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SIGNIFICANCE: This article reviews educational standard, clinical practice, research advances, and challenges associated with optometry in Nepal and provides critical considerations for contemporary and new optometry programs in countries with similar socioeconomic status and health care systems.Optometry education started in Nepal in 1998 with the primary objective of addressing the unmet needs of eye health and vision care in the country. Over the last two decades, this program has made significant contributions to facilitating and improving the delivery of quality eye care and establishing the nation's eye health system as an exemplary model in South Asia. Despite the positive impact in a short time, optometry education and the profession continue to face several challenges, including a shortage of training resources and facilities, poor quality control and regulation of practice standards, lack of professional recognition, limited pathways for entry to governmental jobs via the national public service commission, and limited clinical and academic opportunities in existing eye care programs. This article reviews current education and clinical practice standards, highlights research advances, and discusses present and future challenges in sustaining and improving the quality of education and advancing the scope of practice of optometry in Nepal. Given the limited access to primary eye care services in Nepal, appropriate professional recognition and integration into the national health system, and initiatives targeted at improving the delivery of optometry education in alignment with successful international models may provide a long-sought solution to making eye care services accessible to all and lowering the burden of visual impairment in the country.
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Optometría , Baja Visión , Humanos , Optometría/educación , Nepal , Atención a la Salud , Calidad de la Atención de Salud , EscolaridadRESUMEN
Enhancing the biocompatibility profiles including cell attachment, growth, and viability and mechanical properties of designed synthetic scaffolds have an essential role in tissue engineering applications. Polymer blending is one of the most effective methods for providing new anticipated biomaterials for tissue scaffolds. Here, the blend solution of the different mass weight ratio of polycaprolactone (PCL) to human serum albumin (HSA) was subjected to fabricate nanocomposite spider-web-like membranes using electrospinning process. The physicochemical aspects of fabricated membranes had been characterized by a different state of techniques like that of scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), contact angle meter and universal testing machine. FE-SEM images revealed that all PCL/HSA mats were composed of interlinked nano-nets along with conventional electrospun fibers while nano-nets were not found for pristine PCL mat. Moreover, composite membranes exhibited improved water absorbability, enhanced biodegradation compared to pristine PCL membrane and had much better mechanical properties (tensile strength increased by up to 3-fold, Young's modulus by 2-fold). The cell attachment and proliferation tests were carried by culturing Mc3T3-E1 (pre-osteoblasts) with the designated nanofibrous membranes. The hybrid nanofibers exhibited extraordinary support for the adhesion and proliferation of cells when compared to the pristine PCL membrane. These results indicate that the nano-nets supported PCL/HSA scaffolds can be promising for tissue engineering applications.
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Materiales Biocompatibles , Nanofibras , Ingeniería de Tejidos , Proliferación Celular , Humanos , Poliésteres , Espectroscopía Infrarroja por Transformada de Fourier , Andamios del TejidoRESUMEN
AIM: To understand how maternal and neonatal near-miss reviews could be implemented and scaled-up in rural communities through the existing district health system in Nepal. METHODS: Mixed methods with a modified time series evaluation design were used. The World Health Organization maternal and neonatal near-miss criteria used in multicountry surveys were adapted and used to define maternal and neonatal near-miss cases. RESULTS: The World Health Organization near-miss criteria were mainly applicable at the district hospital setting, but further adaptations were needed for community-level birthing centres, as organ dysfunction and critical intervention criteria were not found appropriate. In birthing centres, disease-based criteria were applicable for maternal near-miss review, and danger and clinical sign-based and condition at birth criteria were applicable for neonatal near-miss review. Primary barriers to implementation were attrition of trained staff due to the frequent transfer of healthcare providers, and time constraints of district hospital medical doctors for case-by-case reviews as they were often busy in hospital and in their private clinics. CONCLUSION: Adapted maternal and neonatal near-miss review process implementation in Nepal is feasible through the existing government health system.
