RESUMEN

AIM: Gastric emptying scintigraphy is used to assess patients with symptoms of dyspepsia or gastroparesis. An alteration of fundus accommodation may explain these symptoms. The aim of this study was to determine the accommodation in gastric emptying scintigraphy studies performed in our institution. MATERIAL AND METHODS: 50 patients (43 children) referred for gastric emptying assessment were evaluated. After fasting for 8 h, and following international guidelines, egg labeling was performed with 37 m Bq of [99mTc]Tc-DTPA and administration of standardized food. Areas of interest were defined in the stomach at different times, and the corresponding retention percentages were calculated. Considering the image at time zero, gastric accommodation was qualitatively and quantitatively assessed, calculating the ratio between proximal stomach counts and total counts. RESULTS: Of the 50 patients studied, 32 had normal emptying, 10 had slowed emptying and 8 had accelerated emptying. Within the group of patients with normal emptying, 8 had altered accommodation (25%) and another 8 in the group with abnormal emptying (44%). Applying the ROC curve analysis to quantitative values, the most appropriate cut-off value was 0.785 with p < 0.001, sensitivity 82.4% and specificity 100%. CONCLUSION: Gastric emptying scintigraphy in addition to determining motility, made it possible to assess both qualitatively and quantitatively the distribution of the radiotracer in the stomach and thus, indirectly, the accommodation in the fundus. It provided added diagnostic information in a simple manner, without protocol changes and allowing more specific treatments to be assessed.

RESUMEN

Background: Symptom accommodation by family members (FMs) of individuals with posttraumatic stress disorder (PTSD) includes FMs' participation in patients' avoidance/safety behaviours and constraining self-expression to minimise conflict, potentially maintaining patients' symptoms. The Significant Others' Responses to Trauma Scale (SORTS) is the only existing measure of accommodation in PTSD but has not been rigorously psychometrically tested.Objective: We aimed to conduct further psychometric analyses to determine the factor structure and overall performance of the SORTS. Method: We conducted exploratory and confirmatory factor analyses using a sample of N = 715 FMs (85.7% female, 62.1% White, 86.7% romantic partners of individuals with elevated PTSD symptoms).Results: After dropping cross-loading items, results indicated good fit for a higher-order model of accommodation with two factors: an anger-related accommodation factor encompassed items related largely to minimising conflict, and an anxiety-related accommodation factor encompassed items related primarily to changes to the FM's activities. Accommodation was positively related to PTSD severity and negatively related to relationship satisfaction, although the factors showed somewhat distinct associations. Item Response Theory analyses indicated that the scale provided good information and robust coverage of different accommodation levels.Conclusions: SORTS data should be analysed as both a single score as well as two factors to explore the factors' potential differential performance across treatment and relationship outcomes.

We examined the Significant Others' Responses to Trauma Scale (SORTS), a measure of symptom accommodation in PTSD, among a large sample of family members.As measured by the SORTS, accommodation in PTSD could be broken down into two aspects: anger-related accommodation and anxiety-related accommodation.Accommodation was positively related to PTSD severity and negatively related to relationship satisfaction.

Asunto(s)

RESUMEN

Presbyopia affects between 1.7 and 2 billion people worldwide. Presbyopia significantly impacts productivity and quality of life in both developed and developing countries. During accommodation, the human eye changes its dioptric power by altering the shape of the lens, but the exact nature of this change has not been fully explained. Recently, topical treatments have been marketed for the treatment of presbyopia and others are under investigation. In order to prepare a review of these novel therapies, we searched the major biomedical search engines. We found 15 randomized clinical trials and 12 reviews that met our review criteria. There are two different strategies for this purpose, the pinhole effect that increases depth of focus and "crystalline lens relaxation" for which parasympathetic mimetics and lens oxidation intermediates have been used. The results are generally favorable in terms of improvement of near visual acuity, although the follow-up period of the studies is short. These are novel strategies in the early stages of research that could be useful in the treatment of presbyopia.

