shape descriptors, and Tear Film Surface Quality (TFSQ) were measured under three different conditions; without NaFl (baseline), with the addition of a single dose NaFl, and using a double dose of NaFl. ResultsCompared to baseline, the Inferior-Superior (IS) index decreased significantly after a single dose (P = 0.034) or double dose of NaFl (P = 0.030). The corneal surface was significantly more regular without NaFl (P = 0.003) or one insertion of NaFl (P = 0.024) when compared to two doses of NaFl. There was no association with age, or dry eye signs or symptoms on the variance observed in any of the indices between baseline, intervention I, and intervention II (P > 0.05). Agreement between corneal surface indices reduced following the addition of NaFl. ConclusionIn comparison to measurements taken without an ocular dye, one dose of NaFl resulted in increased reliability and consistency in corneal topography measurements using the E300 topographer, but 2 doses decreased reliability and consistency. Practitioners ought to be aware that tear film surface regularity and inferior-superior corneal power changed significantly following the addition of NaFl in those with healthy corneas. Its effect in diseased corneas is unknown.

Biomarkers in Tears and Ocular Surface: A Window for Neurodegenerative Diseases.

The purpose of this review is to briefly outline current scientific evidence on the potential role of tear analysis and ocular surface evaluation in diagnosis and monitoring of neurodegenerative diseases, especially Alzheimer disease, Parkinson disease, and glaucoma. A systematic computerized search in the electronic databases PubMed, MEDLINE, and the Cochrane Collaborations was conducted to find eligible articles which their main topic was to investigate the tear and ocular surface in neurodegenerative diseases. After a first screening of titles and abstracts and a full-text review, 26 articles met the inclusion criteria (1 about the neurodegenerative diseases, 3 about the Alzheimer disease, 11 about the Parkinson disease, 11 about glaucoma, and 1 about amyotrophic lateral sclerosis). The ocular surface picture seems to be altered in the setting of neurodegenerative diseases with specific characteristics according to each disease. They seem to be associated with reduced corneal sensitivity and abnormal tear function, and each one presents the expression of specific biomarkers in tears. The study of tears and ocular surface appears to be a new and noninvasive promising way to assist in the diagnosis and monitoring of neurodegenerative diseases.

Effect of Addition of Composite Polyamide Micro Particles and Silicone Dioxide NanoParticle on Some Mechanical Properties of Room Temperature Vulcanized Maxillofacial Silicone Elastomer Before and after Artificial Aging

Background: The most common reason for re-making a maxillofacial prosthesis is the degradation of the mechanical properties of the silicone.Aim of this study: To assess some mechanical properties of VST-50F maxillofacial silicone reinforced with a composite of silicon dioxide nanoparticle and polyamide-6 microparticle before and after artificial aging.Material and Method: Preparing 240 samples tested for tear strength, tensile strength and elongation percentage, hardness, and roughness before and after aging. The Silicon dioxide was added in concentrations of 1% by weight and Polyamide-6 in the concentration of 0.25% and 0.5% by weight to the VST-50F RTV maxillofacial silicone. The one-way ANOVA and post hoc tests were used for inferential statistics.Results: The one-way ANOVA showed a highly significant difference between all tested groups. The effect of the addition of composite fillers showed an increase in tear strength, hardness, and surface roughness but a decrease in tensile and percentage of elongation. However, the effect of artificial aging showed increased in tear strength, Percentage of elongation, and surface roughness, but a decrease in tensile strength and hardness.Conclusion: Addition of composite of fillers into the silicone elastomer allowed enhancement of some mechanical properties. The composite of different types of filler reinforcement improves the anti-aging properties of silicone and maintain some of the mechanical properties to enhance the service life.

