Effect of vision impairment on match-related performance and technical variation in attacking moves in Paralympic judo.

In Paralympic judo for athletes with vision impairment (VI judo) all eligible athletes (i.e. B1, B2 and B3 classes) compete against each other in the same competition. Evidence suggests that athletes with more impairment may be disadvantaged, but that more sensitive measures of performance are necessary to understand the impact of impairment on performance. The aim of this study was to investigate the relationship between Para sport class and technical variation, time-motion variables, and performance in Paralympic judo. All 175 judo matches from the Rio 2016 Paralympic Games were analysed across 129 competitors (82 male and 47 female). The main results indicated that athletes who demonstrated less technical variation also experienced less competitive success, with the functionally blind athletes (class B1) demonstrating less technical variation than partially sighted (class B2 and B3) athletes (p < 0.05). There was no difference in the time-motion variables between sport classes (p > 0.05). We conclude that measures of technical variation are sensitive to differences in impairment and are suitable for studies that investigate the impairment-performance relationship in VI judo. Results further confirm that some athletes with impairment are disadvantaged under the current rules of VI judo.

Human click-based echolocation: Effects of blindness and age, and real-life implications in a 10-week training program.

Understanding the factors that determine if a person can successfully learn a novel sensory skill is essential for understanding how the brain adapts to change, and for providing rehabilitative support for people with sensory loss. We report a training study investigating the effects of blindness and age on the learning of a complex auditory skill: click-based echolocation. Blind and sighted participants of various ages (21-79 yrs; median blind: 45 yrs; median sighted: 26 yrs) trained in 20 sessions over the course of 10 weeks in various practical and virtual navigation tasks. Blind participants also took part in a 3-month follow up survey assessing the effects of the training on their daily life. We found that both sighted and blind people improved considerably on all measures, and in some cases performed comparatively to expert echolocators at the end of training. Somewhat surprisingly, sighted people performed better than those who were blind in some cases, although our analyses suggest that this might be better explained by the younger age (or superior binaural hearing) of the sighted group. Importantly, however, neither age nor blindness was a limiting factor in participants' rate of learning (i.e. their difference in performance from the first to the final session) or in their ability to apply their echolocation skills to novel, untrained tasks. Furthermore, in the follow up survey, all participants who were blind reported improved mobility, and 83% reported better independence and wellbeing. Overall, our results suggest that the ability to learn click-based echolocation is not strongly limited by age or level of vision. This has positive implications for the rehabilitation of people with vision loss or in the early stages of progressive vision loss.

Color and cellular selectivity of retinal ganglion cell subtypes through frequency modulation of electrical stimulation.

Epiretinal prostheses aim at electrically stimulating the inner most surviving retinal cells-retinal ganglion cells (RGCs)-to restore partial sight to the blind. Recent tests in patients with epiretinal implants have revealed that electrical stimulation of the retina results in the percept of color of the elicited phosphenes, which depends on the frequency of stimulation. This paper presents computational results that are predictive of this finding and further support our understanding of the mechanisms of color encoding in electrical stimulation of retina, which could prove pivotal for the design of advanced retinal prosthetics that elicit both percept and color. This provides, for the first time, a directly applicable "amplitude-frequency" stimulation strategy to "encode color" in future retinal prosthetics through a predictive computational tool to selectively target small bistratified cells, which have been shown to contribute to "blue-yellow" color opponency in the retinal circuitry. The presented results are validated with experimental data reported in the literature and correlated with findings in blind patients with a retinal prosthetic implant collected by our group.

The acts of opening and closing the eyes are of importance for congenital blindness: Evidence from resting-state fMRI.

Volitional eye closure is observed only in conscious and awake humans, and is rare in animals. It is believed that eye closure can focus one's attention inward and facilitate activities such as meditation and mental imagery. Congenital blind individuals are also required to close their eyes for these activities. Resting-state functional magnetic resonance imaging (RS-fMRI) studies have found robust differences between the eyes-closed (EC) and eyes-open (EO) conditions in some brain regions in the sighted. This study analyzed data from 21 congenital blind individuals and 21 sighted controls by using amplitude of low-frequency fluctuation (ALFF) of RS-fMRI. The blind group and the sighted group shared similar pattern of differences between the EC and EO condition: ALFF was higher in the EC condition than the EO condition in the bilateral primary sensorimotor cortex, bilateral supplementary motor area, and inferior occipital cortex, while ALFF was lower in the EC condition than the EO condition in the medial prefrontal cortex, highlighting the "nature" effect on the difference between the EC and EO conditions. The results of other matrices such as fractional ALFF (fALFF) and regional homogeneity (ReHo) showed similar patterns to that of ALFF. Moreover, no significant difference was observed between the EC-EO pattern of the two subgroups of congenital blind (i.e., with and without light perception), suggesting that the EC-EO difference is irrespective of residual light perception which reinforced the "nature" effect. We also found between-group differences, i.e., more probably "nurture effect", in the posterior insula and fusiform. Our results suggest that the acts of closing and opening the eyes are of importance for the congenital blind, and that these actions and their differences might be inherent in the nature of humans.