Asunto(s)

RESUMEN

La presbicia es la pérdida gradual y progresiva de la amplitud de acomodación del cristalino que comienza entre los 38 y 40 años de edad y culmina a los 55 años al perderse por completo. Es provocada por el aumento de rigidez del cristalino y, en particular, un mayor cambio en la rigidez del núcleo de su corteza. La presbicia no corregida o hipocorregida tiene un impacto negativo en la calidad de vida en relación con la visión, las personas afectadas experimentan un cambio positivo significativo de productividad en sus actividades diarias al utilizar una corrección óptica adecuada. Las diferentes alternativas de tratamiento deben aplicarse de forma personalizadas para optimizar el rango de enfoque para las tareas diarias, minimizar los efectos visuales adversos y cumplir con las expectativas del paciente según necesidades y alcance económico. Los tratamientos más efectivos y con menos efectos indeseables hasta el momento son los dispositivos ópticos como las gafas y las lentes de contacto. Los métodos quirúrgicos pueden dejar síntomas visuales. El objetivo de este estudio fue realizar una búsqueda bibliográfica sobre las actuales tendencias en el manejo clínico-quirúrgico de la presbicia(AU)

Presbyopia is the gradual and progressive loss of the accommodative range of the crystalline lens that begins between 38 and 40 years of age and culminates at 55 years of age when it is completely lost. It is caused by increased stiffness of the lens and, in particular, a greater change in the stiffness of the nucleus of its cortex. Uncorrected or undercorrected presbyopia has a negative impact on quality of life in relation to vision, affected individuals experience a significant positive change in productivity in their daily activities when using an appropriate optical correction. The different treatment alternatives should be applied in a personalized way to optimize the range of focus for daily tasks, minimize adverse visual effects and meet the patient's expectations according to needs and economic scope. The most effective treatments with the least undesirable effects so far are optical devices such as glasses and contact lenses. Surgical methods may leave visual symptoms. The aim of this study was to perform a literature search on current trends in the clinical-surgical management of presbyopia(AU)

Asunto(s)

RESUMEN

Introducción: La heteroforia es la mala alineación de los ejes oculares, que es compensada durante la fijación binocular, al utilizar el mecanismo de fusión. Tiene una alta prevalencia en la población. Objetivo: Evidenciar la importancia de una corrección óptica personalizada en pacientes con heteroforias. Presentación de casos: Se presentan cuatro pacientes que acudieron a consulta de oftalmología, para refracción por presentar síntomas astenópicos. Después de una evaluación completa de cada uno, se constató en todos, la presencia de heteroforia. Se determinó la existencia de exoforia, en tres de ellos, fundamentalmente asociada a insuficiencia de convergencia y esoforia en uno, con exceso de convergencia. Se indicó en todos los casos la corrección óptica personalizada, teniendo en cuenta los resultados de exámenes y se logró la eliminación de las molestias en los pacientes. Conclusiones: Las heteroforias son una causa frecuente de síntomas astenópicos. Es necesario realizar un adecuado estudio, antes de indicar una corrección refractiva, teniendo en cuenta la identificación y cuantificación de la foria, evaluación de las vergencias fusionales, así como estudio del punto próximo de convergencia y la relación convergencia acomodación(AU)

Introduction: Heterophoria is the misalignment of the ocular axes, which is compensated during binocular fixation using the fusion mechanism. It has a high prevalence in the population. Objective: To demonstrate the importance of a personalized optical correction in patients with heterophorias. Cases report: Four cases who attended an ophthalmology consultation for refraction due to asthenopic symptoms are presented. After a complete evaluation of every one of the cases, the presence of heterophoria was found in all of them. The existence of exophoria, mainly associated with insufficient convergence, was determined in three of them; and convergence excess esophoria was identified in one case. Personalized optical correction was indicated in all cases, taking into account the results of the examinations; also, the discomfort in the patients was eliminated. Conclusions: Heterophorias are a frequent cause of asthenopic symptoms. It is necessary to carry out an adequate study before indicating a refractive correction, considering the identification and quantification of phoria, evaluation of fusional vergences, the study of the near point of convergence, and the accommodation-convergence relationship(AU)

