Contact Lens Wear Research Articles

Influence of Lifestyle Factors on Ocular Surface Parameters in Relation to Age

Purpose: To evaluate how Video Display Terminal (VDT) use, Contact Lens (CL) wear, and eyedrop use affect ocular surface parameters in participants with ocular discomfort and how these factors may vary across different age groups. Methods: The current cross-sectional study initially involved a total of 252 participants who completed a self-administered survey to collect information about ocular discomfort and lifestyle factors. This online survey was composed of an Ocular Surface Disease Index (OSDI) questionnaire and three extra questions regarding lifestyle factors (VDT use, CL wear, and eyedrop use). Only 185 symptomatic participants, those with OSDI values > 12, were scheduled to undergo a comprehensive ocular examination that included tear film osmolarity, Fluorescein Break-Up Time (FBUT), Maximum Blink Interval (MBI), and corneal staining. Results: Differences in ocular parameters and lifestyle factors across age groups (<40 years, 40–60 years, >60 years) were analyzed, along with their correlations and regression. Significant age group differences were found in OSDI, osmolarity, FBUT, and MBI (One-way ANOVA, all p ≤ 0.029). Correlations were observed between CL wear and osmolarity and MBI (Pearson’s correlation, both p ≤ 0.049). Multiple regression confirmed age associations with OSDI, osmolarity, FBUT, and MBI (Multiple linear regression, all p ≤ 0.040) and found links between VDT use and osmolarity and MBI (Multiple linear regression, both p ≤ 0.038) and between eyedrop use and OSDI (Multiple linear regression, p = 0.040). Conclusion: Aging is a primary factor affecting ocular homeostasis, with older adults showing lower FBUT and MBI values and higher osmolarity. Prolonged use of VDTs exacerbates this effect, further contributing to ocular discomfort and destabilized tear film. No associations between CL wear and any of the ocular parameters were found. Eyedrop use shows varied effects on ocular comfort across age groups, emphasizing the need for age-specific ocular care. Overall, these findings confirm that aging and extended VDT use play a significant role in ocular surface discomfort.

Clinical Outcomes of Infectious Keratitis Associated with Contact Lens Wear Following Penetrating Keratoplasty: A Case Series

Clinical Outcomes of Infectious Keratitis Associated with Contact Lens Wear Following Penetrating Keratoplasty: A Case Series

How Can We Better Inform Patients of the Importance of Contact Lens Compliance?: Current Perspectives.

Compliance with contact lens care is important for successful contact lens wear and for minimizing the risk of complications related to lens wear. There are many components of overall lens care guidelines that may potentially be disregarded, forgotten, or misunderstood. Literature has reported copious data on rates of poor compliance for separate lens care recommendations. Knowing the areas of contact lens care where lens wearers perform poorly is helpful when creating strategies for improving patient education. As science evolves and new best-practices are determined, eye care providers must be engaged in educating new lens wearers and reeducating existing wearers. It is vital to make wearers mindful of proper lens care and why proper lens care should be important to them. Various educational strategies can help practitioners to communicate with their patients more effectively. The purpose of this narrative review is to discuss studies of noncompliance with contact lens wear; consequences of these noncompliant behaviors; and studies of lens care education which were found with a literature search. The resulting discussion also includes strategies to improve compliance with patient contact lens wear.

A Narrative Review of Acanthamoeba Isolates in Malaysia: Challenges in Infection Management and Natural Therapeutic Advancements.

