Early Blindness Research Articles

Auditory processing abilities of children with congenital blindness

BackgroundChildren with visual challenges rely on their hearing ability to accomplish daily tasks more efficiently. Many investigations show changes in the auditory pathway in children and adults with early blindness. It can be hypothesized that the auditory processing abilities of children with congenital blindness will be superior to those of typically developing children without any visual challenges. PurposeThe current study was designed to compare some of the auditory processing abilities of children with congenital blindness and typically developing children who do not have any visual challenges. Specifically, the study compared the perception of speech in noise, temporal patterning ability, binaural integration ability as well as auditory memory and sequencing abilities of children in two groups. Research designIt was a prospective cross-sectional study comparing two groups. Study sampleA total of 160 children, 80 typically developing children without any visual challenges (reference group) and 80 children with congenital blindness, in the age range of 7–11 years, participated in the study. Data collection and analysisPitch pattern test (PPT), perception of speech perception in noise test in Marathi (PSIN-M), dichotic digit test in Marathi (DDT-M), and auditory memory and sequencing test in Marathi (AMST-M) were administered. Independent sample T test and Mann Whitney U test were used to compare the performance of the two groups on these tests. ResultsChildren with congenital blindness showed significantly better scores on PPT, PSIN-M, and DDT-M as compared to children in the reference group in all the age groups. A clear trend was not observed on DDT-M. ConclusionIt can be concluded that children with congenital blindness have better auditory processing, auditory memory, and sequencing abilities compared to typically developing children without any visual challenges.

Early attentional processing and cortical remapping strategies of tactile stimuli in adults with an early and late-onset visual impairment: A cross-sectional study.

Neuroplastic changes appear in people with visual impairment (VI) and they show greater tactile abilities. Improvements in performance could be associated with the development of enhanced early attentional processes based on neuroplasticity. Currently, the various early attentional and cortical remapping strategies that are utilized by people with early (EB) and late-onset blindness (LB) remain unclear. Thus, more research is required to develop effective rehabilitation programs and substitution devices. Our objective was to explore the differences in spatial tactile brain processing in adults with EB, LB and a sighted control group (CG). In this cross-sectional study 27 participants with VI were categorized into EB (n = 14) and LB (n = 13) groups. They were then compared with a CG (n = 15). A vibrotactile device and event-related potentials (ERPs) were utilized while participants performed a spatial tactile line recognition task. The P100 latency and cortical areas of maximal activity were analyzed during the task. The three groups had no statistical differences in P100 latency (p>0.05). All subjects showed significant activation in the right superior frontal areas. Only individuals with VI activated the left superior frontal regions. In EB subjects, a higher activation was found in the mid-frontal and occipital areas. A higher activation of the mid-frontal, anterior cingulate cortex and orbitofrontal zones was observed in LB participants. Compared to the CG, LB individuals showed greater activity in the left orbitofrontal zone, while EB exhibited greater activity in the right superior parietal cortex. The EB had greater activity in the left orbitofrontal region compared to the LB. People with VI may not have faster early attentional processing. EB subjects activate the occipital lobe and right superior parietal cortex during tactile stimulation because of an early lack of visual stimuli and a multimodal information processing. In individuals with LB and EB the orbitofrontal area is activated, suggesting greater emotional processing.

Perception and discrimination of real-life emotional vocalizations in early blind individuals.

The capacity to understand others' emotions and react accordingly is a key social ability. However, it may be compromised in case of a profound sensory loss that limits the contribution of available contextual cues (e.g., facial expression, gestures, body posture) to interpret emotions expressed by others. In this study, we specifically investigated whether early blindness affects the capacity to interpret emotional vocalizations, whose valence may be difficult to recognize without a meaningful context. We asked a group of early blind (N = 22) and sighted controls (N = 22) to evaluate the valence and the intensity of spontaneous fearful and joyful non-verbal vocalizations. Our data showed that emotional vocalizations presented alone (i.e., with no contextual information) are similarly ambiguous for blind and sighted individuals but are perceived as more intense by the former possibly reflecting their higher saliency when visual experience is unavailable. Our study contributes to a better understanding of how sensory experience shapes ememotion recognition.