RESUMEN

RESUMEN El objetivo de esta investigación cualitativa, que se apoya en el paradigma hermenéutico, es analizar desde la perspectiva de estudiantes de la educación media el reconocimiento del "valor del cuidado" que realizan sus madres cotidianamente para sostener la vida en el hogar como fundamento en el diseño de estrategias basadas en procesos de aprendizaje de asimilación y acomodación de Piaget, a fin de potenciar el vínculo didáctico madre-Tierra. Se entrevistaron 45 estudiantes de la Institución Educativa Alfonso Builes Correa, del municipio de Planeta Rica, departamento de Córdoba, y se identificaron sus conocimientos sobre el tema ambiental, el valor del cuidado en sus acciones cotidianas y la asociación con la madre-Tierra. Los resultados muestran que pocos estudiantes asumen una postura sistémica del ambiente e, igualmente, que en sus prácticas diarias no relacionan el cuidado materno como potencialidad para cuidar el ambiente; sin embargo, al someterlos a situaciones problematizadoras fueron capaces de relacionarlo. Se concluye que el análisis de las realidades del contexto desde una reflexión crítica permite armonizar la relación humanidad-naturaleza hacia nuevas formas de habitar para sustentar la vida en y del planeta.

ABSTRACT The objective of this qualitative research, which is based on the hermeneutical paradigm, is to analyze from the perspective of high school students the recognition of the "value of care" that their mothers carry out on a daily basis to sustain life at home as a foundation in the design of strategies based on Piaget's assimilation and accommodation learning processes, in order to enhance the mother-Earth didactic bond. 45 students from the Alfonso Builes Correa Educational Institution, from the municipality of Planeta Rica, state of Córdoba, were interviewed and their knowledge on the environmental issue, the value of care in their daily actions and the association with mother-Earth were identified. The results show that few students assume a systemic position of the environment and, likewise, that in their daily practices they do not relate maternal care as a potential to care for the environment; however by subjecting them to problematic situations, they were able to relate it. It is concluded that the analysis of the realities of the context from a critical reflection allows harmonizing the relationship between humanity and nature towards new ways of inhabiting to sustain life on and of the planet.

RESUMO O objetivo desta pesquisa qualitativa, que se baseia no paradigma hermenêutico, é analisar na perspectiva de estudantes do ensino médio o reconhecimento do "valor do cuidado" que suas mães realizam no dia a dia para sustentar a vida em casa como uma fundação em desenho de estratégias a partir dos processos de aprendizagem de assimilação e acomodação de Piaget, de forma a potencializar o vínculo didático mãe-Terra. Foram entrevistados 45 alunos da Instituição de Ensino Alfonso Builes Correa, do município de Planeta Rica, departamento de Córdoba, e identificados seus conhecimentos sobre a questão ambiental, o valor do cuidado no cotidiano e a associação com a mãe-Terra. Os resultados mostram que poucos alunos assumem uma postura sistémica do meio ambiente e, da mesma forma, que em suas práticas cotidianas não relacionam o cuidado materno como uma potencialidade para cuidar do meio ambiente; no entanto, ao submetê-los a situações problemáticas, eles foram capazes de relaciona-lo. Conclui-se que a análise das realidades do contexto a partir de uma reflexão crítica permite harmonizar a relação entre a humanidade e a natureza para novas formas de habitar para sustentar a vida no e no planeta.