Acanthamoeba,a free-living amoeba (FLA) found in diverse ecosystems, poses significant health risks globally, particularly in Malaysia. It causes severe infectious diseases, e.g.,Acanthamoebakeratitis (AK), primarily affecting individuals who wear contact lenses, along with granulomatous amoebic encephalitis (GAE), a rare but often life-threatening condition among immunocompromised individuals. AK has become increasingly prevalent in Malaysia and is linked to widespread environmental contamination and improper contact lens hygiene. Recent studies highlightAcanthamoeba's capacity to serve as a "Trojan horse" for amoeba-resistant bacteria (ARBs), contributing to hospital-associated infections (HAIs). These symbiotic relationships and the resilience ofAcanthamoebacysts make treatment challenging. Current diagnostic methods in Malaysia rely on microscopy and culture, though molecular procedures like polymerase chain reaction (PCR) are employed for more precise detection. Treatment options remain limited due to the amoeba's cyst resistance to conventional therapies. However, recent advancements in natural therapeutics, including using plant extracts such as betulinic acid fromPericampylus glaucusand chlorogenic acid fromLonicera japonica, have shown promising in vitro results. Additionally, nanotechnology applications, mainly using gold and silver nanoparticles to enhance drug efficacy, are emerging as potential solutions. Further, in vivo studies and clinical trials must validate these findings. This review highlights the requirement for continuous research, public health strategies, and interdisciplinary collaboration to address the growing threat ofAcanthamoebainfections in Malaysia while exploring the country's rich biodiversity for innovative therapeutic solutions.

Candida parapsilosis keratitis: A case series

Purposeto describe the diagnosis and management of Candida parapsilosis keratitis Designa retrospective, observational case series. Methodsthis study was carried out in a single-centre tertiary referral eye hospital and includes 20 eyes of 19 patients. Electronic case notes and in vivo confocal microscopy (IVCM) records were searched for the keyword ‘parapsilosis’, with inclusion if there was keratitis with either a corresponding positive polymerase chain reaction (PCR) or microbial culture result for Candida parapsilosis. Individual case notes were reviewed to obtain information regarding diagnosis, treatment, and final visual outcomes. Cases were excluded if a patient was lost to follow-up before the end of antifungal treatment. Resultsthe risk factors for C. parapsilosis keratitis were: ocular surface disease, concurrent topical steroid use, previous corneal surgery and long-term contact lens wear. The mean presenting corrected distance visual acuity (CDVA) was LogMAR 1.49 (range 0.2 – 2.3), with a final CDVA of LogMAR 1.11 (-0.2 – 2.3). Where used, microbiological culture was positive in 19 out of 20 cases, PCR in 6 out of 11 cases, and IVCM in 8 out of 13 cases. Two-thirds of cases were managed with either topical voriconazole or amphotericin B, with four cases surgically managed by therapeutic keratoplasty and two cases requiring evisceration. ConclusionsPatients presenting with microbial keratitis with risk factors for C. parapsilosis keratitis should be managed with a high degree of clinical suspicion. Post-infection visual outcomes are poor but reflect pre-existing ocular comorbidities. Delays in diagnosis can be reduced by through the use of ICVM and PCR.

Raman spectroscopy to investigate early biochemical alterations in human tears caused by contact lenses

ABSTRACT Clinical relevance The interaction between contact lenses and tear film plays a critical role in lens biocompatibility and can influence discomfort during wear. Early detection of biochemical changes is important for improving ocular surface health, preventing complications, and developing advanced lens materials to enhance long-term comfort. Background The pursuit of biocompatible lens materials requires a thorough understanding of their interaction with tear environment. The aim of this study is to evaluate different approaches to investigate early alterations in tear biomolecular profiles induced by lens wear. Methods Two participants wore different CLs and underwent ocular analysis before CL insertion (T0), after 2-hour wear (T2), and two hours after removing the CL (T4), evaluating non-invasive tear break-up time (NIBUT), tear meniscus height (TMH), and osmolarity. Forty CLs were used. At the same time points, tears were collected and analysed by Raman spectroscopy. Results Tear film stability, as measured by NIBUT, decreased post-lens wear (T0 vs T2, p = 0.034 and 0.025 for S1 and S2, respectively) but showed recovery within 2 hours (T0 vs T4, p > 0.05 for both S1 and S2), while TMH and osmolarity remained unchanged (T0 vs T2 vs T4, p > 0.05 for both S1 and S2). Raman spectroscopy highlighted notable changes in the biomolecular profile of tears after lens wear, particularly in the 2700–3200 cm−1 spectral window related to C-H stretching, which is sensitive to CH, CH2 and CH3 groups, their functional chemistry group, and the surrounding microenvironment. Conclusions Contact lens wear induces subtle biochemical, subclinical alterations in tears that can be detected early by Raman spectroscopy. The method is promising for analysing the subject-specific responses to lenses, also with possible individual variability in the timing of these changes. In addition, this approach can provide insights for designing biocompatible materials and for the early detection of subclinical biomarkers.