Altered grid-like coding in early blind people

Cognitive maps in the hippocampal-entorhinal system are central for the representation of both spatial and non-spatial relationships. Although this system, especially in humans, heavily relies on vision, the role of visual experience in shaping the development of cognitive maps remains largely unknown. Here, we test sighted and early blind individuals in both imagined navigation in fMRI and real-world navigation. During imagined navigation, the Human Navigation Network, constituted by frontal, medial temporal, and parietal cortices, is reliably activated in both groups, showing resilience to visual deprivation. However, neural geometry analyses highlight crucial differences between groups. A 60° rotational symmetry, characteristic of a hexagonal grid-like coding, emerges in the entorhinal cortex of sighted but not blind people, who instead show a 90° (4-fold) symmetry, indicative of a square grid. Moreover, higher parietal cortex activity during navigation in blind people correlates with the magnitude of 4-fold symmetry. In sum, early blindness can alter the geometry of entorhinal cognitive maps, possibly as a consequence of higher reliance on parietal egocentric coding during navigation.

A unified model for cross-modal plasticity and skill acquisition.

Historically, cross-modal plasticity following early blindness has been largely studied in the context of visual deprivation. However, more recently, there has been a shift in focus towards understanding cross-modal plasticity from the perspective of skill acquisition: the striking plasticity observed in early blind individuals reflects the extraordinary perceptual and cognitive challenges they solve. Here, inspired by two seminal papers on skill learning (the "cortical recycling" theory) and cross-modal plasticity (the "metamodal" hypothesis) respectively, we present a unified hypothesis of cortical specialization that describes how shared functional, algorithmic, and structural constraints might mediate both types of plasticity.

The impact of early and late blindness on language and verbal working memory: A brain-constrained neural model

Neural circuits related to language exhibit a remarkable ability to reorganize and adapt in response to visual deprivation. Particularly, early and late blindness induce distinct neuroplastic changes in the visual cortex, repurposing it for language and semantic processing. Interestingly, these functional changes provoke a unique cognitive advantage – enhanced verbal working memory, particularly in early blindness. Yet, the underlying neuromechanisms and the impact on language and memory-related circuits remain not fully understood. Here, we applied a brain-constrained neural network mimicking the structural and functional features of the frontotemporal-occipital cortices, to model conceptual acquisition in early and late blindness. The results revealed differential expansion of conceptual-related neural circuits into deprived visual areas depending on the timing of visual loss, which is most prominent in early blindness. This neural recruitment is fundamentally governed by the biological principles of neural circuit expansion and the absence of uncorrelated sensory input. Critically, the degree of these changes is constrained by the availability of neural matter previously allocated to visual experiences, as in the case of late blindness. Moreover, we shed light on the implication of visual deprivation on the neural underpinnings of verbal working memory, revealing longer reverberatory neural activity in ‘blind models’ as compared to the sighted ones. These findings provide a better understanding of the interplay between visual deprivations, neuroplasticity, language processing and verbal working memory.

Novel mutation in the NDP gene associated with Norrie disease in a Chinese pedigree.

Norrie disease (ND) is a rare X-linked recessive disorder characteristic of early childhood blindness. While several mutations in the NDP gene have been reported as causative for ND, the genetic etiology remains unknown for many patients. This study aims to describe a novel mutation and explore the clinical manifestations in a Chinese family with two affected males. Exome sequencing (ES) was employed to identify the causative gene in a four-generation pedigree. Sanger sequencing was subsequently utilized to validate the mutation detected by ES in additional family members. Ophthalmologic examination and diagnostic imaging relevant to ND were conducted. The proband (IV:2), an 8-month-old male infant, presented with binocular retinal detachment. DNA sequencing revealed a novel heterozygous missense mutation (c.174G>C) within the NDP gene in the proband. This mutation affected highly conserved residues and was predicted to disrupt the normal protein structure. Furthermore, the variant co-segregated with the disease phenotypes within the family. Our findings identified a novel missense mutation in the NDP gene associated with Norrie disease in China, expanding the mutation spectrum associated with ND. This discovery holds diagnostic, prognostic, and genetic counseling implications for affected individuals.

The perception of auditory motion in sighted and early blind individuals.

