Prevalence and Causes of Avoidable Blindness in Subjects Over 50 Years of Age in Honduras.

Purpose: To describe the prevalence and causes of avoidable blindness in people aged 50 and over in the areas of influence of doctors in social service during the years 2018-2019. Methods: This observational, descriptive, cross-sectional study, with analysis of association of variables, was conducted on patients 50 years and older at the national level, selected under simple random sampling, where sociodemographic variables, background, and clinical characteristics were studied. An ophthalmological clinical examination was performed with prior informed consent, and the information was processed and analyzed using Epi Info 7.2 statistical package and SPSS version 25. Results: Overall, 7992 people were evaluated, with a mean age of 62 years; 60.8% (4861) were women and 39.2% (3131) were men. The prevalence of blindness for both eyes was 4.5% (356/7992, 95% CI: 4.1-5.1%, p < 0.001). The prevalence of severe and moderate visual impairment was 1.5% (118/127) and 12.9% (1029)/12.6% (1004) for the right and left eyes, respectively. The main causes of blindness were cataract, refractive error, and glaucoma. Conclusion: The prevalence of avoidable blindness found in the study was higher than expected and the respective causes were consistent with previous studies. Consequently, it is recommended to implement health policies aimed at the prevention and management of avoidable blindness.

Validez del tamizaje de agudeza visual realizado por maestros de escuelas primarias / Validity of visual acuity screening by elementary school teachers

Marco conceptual:El manejo y detección de ametropías en la niñez es multidisciplinario. Los programas de tamizaje incluyen maestros, pediatras, oftalmólogos y optometristas, con el fin de corregir y prevenir la ambliopía. Objetivo: Evaluar la efectividad del tamizaje realizado por maestros que fueron capacitados en la toma de agudeza visual. Metodología: Se realizó estudio de concordancia en donde el universo lo constituyeron 33 maestros de las Escuelas primarias República de Nicaragua, Reino de los Países Bajos y República de Paraguay del sector público del municipio del Distrito Central de Honduras.El estudio se llevó a cabo en el año lectivo 2015 entre los meses de mayo a julio. Se evaluaron 840 estudiantes matriculados de primero a sexto grado. La medición de la agudeza visual se realizó utilizando la Cartilla Snellen, tomando como punto de corte mediciones menores a 20/30 en el mejor ojo. Los estudiantes con dicha agudeza visual fueron examinados por los médicos residentes cuya evaluación fue considerada el gold estándar del estudio para determinar la sensibilidad y especificidad de las mediciones realizadas por los maestros. Resultados: La sensibilidad y especificidad del tamizaje ejecutado por los maestros fue de 100% y 74% respectivamente. El resultado de índice de Kappa de Cohen fue de 0.65. Conclusiones: los resultados del presente estudio indican que el tamizaje de agudeza visual realizado por los maestros presenta validez aceptable para identificar casos positivos de disminución de agudeza visual y que es mejor elegir una prueba muy sensible si se prefiere obtener falsos positivos en lugar de falsos negativos...(AU)

Encuesta nacional de ceguera y deficiencia visual evitables en Honduras / National survey of blindness and avoidable visual impairment in Honduras

OBJETIVO: Determinar la prevalencia de ceguera y deficiencia visual en Honduras, sus causas y la respuesta que los servicios de salud están dando a la creciente demanda. MÉTODOS: Estudio poblacional transversal realizado entre junio y diciembre de 2013 mediante la metodología estándar de evaluación rápida de ceguera evitable. Se realizó un muestreo aleatorio en 63 conglomerados de 50 personas de 50 años o más, representativo de todo el país. Se evaluó la agudeza visual (AV) mediante una cartilla de Snellen y el estado del cristalino y del polo posterior por oftalmoscopía directa. Se calculó la cobertura de cirugía de catarata y se evaluó su calidad, las causas de tener AV < 20/60 y las barreras para acceder al tratamiento quirúrgico. RESULTADOS: Se examinaron 2 999 personas (95,2% del total previsto). La prevalencia de ceguera fue de 1,9% (intervalo de confianza de 95%: 1,4-2,4%) y 82,2% de esos casos era evitable. La catarata no operada fue la causa principal de ceguera (59,2%), seguida del glaucoma (21,1%). Los errores de refracción no corregidos fueron la principal causa de deficiencia visual, tanto severa (19,7%) como moderada (58,6%). La cobertura de cirugía de catarata fue de 75,2%. De los ojos operados de catarata, 62,5% alcanzó una AV ≥ 20/60 con la corrección disponible. Las principales barreras para someterse a la cirugía de catarata fueron el costo (27,7%) y la falta de disponibilidad o de acceso geográfico al tratamiento (24,6%). CONCLUSIONES: La prevalencia de ceguera y deficiencia visual en Honduras es similar a la de otros países latinoamericanos. Mejorar la capacidad resolutiva de los servicios oftalmológicos, especialmente de cirugía de catarata, desarrollar los servicios ópticos y la atención ocular incorporada en la atención primaria en salud, podrían resolver el 67% de los casos de ceguera.