Comparative evaluation of tear strength and surface roughness of two maxillofacial silicone materials following disinfection: an invitro study

Comparative evaluation of tear strength and surface roughness of two maxillofacial silicone materials following disinfection: an invitro study

Partial-thickness rotator cuff tear: the secret of spinal needle

Aim The aim of this study is to prospectively evaluate the functional outcome after repair of PTRCT, moreconcisely partial-thickness articular surface tear, through converting it into complete tear and repairing in a routine manner using a spinal needle as a guideline for localization of the tear. Objectives Repair of PTRCT, through converting it into complete tear and repairing in a routine manner using a spinal needle. Background Partial-thickness rotator cuff tears (PTRCTs) involve all tears that do not connect the subacromial space with the glenohumeral joint but the fibers are disrupted. They may be articular-side tear, intertendinous tears, or bursal-side tears. The histopathological changes leading to rotator cuff rupture are gradual and progressive. The exact location and extent of incomplete tear can be shown by shoulder arthroscopy. Methods A total of 50 patients who underwent arthroscopic repair for a partial-thickness articular-sided rotator cuff tear between March 2013 and July 2015 were included in this study. Results Range of motion of the shoulder preoperatively was forward elevation of 135 5.6, mean external rotation of 44 3.5, and mean internal rotation of L3 level. Postoperatively, the range finally improved significantly to forward elevation of 165 4, external rotation of 60 5, and internal rotation of L1 level. Conclusions The use of spinal needle in arthroscopic repair of PTRCT facilitates the site of tear and as a guide for the healthy bursal side of the cuff. The limitations of our study included patient were highly selected regarding PTRCT and there was no postoperative imaging study.

Tear Film Metric Derived from Twyman-Green Interferometry of Tear Films

Purpose An in-vivo tear surface interferometer has been developed to measure the dynamic tear surface shape (TSS). A corresponding prelens tear film (PLTF) metric has been developed. The purpose of this work was to examine whether the metric could distinguish PLTFs by different lens types.

RECENT TRENDS IN MANAGEMENT OF KERATOCONJUNCTIVITIS SICCA (DRY EYE DISEASE)

At the air-water interface, the tear film lipid layer (TFLL), a combination of lipids and proteins plays an important role in surface tension of the tear and is necessary for the physiological hydration of the ocular surface and maintenance of ocular homeostasis. Alteration in lacrimal fluid rheology, differences in lipid constitution or down regulation of particular tear proteins are found in maximum types of ocular surface disease including dry eye disease (DED). Dry eye is a disorder of the tear film due to tear deficiency or excessive tear evaporation, which causes damage to the interpalpebral ocular surface and is associated with symptoms of discomfort. It results in changes on the ocular surface epithelia causing reduced tear quantity and surface sensitivity which leads to inflammation reactions. Managing this inflammation is very helpful in dry eye disease patients. In this article we revise the current understanding of tear film properties, ocular surface and review the effectiveness of topically applied tear supplements, thermo sensitive atelocollagen punctal plug, subtrasal ultrasonic transducers, novel liposome based gelling tear formation and insulin based ophthalmic delivery systems which help in restoring the healthy tear film.

Comparision on the effects of ocular surface tear system between two novel corneal refractive surgery

Objective To investigate the different effects of small incision lenticule extraction(SMILE) and sub-Bowman keratomileusis (SBK) on ocular surface tear system. Methods A prospective study. Total of 63 eyes of 63 cases were selected randomly in this study. There were 33 eyes who underwent SMILE and 30 eyes who underwent SBK. Corneal fluorescein(FL) staining, tear break-up time (BUT), Schirmer I test (SIT), central corneal sensitivity and ocular surface disease index (OSDI) score were estimated periodically before and 3 months after surgery. Results The FL scores in SMILE group were lower than those in SBK group at 1 week postoperatively (Z=2.455, P=0.014). The BUT of SMILE group were larger than those of SBK group at 1 (t=2.432, P=0.018) at 3 months postoperatively (t=2.150, P=0.036). The central corneal sensitivity was observed in SMILE group at any visit postoperatively were higher than that in SBK group (P 0.05). Conclusion The effect of SMILE surgery on ocular surface tear system is smaller than that of SBK. And the former recovers with less time. Key words: Small incision lenticule extraction; Sub-Bowman keratomileusis; Ocular surface; Tear

Lipid Saturation and the Rheology of Human Tear Lipids.