Motion perception is a fundamental sensory task that plays a critical evolutionary role. In vision, motion processing is classically described using a motion energy model with spatiotemporally nonseparable filters suited for capturing the smooth continuous changes in spatial position over time afforded by moving objects. However, it is still not clear whether the filters underlying auditory motion discrimination are also continuous motion detectors or infer motion from comparing discrete sound locations over time (spatiotemporally separable). We used a psychophysical reverse correlation paradigm, where participants discriminated the direction of a motion signal in the presence of spatiotemporal noise, to determine whether the filters underlying auditory motion discrimination were spatiotemporally separable or nonseparable. We then examined whether these auditory motion filters were altered as a result of early blindness. We found that both sighted and early blind individuals have separable filters. However, early blind individuals show increased sensitivity to auditory motion, with reduced susceptibility to noise and filters that were more accurate in detecting motion onsets/offsets. Model simulations suggest that this reliance on separable filters is optimal given the limited spatial resolution of auditory input.

Blindness influences emotional authenticity perception in voices: Behavioral and ERP evidence

The ability to distinguish spontaneous from volitional emotional expressions is an important social skill. How do blind individuals perceive emotional authenticity? Unlike sighted individuals, they cannot rely on facial and body language cues, relying instead on vocal cues alone. Here, we combined behavioral and ERP measures to investigate authenticity perception in laughter and crying in individuals with early- or late-blindness onset. Early-blind, late-blind, and sighted control participants (n = 17 per group, N = 51) completed authenticity and emotion discrimination tasks while EEG data were recorded. The stimuli consisted of laughs and cries that were either spontaneous or volitional. The ERP analysis focused on the N1, P2, and late positive potential (LPP). Behaviorally, early-blind participants showed intact authenticity perception, but late-blind participants performed worse than controls. There were no group differences in the emotion discrimination task. In brain responses, all groups were sensitive to laughter authenticity at the P2 stage, and to crying authenticity at the early LPP stage. Nevertheless, only early-blind participants were sensitive to crying authenticity at the N1 and middle LPP stages, and to laughter authenticity at the early LPP stage. Furthermore, early-blind and sighted participants were more sensitive than late-blind ones to crying authenticity at the P2 and late LPP stages.Altogether, these findings suggest that early blindness relates to facilitated brain processing of authenticity in voices, both at early sensory and late cognitive-evaluative stages. Late-onset blindness, in contrast, relates to decreased sensitivity to authenticity at behavioral and brain levels.

Preserved visual categorical coding in the ventral occipito-temporal cortex despite transient early blindness and permanent alteration in the functional response of early visual regions

Preserved visual categorical coding in the ventral occipito-temporal cortex despite transient early blindness and permanent alteration in the functional response of early visual regions

Late Blindness and Deafness are Associated with Decreased Tactile Sensitivity, But Early Blindness is Not

Perceptual experience is shaped by a complex interaction between our sensory systems in which each sense conveys information on specific properties of our surroundings. This multisensory processing of complementary information improves the accuracy of our perceptual judgments and leads to more precise and faster reactions. Sensory impairment or loss in one modality leads to information deficiency that can impact other senses in various ways. For early auditory or visual loss, impairment and/or compensatory increase of the sensitivity of other senses are equally well described. Investigating individuals with deafness (N = 73), early (N = 51), late blindness (N = 49) and corresponding controls, we compared tactile sensitivity using the standard monofilament test on two locations, the finger and handback. Results indicate lower tactile sensitivity in people with deafness and late blindness but not in people with early blindness compared to respective controls, irrespective of stimulation location, gender, and age. Results indicate that neither sensory compensation nor simple use-dependency or a hindered development of the tactile sensory system is sufficient to explain changes in somatosensation after the sensory loss but that a complex interaction of effects is present.

Penerimaan Diri dengan Orientasi Masa Depan Pada Penyandang Tuna Netra di Panti Pelayanan Sosial Disabilitas Sensorik Netra (PPSDSN) Penganthi Temanggung

Abstract : Blind people experience various challenges in everyday life both with their personal and environmental so to have a future orientation requires self-acceptance. The purpose of this study was to find out the relationship between self-acceptance and future orientation in blind people in the Netra Sensory Disability Social Services (PPSDSN) Penganthi Temanggung. The study used quantitative methods with correlational design with 55 participants, taken with saturated sampling techniques. The self-acceptance variabel measurement instrument uses the Self-Acceptance Scale for Persons with Early Blindness scales of Morgado, Campana, and Tavares and the future orientation scale of the scale compiled by the researcher based on aspects proposed by Seginer. The results showed a significant positive relationship between self-acceptance and future orientation in visually impaired people in PPSDSN Penganthi Temanggung with r = 0.225 with sig = 0.049 (p <0.05) which means the better the self-acceptance of the individual, the better the future orientation and vice versa.