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Salud del Lactante , Salud Materna , Auditoría Médica , Potencial Evento Adverso , Femenino , Implementación de Plan de Salud , Humanos , Recién Nacido , Nepal , Embarazo , Población RuralRESUMEN
The global all-ages prevalence of epidemiologically-measured 'functional' presbyopia was estimated at 24.9% in 2015, affecting 1.8 billion people. This prevalence was projected to stabilise at 24.1% in 2030 due to increasing myopia, but to affect more people (2.1 billion) due to population dynamics. Factors affecting the prevalence of presbyopia include age, geographic location, urban versus rural location, sex, and, to a lesser extent, socioeconomic status, literacy and education, health literacy and inequality. Risk factors for early onset of presbyopia included environmental factors, nutrition, near demands, refractive error, accommodative dysfunction, medications, certain health conditions and sleep. Presbyopia was found to impact on quality-of-life, in particular quality of vision, labour force participation, work productivity and financial burden, mental health, social wellbeing and physical health. Current understanding makes it clear that presbyopia is a very common age-related condition that has significant impacts on both patient-reported outcome measures and economics. However, there are complexities in defining presbyopia for epidemiological and impact studies. Standardisation of definitions will assist future synthesis, pattern analysis and sense-making between studies.
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Presbiopía , Calidad de Vida , Presbiopía/epidemiología , Presbiopía/fisiopatología , Humanos , Prevalencia , Factores de Riesgo , Salud Global , Distribución por EdadRESUMEN
Nitric oxide (NO) research in biomedicine has been hampered by the absence of a method that will allow quantitative measurement of NO in biological tissues with high sensitivity and selectivity, and with adequate spatial and temporal resolution. 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM) is a NO sensitive fluorescence probe that has been used widely for qualitative assessment of cellular NO production. However, calibration of the fluorescent signal and quantification of NO concentration in cells and tissues using fluorescent probes, have provided significant challenge. In this study we utilize a combination of mathematical modeling and experimentation to elucidate the kinetics of NO/DAF-FM reaction in solution. Modeling and experiments suggest that the slope of fluorescent intensity (FI) can be related to NO concentration according to the equation: ddtFI=2αk(1)NO(2)O(2)DAF-FMkNO+DAF-FM where α is a proportionality coefficient that relates FI to unit concentration of activated DAF-FM, k(1) is the NO oxidation rate constant, and k was estimated to be 4.3±0.6. The FI slope exhibits saturation kinetics with DAF-FM concentration. Interestingly, the effective half-maximum constant (EC(50)) increases proportionally to NO concentration. This result is not in agreement with the proposition that N(2)O(3) is the NO oxidation byproduct that activates DAF-FM. Kinetic analysis suggests that the reactive intermediate should exhibit NO-dependent consumption and thus NO(2)() is a more likely candidate. The derived rate law can be used for the calibration of DAF-FM fluorescence and the quantification of NO concentration in biological tissues.
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Fluoresceínas/química , Colorantes Fluorescentes/química , Óxido Nítrico/análisis , Óxido Nítrico/química , Calibración , Fluoresceínas/análisis , Colorantes Fluorescentes/análisis , Cinética , Oxidación-Reducción , Factores de TiempoRESUMEN
l-Arginine and its decarboxylated product, agmatine are important mediators of NO production and vascular relaxation. However, the underlying mechanisms of their action are not understood. We have investigated the role of arginine and agmatine in resistance vessel relaxation of Sprague-Dawley (SD) and Dahl salt-sensitive hypertensive rats. Second or 3rd-order mesenteric arterioles were cannulated in an organ chamber, pressurized and equilibrated before perfusing intraluminally with agonists. The vessel diameters were measured after mounting on the stage of a microscope fitted with a video camera. The gene expression in Dahl rat vessel homogenates was ascertained by real-time PCR. l-Arginine initiated relaxations (EC50, 5.8±0.7mM; n=9) were inhibited by arginine decarboxylase (ADC) inhibitor, difluoromethylarginine (DFMA) (EC50, 18.3±1.3mM; n=5) suggesting that arginine-induced vessel relaxation was mediated by agmatine formation. Agmatine relaxed the SD rat vessels at significantly lower concentrations (EC50, 138.7±12.1µM; n=22), which was compromised by l-NAME (l-N(G)-nitroarginine methyl ester, an eNOS inhibitor), RX821002 (α-2 AR antagonist) and pertussis toxin (G-protein inhibitor). The agmatine-mediated vessel relaxation from high salt Dahl rats was abolished as compared to that from normal salt rats (EC50, 143.9±23.4µM; n=5). The α-2A AR, α-2B AR and eNOS mRNA expression was downregulated in mesenteric arterioles of high-salt treated Dahl hypertensive rats. These findings demonstrate that agmatine facilitated the relaxation via activation of α-2 adrenergic G-protein coupled receptor and NO synthesis, and this pathway is compromised in salt-sensitive hypertension.
