View clinical trials related to Vitamin A Deficiency.
Filter by:Reduced quality of vision and glare in twilight or night are frequently mentioned complaints within the optometric examination. A reason for these problems could be a myopic refractive shift in dark light conditions, commonly known as night myopia or twilight myopia. The aim of this study was to investigate whether quality of vision in twilight or night could be improved by a spectacle correction optimized for mesopic light conditions. Moreover, objective refraction in large pupils measured by aberrometry was compared to subjective mesopic refraction.
This pilot study will evaluate the visual response to infrared (IR) in humans after dark adaptation. The investigators plan to determine which wavelength and intensity the human eye is most sensitive too, using a broad spectrum light source and wavelength-specific bandpass filters. The investigators will then evaluate the electrophysiologic response in healthy humans to IR, followed by studies in those with specific retinal diseases. The long-term goal of this research is to better understand the role that IR plays in visual function, and whether this can be manipulated to allow for vision in certain retinal pathologies that result from loss of photoreceptor cells. The investigators central objective is to test the electrophysiologic response to IR in the dark-adapted retinal and visual pathways. The investigators central hypothesis is that IR evokes a visual response in humans after dark adaptation, and the characteristics of this response suggest transient receptor potential (TRP) channel involvement. The investigators rationale is that a better understanding of how IR impacts vision may allow for an alternative mechanism for vision in a number of diseases that cause blindness from the degradation or loss of function of photoreceptor cells. The investigators will test the investigators hypothesis with the following Aims: Aim 1: To determine the optimal IR wavelength for visual perception in dark-adapted human participants. The investigators hypothesize that the healthy human eye will detect IR irradiation, with a maximum sensitivity at a specific wavelength. Using a broad-spectrum light source with wavelength-specific bandpass filters, the spectral range of visual perception to IR will be evaluated. The same will be done on colorblind participants. Aim 2: To test the electrophysiologic response to IR in healthy humans after dark adaptation. The investigators hypothesize that IR will elicit an amplitude change on electroretinography (ERG) and visual evoked potential (VEP) responses after dark adaptation in healthy human participants. Participants will be tested with both test modalities to evaluate their response to IR. Aim 3: To test the electrophysiologic response to IR after dark adaptation in humans with certain retinal diseases. Participants with retinitis pigmentosa, age related macular degeneration and congenital stationary night blindness, will be tested. Results will be compared to baselines and to those of healthy participants. The investigators hypothesize that there will be a response to IR on ERG and VEP, which will provide clues to the retinal cell layer location of the response to IR and the nature of potential TRP channel involvement.
Corn-soy vitamin and mineral fortified blended foods (FBFs) are primarily used for food aid, although sorghum and cowpea may be suitable alternative FBF commodities. The objective of the Micronutrient Fortified Food Aid Pilot Project (MFFAPP) Tanzania Efficacy Study is to determine whether newly formulated, extruded sorghum- and cowpea-based FBFs have equal, or better, nutritive value and acceptance compared to a traditional corn-soy blend. The effectiveness of each blend will be determined in an efficacy study of Tanzanian children under the age of 5 that are deficient, or at risk for deficiency, in iron and vitamin A.
The purpose of this randomized control trial is to test the impact of provitamin A carotenoid biofortified maize meal consumption on maternal and infant vitamin A status.
The overall objective is to determine the impact of EED on zinc absorption and homeostasis, and its impact on the absorptive capacity of vitamin A absorption of young children (18-24 months of age) in an austere setting with high rates of diarrhea, stunting, and micro-nutrient deficiencies.
The objective will be to quantify the vitamin A equivalence of the provitamin A in transgenic biofortified bananas.
In this study, meals based on multiple food crops (containing either biofortified or commercially-available food crops) will be fed to young children in Madanapalle, Andhra Pradesh, India over a period of nine months to measure growth, cognitive changes, and immune function in comparison to children receiving non-biofortified crops. Mothers of the participating children will also be included in the study.
The study comprises an open-label randomized controlled trial investigating the efficacy of consuming a daily ration of pro-vitamin A biofortified cassava on vitamin A status of Nigerian children, aged 3-4 years old (n=200).
The My Retina Tracker® Registry is sponsored by the Foundation Fighting Blindness and is for people affected by one of the rare inherited retinal degenerative diseases studied by the Foundation. It is a patient-initiated registry accessible via a secure on-line portal at www.MyRetinaTracker.org. Affected individuals who register are guided to create a profile that captures their perspective on their retinal disease and its progress; family history; genetic testing results; preventive measures; general health and interest in participation in research studies. The participants may also choose to ask their clinician to add clinical measurements and results at each clinical visit. Participants are urged to update the information regularly to create longitudinal records of their disease, from their own perspective, and their clinical progress. The overall goals of the Registry are: to better understand the diversity within the inherited retinal degenerative diseases; to understand the prevalence of the different diseases and gene variants; to assist in the establishment of genotype-phenotype relationships; to help understand the natural history of the diseases; to help accelerate research and development of clinical trials for treatments; and to provide a tool to investigators that can assist with recruitment for research studies and clinical trials.
The combination of infectious diseases and malnutrition is the most prevalent, preventable public health problem in the world, responsible for millions of deaths annually, particularly in infants and children. Approximately 13 million children die each year in developing countries from infectious diseases, with the majority of these deaths related to malnutrition. The relationship between infections and malnutrition is synergistic, each further compromising the outcome of the other. Malnutrition compromises natural immunity leading to increased susceptibility to infections, more frequent and prolonged disease episodes, and increased severity of disease. Likewise, infections can aggravate or precipitate malnutrition through decreased appetite and food intake, nutrient malabsorption, nutrient loss or increased metabolic needs. Another issue is that infections (as well as overweight and obesity status) affect nutritional biomarkers making it difficult to assess the real magnitude of some nutritional problems. This is the case of vitamin A. Vitamin A deficiency is defined to be of severe public health importance if 20% or more of a defined population has a serum retinol concentration of less than 0.7 µmol/L. However, circulating concentrations of serum retinol are reduced by infections and in such situations serum retinol concentration is not a good indicator of vitamin A status. Serum acute-phase proteins can indicate the severity and duration of an infection. Correcting vitamin A deficiency is addressed in Ethiopia through vitamin A supplementation of children, dietary diversity and using bio-fortified foods. However, assessing vitamin A status, and the effectiveness of government interventions, is challenging in settings where infectious diseases are endemic, as in most area of the country. Evaluation of vitamin A status is relatively insensitive when based on changes in serum retinol concentrations, which are homeostatically controlled and negatively affected by subclinical infections. Liver stores of vitamin A, the best indicator of vitamin A status, cannot be routinely evaluated. The isotope dilution technique is the preferred method for determining vitamin A status and assessing the efficacy and effectiveness of intervention programs aimed at improving vitamin A status. It is the only indirect assessment method that provides a quantitative estimate of vitamin A status across the continuum of deficient to excessive stores.