Neural network for Braille reading and the speech-reading convergence in the blind: Similarities and differences to visual reading.

All writing systems represent units of spoken language. Studies on the neural correlates of reading in different languages show that this skill relies on access to brain areas dedicated to speech processing. Speech-reading convergence onto a common perisylvian network is therefore considered universal among different writing systems. Using fMRI, we test whether this holds true also for tactile Braille reading in the blind. The neural networks for Braille and visual reading overlapped in the left ventral occipitotemporal (vOT) cortex. Even though we showed similar perisylvian specialization for speech in both groups, blind subjects did not engage this speech system for reading. In contrast to the sighted, speech-reading convergence in the blind was absent in the perisylvian network. Instead, the blind engaged vOT not only in reading but also in speech processing. The involvement of the vOT in speech processing and its engagement in reading in the blind suggests that vOT is included in a modality independent language network in the blind, also evidenced by functional connectivity results. The analysis of individual speech-reading convergence suggests that there may be segregated neuronal populations in the vOT for speech processing and reading in the blind.

Restoring Color Perception to the Blind: An Electrical Stimulation Strategy of Retina in Patients with End-stage Retinitis Pigmentosa.

PURPOSE: Bioelectronic retinal prostheses that stimulate the remaining inner retinal neurons, bypassing degenerated photoreceptors, have been demonstrated to restore some vision in patients blinded by retinitis pigmentosa (RP). These implants encode luminance of the visual scene into electrical stimulation, however, leaving out chromatic information. Yet color plays an important role in visual processing when it comes to recognizing objects and orienting to the environment, especially at low spatial resolution as generated by current retinal prostheses. In this study, we tested the feasibility of partially restoring color perception in blind RP patients, with the aim to provide chromatic information as an extra visual cue. DESIGN: Case series. PARTICIPANTS: Seven subjects blinded by advanced RP and monocularly fitted with an epiretinal prosthesis. METHODS: Frequency-modulated electrical stimulation of retina was tested. Phosphene brightness was controlled by amplitude tuning, and color perception was acquired using the Red, Yellow, Green, and Blue (RYGB) hue and saturation scaling model. MAIN OUTCOME MEASURES: Brightness and color of the electrically elicited visual perception reported by the subjects. RESULTS: Within the tested parameter space, 5 of 7 subjects perceived chromatic colors along or nearby the blue-yellow axis in color space. Aggregate data obtained from 20 electrodes of the 5 subjects show that an increase of the stimulation frequency from 6 to 120 Hz shifted color perception toward blue/purple despite a significant inter-subject variation in the transition frequency. The correlation between frequency and blue-yellow perception exhibited a good level of consistency over time and spatially matched multi-color perception was possible with simultaneous stimulation of paired electrodes. No obvious correlation was found between blue sensations and array placement or status of visual impairment. CONCLUSIONS: These findings present a strategy for the generation and control of color perception along the blue-yellow axis in blind patients with RP by electrically stimulating the retina. It could transform the current prosthetic vision landscape by leading in a new direction beyond the efforts to improve the visual acuity. This study also offers new insights into the response of our visual system to electrical stimuli in the photoreceptor-less retina that warrant further mechanistic investigation.

May the best-sighted win? The relationship between visual function and performance in Para judo.

This study aimed to establish the optimal cut-off point(s) between classes in a new, evidence-based classification system for VI judo. We collected results from international VI judo competitions held between 2012 and 2018. Data on visual acuity (VA) and visual field (VF) measured during classification were obtained. Performance was determined by calculating a win ratio for each athlete. VA was significantly associated with judo performance (r = -.33, p <.001), VF was not (r =.30, p =.15). Decision tree analysis suggested to split the data into two groups with a VA cut-off of 2.5 logMAR units. Stability assessment using bootstrap sampling suggested a split into two groups, but showed considerable variability in the cut-off point between 2.0 and 3.5 logMAR. We conclude that to minimise the impact of impairment on the outcome of competition, VI judo should be split into two sport classes to separate partially sighted from functionally blind athletes. To establish an exact cut-off point and to decide if other measures of visual function need to be included, we argue for continued research efforts together with careful evaluation of research results from a multidisciplinary perspective.