OBJECTIVES: To determine the prevalence of blindness and visual impairment in Honduras, its causes and the response by the health services to growing demand. METHODS: A cross-sectional population study was conducted between June and December 2013 using the standard methodology of the Rapid Assessment of Avoidable Blindness. A random sample survey was done in 63 clusters of 50 individuals aged ≥ 50, representative of the country as a whole. Visual acuity (VA) was assessed using a Snellen eye chart, and the condition of the lens and posterior pole was examined by direct ophthalmoscopy. Cataract surgical coverage was calculated and an assessment made of its quality, the causes of VA < 20/60 and the barriers to accessing surgical treatment. RESULTS: A total of 2 999 people were examined (95.2% of the forecast total). Blindness prevalence was 1.9% (confidence interval of 95%: 1.4-2.4%) and 82.2% of these cases were avoidable. The main causes of blindness were unoperated cataracts (59.2%) and glaucoma (21.1%). Uncorrected refraction error was the main cause of severe (19.7%) and moderate (58.6%) visual impairment. Cataract surgical coverage was 75.2%. 62.5% of the eyes operated for cataracts achieved a VA > 20/60 with available correction. The main barriers against cataract surgery were cost (27.7%) and the lack of availability or difficulty of geographical access to the treatment (24.6%). CONCLUSIONS: The prevalence of blindness and visual impairment in Honduras is similar to that of other Latin American countries. 67% of cases of blindness could be resolved by improving the response capacity of the ophthalmological services, especially of cataract surgery, improving optician services and incorporating eye care in primary health care.

[National survey of blindness and avoidable visual impairment in Honduras]. / Encuesta nacional de ceguera y deficiencia visual evitables en Honduras.

OBJECTIVES: To determine the prevalence of blindness and visual impairment in Honduras, its causes and the response by the health services to growing demand. METHODS: A cross-sectional population study was conducted between June and December 2013 using the standard methodology of the Rapid Assessment of Avoidable Blindness. A random sample survey was done in 63 clusters of 50 individuals aged ≥ 50, representative of the country as a whole. Visual acuity (VA) was assessed using a Snellen eye chart, and the condition of the lens and posterior pole was examined by direct ophthalmoscopy. Cataract surgical coverage was calculated and an assessment made of its quality, the causes of VA < 20/60 and the barriers to accessing surgical treatment. RESULTS: A total of 2 999 people were examined (95.2% of the forecast total). Blindness prevalence was 1.9% (confidence interval of 95%: 1.4-2.4%) and 82.2% of these cases were avoidable. The main causes of blindness were unoperated cataracts (59.2%) and glaucoma (21.1%). Uncorrected refraction error was the main cause of severe (19.7%) and moderate (58.6%) visual impairment. Cataract surgical coverage was 75.2%. 62.5% of the eyes operated for cataracts achieved a VA > 20/60 with available correction. The main barriers against cataract surgery were cost (27.7%) and the lack of availability or difficulty of geographical access to the treatment (24.6%). CONCLUSIONS: The prevalence of blindness and visual impairment in Honduras is similar to that of other Latin American countries. 67% of cases of blindness could be resolved by improving the response capacity of the ophthalmological services, especially of cataract surgery, improving optician services and incorporating eye care in primary health care.