RESUMEN

AIM: The aim of this study was to explore associations between reduced stereoacuity and clinical measures of accommodation, vergences, and symptoms which could facilitate the development of quick and reliable screening tools. METHODS: Using a multi-stage random cluster sampling, 1211 high school students (481 males and 730 females) between 13 and 18 years of age, were selected and examined. Visual acuity, stereoacuity and suppression, refractive errors, near point of convergence, heterophoria and fusional vergences, as well as, amplitude of accommodation, accommodative response, facility and relative accommodation were evaluated. Correlations among variables and the validity of Randot stereoacuity to distinguish between children with and without defective clinical measures as well as symptomatic versus asymptomatic children were characterized by the sensitivity and specificity of the tests. RESULTS: The overall mean stereoacuity was 43.9 ±â€¯25.23 s arc, and 18.9% [95% Confidence Interval, 16.6-21.4%)] of the participants had reduced stereoacuity (defined as ≥60). Stereoacuity values and symptoms scores were worse in children with defective clinical measures. The Receiver Operation Curve showed that maximum sensitivity and specificity was obtained with near point of convergence break (≥10 cm) of (0.70 95% confidence interval: 0.63-0.77) with Randot stereoacuity test (defined as ≥60 s arc). The correlations between reduced stereoacuity and symptoms scores was moderately strong and statistically significant (Pearson's, r = 0.507, p = 0.01). The Receiver Operation Curve showed that maximum sensitivity and specificity obtained with the Convergence Insufficiency Symptoms Survey was 0.57 (95% Confidence interval = 0.53-0.62, p = 0.001), sensitivity of 90.26%, and specificity 15.26% with the Randot stereoacuity test. CONCLUSION: Reduced stereoacuity, defective clinical measures and symptoms of asthenopia were prevalent among sample of school children studied. Randot stereoacuity test could fairly distinguish between defective and normal clinical measures; though the accuracy to differentiate between symptomatic and asymptomatic school children is poor. These findings highlight the need for validation of a simple and fast screening tool in school settings. Further studies to confirm above findings will be needed.

Asunto(s)

RESUMEN

BACKGROUND: To investigate the change between accommodative and vergence facilities before and after exposure to gaming in a virtual reality (VR) device amongst participants with normal binocular visual function. METHODS: 62 participants between the ages of 18-30 years with normal binocular visual function and inter-pupillary distances between 51 and 70 mm were selected for the study. Spectacle and contact lenses users were excluded. The experimental group (n = 42) was exposed to gaming using Samsung Gear VR(SM -R323) whilst the control group (n = 20) watched a television film projected on a two-dimensional screen at 1 m. Pre-test and post-test binocular amplitude-scaled facilities and vergence facilities were obtained for both groups after exposures of 25 min. RESULTS: Binocular accommodative facilities for the experimental group had a mean pre-test and post-test facility of 11.14 ± 3.67 cpm and 13.38 ± 3.63 cpm, respectively, after gaming using VR device. The vergence facilities for the experimental group had a mean pre-test and post-test facility of 11.41 ± 3.86 cpm and 15.28 ± 4.93 cpm, respectively, after gaming using a VR device. Binocular accommodative facilities for the control group had a mean pre-test and post-test facility of 11.70 ± 3.2 cpm and 11.95 ± 3.4 cpm, respectively. Vergence facilities for the control group had a mean pre-test and post-test facility of 11.55 ± 6.4 cpm and 11.70 ± 4.9 cpm, respectively. The mean change for binocular accommodative facilities was 2.24 ± 3.43 cpm and 0.25 ± 1.25 cpm for the experimental and control group, respectively. The mean change for vergence facilities was 3.81 ± 3.09 cpm and 0.15 ± 2.72 cpm for the experimental and control group, respectively. Binocular accommodative facilities and vergence facility showed a statistically significant mean increase greater than the control group after gaming using a VR device using an independent t-test (p < 0.05). CONCLUSION: The results showed that binocular accommodative facilities and vergence facilities increased after 25 min of VR gaming in emmetropic participants under 30 years of age with inter-pupillary distances between 51 mm and 70 mm.

Asunto(s)

RESUMEN

Phakic intraocular lenses (pIOL) are the main treatment for patients who have either high ametropia or contraindications for laser refractive surgery. The main feature that makes this kind of lenses suitable for its implantation in young adults searching for independence of optical prescription is the conservation of accommodation, since lens extraction is not required. A systematic review has been performed to evaluate the scientific literature on the effect of pIOL implantation on accommodation. Critical assessment of the articles included in the review was achieved using the tool Critical Appraisal Skills Programme in its Spanish form (CASPe). After revising the complete text of 10 articles pre-selected, two quasi-experimental pre-post studies evaluating the outcomes of a specific model of posterior chamber pIOL were included in the systematic review. The CASPe scoring of both studies were 5/11. According to this outcome, the evidence describing the impact of the pIOL implantation on the accommodative function can be defined poor. Some trends are reported as the decrease in the amplitude of accommodation, a decrease positive relative accommodation and improvement of accommodation. However, these results should be confirmed in future controlled studies.