Elevated levels of acyl chain saturation of meibomian lipids are associated with enhanced tear film (TF) stability in infants to shortened TF breakup time with meibomian gland dysfunction. Thus, the effect of saturation on the surface properties of human TF lipids (TFLs) using a Langmuir surface balance and Brewster angle microscopy was studied. Lipid phase transitions were measured using infrared spectroscopy. The raise in the % of saturation resulted in thicker, and more elastic films at π = 12 mN/m, with the effects being proportional to the saturation level. At the same time, at lower (≤10 mN/m) π, the raise in saturation resulted in an altered spreading and modified structure of TFL layers. The strong impact of saturation on TFL surface properties correlated with a saturation induced increase of the TFL acyl chain order, phase transition temperature, and lipid–lipid interactions. The native TFL order and πmax were significantly greater, compared with native meibum collected from the same individual. Aggregation of lipids on the tear surface due to saturation was not as significant as it was for meibum. Although the surface pressure/area isotherms for TFL were similar for meibum, differences in rheology and phase transition parameters warrant the study of both.

Contribution du break up time au diagnostic et à la prise en charge du syndrome sec oculaire en milieu tropical : à propos de 234 yeux à Abidjan

Dry eye disease (DED) can be evaluated clinically by the tear film break up time (BUT). There is a discrepancy between symptoms in relationship with dry eye disease and objectives measures of BUT. So we tried to evaluate the reliability of BUT in the diagnosis and treatment of this disease in black African people. We carried out a prospective study of 6 months where melanoderms adults presenting subjective symptoms of dry eye disease according a questionnaire of 7 items were included. Then the measure of BUT is performed after ocular instillation of fluorescein eyedrop. This measured is done by recording the time elapsed from the last complete palpebral blink to the appearance of the first dry spot. Patients with subjective symptoms and time of BUT lower than 10seconds were called concordants (suffering really of DED). The discrepant group was represented by a BUT upper than 10seconds despite the fact that these patients answered positively to the questionnaire. This survey included 234 patients and the average age was 49.1 years. Sex-ratio was 0.68 and we noticed predominance of BUT between 5 and 10seconds in 42.3% of cases. Subjective symptoms were strengthened clinically by a BUT lower to 10seconds in 149 patients. Therefore, the reliability of BUT as clinic tool for the diagnosis after symptoms in relationship with DED was 63.7%. In the group of concordants, women were more likely than men to experience symptoms of DED (P=0.0005). Age upper than 50 years and computer usage were risk factors of DED (P<0.01). Dry eye disease is a multifactorial affection of tear and ocular surface frequently seen in female and people using computer and older than 50. The reliability of BUT near to 65% is a reason to perform this test in our daily practice. Tear BUT is a reliable clinical test which must be performed systematically to assess the diagnosis of DED in black African people.

Investigation of surface topology in ball nose end milling process of Inconel 718

Inconel 718 known as hard-to-cut material due to its superior mechanical properties; high creep resistance, high fatigue strength, and able to withstand at elevated temperature which remains as challenge to possesses a lower surface roughness (Ra) during machining. The surface topology indicates the integrity of the machined parts. The quality of the Inconel 718 surface during end milling process was investigated. The experiments involved the use of PVD coated with TiAlN/ AlCrN ball nose tungsten carbide with varying of cutting speeds (Vc) ranging between 100 and 140 m/min, a feed rate (fz) of 0.1–0.2 mm/tooth, and an axial depth of cut (DoC) of 0.5–1.0 mm. The effects of the width of cut (WoC) between 0.2 and 1.8 mm were carried out. Due to the profile of the milled surface is complex; some variations in gap distance on the spiral profile were detected. The cutting path area to be found that, the new cut is overlapped which generate a new surface roughness by eliminating the previous cut thus the non-uniform feed marks being created on the machined surface. The surface roughness measured in feed direction was found to be lowered than pick a direction. Furthermore it was found that the WoC are causes the variation in Ra. During machining at low feed rates, the phenomenon of carbide particles was observed which results third body abrasion of machined surface. The particles are then trapped between the fragments and tear surface of the workpiece, thus increases the surface roughness. Based on the interaction effect of WoC and fz, it can be concluded that the feed rate effects on the quality of machined surface whilst WoC controls Ra variation.