Comfort advantages demonstrated with a novel soft contact lens: A randomized clinical trial

PurposeTo compare comfort outcomes between a novel daily disposable contact lens – designed to maximize comfort – and an established control. The hypothesis was that the test lens would be superior to the control for four key comfort questionnaire items: end-of-day comfort, all-day comfort, visual comfort while driving at night, and reduction of ocular fatigue from digital device use. MethodsThis randomized, controlled, subject-masked, parallel-arm study enrolled young (18–39 years), healthy, myopic, contact lens wearers with an up-to-date prescription at 19 investigational sites in the United States. Subjects wore either the test (ACUVUE® OASYS MAX 1-Day, senofilcon A) or control (Dailies Total1®, delefilcon A) lens for 2 weeks of bilateral, daily disposable wear before completing comfort questionnaire items, each of which had 5 or 6 response options. For each item, the odds ratio for positive (top-two-box) responses was estimated from a binomial generalized linear mixed model. A gatekeeping approach combined with the truncated Hochberg procedure was used for multiplicity adjustment. ResultsOf 344 enrolled subjects, 342 subjects were randomized and dispensed lenses, with 171 subjects per lens group. Among the 342 subjects, 68.4% were female, 83.6% were White, and the average age was 29.7 (±5.53) years. The test lens was statistically superior to the control for all four comfort questions: odds ratios (test vs. control) were 2.01 (95% CI: 1.25, 3.22) for end-of-day comfort, 2.17 (alpha-adjusted CI: 1.30, 3.64) for all-day comfort, 2.00 (alpha-adjusted CI: 1.18, 3.41) for reducing ocular fatigue from digital device use, and 1.77 (95% CI: 1.04, 3.02) for comfortable vision while driving at night. ConclusionThe test lens demonstrated statistically superior physical and visual comfort, as measured by the four comfort endpoints, compared to the control. The test lens had significantly greater odds of favorable responses for all comfort items compared to the control.

Influence of fatty acid composition on contact angle and wear rate of Jatropha curcas and sunflower’s mixture by varying compositions mixture

United Nation Sustainable Development Goals make sustainability become common goals which drives into investments of innovative product and technology focusing on sustainability. Cutting oils are generally made from mineral oil and the renewable replacement is sought after and one of them are Jatropha curcas and sunflower oil or blend of them. Viscosity and adsorption will influence the properties of cutting oil. The study concern on the relationship between percentage of JCO in the mixture to anti-wear properties and contact angle measured using goniometer contact angle and pin-on-disk tribometer by varying percentage of Jatropha curcas oil in mixtures for 2.5 %, 5 %, 10 %, 20 %, and 30 %. Also, molecular simulation is conducted through molecular dynamic in search of dipole moment, electrostatic potential, polarizability and bond energy. The approach is employed to connect molecular interaction and non-linearity trending of experiment. The experiment shows contact angle and wear scar width and also wear rate become higher when percentage of Jatropha curcas oil is higher. The lowest contact angle is 26.9 deg. and the highest is 36.9 deg. of 2.5 % and 30 % Jatropha oil. The highest wear rate is 6.77e-7 and the lowest is 2.74e-7 of 2.5 % and 30 % Jatropha oil. The simulation gives supporting basis in the finding of experiment in which the viscosity is more prominent in governing wear rate than adsorption. Increases of Jatropha curcas percentages have inversely proportional to dipole moment, polarizability, electrostatic potential and bonding which explain why the fatty acids become more adhere to the fatty acid than to surface. The finding is restricted only for idealized conditions both of molecular structure and surface.