Asunto(s)

RESUMEN

Measurement of the amplitude of accommodation is established as a procedure in a routine optometric eye examination. However, clinical methods of measurement of this basic optical function have several sources of error. They are numerous and diverse, and include depth of focus, reaction time, instrument design, specification of the measurement end-point, specification of the reference point of measurement, measurement conditions, consideration of refractive error, and psychological factors. Several of these sources of inaccuracy are composed of multiple sub-sources, and many of the sub-sources influence the common methods of measurement of amplitude of accommodation. Consideration of these sources of measurement error casts doubt on the reliability of the results of measurement, on the validity of established normative values that have been produced using these methods, and on the value of reports of the results of surgery designed to restore accommodation. Clinicians can reduce the effects of some of the sources of error by modifying techniques of measurement with existing methods, but a new method may further improve accuracy.

Asunto(s)

RESUMEN

PURPOSE: We tested the hypothesis that changes in accommodation after instillation of Phenylephrine Hydrochloride (PHCl) observed in some studies could be caused by changes in optics. METHODS: We performed two experiments to test the effects of PHCl on static and on dynamic accommodation in 8 and 6 subjects, respectively. Objective wavefront measurements were recorded of the static accommodation response to a stimulus at different distances or dynamic accommodation response to a sinusoidally moving stimulus (between 1 and 3 D of accommodative demand at 0.2Hz). The responses were characterized using two methods: one that takes into account the mydriatic optical effects on the accommodation produced by higher-order aberrations of the eye and another that takes into account only power changes paraxially due to the action of the ciliary muscle and regardless of the pupil size. RESULTS: When mydriatic optical effects were taken into account, differences in responses before and after PHCl instillation were 0.51±0.53 D, and 0.12±0.15, for static and dynamic accommodation, respectively, and were statistically significant (p<0.039). When mydriatic optical effects were not taken into account, the differences in responses before and after PHCl instillation were -0.20±0.51 D, and -0.05±0.14, for static and dynamic accommodation, respectively, and were not statistically significant (p>0.313). CONCLUSIONS: The mydriatic effect of the PHCl causes optical changes in the eye that can reduce the objective and subjective measurement of accommodation.

Asunto(s)

RESUMEN

PURPOSE: To develop a flexible model of the average eye that incorporates changes with age and accommodation in all optical parameters, including entrance pupil diameter, under photopic, natural, environmental conditions. METHODS: We collated retrospective in vivo measurements of all optical parameters, including entrance pupil diameter. Ray-tracing was used to calculate the wavefront aberrations of the eye model as a function of age, stimulus vergence and pupil diameter. These aberrations were used to calculate objective refraction using paraxial curvature matching. This was also done for several stimulus positions to calculate the accommodation response/stimulus curve. RESULTS: The model predicts a hyperopic change in distance refraction as the eye ages (+0.22D every 10 years) between 20 and 65 years. The slope of the accommodation response/stimulus curve was 0.72 for a 25 years-old subject, with little change between 20 and 45 years. A trend to a more negative value of primary spherical aberration as the eye accommodates is predicted for all ages (20-50 years). When accommodation is relaxed, a slight increase in primary spherical aberration (0.008µm every 10 years) between 20 and 65 years is predicted, for an age-dependent entrance pupil diameter ranging between 3.58mm (20 years) and 3.05mm (65 years). Results match reasonably well with studies performed in real eyes, except that spherical aberration is systematically slightly negative as compared with the practical data. CONCLUSIONS: The proposed eye model is able to predict changes in objective refraction and accommodation response. It has the potential to be a useful design and testing tool for devices (e.g. intraocular lenses or contact lenses) designed to correct the eye's optical errors.