Disrupted voxel-mirrored homotopic connectivity in congenital nystagmus using resting-state fMRI.

Idiopathic congenital nystagmus (CN) is a rare eye disease that can cause early blindness (EB). CN deficits are observed most frequently with oculomotor dysfunction; however, it is still unclear what neuromechanics underly CN with EB. Based on that visual experience requires the functional integration of both hemispheres, we hypothesized that CN adolescents with EB might exhibit impaired interhemispheric synchrony. Our study aimed to investigate the interhemispheric functional connectivity alterations using voxel-mirrored homotopic connectivity (VMHC) and their relationships with clinical features in CN patients. This study included 21 patients with CN and EB, and 21 sighted controls (SC), who were matched for sex, age and educational level. The 3.0 T MRI scan and ocular examination were performed. The VMHC differences were examined between the two groups, and the relationships between mean VMHC values in altered brain regions and clinical variables in the CN group were evaluated by Pearson correlation analysis. Compared with the SC group, the CN had increased VMHC values in the bilateral cerebellum posterior and anterior lobes/cerebellar tonsil/declive/pyramis/culmen/pons, middle frontal gyri (BA 10) and frontal eye field/superior frontal gyri (BA 6 and BA 8). No particular areas of the brain had lower VMHC values. Furthermore, no correlation with the duration of disease or blindness could be demonstrated in CN. Our results suggest the existence of interhemispheric connectivity changes and provide further evidence for the neurological basis of CN with EB.

Fast Food and Malnutrition can lead to Blindness and Structural Changes in the Central Nervous System (CNS)

Background: An increasing awareness regarding consumption of fast food in early childhood and blindness with serious metabolic changes combined with morphological changes in the central nervous system should be considered. Method: This study conducted a systematic search in the PubMed database for articles related to Optic Neuropathy. The only risk factor was malnutrition due to fast food consumption, which led to Blindness due to nutritional optic neuropathy. Discussion and Conclusion: Early detection and management could prevent permanent loss of vision in both eyes, or at least protect the only Seeing Eye. Educational programs are required to encourage children to follow healthy eating habits and to emphasize the serious effects of fast food on vision. Routine screening in schools and pediatric clinics including detailed dietary history is mandatory early detection and prevention of potential complications.

Adeno-associated virus vector intraperitoneal injection induces colonic mucosa and submucosa transduction and alters the diversity and composition of the faecal microbiota in rats.

Viral vector technology, especially recombinant adeno-associated virus vector (rAAV) technology, has shown great promise in preclinical research for clinical applications. Several studies have confirmed that rAAV can successfully transduce the enteric nervous system (ENS), and rAAV gene therapy has been approved by the Food and Drug Administration (FDA) for the treatment of the early childhood blindness disease Leber congenital amaurosis and spinal muscular atrophy (SMA). However, until now, it has not been possible to determine the effect of AAV9 on intestinal microbiota. We examined the efficiency of AAV9-mediated ascending colon, transverse colon and descending colon transduction through intraperitoneal (IP) injection, performed 16S rRNA gene amplicon sequencing and analysed specific faecal microbial signatures following AAV9 IP injection via bioinformatics methods in Sprague-Dawley (SD) rats. Our results showed (1) efficient transduction of the mucosa and submucosa of the ascending, transverse, and descending colon following AAV9 IP injection; (2) a decreased alpha diversity and an altered overall microbial composition following AAV9 IP injection; (3) significant enrichments in a total of 5 phyla, 10 classes, 13 orders, 15 families, 29 genera, and 230 OTUs following AAV9 IP injection; and (4) AAV9 can significantly upregulate the relative abundance of anaerobic microbiota which is one of the seven high-level phenotypes that BugBase could predict. In summary, these data show that IP injection of AAV9 can successfully induce the transduction of the colonic mucosa and submucosa and alter the diversity and composition of the faecal microbiota in rats.

