Alterations in Heart rate Variability in Blind Patients

Blindness affect the daily life activities and the causes and prevalence are different worldwide. This study aimed to investigate the pattern of the autonomic nervous system modulation on the heart in blind and normal vision subjects submitted acutely to low vision. Normal vision (NV) subjects (N = 32) and blind patients (N = 24) were submitted to HRV analysis during resting, intervention and recovery periods. Intervention consisted of handling objects, short walking, and cognitive activities performed with pedagogic games while using sleeping masks. No difference was observed in indexes in the time and frequency domain, and in the geometric indexes comparing blind and NV subjected to acute low vision during resting and recovery. Nevertheless, during intervention, RMSSD, pNN50, and SD1were found lower in blind than in NV subjects. Therefore, blind patients showed similar HRV at resting or upon possible stressful challenges compared to NV subjects acutely subjected to low vision, indicating absence of differences in the cardiovascular risk between groups. In addition, blind patients show a smaller reduction in parasympathetic modulation on the heart during possible stressful challenges than NV individuals submitted to low vision, which is likely an important physiological adaptation for an adequate function of the cardiovascular system in blindness.

Naturalistic spatiotemporal stimulus modulation during epiretinal stimulation increases the persistence of retinal ganglion cell responsivity

ObjectiveRetinal stimulation in blind patients evokes the sensation of discrete points of light called phosphenes, which allows them performing visual guided tasks, such as orientation, navigation, object recognition, object manipulation and reading. However, the clinical benefit of artificial vision in profoundly blind patients is still tenuous, as several engineering and biophysical obstacles keep it away from natural perception. The relative preservation of the inner retinal neurons in hereditary degenerative retinal diseases, such as retinitis pigmentosa, supports artificial vision through the network-mediated stimulation of retinal ganglion cells. However, the response of retinal ganglion cells to repeated electrical stimulation rapidly declines, primarily because of the intrinsic desensitisation of their excitatory network. In patients, upon repetitive stimulation, phosphenes fade out in less than half of a second, which drastically limits the understanding of the percept.ApproachA more naturalistic stimulation strategy, based on spatiotemporal modulation of electric pulses, could overcome the desensitisation of retinal ganglion cells. To investigate this hypothesis, we performed network-mediated epiretinal stimulations paired to electrophysiological recordings in retinas explanted from both male and female retinal degeneration 10 mice.Main resultsThe results showed that the spatial and temporal modulation of the network-mediated epiretinal stimulation prolonged the responsivity of retinal ganglion cells from 400 ms up to 4.2 s.SignificanceA time-varied, non-stationary and interrupted stimulation of the retinal network, mimicking involuntary microsaccades, might reduce the fading of the visual percept and improve the clinical efficacy of retinal implants.

Virtual reality simulation of epi-retinal prosthetic vision highlights the relevance of the visual angle

ObjectiveRetinal prostheses hold the potential to restore artificial vision in blind patients suffering from outer retinal dystrophies. The optimal number, density, and coverage of the electrodes that a retinal prosthesis should have to provide adequate artificial vision in daily activities is still an open question and an important design parameter needed to develop better implants.ApproachTo address this question, we investigated the interaction between the visual angle, the pixel number and the pixel density without being limited by a small electrode count, as in previous research reports. We implemented prosthetic vision in a virtual reality environment in order to simulate the real-life experience of using a retinal prosthesis. We designed four different tasks simulating: object recognition, word reading, perception of a descending step and crossing a street.Main resultsThe results of our study showed that in all the tasks the visual angle played the most significant role in improving the performance of the participant.SignificanceThe design of new retinal prostheses should take into account the relevance of the restored visual angle to provide a helpful and valuable visual aid to profoundly or totally blind patients.

Retinal Prosthetic Approaches to Enhance Visual Perception for Blind Patients

Retinal prostheses are implantable devices that aim to restore the vision of blind patients suffering from retinal degeneration, mainly by artificially stimulating the remaining retinal neurons. Some retinal prostheses have successfully reached the stage of clinical trials; however, these devices can only restore vision partially and remain insufficient to enable patients to conduct everyday life independently. The visual acuity of the artificial vision is limited by various factors from both engineering and physiological perspectives. To overcome those issues and further enhance the visual resolution of retinal prostheses, a variety of retinal prosthetic approaches have been proposed, based on optimization of the geometries of electrode arrays and stimulation pulse parameters. Other retinal stimulation modalities such as optics, ultrasound, and magnetics have also been utilized to address the limitations in conventional electrical stimulation. Although none of these approaches have been clinically proven to fully restore the function of a degenerated retina, the extensive efforts made in this field have demonstrated a series of encouraging findings for the next generation of retinal prostheses, and these could potentially enhance the visual acuity of retinal prostheses. In this article, a comprehensive and up-to-date overview of retinal prosthetic strategies is provided, with a specific focus on a quantitative assessment of visual acuity results from various retinal stimulation technologies. The aim is to highlight future directions toward high-resolution retinal prostheses.

Changes in perilesional V1 underlie training-induced recovery in cortically-blind patients

Damage to the primary visual cortex (V1) causes profound, homonymous visual-field loss termed cortical blindness (CB). Though long considered intractable, multiple studies now show that perceptual training can recover visual functions in chronic CB. A popular hypothesis is that training recruits intact extrageniculostriate pathways. Alternatively, training may induce plastic changes within spared regions of the damaged V1. Here, we linked changes in luminance detection sensitivity with retinotopic fMRI activity in eleven chronic CB patients, before and after extensive visual discrimination training. Our results show that the strength of spared V1 activity representing perimetrically blind-field locations before training predicts the amount of training-induced recovery of luminance detection sensitivity. Additionally, training caused an enlargement of population receptive fields in perilesional V1 cortex, which increased blind-field coverage. These findings uncover fundamental changes in perilesional V1 cortex underlying training-induced restoration of conscious luminance detection sensitivity in cortically-blind patients.

Exploring Nursing Students' Experiences of Blindness Simulation: A Phenomenological Study

Background: Simulation-based teaching skill is important for nurses who care for blind patients. Nurses should be able to understand their clients in order to provide them with better care. Also, better understanding of blindness enables nurses to take a more appropriate approach in dealing with blind patients and solving their problems. The aim of this study was to explore the experiences of blindness simulation among a group of nursing students.Methods: This qualitative study was conducted using an interpretive phenomenological method. Using purposeful sampling method, 8 participants were selected to share their experiences regarding blindness simulation through individual in-depth and semi-structured interviews. The transcribed interviews were analyzed by Diekelmann’s approach.Results: The results of data analysis resulted in three main categories and nine subcategories, which were conceptually named based on their nature. The main categories included; abandoned in the labyrinth of life, seeing with the eyes of heart, and personality alienation.Conclusions: The findings of this study provide a clear picture of students' experiences of blindness simulation. Understanding students' descriptions and perceptions of visually impaired patients in different aspects can provide valuable data in reducing and removing existing problems and planning to improve the quality of care. Therefore, improving and modifying care plan can guarantee the quality of professional services provided to patients.