Asunto(s)

RESUMEN

BACKGROUND: Accommodation is often recorded at a low sampling rate using devices such as autorefractors that are designed to measure the static refractive error. It is therefore important to determine if that resolution is sufficient to accurately measure the dynamic properties of accommodation. The current study provides both theoretical and empirical evidence on the ideal sampling rate necessary to measure a dynamic response. METHODS: Accommodative and disaccommodative step stimuli ranging from 1-3D (1D steps) were presented using a Badal optical system. Responses from 12 children (8-13 years) and 6 adults (20-35 years) were recorded using a dynamic photorefractor (DPR). Fast Fourier transformation was applied to the unsmoothed dynamic responses including position, velocity and acceleration. Also, velocity and acceleration main sequence (MS) characteristics were compared between three photorefractor conditions on 3 subjects. RESULTS: The Nyquist sampling limit necessary to accurately estimate position, velocity and acceleration was at least 5, 10 and 70Hz, respectively. Peak velocity and acceleration were significantly underestimated at a lower rate (p<0.5). However, the slope of MS remained invariant with sampling rate (p>0.5). CONCLUSION: Contrary to the previous findings, a dynamic accommodative response exhibited frequencies larger than 10Hz. Stimulus direction and amplitude had no influence on the frequencies present in the dynamic response. Peak velocity and acceleration can be significantly underestimated when sampled at a lower rate. Taken as a whole, low sampling rate instruments can accurately estimate static accommodation, however, caution needs to be exercised when using them for dynamic accommodation.

Asunto(s)

RESUMEN

PURPOSE: To compare changes in the ciliary muscle area at different sectors between pre-presbyopic and presbyopic eyes during accommodation by means of an anterior segment optical coherence tomographer (OCT). METHODS: The anterior ciliary muscle area was measured in 20 healthy and phakic pre-presbyopic eyes, whose mean age was 23.3±4.4 years, and in 20 healthy and phakic presbyopic eyes, whose mean age was 46.5±5.2 years. The relative change in the cross-sectional area of the ciliary muscle was measured at the nasal, inferior, and temporal sectors between 0 and -3 D of vergence, in -1 D step. A linear model was used to assess the correlation of each eye parameter with the accommodative demand. RESULTS: Each population group showed a significant increase in the anterior ciliary muscle area for each sector. The maximum increase in the ciliary muscle area within the pre-presbyopic group was about 30%, and for the presbyopic one was about 25%. At the same time, it was obtained that the larger the vergence, the larger the variability. Furthermore, the linear model showed a positive tendency between the change in the ciliary muscle area of each sector and the vergence for both population groups, which coefficient of determination was in all cases greater than 0.93. CONCLUSION: The anterior ciliary muscle area tends to increase with accommodation. The presbyopic nasal, inferior, and temporal ciliary muscle seem to have the same contractile capability as the young presbyopic ciliary muscle. These results might help to increase the evidences in the knowledge regarding the modern understanding of accommodation biometry and biomechanics.

Asunto(s)

RESUMEN

La incompatibilidad de grupo sanguíneo ABO y la sensibilización al HLA constituyen grandes barreras a vencer en pro de la óptima utilización de riñones de donante vivo. Describimos en nuestro medio el primer trasplante renal exitoso ABO incompatible en un paciente de 24 años, retrasplantado renal, altamente sensibilizado (PRA: 89%) y sin opción alguna en disponer de donantes cadavéricos ni familiares. Sin embargo, su único donante vivo HLA compatible era de grupo sanguíneo A incompatible con el grupo O del receptor. El paciente requirió de un régimen precondicionante consistente en recambios plasmáticos, rituximab, imunoglobulina y terapia inmunosupresora cuádruple, a fin de reducir los títulos elevados de isoaglutininas anti A de 1:128 a niveles de seguridad de 1:8, para el éxito del trasplante. Este fue realizado en Coordinación con la Unidad de Trasplante Renal del Hospital Clínic de Barcelona España (HCB). La ausencia de rechazo mediado por isoaglutininas muestra el potencial beneficio del protocolo al remover los anticuerpos anti grupo sanguíneo. A los dos años del trasplante, la función renal se mantiene estable con niveles de creatinina 1,5 mg%. Concluimos que el trasplante renal ABO incompatible (ABOi) es opción viable para pacientes cuyo único donante sea grupo sanguíneo incompatible, y entre nosotros representa esperanzadora fuente de órganos.