Do you hear what I see? How do early blind individuals experience object motion?

One of the most important tasks for 3D vision is tracking the movement of objects in space. The ability of early blind individuals to understand motion in the environment from noisy and unreliable auditory information is an impressive example of cortical adaptation that is only just beginning to be understood. Here, we compare visual and auditory motion processing, and discuss the effect of early blindness on the perception of auditory motion. Blindness leads to cross-modal recruitment of the visual motion area hMT+ for auditory motion processing. Meanwhile, the planum temporale, associated with auditory motion in sighted individuals, shows reduced selectivity for auditory motion. We discuss how this dramatic shift in the cortical basis of motion processing might influence the perceptual experience of motion in early blind individuals. This article is part of a discussion meeting issue 'New approaches to 3D vision'.

Tactile expectancy modulates occipital alpha oscillations in early blindness

Alpha oscillatory activity is thought to contribute to visual expectancy through the engagement of task-relevant occipital regions. In early blindness, occipital alpha oscillations are systematically reduced, suggesting that occipital alpha depends on visual experience. However, it remains possible that alpha activity could serve expectancy in non-visual modalities in blind people, especially considering that previous research has shown the recruitment of the occipital cortex for non-visual processing. To test this idea, we used electroencephalography to examine whether alpha oscillations reflected a differential recruitment of task-relevant regions between expected and unexpected conditions in two haptic tasks (texture and shape discrimination). As expected, sensor-level analyses showed that alpha suppression in parieto-occipital sites was significantly reduced in early blind individuals compared with sighted participants. The source reconstruction analysis revealed that group differences originated in the middle occipital cortex. In that region, expected trials evoked higher alpha desynchronization than unexpected trials in the early blind group only. Our results support the role of alpha rhythms in the recruitment of occipital areas in early blind participants, and for the first time we show that although posterior alpha activity is reduced in blindness, it remains sensitive to expectancy factors. Our findings therefore suggest that occipital alpha activity is involved in tactile expectancy in blind individuals, serving a similar function to visual anticipation in sighted populations but switched to the tactile modality. Altogether, our results indicate that expectancy-dependent modulation of alpha oscillatory activity does not depend on visual experience. Significance statementAre posterior alpha oscillations and their role in expectancy and anticipation dependent on visual experience? Our results show that tactile expectancy can modulate posterior alpha activity in blind (but not sighted) individuals through the engagement of occipital regions, suggesting that in early blindness, alpha oscillations maintain their proposed role in visual anticipation but subserve tactile processing. Our findings bring a new understanding of the role that alpha oscillatory activity plays in blindness, contrasting with the view that alpha activity is task unspecific in blind populations.

Peripapillary Atrophy Segmentation and Classification Methodologies for Glaucoma Image Detection: A Review.

Information-based image processing and computer vision methods are utilized in several healthcare organizations to diagnose diseases. The irregularities in the visual system are identified over fundus images with a fundus camera. Among ophthalmology diseases, glaucoma is the most common case leading to neurodegenerative illness. The unsuitable fluid pressure inside the eye within the visual system is described as the major cause of those diseases. Glaucoma has no symptoms in the early stages, and if it is not treated, it may result in total blindness. Diagnosing glaucoma at an early stage may prevent permanent blindness. Manual inspection of the human eye may be a solution, but it depends on the skills of the individuals involved. The diagnosis of glaucoma by applying a consolidation of computer vision, artificial intelligence, and image processing can aid in the prevention and detection of those diseases. In this review article, we aim to introduce numerous approaches based on peripapillary atrophy segmentation and classification that can detect these diseases, as well as details regarding the publicly available image benchmarks, datasets, and measurement of performance. The review article highlights the research carried out on numerous available study models that objectively diagnose glaucoma via peripapillary atrophy from the lowest level of feature extraction to the current direction based on deep learning. The advantages and disadvantages of each method are addressed in detail, and tabular descriptions are included to highlight the results of each category. Moreover, the frameworks of each approach and fundus image datasets are provided. Our study would help in providing possible future work directions to diagnose glaucoma.