Waterborne polyurethane/graphene oxide-silica nanocomposites with improved mechanical and thermal properties for leather coatings using screen printing

Waterborne polyurethane (WPU) has been broadly used as adhesive and coating materials in many applications. In this work, the graphene oxide-silica (GOSI) nanocomposites, used as nanofillers in the WPU matrix, were produced by functionalizing graphene oxide with epoxy groups and nanosilica with amine groups using silane terminated coupling agents. The nanocomposite surface structures were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The polymer nanocomposite films show the excellent improvement in the mechanical and thermal properties. In the fractured surface study of the composite films by SEM, it was observed that the agglomeration of GO appears while the GOSI is uniformly distributed in the WPU matrix. Furthermore, the WPU/GOSI have regained the maximum tensile strength properties after two weeks of hydrolysis. The GOSI nanocomposites have enhanced interfacial crosslinking with the WPU matrix which is the prime reason for such development in the mechanical properties. The screen printing method was illustrated to cast the thin and transparent layer WPU nanocomposites on the leather surfaces. The WPU/GOSI coatings exhibit outstanding tear resistance, surface adhesiveness, and abrasion resistance properties. This approach of using GOSI composites as nanofiller in the polymer matrix may pave a novel path for surface coating strategies.

The Influence of Halloysite Nanotube Addition on Some Properties of Room Temperature Vulcanized Maxillofacial Silicone before and after Simulated Aging

Although silicone is the most commonly used material in face and neck prostheses, but there are some drawbacks concerning its mechanical performance and durability. Therefore, this study was carried out to investigate the impact of halloysite nanotube (HNTs) on selected properties of VST-50F silicone before and after simulated weathering. A pilot study was conducted to determine the most suitable weight percentage of HNTs to be incorporated into VST-50F silicone. Accordingly, 1% and 1.5% weight percentage were chosen to be the experimental groups and compared with control. The main study involved the preparation of 240 samples divided equally into two groups;group 1 (before weathering) and group 2 (after weathering). Group 2 samples were subjected to simulated aging for 200 hour. After that, all sample wre subjected to five mechanical tests, namely tear strength, tensile strength, elongation percentage, surface roughness and hardness. The research readings were collected and statistically analyzed using ANOVA, post-hoc and paired t-test tests. Additional tests were also performed including Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) that test revealed a well dispersion fashion of HNTs within VST-50F silicone, while FTIR didn't exhibit any chemical reaction between the silicone and HNTs. However, mechanical tests results before aging showed significant rise in all tests readings except for roughness, where the change was non-significant. Meanwhile, the study results after weathering revealed a significant decline in tear strength, tensile strength and elongation percentages, yet roughness didn't change significantly, but hardness increased remarkably. Reinforcing VST-50F with HNTs improved some of its mechanical properties but didn't protect it from aging consequences.

Effects of the Addition of Untreated and Oxygen Plasma Treated Polyamide fibers on Tear strength and Surface roughness of Room Temperature Vulcanized Maxillofacial Silicon Elastomers (Pilot Study)

Effects of the Addition of Untreated and Oxygen Plasma Treated Polyamide fibers on Tear strength and Surface roughness of Room Temperature Vulcanized Maxillofacial Silicon Elastomers (Pilot Study)

