Recovery Of Sight Research Articles

Sound suppresses earliest visual cortical processing after sight recovery in congenitally blind humans

Neuroscientific research has consistently shown more extensive non-visual activity in the visual cortex of congenitally blind humans compared to sighted controls; a phenomenon known as crossmodal plasticity. Whether or not crossmodal activation of the visual cortex retracts if sight can be restored is still unknown. The present study, involving a rare group of sight-recovery individuals who were born pattern vision blind, employed visual event-related potentials to investigate persisting crossmodal modulation of the initial visual cortical processing stages. Here we report that the earliest, stimulus-driven retinotopic visual cortical activity (<100 ms) was suppressed in a spatially specific manner in sight-recovery individuals when concomitant sounds accompanied visual stimulation. In contrast, sounds did not modulate the earliest visual cortical response in two groups of typically sighted controls, nor in a third control group of sight-recovery individuals who had suffered a transient phase of later (rather than congenital) visual impairment. These results provide strong evidence for persisting crossmodal activity in the visual cortex after sight recovery following a period of congenital visual deprivation. Based on the time course of this modulation, we speculate on a role of exuberant crossmodal thalamic input which may arise during a sensitive phase of brain development.

Early visual experience refines the retinotopic organization within and across visual cortical regions

Early visual areas are retinotopically organized in human and non-human primates. Population receptive field (pRF) size increases with eccentricity and from lower- to higher-level visual areas. Furthermore, the cortical magnification factor (CMF), a measure of how much cortical space is devoted to each degree of visual angle, is typically larger for foveal as opposed to peripheral regions of the visual field. Whether this fine-scale organization within and across visual areas depends on early visual experience has yet been unknown. Here, we employed 7T functional magnetic resonance imaging pRF mapping to assess the retinotopic organization of early visual regions (i.e., V1, V2, and V3) in eight sight recovery individuals with a history of congenital blindness until a maximum of 4 years of age. Compared with sighted controls, foveal pRF sizes in these individuals were larger, and pRF sizes did not show the typical increase with eccentricity and down the visual cortical processing stream (V1-V2-V3). Cortical magnification was overall diminished and decreased less from foveal to parafoveal visual field locations. Furthermore, cortical magnification correlated with visual acuity in sight recovery individuals. The results of this study suggest that early visual experience is essential for refining a presumably innate prototypical retinotopic organization in humans within and across visual areas, which seems to be crucial for acquiring full visual capabilities.

White matter plasticity following cataract surgery in congenitally blind patients

The visual system develops abnormally when visual input is absent or degraded during a critical period early in life. Restoration of the visual input later in life is generally thought to have limited benefit because the visual system will lack sufficient plasticity to adapt to and utilize the information from the eyes. Recent evidence, however, shows that congenitally blind adolescents can recover both low-level and higher-level visual function following surgery. In this study, we assessed behavioral performance in both a visual acuity and a face perception task alongside longitudinal structural white matter changes in terms of fractional anisotropy (FA) and mean diffusivity (MD). We studied congenitally blind patients with dense bilateral cataracts, who received cataract surgery at different stages of adolescence. Our goal was to differentiate between age- and surgery-related changes in both behavioral performance and structural measures to identify neural correlates which might contribute to recovery of visual function. We observed surgery-related long-term increases of structural integrity of late-visual pathways connecting the occipital regions with ipsilateral fronto-parieto-temporal regions or homotopic contralateral areas. Comparison to a group of age-matched healthy participants indicated that these improvements went beyond the expected changes in FA and MD based on maturation alone. Finally, we found that the extent of behavioral improvement in face perception was mediated by changes in structural integrity in late visual pathways. Our results suggest that sufficient plasticity remains in adolescence to partially overcome abnormal visual development and help localize the sites of neural change underlying sight recovery.