Decoding Natural Sounds in Early "Visual" Cortex of Congenitally Blind Individuals.

Complex natural sounds, such as bird singing, people talking, or traffic noise, induce decodable fMRI activation patterns in early visual cortex of sighted blindfolded participants [1]. That is, early visual cortex receives non-visual and potentially predictive information from audition. However, it is unclear whether the transfer of auditory information to early visual areas is an epiphenomenon of visual imagery or, alternatively, whether it is driven by mechanisms independent from visual experience. Here, we show that we can decode natural sounds from activity patterns in early "visual" areas of congenitally blind individuals who lack visual imagery. Thus, visual imagery is not a prerequisite of auditory feedback to early visual cortex. Furthermore, the spatial pattern of sound decoding accuracy in early visual cortex was remarkably similar in blind and sighted individuals, with an increasing decoding accuracy gradient from foveal to peripheral regions. This suggests that the typical organization by eccentricity of early visual cortex develops for auditory feedback, even in the lifelong absence of vision. The same feedback to early visual cortex might support visual perception in the sighted [1] and drive the recruitment of this area for non-visual functions in blind individuals [2, 3].

The role of spatial selective attention in the processing of affective prosodies in congenitally blind adults: An ERP study.

The question whether spatial selective attention is necessary in order to process vocal affective prosody has been controversially discussed in sighted individuals: whereas some studies argue that attention is required in order to process emotions, other studies conclude that vocal prosody can be processed even outside the focus of spatial selective attention. Here, we asked whether spatial selective attention is necessary for the processing of affective prosodies after visual deprivation from birth. For this purpose, pseudowords spoken in happy, neutral, fearful or threatening prosodies were presented at the left or right loudspeaker. Congenitally blind individuals (N = 8) and sighted controls (N = 13) had to attend to one of the loudspeakers and detect rare pseudowords presented at the attended loudspeaker during EEG recording. Emotional prosody of the syllables was task-irrelevant. Blind individuals outperformed sighted controls by being more efficient in detecting deviant syllables at the attended loudspeaker. A higher auditory N1 amplitude was observed in blind individuals compared to sighted controls. Additionally, sighted controls showed enhanced attention-related ERP amplitudes in response to fearful and threatening voices during the time range of the N1. By contrast, blind individuals revealed enhanced ERP amplitudes in attended relative to unattended locations irrespective of the affective valence in all time windows (110-350 ms). These effects were mainly observed at posterior electrodes. The results provide evidence for "emotion-general" auditory spatial selective attention effects in congenitally blind individuals and suggest a potential reorganization of the voice processing brain system following visual deprivation from birth.

Reorganization of Sound Location Processing in the Auditory Cortex of Blind Humans.

Auditory spatial tasks induce functional activation in the occipital-visual-cortex of early blind humans. Less is known about the effects of blindness on auditory spatial processing in the temporal-auditory-cortex. Here, we investigated spatial (azimuth) processing in congenitally and early blind humans with a phase-encoding functional magnetic resonance imaging (fMRI) paradigm. Our results show that functional activation in response to sounds in general-independent of sound location-was stronger in the occipital cortex but reduced in the medial temporal cortex of blind participants in comparison with sighted participants. Additionally, activation patterns for binaural spatial processing were different for sighted and blind participants in planum temporale. Finally, fMRI responses in the auditory cortex of blind individuals carried less information on sound azimuth position than those in sighted individuals, as assessed with a 2-channel, opponent coding model for the cortical representation of sound azimuth. These results indicate that early visual deprivation results in reorganization of binaural spatial processing in the auditory cortex and that blind individuals may rely on alternative mechanisms for processing azimuth position.

Unique Features of Subcortical Circuits in a Macaque Model of Congenital Blindness.