Clinical Issues — November 2024

THIS MONTH Reducing the perioperative carbon footprint Key words: sustainability, carbon footprint, greenhouse gas (GHG), energy, consumption. Exsanguination before tourniquet use Key words: elastic wrap, exsanguination, gravity, pneumatic tourniquet, limb. Using augmented reality technology in the OR Key words: augmented reality (AR), virtual reality (VR), extended reality (XR), headset, navigation. Patients wearing contact lenses during a procedure Key words: contact lens, corneal abrasion, patient positioning, eye injury, risk factors.

Keratoconus.

Keratoconus is a progressive eye disorder primarily affecting individuals in adolescence and early adulthood. The ectatic changes in the cornea cause thinning and cone-like steepening leading to irregular astigmatism and reduced vision. Keratoconus is a complex disorder with a multifaceted aetiology and pathogenesis, including genetic, environmental, biomechanical and cellular factors. Environmental factors, such as eye rubbing, UV light exposure and contact lens wearing, are associated with disease progression. On the cellular level, a complex interplay of hormonal changes, alterations in enzymatic activity that modify extracellular membrane stiffness, and changes in biochemical and biomechanical signalling pathways disrupt collagen cross-linking within the stroma, contributing to structural integrity loss and distortion of normal corneal anatomy. Clinically, keratoconus is diagnosed through clinical examination and corneal imaging. Advanced imaging platforms have improved the detection of keratoconus, facilitating early diagnosis and monitoring of disease progression. Treatment strategies for keratoconus are tailored to disease severity and progression. In early stages, vision correction with glasses or soft contact lenses may suffice. As the condition advances, rigid gas-permeable contact lenses or scleral lenses are prescribed. Corneal cross-linking has emerged as a pivotal treatment aimed at halting the progression of corneal ectasia. In patients with keratoconus with scarring or contact lens intolerance, surgical interventions are performed.

Research on the wheel wear and rolling contact fatigue of metro vehicle induced by the rail corrugation

The rail corrugation is a common disease on the track, which exacerbates the wheel-rail interaction and accelerates wheel wear and crack propagation. This study focuses on the wheel wear and rolling contact fatigue of metro vehicle under the rail corrugation. Firstly, the characteristics of the rail corrugation under service conditions are determined by the statistical analysis of the field data, and the rail corrugation is applied to the established vehicle-track coupled dynamics model. Then, the wear index and the work of friction force as indicators of wheel wear are studied. Finally, based on the Shakedown Map and the criterion of maximum amplitude of shear stress, the simulation analysis of wheel-rolling contact fatigue under the rail corrugation is carried out. The results show that the increases in superficial fatigue index and accumulated fatigue are 1.52 and 6.16 times in the wavelength range of 30-90 mm larger than those in the range of 90-210 mm, respectively. Furthermore, the cracks more easily occur 2-4 mm from the outer surface of wheel, and expand along the wheel tread.

Hand-Washing Habits in a Sample of Spanish Soft Contact Lens Wearers

Contact lens (CL) wear is a safe method for the correction of refractive errors. However, rare, severe ocular complications may occur which may lead to visual loss. As most of these complications are related to poor patient compliance with care and maintenance instructions, resulting in the contamination of hands, CLs and accessories, it was the purpose of this study to assess hand-washing habits in a sample of Spanish soft CL wearers. Hand hygiene was explored through a self-reported online survey and via an in-office practical demonstration in a subset of those users answering the survey. A total of 198 surveys were analyzed, and 18 CL users participated in the practical demonstration. Overall, hand-washing habits were not adequate, with 35 (17.8%) and 103 (52.2%) participants reporting not always washing their hands prior to CL or storage case manipulation, respectively. While 161 (81.3%) participants dried their hands after washing, 132 of these (82.1%) used non-disposable cloth towels. Participants receiving specific hand-washing information from their practitioners (141, or 71.1%) had better hand hygiene (p < 0.05). During the practical demonstration, 13 (72.2%) participants used water and soap to wash their hands, but only 3 (16.7%) displayed correct hand washing routines. Complete patient education, as well as practical reminders at all follow-up visits, are essential to ensure better hand hygiene in order to reduce the probability of ocular complications and to guarantee safe and satisfactory CL use.