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Agmatina/farmacología , Hipertensión/fisiopatología , Arterias Mesentéricas/efectos de los fármacos , Óxido Nítrico/metabolismo , Vasodilatación/efectos de los fármacos , Animales , Arginina/farmacología , Carboxiliasas/antagonistas & inhibidores , Carboxiliasas/metabolismo , Masculino , Arterias Mesentéricas/fisiología , Ratas , Ratas Endogámicas Dahl , Ratas Sprague-DawleyRESUMEN
Dealing with the threats of vector-borne diseases necessitates robust disease surveillance systems. The gathered information from surveillance studies is used to evaluate the effectiveness of control measures. It also guides the allocation of resources within the healthcare system. The disease surveillance data also identify high-risk populations or geographic areas to target interventions. Because of the importance of surveillance in decision-making and its timely requirement, real-time data collection is vital. A few advantages of real-time data collection apps are building powerful digital forms, exporting data for quick analysis in various formats, and being open-source. These apps automate data collection and transfer to an online server even without an internet connection. While collecting disease surveillance data digitally one crucial aspect lacking is data quality. This paper aims to present the importance of dashboards that includes paradata in improving data quality using real-time data collection tools in disease surveillance. Various types of paradata such as timestamps, geo-referencing, audio recording and so on help enhance the quality of data and can help monitor and evaluate surveillance staff. The outcomes of the paradata analysis may lead to the retraining of the surveillance team and even re-planning of surveillance. Undoubtedly, real-time data collection is the way of the future in any field-based study, and studies should be planned in conjunction with paradata to ensure that high-quality data are recorded.
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BACKGROUND: Keratoconus is associated with thinning and anterior protrusion of the cornea resulting in the symptoms of blurry and distorted vision. The commonly used clinical vision tests such as visual acuity and contrast sensitivity may not reflect the symptoms experienced in keratoconus and there are no quantitative tools to measure visual distortion. In this study, we used a quantitative test based on vernier alignment and field matching techniques to quantify visual distortion in keratoconus and assess its relation to corneal structural changes. METHODS: A total of 50 participants (25 keratoconus and 25 visually normal) completed the experiment where they aligned supra-threshold white target circles in opposite field in reference to guidelines and circles to complete a square structure monocularly. The task was repeated five times and the global distortion index (GDI) and global uncertainty index (GUI) were calculated as the mean and standard deviation respectively of local perceived misalignment of target circles over five trials. RESULTS: Both GDI and GUI were higher in participants with keratoconus compared to controls (p < 0.01). Both parameters correlated with the best corrected visual acuity, maximum corneal curvature (Kmax), topographical keratoconus classification (TKC) and central corneal thickness (CCT). CONCLUSION: Our findings show that the quantitative measure of distortion could be a useful tool for behavioural assessment of progressive keratoconus.