ODP142 Concentric Reversible Visual Field Loss, Nyctalopia and Dyschromatopsia With Ezetimibe Therapy - A Case Report

Abstract Background Ezetimibe is a lipid lowering agent that selectively inhibits intestinal cholesterol absorption. It is clinically indicated in patients with hypercholesterolemia in combination with statin or as monotherapy in patients who are contraindicated or intolerant to statin. Musculoskeletal and gastrointestinal symptoms are the commonly reported adverse drug reactions for ezetimibe monotherapy, but to date there are no published reports of ezetimibe induced visual disorders. Number of medications (including ezetimbe) associated with secondary cone-rod dystrophies (CRDs) have been reported in the Rare Disease Hub, but its mechanism of action is not well understood. Clinical case: A 55 year-old Caucasian women with a 2 years history of increasing concentric visual field loss, blurred vision, photophobia, nyctalopia (loss of night vision), dyschromatopsia (colour blindness), and new visual migraines with bright aura after commencing ezetimbe and montelukast therapy around the same time. She had a background of asthma, rosacea, and hypercholesterolemia. She does not report drug related hypersensitivity reactions other than statin intolerance and is otherwise medically well with no family history of retinal dystrophy. On investigation, pertinent positives included repeated visual field constriction on Humphrey visual fields 30'2, and significantly impaired colour vision bilaterally (R1/17, L1/17) on Ishihara charts not previously reported. MRI of orbits and brain was unremarkable. Retinal examination and electrophysiology testing were completely normal for all test conditions. Baseline blood tests including FBC, LFT, EUC, CRP, ESR, TSH, ACE, and fasting glucose were normal. Autoimmune screens including anti-retinal antibodies, ENA, ANA, anti-dsDNA, serum electrophoresis, complements, lupus anti-coagulants, and thrombophilia studies were all within normal limits. Recent abdominal US, CXR and mammography were normal. Work up for carcinoma associated retinopathy and was negative. Visual symptoms completely resolved after cessation of both ezetimibe and montelukast therapy. Rechallenge on montelukast therapy alone did not result in recurrent visual field constrictions. Clinical review after 3 months demonstrated normalization of the concentric visual field loss on Humphrey field analyzer. Conclusion This is the first case demonstrating association between ezetimibe and CRD related visual impairments. There is literature reporting multiple different medications causing cone-rod dystrophy. This includes commonly used pharmacotherapies to treat diabetes, such as sitagliptin/metformin combinations. Clinical course of CRDs is rapid and can lead to early legal blindness if left untreated. Therefore, we emphasise the importance of considering commonly used medications as a cause of patient symptoms in unexplained clinical presentations, and to systematically go through the options. Reference: (1) Cone-rod dystrophy. Rare diseases InfoHub. https://rarediseases.oscar.ncsu.edu/disease/cone-rod-dystrophy/resources/ Presentation: No date and time listed

Brain structural plasticity in rats subjected to early binocular enucleation characterized by high resolution anatomical magnetic resonance imaging and diffusion tensor imaging

Visual deprivation leads to structural neuroplasticity in the blind subjects, including gray matter (GM) and white matter (WM) atrophy and alterations in structural connectivity. The rat model of binocular enucleation (BE) is a frequently used animal model for studying brain plasticity induced by early blindness. Yet few neuroimaging studies have been performed on this model to investigate whether or not the BE rats have image phenotypes similar to or comparable to, those observed in the early blind subjects. The current study aimed to assess brain structural plasticity in BE rats using anatomical magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). The results demonstrated that early BE at postnatal day 4 (P4) caused almost complete degeneration of optic nerve (ON) and optic chiasma (OCH), atrophy in a number of visual and non-visual structures, including optic tract (OT), dorsal lateral geniculate nucleus (DLG) and corpus callosum (CC). The BE rats also exhibited impairments of WM microstructural integrity in the OT, and reduction of structural connectivity between the normal-appearing visual cortex (VC) and somatosensory/motor cortices at 4 months of age, likely as manifestations of deafferentation-induced maldevelopment. The structural neuroplasticity in BE rats observable to structural MRI parallels largely with what has been reported in blind subjects, suggesting that longitudinal neuroimaging studies on animal models of sensory deprivation can provide insights into how the brain changes its wiring and function during development/adaption in response to the lack of sensory stimuli.