Axis "microbiota – gut – eye": a review

Every organ in the human body has its own microbiota, and the eye, a complex multi-component organ, is no exception. Due to the limitations of traditional methods, detailed study of the ocular microbiome began only in 2010 as part of the Eye Microbiome Project, when advances in research methods made it possible to obtain detailed data, although there had been debate previously about whether microorganisms were even able to attach to the ocular surface due to the layers of the tear film, which have antibacterial properties. The cornea, conjunctiva, lacrimal glands and tear film, meibomian glands and microbiome form the microenvironment of the ocular surface, interacting together and resisting irritants, allergens and pathogens. Homeostasis of the ocular microbiota is critical for maintaining the health of the visual organ. Most microorganisms are found on the cornea and conjunctiva, and modern research methods, including 16S rRNA sequencing, have allowed us to establish the "core" of the ocular surface microbiota, identifying the most common types: Staphylococcus, Corynebacterium, Propionibacterium, and Streptococcus, although the exact composition of the “core” remains debatable. Many factors can influence the composition of the microbiome, including age, contact lens wear, ophthalmic medications, and antibiotics. Like the microbiome of many other organs, the ocular surface microbiome is influenced by the gut microbiome: this relationship has been called the "microbiota – gut – eye" axis. Within the "gut – eye" axis, healthy gut microbiota produce short-chain fatty acids, indoles, polyamines, and other substances that have a beneficial effect on the immune system and retinal health. The state of dysbiosis leads to disruption of homeostasis, and the increasing inflammatory reaction can contribute to damage to the optic nerve and progression of eye disease. Some ophthalmologic diseases, such as diabetic retinopathy, age-related macular degradation, choroidal neovascularization, uveitis, primary open-angle glaucoma, Sjogren's syndrome, dry eye syndrome are associated with dysbiosis of the intestinal microbial composition. Correction of intestinal dysbiosis using various methods can lead to a decrease in the risk of eye diseases, although additional research is needed to discover new methods for treating ophthalmologic pathologies along the "microbiota – gut – eye" axis.

Prevalence of dry eye disease symptoms, associated factors and impact on quality of life among medical students during the pandemic

This cross-sectional study aimed to evaluate the prevalence of dry eye disease (DED) symptoms, their associated factors, and the impact on quality of life (QOL) and mental health among medical students during the COVID-19 pandemic using online surveys. Participants completed questionnaires covering demography, medical history, and personal data. The Thai version of the Dry Eye-related Quality-of-Life Score (DEQS-Th) was used for DED screening. The QOL and mental health challenges (support, coping, stress, and depression) were evaluated by the EuroQoL-5 dimensions-5 levels (EQ-5D-5L) and Thymometer questionnaires. A total of 449 participants were analyzed, with a mean age of 21.8 years and 61.5% female. The prevalence of DED symptoms was 60.4% (95%CI 55.7–64.8). The DEQS-Th score, the EQ-5D-5L score, and all aspects of mental health challenges were significantly worse in DED participants compared to non-DED participants. Associated factors for DED symptoms included preexisting DED (p = 0.001), refractive errors (p = 0.007), allergic conjunctivitis (p = 0.001), artificial tears use (p < 0.001), and decreased EQ-5D-5L score (p < 0.001). This study highlighted the high prevalence of DED symptoms among medical students during the pandemic and its negative impact on QoL and mental health. Notably, female gender, contact lens wear, screen time, and mask-wearing duration were not associated with DED symptoms.