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Queratocono , Humanos , Queratocono/diagnóstico , Topografía de la Córnea , Córnea , Agudeza Visual , Visión OcularRESUMEN
In clinical testing of visual acuity, it is often assumed that performance reflects sensory abilities and observers do not exhibit strong biases for or against specific letters, but this assumption has not been extensively tested. We re-analyzed single-letter identification data as a function of letter size, spanning the resolution threshold, for 10 Sloan letters at central and paracentral visual field locations. Individual observers showed consistent letter biases across letter sizes. Preferred letters were named much more often and others less often than expected (group averages ranged from 4% to 20% across letters, where the unbiased rate was 10%). In the framework of signal detection theory, we devised a noisy template model to distinguish biases from differences in sensitivity. When bias varied across letter templates the model fitted very well - much better than when sensitivity varied without bias. The best model combined both, having substantial biases and small variations in sensitivity across letters. The over- and under-calling decreased at larger letter sizes, but this was well-predicted by template responses that had the same additive bias for all letter sizes: with stronger inputs (larger letters) there was less opportunity for bias to influence which template gave the biggest response. The neural basis for such letter bias is not known, but a plausible candidate is the letter-recognition machinery of the left temporal lobe. Future work could assess whether such biases affect clinical measures of visual performance. Our analyses so far suggest very small effects in most settings.
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Sensibilidad de Contraste , Campos Visuales , Humanos , Agudeza Visual , Ruido , SesgoRESUMEN
INTRODUCTION: Contact lens (CL) practice is an ever-changing field with clinical knowledge, techniques and equipment continuously evolving. These new developments are backed with clinical trials and research to ensure that practitioners feel confident that there is an evidence base to support these advances. Evidence-based practice is now a crucial part of CL practice, and its importance also filters down to CL education. For example, lectures are one of the most popular tools for an educator but, is standing at the front of a lecture theatre full of students a more effective way of teaching than providing the same material for students to read by themselves? What evidence exists specific to CL education? METHOD: An expert panel of educators completed a comprehensive literature review of current evidence of teaching methods in CL training, or if not available then what can be learnt from other health care professional training that could be potentially applicable to CL education. RESULTS: Due to the amount of evidence available in the overall subject area relating to healthcare education, the initial plan of compiling evidence into one narrative review paper was discarded in favour of producing two linked papers. Here, the first paper details definitions of terminology, and also teaching methods. The second paper focuses on assessment and specific clinical training required to attain CL practice competency. In this first paper, no direct evidence of the spreading and benefit of new education strategies evidence such as flipped classrooms, spaced learning, test-enhanced learning, group work, CBL, PBL, TBL, and reflective practice in CL education was found. The only technique that was widely used in the CL field was case reports and the group discussion of them. Nevertheless, the authors found a consensus of opinion from other disciplines that are transferable to CL teaching and could help students meet the intended learning outcomes. CONCLUSION: There is a small amount of evidence supporting CL education, but most of this seems to be related to the practical element of the training. However, there is a lot of evidence in the field of healthcare education from related disciplines which provides additional but important learning tools that may be effectively implemented in CL education.
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Personal de Salud , Estudiantes , Humanos , EnseñanzaRESUMEN
PURPOSE: All neophyte contact lens wearers require training on how to handle contact lenses. Currently, almost no published information exists describing the most common approaches used by those involved in such training in soft contact lens wearers. This study aimed to gather information on the approaches taken by those conducting this training worldwide. METHODS: An online survey was created in English and translated to Spanish and distributed internationally via social media, conference attendees, and professional contacts. The anonymous survey included information on workplace setting of respondents, information about the typical approaches used for application and removal of soft contact lenses, length of the appointment, and success rate with their approach. Survey responses were received between May 2021 and April 2022. RESULTS: A total of 511 individuals completed the survey and responses were received from 31 countries with 48.7% from the UK. The most common approach taught for application was to have the patient hold the upper eyelashes (84.7%) and to hold the lower eyelid with the same hand as the lens (89.4%). Lenses were applied directly to the cornea by 57.7% of the respondents. The most common approach taught for lens removal was to drag the lens inferiorly from the cornea prior to removal (49.3%). Most respondents did not use videos to aid the teaching appointment (62.0%); however, they felt that their approach was successful in most cases (90). Application and removal training sessions lasted a median of 30 min and contact lenses were typically dispensed after the instructor witnessing successful application and removal three times. CONCLUSION: Various methods are adopted globally for training of application and removal of soft contact lenses, with many advising a patient-specific approach is required for success. The results of this survey provide novel insights into soft contact lens handling training in clinical practice.