There is an extensive modification of the functional organization of the brain in the congenital blind human, although there is little understanding of the structural underpinnings of these changes. The visual system of macaque has been extensively characterized both anatomically and functionally. We have taken advantage of this to examine the influence of congenital blindness in a macaque model of developmental anophthalmia. Developmental anophthalmia in macaque effectively removes the normal influence of the thalamus on cortical development leading to an induced "hybrid cortex (HC)" combining features of primary visual and extrastriate cortex. Here we show that retrograde tracers injected in early visual areas, including HC, reveal a drastic reduction of cortical projections of the reduced lateral geniculate nucleus. In addition, there is an important expansion of projections from the pulvinar complex to the HC, compared to the controls. These findings show that the functional consequences of congenital blindness need to be considered in terms of both modifications of the interareal cortical network and the ascending visual pathways.

A thalamocortical pathway for fast rerouting of tactile information to occipital cortex in congenital blindness.

In congenitally blind individuals, the occipital cortex responds to various nonvisual inputs. Some animal studies raise the possibility that a subcortical pathway allows fast re-routing of tactile information to the occipital cortex, but this has not been shown in humans. Here we show using magnetoencephalography (MEG) that tactile stimulation produces occipital cortex activations, starting as early as 35 ms in congenitally blind individuals, but not in blindfolded sighted controls. Given our measured thalamic response latencies of 20 ms and a mean estimated lateral geniculate nucleus to primary visual cortex transfer time of 15 ms, we claim that this early occipital response is mediated by a direct thalamo-cortical pathway. We also observed stronger directed connectivity in the alpha band range from posterior thalamus to occipital cortex in congenitally blind participants. Our results strongly suggest the contribution of a fast thalamo-cortical pathway in the cross-modal activation of the occipital cortex in congenitally blind humans.

Investigating the Effect of Visual Imagery and Learning Shape-Audio Regularities on Bouba and Kiki.

This article presents a protocol for investigating the role of visual imagery in the bouba/kiki-effect, whether training in noticing the bouba/kiki shape-audio regularities affects the bouba/kiki-effect and the recognition of individual bouba and kiki shapes, and finally what mental images these regularities produce. To generate bouba/kiki shape-audio regularities, there were two types of shapes (filled; outlined) and two types of audio (word; non-word sound). Three groups of individuals participated in three experiments: Blind, blindfold, and vision. The experiments were conducted in fixed order across participants, with no break between them. In Experiment 1 (pre-test-post-test design with three repeated within-group measures) the participants were asked to pick out the shape they associated with the auditory bouba/kiki; in Experiment 2 (within-subject design), to name one shape and some audio (sometimes congruous; sometimes incongruous) as 'bouba' or 'kiki;' and in Experiment 3 (post-test only design), to draw the shape they associated with the auditory bouba/kiki. The results suggest that the blindfold-group draw upon visual imagery to solve new problems, but not long term; that training in noticing bouba/kiki shape-audio regularities affects the bouba/kiki-effect and the recognition of individual bouba and kiki shapes, but differently in each experimental group; and that all experimental groups create mental images of the most characteristic shape feature of bouba (curve) and kiki (angle). In fact, the effect of visual imagery is robust across tasks, but not long term; the effect of learning shape-audio regularities is robust long term, but not across tasks. The presented protocol is appropriate for investigating the effect of visual imagery and learning shape-audio regularities, when they occur and how robust they are; in specific individuals and groups of individuals. This protocol is unique in that it keeps under control both the visual imagery and the sensory information during training and testing.

Naturalistic Audio-Movies and Narrative Synchronize "Visual" Cortices across Congenitally Blind But Not Sighted Individuals.

How does developmental experience, as opposed to intrinsic physiology, shape cortical function? Naturalistic stimuli were used to elicit neural synchrony in individuals blind from birth (n = 18) and those who grew up with sight (n = 18). Blind and blindfolded sighted participants passively listened to three audio-movie clips, an auditory narrative, a sentence shuffled version of the narrative (maintaining language but lacking a plotline), and a version of the narrative backward (lacking both language and plot). For both groups, early auditory cortices were synchronized to a similar degree across stimulus types, whereas higher-cognitive temporoparietal and prefrontal areas were more synchronized by meaningful, temporally extended stimuli (i.e., audio movies and narrative). "Visual" cortices were more synchronized across blind than sighted individuals, but only for audio-movies and narrative. In the blind group, visual cortex synchrony was low for backward speech and intermediate for sentence shuffle. Meaningful auditory stimuli synchronize visual cortices of people born blind.SIGNIFICANCE STATEMENT Naturalistic stimuli engage cognitive processing at many levels. Here, we harnessed this richness to investigate the effect of experience on cortical function. We find that listening to naturalistic audio movies and narrative drives synchronized activity across "visual" cortices of blind, more so than sighted, individuals. Visual cortex synchronization varies with meaningfulness and cognitive complexity. Higher synchrony is observed for temporally extended meaningful stimuli (e.g., movies/narrative), intermediate for shuffled sentences, lowest for time varying complex noise. By contrast, auditory cortex was synchronized equally by meaningful and meaningless stimuli. In congenitally blind individuals most of visual cortex is engaged by meaningful naturalistic stimuli.