P-110 Stimulus-evoked and resting-state alpha oscillations are jointly reduced in sight recovery individuals with a history of a congenital blindness

P-110 Stimulus-evoked and resting-state alpha oscillations are jointly reduced in sight recovery individuals with a history of a congenital blindness

Resting-State Functional Organization of the Brain in Blindness and Sight Recovery

Resting-State Functional Organization of the Brain in Blindness and Sight Recovery

Visual motion perception before and after sight recovery from early-onset and prolonged near-blindness

Visual motion perception before and after sight recovery from early-onset and prolonged near-blindness

Social action understanding after late sight recovery from congenital near-blindness

Social action understanding after late sight recovery from congenital near-blindness

Brain mechanism of sight recovery

AbstractPatients who were born with total bilateral cataracts and who were treated late in life show permanent deficits in visual acuity and other basic visual functions. Some higher visual functions are more (face identity processing, coherent motion processing) and other higher order visual functions (biological motion processing, visual exploration) are less impaired than expected from the visual acuity loss. Moreover, the integration of the late available visual input with the intact sensory inputs (hearing, touch) seems to be partially altered. The present talk will focus on new behavioural, electrophysiological and both functional and structural brain imaging results aiming to uncover the neural mechanisms of sight recovery in patients who had suffered from an extended period of blindness before they underwent cataract removal surgery.

Sight restoration reverses blindness-induced cross-modal functional connectivity changes between the visual and somatosensory cortex at rest.

Resting-state functional connectivity (rsFC) has been used to assess the effect of vision loss on brain plasticity. With the emergence of vision restoration therapies, rsFC analysis provides a means to assess the functional changes following sight restoration. Our study demonstrates a partial reversal of blindness-induced rsFC changes in Argus II retinal prosthesis patients compared to those with severe retinitis pigmentosa (RP). For 10 healthy control (HC), 10 RP, and 7 Argus II subjects, four runs of resting-state functional magnetic resonance imaging (fMRI) per subject were included in our study. rsFC maps were created with the primary visual cortex (V1) as the seed. The rsFC group contrast maps for RP > HC, Argus II > RP, and Argus II > HC revealed regions in the post-central gyrus (PostCG) with significant reduction, significant enhancement, and no significant changes in rsFC to V1 for the three contrasts, respectively. These findings were also confirmed by the respective V1-PostCG ROI-ROI analyses between test groups. Finally, the extent of significant rsFC to V1 in the PostCG region was 5,961 in HC, 0 in RP, and 842 mm3 in Argus II groups. Our results showed a reduction of visual-somatosensory rsFC following blindness, consistent with previous findings. This connectivity was enhanced following sight recovery with Argus II, representing a reversal of changes in cross-modal functional plasticity as manifested during rest, despite the rudimentary vision obtained by Argus II patients. Future investigation with a larger number of test subjects into this rare condition can further unveil the profound ability of our brain to reorganize in response to vision restoration.

Active vision in sight recovery individuals with a history of long-lasting congenital blindness.

What we see is intimately linked to how we actively and systematically explore the world through eye movements. However, it is unknown to what degree visual experience during early development is necessary for such systematic visual exploration to emerge. The present study investigated visual exploration behavior in 10 human participants whose sight had been restored only in childhood or adulthood, after a period of congenital blindness because of dense bilateral congenital cataracts. Participants freely explored real-world images while their eye movements were recorded. Despite severe residual visual impairments and gaze instability (nystagmus), visual exploration patterns were preserved in individuals with reversed congenital cataract. Modeling analyses indicated that, similar to healthy control subjects, visual exploration in individuals with reversed congenital cataract was based on the low-level (luminance contrast) and high-level (object components) visual content of the images. Moreover, participants used visual short-term memory representations for narrowing down the exploration space. More systematic visual exploration in individuals with reversed congenital cataract was associated with better object recognition, suggesting that active vision might be a driving force for visual system development and recovery. The present results argue against a sensitive period for the development of neural mechanisms associated with visual exploration.