Patient evaluated economic impact of keratoconus in New Zealand

ABSTRACT Clinical relevance Few studies have investigated the economic burden of keratoconus to patients and society including a patient’s lifetime expenditure. Analysing disease cost is important in advocating funding and planning for appropriate management and treatment. Background Keratoconus can be an expensive disease, including costs associated with visual rehabilitation and surgery. This study aimed to assess direct and indirect expenditures incurred by keratoconus subjects, to estimate the lifetime per capita cost and the total costs of keratoconus per year in Auckland, New Zealand. Methods A cross-sectional study where participants with keratoconus were recruited from public and private clinics to complete an anonymous questionnaire. A keratoconus health expenditure questionnaire was used to assess direct and indirect expenditures for participants. Estimated lifetime per capita costs and total direct and indirect costs associated with keratoconus were calculated. Results Responses from 110 participants were recorded. Most participants (55.5%) were between the ages of 21 and 30, 59.1% were male, and Pacific People were over-represented (14.5%) compared to the national population. The prevalence of visual rehabilitation was low with 74.5% of participants never wearing contact lenses and 32.7% of subjects wearing spectacles purchased over 24 months prior. Few participants (26.5%) had subsidised care, including private health insurance with optical cover or the contact lens subsidy. Total direct and indirect costs are estimated to be NZD 30.9 million per year with an estimated lifetime per capita out-of-pocket cost of NZD 79,254. Conclusion Subjects with keratoconus experience significant direct and indirect costs with limited subsidisation from the government and private health insurance. The significant out-of-pocket costs required for managing keratoconus are likely a significant barrier to accessing appropriate visual rehabilitation in New Zealand.

Characterization of infectious bacterial keratitis in Östergötland County, Sweden: a 10-year retrospective study.

The aim of this study was to characterize bacterial species, aetiology and antibiotic susceptibility connected to bacterial keratitis infections in Östergötland, Sweden. Retrospective cross-sectional study based on electronic health records for the period 2010-2019. Records of patients diagnosed with infectious keratitis were screened for microbiology confirmed infectious bacterial keratitis. Bacterial species and their susceptibility to antibiotics were determined from microbiology test results. One-hundred and ninety patients with lab culture-confirmed infectious bacterial keratitis were included in the analysis. The most frequently found bacterial species were coagulase-negative staphylococci (39%), Staphylococcus aureus (17%) and Cutibacterium acnes (10%). Pseudomonas spp. was the most frequently found Gram-negative bacterial species (7%). Contact lens wear and severely ill/blind eye were the top two aetiologies associated with bacterial keratitis, 22% of the patients with bacterial keratitis were also diagnosed with glaucoma. Most isolates, 157 out of 173, were susceptible to fluoroquinolones, and 145 out of 155 isolates were susceptible to chloramphenicol. Our results revealed a positive rate of bacterial keratitis of 59% for the samples sent to the laboratory. There was a high susceptibility of the bacterial species to the recommended antibiotics. Our results indicate that it is likely that patients are receiving the correct treatment. Future studies are necessary to monitor changes in antibiotic susceptibility.

An investigation on tribology performance of Abutilon Indicum fibre reinforced polymer composites

This research work investigates the tribological characteristics of Abutilon Indicum Fiber (AIF) reinforced composites with epoxy as the binding agent. The Abutilon Indicum fiber reinforced composites were manufactured by compression molding technique. These composites were fabricated by varying the fiber volume fraction ranging from 5%, 10%, 15% and 20% respectively and considering the fiber length as a fixed factor due to its short length. This research paper illustrates the effects of different fiber volume fractions (5,10,15 and 20%) on the tribological properties such as Specific wear rate (SWR) and Coefficient of friction (µ) of Abutilon Indicum fiber reinforced composites. Sliding wear tests were carried out under dry environment conditions with pin-on-disc wear testing machine. The experiments were performed for each composite with different combinations of testing parameters, sliding loads (10, 20 and 30 N); sliding distances (1,2 and 3 km); sliding speeds (1,2 and 3 m/s). Shore D hardness of 78.22 is determined to be higher for 15% volume fraction of AIF composites. Results conclude that the addition of AIFs in these composites enhanced the tribological performance with good wear resistance in relation with the pure epoxy-based composites with 15% volume fraction of AIFs displaying best results with higher resistance to wear at various operating conditions. Composites produced with 20% volume fraction displays the effects of fiber agglomeration which in turn has an inverse effect on hardness; limits the wear resistance with higher friction and wear rate and such results agree well with the wear debris, pits and contact patches in micrographs. Optimal fiber volume fraction of 15% was suggested in fabrication of composites for usage of AIFs as friction material.