A new method for respiratory gating during microcomputed tomography of lung in mice.

This study investigated the use of regulated cyclic breath-holds to improve microcomputed tomography (microCT) imaging of small (diameter, less than 1 mm) mouse lung tumors in vivo. Two novel techniques that use a modified small-animal ventilator were examined and compared with a previously used respiratory gating microCT technique and a free-breathing microCT technique. Two mice were scanned with each of these 4 microCT techniques (voxel size, 92 microm). The appearance of small lung tumors (maximal diameter, 0.5 to 1.0 mm) and the characteristics of line profiles of the lung-diaphragm boundary were used to compare the images obtained from the 4 acquisition techniques. The use of cyclic breath-holds, synchronized with the CT exposures, led to marked improvement in the visualization of the mouse lung structure and lesion conspicuity. A secondary experiment was performed to assess the stress placed on mice by the acquisition techniques.

Hyaluronic acid-paclitaxel: antitumor efficacy against CD44(+) human ovarian carcinoma xenografts.

Numerous human tumor types, including ovarian cancer, display a significant expression of the CD44 family of cell surface proteoglycans. To develop tumor-targeted drugs, we have initially evaluated whether the CD44 ligand hyaluronic acid (HA) could serve as a backbone for paclitaxel (TXL) prodrugs. HA-TXL was prepared by modification of previous techniques. The in vitro cytotoxicity of HA-TXL against the CD44(+) human ovarian carcinoma cell lines SKOV-3ip and NMP-1 could be significantly blocked by preincubation with a molar excess of free HA. Female nude mice bearing intraperitoneal implants of NMP-1 cells were treated intraperitoneally with a single sub-maximum tolerated dose dose of HA-TXL or with multiple-dose regimens of paclitaxel (Taxol; Mead Johnson, Princeton, NJ) to determine the effects of these regimens on host survival and intraperitoneal tumor burden, with the latter being assessed by magnetic resonance imaging. NMP-1 xenografts were highly resistant to Taxol regimens, as host survival was only nominally improved compared to controls (T//C approximately 120), whereas single-dose HA-TXL treatment significantly improved survival in this model (T//C approximately 140; P = .004). In both NMP-1 and SKOV-3ip models, MR images of abdomens of HA-TXL-treated mice obtained shortly before controls required humane sacrifice revealed markedly reduced tumor burdens compared to control mice. This study is among the first to demonstrate that HA-based prodrugs administered locoregionally have antitumor activity in vivo.

Magnetic resonance imaging of therapy-induced necrosis using gadolinium-chelated polyglutamic acids.

PURPOSE: Necrosis is the most common morphologic alteration found in tumors and surrounding normal tissues after radiation therapy or chemotherapy. Accurate measurement of necrosis may provide an early indication of treatment efficacy or associated toxicity. The purpose of this report is to evaluate the selective accumulation of polymeric paramagnetic magnetic resonance (MR) contrast agents--gadolinium p-aminobenzyl-diethylenetriaminepentaacetic acid-poly(glutamic acid) (L-PG-DTPA-Gd and D-PG-DTPA-Gd)--in necrotic tissue. METHODS AND MATERIALS: Two different solid tumor models, human Colo-205 xenograft and syngeneic murine OCA-1 ovarian tumors, were used in this study. Necrotic response was induced by treatment with poly(L-glutamic acid)-paclitaxel conjugate (PG-TXL). T(1)-weighted spin-echo images were obtained immediately and up to 4 days after contrast injection and compared with corresponding histologic specimens. Two low-molecular-weight contrast agents, DTPA-Gd and oligomeric(L-glutamic acid)-DTPA-Gd, were used as nonspecific controls. RESULTS: Initially, there was minimal tumor enhancement after injection of either L-PG-DTPA-Gd or D-PG-DTPA-Gd, but rapid enhancement after injection of low-molecular-weight agents. However, polymeric contrast agents, but not low-molecular-weight contrast agents, caused sustained enhancement in regions of tumor necrosis in both tumors treated with PG-TXL and untreated tumors. These data indicate that high molecular weight, rather than in vivo biodegradation, is necessary for the specific localization of polymeric MR contrast agents to necrotic tissue. Moreover, biotinylated L-PG-DTPA-Gd colocalized with macrophages in the tumor necrotic areas, suggesting that selective accumulation of L- and D-PG-DTPA-Gd in necrotic tissue was mediated through residing macrophages. CONCLUSIONS: Our data suggest that MR imaging with PG-DTPA-Gd may be a useful technique for noninvasive characterization of treatment-induced necrosis.