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Lentes de Contacto Hidrofílicos , Humanos , Córnea , Párpados , Encuestas y CuestionariosRESUMEN
With the expected rise in Alzheimer's disease and related dementias (ADRD) in the coming decades due to the aging population and a lack of effective disease-modifying treatments, there is a need for preventive strategies that may tap into resilience parameters. A wide array of resilience strategies has been proposed including genetics, socioeconomic status, lifestyle modifications, behavioral changes, and management of comorbid disease. These different strategies can be broadly classified as distinguishing between modifiable and non-modifiable risk factors, some of which can be quantified so that their clinical intervention can be effectively accomplished. A clear shift in research focus from dementia risk to addressing disease resistance and resilience is emerging that has provided new potential therapeutic targets. Here we review and summarize the latest investigations of resilience mechanisms and methods of quantifying resilience for clinical research. These approaches include identifying genetic variants that may help identify novel pathways (e.g., lipid metabolism, cellular trafficking, synaptic function, inflammation) for therapeutic treatments and biomarkers for use in a precision medicine-like regimen. In addition, innovative structural and molecular neuroimaging analyses may assist in detecting and quantifying pathological changes well before the onset of clinical symptoms setting up the possibility of primary and secondary prevention trials. Lastly, we summarize recent studies demonstrating the study of resilience in caregivers of persons living with dementia may have direct and indirect impact on the quality of care and patient outcomes.
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Enfermedad de Alzheimer , Humanos , Anciano , Enfermedad de Alzheimer/patología , Encéfalo/diagnóstico por imagen , Encéfalo/patología , Envejecimiento/patología , Estilo de Vida , CogniciónRESUMEN
Optometry education in Nepal began in 1998 in collaboration with the University of Auckland, New Zealand, with the primary objective of addressing the unmet needs of eye health and vision care. Over the last two decades, the development of optometry education has seen significant progress, including a shift from a three-year to a four-year curriculum, an increase in the uptake of students, and recent launches of two additional bachelor's degree and a master's degree programmes. Complementary to the educational progress, several professional advances have occurred in the intervening years. These include the formation of the Nepalese Association of Optometrists that oversees the professional development and the rights, welfare, security, and protection of Optometrists, memberships into the World Council of optometry and the Asia Pacific Council of optometry, integration of the profession into the governmental regulatory body Nepal Health Professional Council, and formulation of the code of ethics and minimum requirements for a Bachelor's level University degree in optometry. This article briefly presents the historical events leading to the establishment of optometry in Nepal and the evolution of the program in the intervening years.
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Optometristas , Optometría , Personal de Salud , Humanos , Nepal , UniversidadesRESUMEN
Agricultural waste-based cellulose fibers have gained significant interest for a myriad of applications. Grewia optiva (G. optiva), a plant species, has been widely used for feeding animals, and the small branches' bark is used for making rope. Herein, we have extracted cellulose fibers from the bark of G. optiva species via chemical treatments (including an alkaline treatment and bleaching). The gravimetric analysis revealed that the bark of G. Optiva contains cellulose (63.13%), hemicellulose (13.52%), lignin (15.13%), and wax (2.8%). Cellulose microfibre (CMF) has been synthesized from raw fibre via chemical treatment methods. The obtained cellulose fibers were crosslinked and employed as the matrix to encapsulate the bioactive plant extracts derived from the root of Catharanthus roseus (C. roseus). The microscopic images, XRD, FTIR, and antibacterial/antioxidant activity confirmed the encapsulation of natural extracts in the cellulose microfiber. The microscopic images revealed that the encapsulation of the natural extracts slightly increased the fiber's diameter. The XRD pattern showed that the extracted cellulose microfiber had an average crystalline size of 2.53 nm with a crystalline index of 30.4% compared to the crystalline size of 2.49 nm with a crystalline index of 27.99% for the plant extract incorporated membrane. The water uptake efficiency of the synthesized membrane increased up to 250%. The antimicrobial activity of the composite (the CMF-E membrane) was studied via the zone inhibition against gram-positive and gram-negative bacteria, and the result indicated high antibacterial activity. This work highlighted G. optiva-derived cellulose microfiber as an optimum substrate for antimicrobial scaffolds. In addition, this paper first reports the antimicrobial/antioxidant behavior of the composite membrane of the C. roseus extract blended in the G. optiva microfiber. This work revealed the potential applications of CMF-E membranes for wound healing scaffolds.