Ipsilateral transient amaurosis, mydriasis and light reflex absence after subconjunctival local anesthesia with mepivacaine in three patients with refractory glaucoma - a case report.

BACKGROUND: The subconjunctival anesthesia with local anesthetics is considered as a low-risk procedure allowing ocular surgery without serious complications typical for retro- or parabulbar anesthesia, especially in patients with preexisting Optic Nerve damage. We report development of ipsilateral transient amaurosis accompanied with mydriasis and both, direct and consensual light response absence. CASE PRESENTATION: Three patients with advanced refractory glaucoma undergoing laser cyclophotocoagulation (CPC) for intraocular pressure lowering experienced these adverse effects just few minutes after subconjunctival injection of mepivacaine 2% solution (Scandicaine® 2%, without vasoconstrictor supplementation). The vision was completely recovered to usual values in up to 20 h after mepivacaine application. Extensive ophthalmological examination, including cranial magnetic resonance imaging (MRI), revealed no further ocular abnormalities, especially no vascular constriction or thrombotic signs as well as no retinal detachment. The oculomotor function remained intact. The blockade of ipsilateral ciliary ganglion parasympathetic fibers by mepivacaine may be the responsible mechanism. Systemic pathways as drug-drug interactions seem to be unlikely involved. Importantly, all three patients tolerated the same procedure previously or at a later date without any complication. Overall, our thoroughly elaborated risk management could not determine the causative factor explaining the observed ocular complications just in the current occasion and not at other time points. CONCLUSIONS: Doctors should be aware and patients should be informed about such rare complications after subconjunctival local anesthetics administration. Adequate risk management should insure patients' safety.

Incidence and impact factors of intraoperative loss of light perception under sub-Tenon's anesthesia in patients with macular diseases.

PURPOSE: To investigate the incidence and impact factors of intraoperative loss of light perception (LP) under sub-Tenon's anesthesia in patients with macular diseases. METHODS: Eighty-five consecutive patients received standard phacoemulsification combined pars plana vitrectomy (PPV) under sub-Tenon's anesthesia. At several checkpoints during the surgery (the end of phacoemulsification, the end of vitrectomy, and the end of surgery), participants were interviewed about whether they had LP or not after removing the influence of contralateral eye and the photo-bleaching effect. In patients treated with retinal photocoagulation, visual experience on laser flashes was evaluated. RESULTS: Under routine draping, no patients reported loss of LP at all the checkpoints. When the contralateral eye was tightly covered, the rates of LP loss were 84.7%, 97.6%, and 87.1% at the end of phacoemulsification, the end of vitrectomy, and the end of surgery, respectively. When the photo-bleaching effect was also removed, the rates of LP loss were 61.2%, 82.4%, and 56.5% at each checkpoint, respectively, and there were 87.1% (74/85) of patients reporting visual loss in at least one checkpoint. In addition, 76.9% (50/65) of patients could not feel laser flashes during retinal photocoagulation. CONCLUSION: Intraoperative loss of LP under sub-Tenon's anesthesia was a relatively common and reversible event. The conduction block of optic nerve by anesthetic mainly contributed to the visual loss during surgery. Photo-bleaching effect also has some effect on the LP evaluation. Surgeons need to inform and counsel the patients about the intraoperative loss of LP, to prevent any sudden panic attacks in them.

Knowledge of animal appearance among sighted and blind adults.

How does first-person sensory experience contribute to knowledge? Contrary to the suppositions of early empiricist philosophers, people who are born blind know about phenomena that cannot be perceived directly, such as color and light. Exactly what is learned and how remains an open question. We compared knowledge of animal appearance across congenitally blind (n = 20) and sighted individuals (two groups, n = 20 and n = 35) using a battery of tasks, including ordering (size and height), sorting (shape, skin texture, and color), odd-one-out (shape), and feature choice (texture). On all tested dimensions apart from color, sighted and blind individuals showed substantial albeit imperfect agreement, suggesting that linguistic communication and visual perception convey partially redundant appearance information. To test the hypothesis that blind individuals learn about appearance primarily by remembering sighted people's descriptions of what they see (e.g., "elephants are gray"), we measured verbalizability of animal shape, texture, and color in the sighted. Contrary to the learn-from-description hypothesis, blind and sighted groups disagreed most about the appearance dimension that was easiest for sighted people to verbalize: color. Analysis of disagreement patterns across all tasks suggest that blind individuals infer physical features from non-appearance properties of animals such as folk taxonomy and habitat (e.g., bats are textured like mammals but shaped like birds). These findings suggest that in the absence of sensory access, structured appearance knowledge is acquired through inference from ontological kind.