Breath-hold device for laboratory rodents undergoing imaging procedures.

The increased use in noninvasive imaging of laboratory rodents has prompted innovative techniques in animal handling. Lung imaging of rodents can be a difficult task because of tissue motion caused by breathing, which affects image quality. The use of a prototype flat-panel computed tomography unit allows the acquisition of images in as little as 2, 4, or 8 s. This short acquisition time has allowed us to improve the image quality of this instrument by performing a breath-hold during image acquisition. We designed an inexpensive and safe method for performing a constant-pressure breath-hold in intubated rodents. Initially a prototypic manual 3-way valve system, consisting of a 3-way valve, an air pressure regulator, and a manometer, was used to manually toggle between the ventilator and the constant-pressure breath-hold equipment. The success of the manual 3-way valve system prompted the design of an electronically actuated valve system. In the electronic system, the manual 3-way valve was replaced with a custom designed 3-way valve operated by an electrical solenoid. The electrical solenoid is triggered by using a hand-held push button or a foot pedal that is several feet away from the gantry of the scanner. This system has provided improved image quality and is safe for the animals, easy to use, and reliable.

Intraperitoneal administration of an iodine-based contrast agent to improve abdominal micro-computed tomography imaging in mice.

The purpose of this study was to estimate the optimal volume of an iodine-based contrast agent to administer to mice via intraperitoneal injection and the optimal time after injection to perform micro-computed tomography for maximal enhancement of abdominal organs. Eight mice were paired randomly; three pairs underwent imaging after receiving intraperitoneal injections of 125, 250, or 500 microl of contrast agent, and the fourth pair underwent imaging without receiving an injection. Each mouse was scanned three consecutive times, and each scan lasted 25 min so that we could observe the clearance of the contrast agent from the abdomen. We determined that introducing 250 microl of contrast agent into the abdominal cavity of the mice and then having the mice undergo micro-computed tomography 15 min after injection provided the optimal degree of contrast enhancement needed to distinguish the abdominal organs. These results may lead to expanded use of this imaging modality to assess abdominal organ margins in small-animal studies in vivo.

Effects of insulin-like growth factor-1 (IGF-1) and amifostine in spinal cord reirradiation.

PURPOSE: To test whether insulin-like growth factor-1 (IGF-1) and amifostine modulate the reirradiation tolerance of rat cervical spinal cord. Initial experiments by the authors' group suggested that administration of each agent alone significantly increased the median latent time to radiation myelopathy (RM) in previously unirradiated animals but did not change the dose-response relationship. Because of different modes of action, a follow-up study was undertaken to test the combined treatment. MATERIAL AND METHODS: The cervical spinal cord of 51 adult Fisher F-344 rats received a single fraction of 16 Gy, which corresponds to approximately 75% of the median paresis dose (ED(50)), followed 5 months later by a second radiation dose, which ranged from 17 to 21 Gy. The study animals received a single intrathecal injection of 0.3 mg amifostine into the cisterna magna 30-60 min before reirradiation plus three subcutaneous doses of IGF-1 (700 microg) starting from 24 h before to 24 h after reirradiation. Control animals received saline injections via the same routes. Animals were followed until RM developed or until 12 months from reirradiation. Histopathologic examinations were performed post mortem. RESULTS: No animals showed any neurologic abnormalities before reirradiation. RM occurred in controls versus treated rats after a mean latency of 218 versus 314 days (19 Gy; p = 0.11) and 104 versus 186 days (21 Gy; p = 0.002) from second dose (Figure 1). ED(50) was 18.2 versus 19.4 Gy (p = 0.15; Figure 2). Treatment with IGF-1 and amifostine did not significantly influence the rates of tumor induction or intercurrent death. CONCLUSION: IGF-1 and amifostine significantly reduced RM rates after 21 Gy. The shift of the dose-response curve suggests an increase of the ED(50) for single-dose treatment by approximately 7%. Thus, brief therapeutic intervention might slightly decrease radiation-induced neurotoxicity in a retreatment situation.