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AIM: To determine if a gradual adaptation period is necessary for neophytes when fitted with modern hydrogel or silicone hydrogel reusable disposable contact lenses. METHOD: Across four sites, 74 neophytes (18-28 years) were randomly assigned to a reusable lens cleaned nightly with Opti-Free® Puremoist® multi-purpose contact lens solution: Proclear® (hydrogel) or Biofinity® (silicone hydrogel) and an adaptation schedule: fast (10 h wear from the first day) or gradual (4 h on the first day, increasing their wear time by 2 h on each subsequent day until they had reached 10 h). Masked investigators graded ocular surface physiology and non-invasive tear breakup time (NIBUT) and a range of comfort, vision and lens handling subjective ratings (0-100 visual analogue scales) were recorded at the baseline visit and after 10 h of lens wear, 4-6 days and 12-14 days after lens fitting. Subjective scores were also repeated after 7 days. RESULTS: There was no difference (p > 0.05) in ocular surface physiology or NIBUT between fast and gradual adaptation groups at any time point in either lens type with the exception of increased corneal staining (p = 0.019) in the silicone hydrogel fast adaptation group after 4-6 days, but was similar by 12-14 days. Subjective scores were also similar across the visits and lens types with the exception of 'lens awareness' (p = 0.019) which was less in the gradual versus the fast adaptation silicone hydrogel lens group at 12-14 days. CONCLUSION: There seems to be no clinical benefit for recommending a gradual adaptation period in new wearers fitted with modern soft reusable disposable contact lenses. The findings of this work add to a growing body of evidence suggesting that such advice is unnecessary in regular soft contact lens wear, which has important ramifications for the initial clinical management of these patients.
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Lentes de Contacto Hidrofílicos , Hidrogel de Polietilenoglicol-Dimetacrilato , Humanos , Hidrogeles , Satisfacción del Paciente , SiliconasRESUMEN
Sloan letters are one of the most commonly used optotypes in clinical practice. Sloan letters have different relative legibility which could be due to three factors: perceivability, response bias, and similarity. Similarities between Sloan letters are known to be the major source of errors in threshold determination. However, little is known about the effect of response biases on the resolution thresholds. The aim of the present study was to investigate the effect of response bias and similarity on resolution thresholds of Sloan letters in central and paracentral vision. Eight subjects with normal ocular health participated in this study. Using the method of constant stimuli, we measured resolution thresholds for the Sloan letters set at 0° (central) and ± 3° eccentricity along the vertical meridian of the visual field. We calculated thresholds from data pooled across the 10 Sloan letters (pooled threshold). For further analysis we also calculated thresholds for each of the 10 Sloan letters (individual threshold). Response biases and letter similarities were determined using Luce's choice model. Results showed statistically significant differences between the mean individual thresholds of Sloan letters at the central and the upper visual field, but not at the lower visual field. For equally-sized letters at pooled threshold, unlike letter similarity, response biases showed statistically significant correlations to the differences in individual thresholds at the central, upper and lower visual field locations. For equally legible letters at individual thresholds, response biases and similarities showed no significant correlations to the differences in individual thresholds at the central, the upper and the lower visual field locations. These results suggest that, for equally-sized letters at pooled threshold, the response biases may lead to an underestimation of the pooled threshold, i.e. an overestimation of visual acuity measurements when using Sloan letters.