Early Blindness Shapes Cortical Representations of Auditory Frequency within Auditory Cortex.

Early loss of vision is classically linked to large-scale cross-modal plasticity within occipital cortex. Much less is known about the effects of early blindness on auditory cortex. Here, we examine the effects of early blindness on the cortical representation of auditory frequency within human primary and secondary auditory areas using fMRI. We observe that 4 individuals with early blindness (2 females), and a group of 5 individuals with anophthalmia (1 female), a condition in which both eyes fail to develop, have lower response amplitudes and narrower voxelwise tuning bandwidths compared with a group of typically sighted individuals. These results provide some of the first evidence in human participants for compensatory plasticity within nondeprived sensory areas as a result of sensory loss.SIGNIFICANCE STATEMENT Early blindness has been linked to enhanced perception of the auditory world, including auditory localization and pitch perception. Here we used fMRI to compare neural responses with auditory stimuli within auditory cortex across sighted, early blind, and anophthalmic individuals, in whom both eyes fail to develop. We find more refined frequency tuning in blind subjects, providing some of the first evidence in human subjects for compensation within nondeprived primary sensory areas as a result of blindness early in life.

Working memory training integrates visual cortex into beta-band networks in congenitally blind individuals.

Congenitally blind individuals have been shown to activate the visual cortex during non-visual tasks. The neuronal mechanisms of such cross-modal activation are not fully understood. Here, we used an auditory working memory training paradigm in congenitally blind and in sighted adults. We hypothesized that the visual cortex gets integrated into auditory working memory networks, after these networks have been challenged by training. The spectral profile of functional networks was investigated which mediate cross-modal reorganization following visual deprivation. A training induced integration of visual cortex into task-related networks in congenitally blind individuals was expected to result in changes in long-range functional connectivity in the theta-, beta- and gamma band (imaginary coherency) between visual cortex and working memory networks. Magnetoencephalographic data were recorded in congenitally blind and sighted individuals during resting state as well as during a voice-based working memory task; the task was performed before and after working memory training with either auditory or tactile stimuli, or a control condition. Auditory working memory training strengthened theta-band (2.5-5 Hz) connectivity in the sighted and beta-band (17.5-22.5 Hz) connectivity in the blind. In sighted participants, theta-band connectivity increased between brain areas typically involved in auditory working memory (inferior frontal, superior temporal, insular cortex). In blind participants, beta-band networks largely emerged during the training, and connectivity increased between brain areas involved in auditory working memory and as predicted, the visual cortex. Our findings highlight long-range connectivity as a key mechanism of functional reorganization following congenital blindness, and provide new insights into the spectral characteristics of functional network connectivity.

Current understanding of photophobia, visual networks and headaches.

OBJECTIVE: To review clinical and pre-clinical evidence supporting the role of visual pathways, from the eye to the cortex, in the development of photophobia in headache disorders. BACKGROUND: Photophobia is a poorly understood light-induced phenomenon that emerges in a variety of neurological and ophthalmological conditions. Over the years, multiple mechanisms have been proposed to explain its causes; however, scarce research and lack of systematic assessment of photophobia in patients has made the search for answers quite challenging. In the field of headaches, significant progress has been made recently on how specific visual networks contribute to photophobia features such as light-induced intensification of headache, increased perception of brightness and visual discomfort, which are frequently experienced by migraineurs. Such progress improved our understanding of the phenomenon and points to abnormal processing of light by both cone/rod-mediated image-forming and melanopsin-mediated non-image-forming visual pathways, and the consequential transfer of photic signals to multiple brain regions involved in sensory, autonomic and emotional regulation. CONCLUSION: Photophobia phenotype is diverse, and the relative contribution of visual, trigeminal and autonomic systems may depend on the disease it emerges from. In migraine, photophobia could result from photic activation of retina-driven pathways involved in the regulation of homeostasis, making its association with headache more complex than previously thought.