Canine transmissible venereal tumor: a large-animal transplantable tumor model.

The canine transplantable venereal tumor is a naturally occurring transplantable round-cell tumor in dogs. Although experimental transplantable tumor models in rodents and rabbits are readily available, a reliable transplantable tumor model in a large animal that more closely resembles the physical dimensions of humans has not been available. A tumor model in a large animal would have a wide range of biomedical research applications, including the study of various interventional imaging techniques. In this report, we characterize the experimental transplantation of the canine transmissible venereal tumor in the brain, skin, muscle, prostate, lung, liver, and bone of dogs and provide X-ray computed tomographic and magnetic resonance imaging characteristics of the tumors in the brain, muscle, lung, and prostate.

Potential role of growth factors in diminishing radiation therapy neural tissue injury.

Human growth factors are firmly established in treatment of cytopenias that are associated with cancer chemotherapy, and have been used successfully to reduce severe mucositis in patients receiving radiation therapy and chemotherapy in the setting of autologous bone marrow transplantation. The ability of growth factors that are involved in differentiation and proliferation of neural tissue cells to prevent or accelerate recovery from radiation injury currently is being evaluated in preclinical studies. Data from these studies indicate that brief therapeutic intervention with platelet-derived growth factor, insulin-like growth factor-1, vascular endothelial growth factor, and the combination of insulin-like growth factor-1 and basic fibroblast growth factor can prevent or delay radiation myelopathy after spinal cord irradiation. Additional investigation is required to define potentially clinically useful growth factor regimens in the clinic.

Evaluation of insulin-like growth factor-1 for prevention of radiation-induced spinal cord damage.

AIM: To test whether insulin-like growth factor-1 (IGF-1) ameliorates radiation-induced spinal cord myelopathy and to establish the dose-effect relationship for this growth factor which has not been administered in conjunction with spinal cord irradiation to date. METHODS: Animal experiments were conducted to test the feasibility of IGF-1 injection in a model of cervical spinal cord irradiation in adult Fisher F-344 rats and to determine the most effective dose level of IGF-1. Irradiation was given in two fractions (16 Gy followed by 18 Gy) and animals were examined for the development of paresis (follow-up 12 months). RESULTS: The dose-finding experiment revealed significant differences in the incidence of radiation myelopathy (RM). The most effective dose of IGF-1 was 50 microg per day. CONCLUSIONS: IGF-1 showed promising activity as a radioprotective agent in a model of high-dose spinal cord irradiation. Further studies are needed to examine the results with multiple small doses of radiation as widely applied in clinical protocols.

A novel method for endotracheal intubation of mice and rats used in imaging studies.

A safe and efficient method for endotracheal intubation was needed to mechanically ventilate mice and rats for various research projects. We developed an easy, reliable, and expeditious method for intubating these rodents. Inexpensive disposable Teflon intravenous catheters are used as endotracheal tubes. Both mice and rats are anesthetized using a combination of injectable and inhalational anesthetics before intubation. A relatively inexpensive custom-designed fiber-optic light guide and battery-powered light source allows visualization of the oropharynx for quick and easy intubation. The fiber-optic light guide has two functions: 1) the light guide transports light from the illuminator to the tip of the fiber for direct visualization of the larynx, and 2) the fiber is used as a stylet to stiffen the Teflon catheter. Direct illumination of the larynx allows its clear visualization and makes the procedure easier and more efficient and, as a result, less traumatic to the animals. This method has been easy to learn, and it allows repeated intubations, even in debilitated or dyspneic animals, for respiratory-gated, noninvasive imaging procedures. With it, we can acquire higher-quality images with fewer motion artifacts than we could before.

Modulation of rodent spinal cord radiation tolerance by administration of platelet-derived growth factor.