Learning to see again: Perceptual learning of simulated abnormal on- off-cell population responses in sighted individuals

Many forms of artificial sight recovery, such as electronic implants and optogenetic proteins, generally cause simultaneous, rather than complementary firing of on- and off-center retinal cells. Here, using virtual patients—sighted individuals viewing distorted input—we examine whether plasticity might compensate for abnormal neuronal population responses. Five participants were dichoptically presented with a combination of original and contrast-reversed images. Each image (I) and its contrast-reverse (Iʹ) was filtered using a radial checkerboard (F) in Fourier space and its inverse (Fʹ). [I * F′] + [Iʹ * F] was presented to one eye, and [I * F] + [Iʹ * F′] was presented to the other, such that regions of the image that produced on-center responses in one eye produced off-center responses in the other eye, and vice versa. Participants continuously improved in a naturalistic object discrimination task over 20 one-hour sessions. Pre-training and post-training tests suggest that performance improvements were due to two learning processes: learning to recognize objects with reduced visual information and learning to suppress contrast-reversed image information in a non–eye-selective manner. These results suggest that, with training, it may be possible to adapt to the unnatural on- and off-cell population responses produced by electronic and optogenetic sight recovery technologies.

Misi dan Diakonia dalam Gereja

Mission and diakonia are two things but unity which is integrated within a church body. A church not as a church if it doesn’t do mission and diakonia. Diakonia is a mission in action. To do diakonia it means to be ready to witness about God’s love. The existence of the church is to proclaim the Good News to the poor; to heal the sick and brokenhearted; freedom to the prisoners and recovery of sight for the blind, to set the oppressed free and to create serenity to the people in hardship, injustice, and the victim of violence, sex abuse and other difficult circumstances. Proclaiming of the church through diakonia services by using hands, feet, eyes, noses, mouths, ears, heart and all part of the church body. Preach the Gospel it’s not only from the pulpit but go in to amid of people in need and do diakonia services.

Steady state evoked potentials indicate changes in nonlinear neural mechanisms of vision in sight recovery individuals

Humans with a transient phase of congenital pattern vision deprivation have been observed to feature prevailing deficits, particularly in higher order visual functions. However, the neural correlates of these prevalent visual impairments remain unclear. To probe different visual processing stages, we measured steady state visual evoked potentials (SSVEPs) generated by luminance flicker stimuli at 6.1 Hz, with superimposed horizontal periodic motion at 2.1 Hz or 2.4 Hz. SSVEP responses at the fundamental and second harmonic of luminance flicker frequency, and at their intermodulation frequencies with motion information, were analyzed. Three groups were tested: (1) 15 individuals who had suffered a lack of pattern vision from birth due to the presence of bilateral total congenital cataracts (CC group), which were surgically removed between 4 months and 22 years of age, (2) 13 individuals with reversed developmental i.e., later developing cataracts (DC group), and (3) normally sighted control participants (SC group; n = 13) matched in age and sex to the CC individuals. SSVEPs at the second harmonic frequency (i.e., 12.2 Hz) and at the intermodulation frequencies (8.2 Hz, and 8.5 Hz) were attenuated in the CC group. In contrast, fundamental frequency responses (i.e., at 6.1 Hz) were not significantly altered in the CC group compared to the control groups (SC and DC groups). Based on previous evidence on the role of striate vs. extrastriate generators of fundamental vs. second harmonics of SSVEPs, these results provide evidence for a stronger experience dependence of extrastriate than striate cortical processing, and furthermore, suggest a sensitive period for the development of putative nonlinear neural mechanisms hypothesized to mediate visual feature binding.