ABO blood group incompatibility and HLA sensitization are major barriers that need to be overcome in order to make optimum use of kidneys from living donors possible. We report the first successful ABO- incompatible kidney transplant in a 24-year old, highly sensitized (panel reactive antibodies (PRA) 89% kidney retransplantation patient, who lacked any option to get a cadaveric or family donor. However, the patient's sole HLA-compatible living donor had group A blood incompatible with the recipient's O blood group. The < patient required a pre-conditioning regime that consisted of plasma exchange, rituximab, immunoglobulin, and quadruple immunosuppressive therapy in order to reduce high titers of anti-A isoagglutinins from 1:128 to a safe level of 1:8, for successful transplant. This was performed in coordination with the Renal Transplant Unit of Hospital Clinic de Barcelona (HCB), Spain. Absence of rejection mediated by isoagglutinins shows the potential benefit of a protocol consisting in removing antibodies from the anti-blood group. Two yearsafter transplantation, the kidney function remains stable, with creatinine levels of 1.5 mg%. We conclude that an ABO-incompatible kidney transplant is a viable option for patients whose only donor has blood of an incompatible blood group and for us this represents a hope-inspiring source of organs .

RESUMEN

PURPOSE: To evaluate the changes in the stimulus and response Accommodative Convergence to Accommodation (AC/A) ratio following vision therapy (VT) in Convergence Insufficiency (CI). METHODS: Stimulus and response AC/A ratio were measured on twenty five CI participants, pre and post 10 sessions of VT. Stimulus AC/A ratio was measured using the gradient method and response AC/A ratio was calculated using modified Thorington technique with accommodative responses measured using WAM-5500 open-field autorefractor. The gradient stimulus and response AC/A cross-link ratios were compared with thirty age matched controls. RESULTS: Mean age of the CI and control participants were 23.3±5.2 years and 22.7±4.2 years, respectively. The mean stimulus and response AC/A ratio for CI pre therapy was 2.2±0.72 and 6.3±2.0 PD/D that changed to 4.2±0.9 and 8.28±3.31 PD/D respectively post vision therapy and these changes were statistically significant (paired t-test; p<0.001). The mean stimulus and response AC/A ratio for controls was 3.1±0.81 and 8.95±2.5 PD/D respectively. CONCLUSIONS: Stimulus and response AC/A ratio increased following VT, accompanied by clinically significant changes in vergence and accommodation parameters in subjects with convergence insufficiency. This represents the plasticity of the AC/A crosslink ratios that could be achieved with vision therapy in CI.

Asunto(s)

RESUMEN

PURPOSE: When observers focus their stereoscopic visual system for a long time (e.g., watching a 3D movie) they may experience visual discomfort or asthenopia. We tested two types of models for predicting visual fatigue in a task in which subjects were instructed to discriminate between 3D characters. One model was based on viewing distance (focal distance, vergence distance) and another in visual direction (oculomotor imbalance). METHOD: A 3D test was designed to assess binocular visual fatigue while looking at 3D stimuli located in different visual directions and viewed from two distances from the screen. The observers were tested under three conditions: (a) normal vision; (b) wearing a lens (-2 diop.); (c) wearing a base-out prism (2▿) over each eye. Sensitivity and specificity were calculated (as Signal Detection Theory parameters: SDT). RESULTS: An ANOVA and SDT analyses revealed that impaired visual performance were directly related to short distance and larger deviation in visual direction, particularly when the stimuli were located nearer and at more than 24° to the centre of the screen in dextroversion and beyond. CONCLUSION: This results support a mixed model, combining a model based on the visual angle (related to viewing distance) and another based on the oculomotor imbalance (related to visual direction). This mixed model could help to predict the distribution of seats in the cinema room ranging from those that produce greater visual comfort to those that produce more visual discomfort. Also could be a first step to pre-diagnosis of binocular vision disorders.