PURPOSE: To examine the role of platelet-derived growth factor (PDGF) for ameliorating radiation myelopathy of the cervical spinal cord in a rodent model. METHODS AND MATERIALS: After developing the technique for cannulation of the basal cistern, initial animal experiments were conducted to test the feasibility of intrathecal continuous infusion of PDGF in a model of cervical spinal cord irradiation in adult Fisher F-344 rats and to determine the most effective dose level of PDGF. Subsequently, the dose-modification factor was determined in a larger group of rats. Irradiation was given in 2 fractions (16 Gy followed by 14-24 Gy) and animals were examined for the development of paresis. RESULTS: The initial dose-finding experiment revealed significant differences in the incidence of radiation myelopathy (100% in saline-treated control rats, 25% with the most effective dose of PDGF, up to 100% with less effective doses). The most effective dose of PDGF was 0.014 mug per day. Subsequent experiments revealed a median effective dose (ED(50)) of 35.6 Gy (95% confidence interval, 34.7-36.5 Gy) for animals receiving this dose of PDGF in contrast to 33.8 Gy (33.4-34.3 Gy) for the control group (p = 0.003). The dose-modification factor obtained with this dose of PDGF was 1.05. CONCLUSIONS: Intrathecal administration of PDGF concomitant to irradiation of the cervical spinal cord in rats was feasible. Treatment with PDGF significantly increased the tolerance of the spinal cord. The PDGF experiments should be viewed as a proof of principle that brief therapeutic intervention in the earliest phase of damage induction can reduce late effects in the spinal cord. They form the basis for further studies of growth factor administration in this particular model.

Innovative prevention strategies for radiation necrosis of the central nervous system.

The authors have reviewed the experimental data on the radio-response of the central nervous system (CNS) and summarize the development of rational prevention strategies for radiation necrosis. Currently, radiation necrosis is thought to result from complex dynamic interactions between parenchymal and vascular endothelial cells within the CNS. The latent time, preceding the clinical manifestation of damage, is viewed as an active phase where cytokines and growth factors play important roles in inter- and intracellular communication. The present pathogenetic model forms the basis of rational innovative prevention strategies, which are now being studied in vivo. They include treatment with growth factors as well as neural stem cell transplantation and neoangiogenesis.

[Experimental data for administration of insulin-like growth factor 1 (IGF-1) and basic fibroblast growth factor (bFGF) for prevention of radiation myelopathy]. / Experimentelle Daten zum Einsatz von Insulin-Like Growth Factor-1 (IGF-1) und Basic Fibroblast Growth Factor (bFGF) zur Prävention einer Strahlenmyelopathie.

BACKGROUND: Current models of radiation myelopathy provide a rationale for growth factor-based prevention strategies. Thus, we tested whether insulin-like growth factor-1 (IGF-1) and basic fibroblast growth factor (bFGF) alone or in combination modulate radiation tolerance of the rat cervical spinal cord. MATERIALS AND METHODS: The cervical spinal cord of 68 adult Fisher F344 rats received a total dose of 30-36 Gy, given as a single fraction of 16 Gy followed by a second radiation dose of 14-20 Gy. Continuous intrathecal infusion of bFGF (44 rats) or saline (24 rats) into the cisterna magna was given concomitantly. A further experiment included 14 additional rats which were treated with subcutaneous injection of IGF-1 parallel to irradiation with a total dose of 34 Gy or 36 Gy. 20 rats received combined treatment, i.e. intrathecal infusion of bFGF plus subcutaneous injection of IGF-1, starting 24 hours before irradiation (total dose 33 Gy or 36 Gy) for a total of 4 days. Animals were followed until myelopathy developed or for a maximum of 12 months. Histopathologic examinations were performed post mortem. RESULTS: Treatment with bFGF alone or IGF-1 alone increased the median time to myelopathy significantly. In the 36-Gy group, after combination treatment a comparable prolongation of latency was seen. Moreover, rats treated with 33 Gy and combined bFGF plus IGF-1 showed a significantly reduced risk of myelopathy, too (p = 0.0015, Figures 1 and 2). CONCLUSION: Combination of IGF-1 and bFGF was more potent than single agent treatment. We observed a significantly reduced myelopathy rate at an intermediate radiation dose level and a longer time to myelopathy at a high-dose level. This finding strengthens the evidence that brief therapeutic intervention can decrease radiation-induced neurotoxicity. Further studies will be undertaken to optimize this strategy.