Comparison of visual acuity and post-operative inflammation in phacoemulsification and removal of silicone oil with and without injection of Enoxaparin Sodium (40mg/0.04ml)

Background: Phacoemulsification and removal of silicone oil (ROSO) is a combined, frequently done procedure in retina theatre. A common problem in this procedure is the post inflammation that affects the recovery of the patients. Thus to counter this post-operative inflammation, the study has used Enoxaparin Sodium (an anti-inflammatory enoxaparin) to counter the post-operative inflammation in phacoemulsification and ROSO.&#x0D; Patients and methods: Prospective interventional study done at Ophthalmology Department, Lahore General Hospital, included 60 patients which were operated and observed for results over a period of 3 months. Total 60 patients were randomly allocated in two groups, Group A and B. Both groups underwent phacoemulsification and ROSO. Group A had Enoxaparin Sodium, admixed in infusion bottles with a dosage of 40mg/0.04ml while Group B was operated without Enoxaparin Sodium. Patients were examined on slit lamp on the 1st day after the surgery then on the 7th day and every month for 3 months for post-operative inflammation and visual recovery. The effectiveness of the procedure was defined by the comparison of post-operative inflammation as well as speedy recovery of sight.&#x0D; Results: Total 60 patients were randomly allocated in two groups. Group A had 30 patients, 23 males and 7 females, with mean age of 49.43 years. Group B included 30 patients, 19 males and 11 females, with mean age of 47.73 years. Post-operative BCVA in Group A was above vision 6/60 (Snellen’s Chart) in 90% of cases while it improved to vision 6/36 and better in 93% of cases at 7th day while 93% of cases crossed recovery of Vision 6/18 by 3rd Month. While in Group B, Vision 6/60 was observed in 70% of cases while it improved to vision 6/36 and better in 67% of cases at 7th day while 53% of cases crossed recovery of vision 6/18 by 3rd Month. Post-operative results for inflammation of Group B showed grade 3 reaction on first day (94%) while it reduced to grade 2 reaction on 7th day in 97% of the cases. While Group A was observed with occasional activity in 25 out of 30 cases (84%) on the first day and grade 2 reaction in 5 (16%) cases. 100% cases of Group A showed occasional activity on 7th day with better visual recovery.&#x0D; Conclusion: Intraoperative use of Enoxaparin Sodium helped in reducing post-operative inflammation as well as aided in better visual acuity after phacoemulsification and ROSO thus proving to be a viable enoxaparin agent to reduce post-operative reactions in these surgeries.

Fouling in ocular devices: implications for drug delivery, bioactive surface immobilization, and biomaterial design.

The last 30years has seen a proliferation of research on protein-resistant biomaterials targeted at designing bio-inert surfaces, which are prerequisite for optimal performance of implantable devices that contact biological fluids and tissues. These efforts have only been able to yield minimal results, and hence, the ideal anti-fouling biomaterial has remained elusive. Some studies have yielded biomaterials with a reduced fouling index among which high molecular weight polyethylene glycols have remained dominant. Interestingly, the field of implantable ocular devices has not experienced an outflow of research in this area, possibly due to the assumption that biomaterials tested in other body fluids can be translated for application in the ocular space. Unfortunately, progression in the molecular understanding of many ocular conditions has brought to the fore the need for treatment options that necessitates the use of anti-fouling biomaterials. From the earliest implanted horsehair and silk seton for glaucoma drainage to the recent mini telescopes for sight recovery, this review provides a concise incursion into the gradual evolution of biomaterials for the design of implantable ocular devices as well as approaches used to overcome the challenges with fouling. The implication of fouling for drug delivery, the design of immune-responsive biomaterials, as well as advanced surface immobilization approaches to support the overall performance of implantable ocular devices are also reviewed.

Visual experience dependent plasticity in humans.

While sensitive periods in brain development have often been studied by investigating the recovery of visual functions after a congenital phase of visual deprivation in non-human animals, research in humans who had recovered sight after a transient phase of congenital blindness is still scarce. Here, we discuss the hypothesis put forward based on non-human primate work which states that the effects of experience increase downstream the visual processing hierarchy. Recent results from behavioral and neuroscience studies in sight recovery individuals are discussed in the context of research findings from permanently congenitally blind humans as well as from prospective studies in infants and children.