Asunto(s)

RESUMEN

PURPOSE: To investigate the change in visual acuity (VA) produced by different types of astigmatism (on the basis of the refractive power and position of the principal meridians) on normal accommodating eyes. METHODS: The lens induced method was employed to simulate a set of 28 astigmatic blur conditions on different healthy emmetropic eyes. Additionally, 24 values of spherical defocus were also simulated on the same eyes for comparison. VA was measured in each case and the results, expressed in logMAR units, were represented against of the modulus of the dioptric power vector (blur strength). RESULTS: LogMAR VA varies in a linear fashion with increasing astigmatic blur, being the slope of the line dependent on the accommodative demand in each type of astigmatism. However, in each case, we found no statistically significant differences between the three axes investigated (0°, 45°, 90°). Non-statistically significant differences were found either for the VA achieved with spherical myopic defocus (MD) and mixed astigmatism (MA). VA with simple hyperopic astigmatism (SHA) was higher than with simple myopic astigmatism (SMA), however, in this case non conclusive results were obtained in terms of statistical significance. The VA achieved with imposed compound hyperopic astigmatism (CHA) was highly influenced by the eye's accommodative response. CONCLUSIONS: VA is correlated with the blur strength in a different way for each type of astigmatism, depending on the accommodative demand. VA is better when one of the focal lines lie on the retina irrespective of the axis orientation; accommodation favors this situation.

Asunto(s)

RESUMEN

PURPOSE: To determine if a fogging lens ameliorates accommodative effects driven by the closed-view design of the BHVI-EyeMapper (EM) instrument. We compared cycloplegic refraction and higher-order aberration measurements of the EM with those obtained with a fogging lens. METHODS: Twenty-six, young, participants (15F, 25±5 years, range: 18-35 years, SE: +0.25 D and -3.50 D) with good ocular health were recruited. Five independent measurements of on- and off-axis refraction and higher-order aberrations were recorded across the horizontal visual field, under two conditions: non-cycloplegic measurements with +1.00 D fogging lens and cycloplegia, always in the same sequence. The contralateral eye was occluded during the measurements. Two drops of 1% Tropicamide delivered within 5 min facilitated cycloplegic measurements. All participants were refracted 30 min after installation of the second drop. RESULTS: Mean spherical equivalent measures of the non-cycloplegic condition were significantly more myopic than their cycloplegic counterparts (p<0.05); approximately by 0.50 D centrally, increasing to 1.00 D towards the periphery. The horizontal astigmatic component, J180, demonstrated small but statistically significant differences between the test conditions. Differences were predominant for eccentricities greater than 30°, in both nasal and temporal meridians. The oblique astigmatic component, J45, was not significantly different between the test conditions. The primary spherical aberration coefficient C(4, 0) was significantly less positive for the non-cycloplegic state than its cycloplegic counterpart. This result held true across the entire horizontal visual field. The horizontal coma and trefoil coefficients C(3, 1) and C(3, 3) were not significantly different between the two conditions. CONCLUSIONS: The use of +1.00 D fogging lens without cycloplegia did not provide complete relaxation of accommodation. The discrepancies between cycloplegic and non-cycloplegic EM measurements were found to be more pronounced for peripheral field angles than central measures, for both M and J180 components.

Asunto(s)

RESUMEN

We investigated the dynamics of accommodative and pupillary responses to random-dot stereograms presented in crossed and uncrossed disparity in six visually normal young adult subjects (mean age=25.8±3.1 years). Accommodation and pupil measures were monitored monocularly with a custom built photorefraction system while subjects fixated at the center of a random-dot stereogram. On each trial, the stereogram initially depicted a flat plane and then changed to depict a sinusoidal corrugation in depth while fixation remained constant. Increase in disparity specified depth resulted in pupil constriction during both crossed and uncrossed disparity presentations. The change in pupil size between crossed and uncrossed disparity conditions was not significantly different (p>0.05). The change in pupil size was also accompanied by a small concomitant increase in accommodation. In addition, the dynamic properties of pupil responses varied as a function of their initial (starting) diameter. The finding that accommodation and pupil responses increased with disparity regardless of the sign of retinal disparity suggests that these responses were driven by apparent depth rather than shifts in mean simulated distance of the stimulus. Presumably the need for the increased depth of focus when viewing stimuli extended in depth results in pupil constriction which also results in a concomitant change in accommodation. Starting position effects in pupil response confirm the non-linearity in the operating range of the pupil.

Asunto(s)