Dynamic response and fatigue life of Vacuum cast Polyurethane polymer material

The objective of this paper is to measure the dynamic response transmissibility and fatigue life of vacuum cast Polyurethane (PU) polymer material used in the construction of automotive lamps. Polymers used in automotive lamps, if mass produced, are injection moulded. For ultra-low volume production, however, the cost of tooling for these traditional manufacturing methods is often very high. Hence, alternative approaches such as Silicone Tool – Vacuum (STV) casting are used. The parts produced using alternative approaches may have inferior dynamic performance. The specimens for dynamic response and fatigue testing were cut-out from a vacuum cast polyurethane plate. An instrumented beam was mounted on a shaker table and using sine sweep base excitation the dynamic response was measured. Using measured acceleration, response transmissibility was calculated. The bending fatigue properties were measured on a vibration shaker using a 4-point bending based resonance test apparatus. A series of tests were carried out to obtain average performance parameters. The dynamic response shows nonlinearity, as expected of polymers, and a large variation in dynamic properties is observed. The obtained fatigue life curve shows significant scatter at 40% fatigue load level. The assessed fracture surface micrograph of the fatigued specimens at three load levels shows surface tear at 80% and 60% load levels. Overall, the Vacuum cast polyurethane shows less fatigue performance than the conventional polymers of automotive lamps.

Autologous Serum and Serum Components.

Dry eye syndrome is a multifactorial condition on the tear and ocular surface. Autologous serum eye drop is an effective method for treating dry eye. Autologous serum eye drops are now widely used by specialists since a first report in 1975. The results of a systematic study showed that the efficacy of autologous serum eye drops remains ambiguous because its preparation methods and clinical application have not been standardized. To elucidate the efficacy of autologous serum eye drops, well-designed, large-scale, high-quality randomized controlled trials need to be conducted with standardized treatment and use. Since serum components are partially similar to tear components, autologous serum eye drops improve dry eye by supplying tear components such as growth factors, proteins, and vitamins. Adding to the evidence based on the treatment of dry eye, we have found a new treatment candidate from serum: selenoprotein P (SeP). The efficacy of SeP as a treatment for dry eye was revealed by applying SeP eye drops to a dry eye rat model. Compared with phosphate-buffered saline treatment, SeP eye drops significantly reduced the fluorescein score of the cornea and suppressed the oxidative stress in the cornea, which is related to onset of dry eye, leading to improved corneal disorder. We have developed a new dry eye model caused by oxidative stress that will be used to screen candidate molecules for antioxidative activity.

An investigation of the relationship between corneal sensation, blinking, ocular surface temperature and tear film quality

An investigation of the relationship between corneal sensation, blinking, ocular surface temperature and tear film quality

Evaluation of some mechanical properties of a new silicone elastomer for maxillofacial prostheses after addition of intrinsic pigments

ObjectiveThe approximate life span of a silicone maxillofacial prosthesis is as short as 1.5–2 years of clinical service, then a new prosthesis should be fabricated. The most common reason for re-making the prosthesis is silicone mechanical properties degradation. The aim of this study was to assess some mechanical properties of VST-30 silicone for maxillofacial prostheses after addition of intrinsic pigments. MethodsTwo types of intrinsic pigments (rayon flocking and burnt sienna); each of them was incorporated into silicone. One hundred and twenty samples were prepared and split into 4 groups according to the conducted tests (tear strength, hardness, surface roughness, and tensile strength and elongation percentage) with 30 samples for each test. Each group was equally split into three subgroups. Group (A) was without pigment (control group), group (B) was with rayon flocking and group (C) was with burnt sienna. ResultsSamples with rayon flocking showed a highly significant decrease in hardness and there was a significant increase in tear strength, while there were non-significant differences in surface roughness, tensile strength and elongation percentage. Samples with burnt sienna showed a highly significant increase in tear strength and a highly significant decrease in hardness, but surface roughness, tensile strength and elongation percentage showed non-significant differences. However, there were non-significant differences between experimental groups in all tests. ConclusionsThe addition of each of rayon flocking and burnt sienna changed the mechanical properties of the VST-30 silicone, while no superior pigment-silicone combination was revealed in all the conducted tests.