Successful visually guided eye movements following sight restoration after congenital cataracts.

Sensitive periods have previously been identified for several human visual system functions. Yet, it is unknown to what degree the development of visually guided oculomotor control depends on early visual experience—for example, whether and to what degree humans whose sight was restored after a transient period of congenital visual deprivation are able to conduct visually guided eye movements. In the present study, we developed new calibration and analysis techniques for eye tracking data contaminated with pervasive nystagmus, which is typical for this population. We investigated visually guided eye movements in sight recovery individuals with long periods of visual pattern deprivation (3–36 years) following birth due to congenital, dense, total, bilateral cataracts. As controls we assessed (1) individuals with nystagmus due to causes other than cataracts, (2) individuals with developmental cataracts after cataract removal, and (3) individuals with normal vision. Congenital cataract reversal individuals were able to perform visually guided gaze shifts, even when their blindness had lasted for decades. The typical extensive nystagmus of this group distorted eye movement trajectories, but measures of latency and accuracy were as expected from their prevailing nystagmus—that is, not worse than in the nystagmus control group. To the best of our knowledge, the present quantitative study is the first to investigate the characteristics of oculomotor control in congenital cataract reversal individuals, and it indicates a remarkable effectiveness of visually guided eye movements despite long-lasting periods of visual deprivation.

Bionic Eye from the Point of View of Functional Magnetic Resonance and Electrophysiological Examination – Review

The aim of the study was to show not only a possible visual replacement in patients with loss of sight, but also to discuss its efficiency. The study is focused on the issue of transmission of electrical voltage changes in the visual pathway under physiological and pathological conditions. In particular, it points to the feedback autoregulatory damage, not only of the primarily altered cellular structures, but also of all other structures localised both horizontally and vertically. Based on the results of the functional magnetic resonance imaging and electrophysiological methods, it demonstrates the pathology of the entire visual pathway in three important eye diseases: pigmentary retinal dystrophy, age-related macular degeneration, and glaucoma. The study also provides an overview of possible systems used to replace loss of vision, ranging from epiretinal, subretinal, suprachoroidal implants to stimulation of the optic nerve, lateral geniculate nucleus and visual cortex. Regarding the pathophysiology of neurotransmission, it is assumed that recovery of sight using these systems is not possible.

Color vision in sight recovery individuals.

Color vision has been consistently shown to be unaffected in animals that are raised in dark or in color-deprived environments. However, there are only a few studies that directly addressed the effect of congenital visual deprivation in color perception in humans. The goal of the current study was to assess the effect of congenital visual deprivation on color vision using a panel based color arrangement test. We investigated the recovery of color vision using the Farnsworth D15 test in a group of individuals who had experienced visual deprivation since birth due to bilateral dense congenital cataracts before undergoing cataract-reversal surgery (Congenital cataract, CC, n = 12). In addition, we tested two groups of control participants: (1) individuals who had had non-dense congenital cataract or developed cataract later in their childhood (Developmental cataract, DC, n = 10), and (2) sighted controls with normal or corrected to normal vision (n = 14). Based on the methods proposed by Vingrys and King-Smith (1988), we derived the following metrics of color vision performance: (1) total error score, (2) confusion index, (3) confusion angle, and (4) selectivity index. All of the measured indices of color vision performance were unaltered by a period of congenital visual deprivation. Our results support the view that, development of visual functions such as color discrimination and color arrangement does not depend on typical visual experience during a sensitive phase in early childhood.

Vanuatu

Four years after Cyclone Pam struck Vanuatu causing extensive damages, reconstruction is near completion with full recovery in sight. The authorities are now focused on implementing their broader development plans that were slowed by the rebuilding process, which will require fiscal discipline and reforms to maintain debt sustainability. The authorities should continue their constructive engagement with development partners for technical assistance, capacity development, and concessional and grant-based funding. In parallel continuing to reform and strengthen the governance of institutions and removing vulnerabilities to corruption will be important.