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Pruebas de Visión , Campos Visuales , Sesgo , Ojo , Humanos , Umbral Sensorial , Agudeza VisualRESUMEN
PURPOSE: To determine the causes of visual impairment and the use of low vision devices in patients attending the low vision clinic in Trinidad and Tobago. METHODS: A retrospective study of the 222 patients attending the low vision clinic at the University of the West Indies, St Augustine Campus was conducted. The presenting visual acuity, causes of low vision and blindness, and prescribed low vision devices were recorded and analysed to determine the major causes of visual impairment and improvement in visual acuity with low vision aids. RESULTS: Out of the total 222 participants, 66.66% (n = 148) had low vision while the rest (33.33%, n = 74) were legally blind. Glaucoma was the major cause of low vision (31.08%) and blindness (28.38%) followed by diabetic retinopathy (20.94%, low vision and 20.27%, blindness). A total of 193 low vision devices were prescribed, 79.79% (n = 154) near devices and 20.20% (n = 39) distance devices. The low vision devices were effective in improving both near visual acuity (120 participants reading 1M or 2M) and distance visual acuity (VA better than 3/60). CONCLUSION: The major causes of vision impairment in Trinidad and Tobago were glaucoma and diabetic retinopathy and low vision devices are effective in improving visual acuity. A comprehensive approach to dealing with the causes of low vision and low vision services are required to mitigate the burden of visual impairment in the country.
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Baja Visión , Ceguera , Humanos , Prevalencia , Estudios Retrospectivos , Trinidad y Tobago/epidemiología , Trastornos de la Visión , Baja Visión/epidemiología , Baja Visión/etiologíaRESUMEN
Global motion and global form are proposed to be processed through functionally differentiated independent channels along dorsal (motion) and ventral (form) pathways. However, more recent studies show significant interactions between these pathways by inducing the perception of motion (implied motion) from presenting the independent frames of static Glass patterns. The mechanisms behind such interaction are not adequately understood with studies showing a larger contribution of either a motion or form processing mechanism. In the current study, we adapted the equivalent noise paradigm to disentangle the effect of internal noise (local processing) and sampling efficiency (global processing) on global motion, global form, and the interaction of both on the perception of implied motion using physically equivalent stimuli. Six visually normal observers discriminated the direction or orientation of random dot kinematograms (RDK), static Glass patterns (Glass), and dynamic Glass patterns (dGlass) whose directions/orientations were determined by the means of normal distributions with a range of direction/orientation variances that served as external noise. Thresholds (τ) showed a consistent pattern across observers and external noise levels, where τGlass > τdGlass > τRDK. Nested model comparisons where the thresholds were related to the external noise, internal noise, and the sampling efficiency revealed that the difference in performance between the tasks was best described by the change in sampling efficiency with invariable internal noise. Our results showed that the higher thresholds for implied motion compared to real motion could be due to inefficient pooling of local dipole orientation cues at global processing stages involving motion mechanisms.
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Percepción de Forma , Percepción de Movimiento , Señales (Psicología) , Movimientos Oculares , Movimiento (Física) , Distribución Normal , Estimulación Luminosa , Umbral SensorialRESUMEN
Natural hydrogel scaffolds usually exhibit insufficient mechanical strength which remains a major challenge in bone tissue engineering. In this study, the limitation was addressed by incorporating regenerated cellulose (rCL) nanofibers into chitosan (CS) hydrogel. The rCL nanofibers were regenerated from deacetylation of electrospun cellulose acetate (CA) nanofibers. As-prepared rCL/CS composite scaffold showed unique porous morphology with rCL nanofibers imbibed CS matrix. The compressive strength test exhibited that the rCL/CS scaffold have higher compressive strength compared to pure CS. The rCL/CS scaffold showed increased biomineralization and enhanced pre-osteoblast cell (MC3T3-E1) viability, attachment, and proliferation. The alkaline phosphatase (ALP) and alizarin red (ARS) staining results suggested that the osteogenic differentiation ability was improved in rCL/CS composite scaffold. Hence, the novel fabrication idea and the obtained results suggested that the rCL/CS composite hydrogel scaffolds could be a promising three-dimensional bio-scaffold for bone tissue engineering.