Antimicrobial and antifouling hyaluronic acid-cobalt nanogel coatings built sonochemically on contact lenses

The wearing of contact lenses (CLs) may cause bacterial infections, leading in turn to more serious complications and ultimately vision impairment. In this scenario, the first step is the adhesion of tear proteins, which provide anchoring points for bacterial colonization. A possible solution is the functionalization with an antimicrobial coating, though the latter may also lead to sight obstruction and user discomfort. In this study, adipic acid dihydrazide-modified hyaluronic acid-cobalt (II) (HA-ADH-Co) nanogels (NGs) were synthesized and deposited onto commercial CLs in a single-step sonochemical process. The coating hindered up to 60 % the protein adsorption and endowed the CLs with strong antibacterial activity against major ocular pathogens like Staphylococcus aureus and Pseudomonas aeruginosa, reducing their concentration by around 3 logs. Cytotoxicity assessment with human corneal cells demonstrated viabilities above 95 %. The nanocomposite coating did not affect the optical power and the light transmission of the CLs and provided enhanced wettability, important for the wearer comfort.

Microstructure Evolution and Mechanical Properties of High-Temperature Carburized 18Cr2Ni4WA Steel

Surface carburized steels are extensively utilized in gears due to their exceptional properties. The quality of the carburized layer is crucial in enhancing the contact fatigue and wear resistance of the components. However, the conventional carburizing method takes a long time and induces a carbon emissions problem. In this study, the 18Cr2Ni4WA steel was double tempered (650 °C/4 h) after carburizing at 930 °C and 950 °C. The microstructural evolution, carbide precipitation, and mechanical properties of different carburized layers were analyzed. The results showed that increasing the carburizing temperature can control the microstructure of the carburized layer while reducing the carburizing time by over 60%. The high carbon content improves the strength of the carburized materials at 950 °C, and the inhibition of dislocation motion and grain boundary by the precipitation of more carbides ensures the stability of grain size, maintaining the strength of the materials. The carburized specimens at 950 °C showed an excellent combination of strength and plasticity in different carburized layers due to the variations in solid solution strengthening, dislocation strengthening, precipitation strengthening, and grain boundary strengthening induced by carbon atoms. This study holds significant reference for the advancement of modern steels carburized at high temperatures in a short time.

Epidemiological survey of two morphotypes of Demodex folliculorum (Prostigmata: Demodicidade) in young people from southern Spain

Different morphotypes of Demodex from humans have been described. Among them, molecular studies have made it possible to discern between the Demodex folliculorum and Demodex brevis. Further studies showed two morphotypes of D. folliculorum harboured two different habits (human skin and human eyelashes), both of them with finger-shaped terminal opisthosoma difficult to differentiate and that can be assigned to D. folliculorum,Thus, a complete morphometric study of the species, which in this study are referred to as Demodex folliculorum species complex, was carried out. From this morphometric and meristic study two distinct morphological forms (short and long) could be identified within the Demodex folliculorum species complex. These forms differ significantly in four out of the six biometric parameters we analysed: gnathosomal length and width, podosomal width, and opisthosomal length. Moreover, a comprehensive survey of the two morphotypes from different habitats (skin and eyelashes), was carried out in young people of Southern Spain. Therefore, an analysis of 104 asymptomatic students, which were contact lens wearers, and the presence of D. folliculorum was carried out. A statistical analysis based on Bayesian zero inflated Poisson GLM has been applied to our sample data. For the age group considered (18–24 years old), the overall D. folliculorum prevalence for skin face or eye infections (at least one of them) was 19.31 % (51 people), with a statistically significant higher prevalence in males men. Furthermore, there is a slight statistical correlation between the presence of Demodex in silicone hydrogel soft contact lens wearers. This study confirms: i) the existence of two morphotypes of D. folliculorum that appear segregated due to the parasitization microhabitats,ii) a higher prevalence of mites in men than in women, iii) the existence of a high number of statistically supported double infections (skin-eyelashes). It also provides epidemiological data on the prevalence of long and short forms of D. folliculorum in a healthy young population.