Visual Behavior Research Articles

Digital health and wearable devices for retinal disease monitoring

AbstractDigital health is wielding a growing influence across all areas of healthcare, encompassing various facets such as telemedicine, artificial intelligence (AI), and electronic healthcare records. In Ophthalmology, digital health innovations can be broadly divided into four categories: (i) self-monitoring home devices and apps, (ii) virtual and augmented reality visual aids, (iii) AI software, and (iv) wearables. Wearable devices can work in the background, collecting large amounts of objective data while we do our day-to-day activities, which may be ecologically more valid and meaningful to patients than that acquired in traditional hospital settings. They can be a watch, wristband, piece of clothing, glasses, cane, smartphone in our pocket, earphones, or any other device with a sensor that we carry with us. Focusing on retinal diseases, a key challenge in developing novel therapeutics has been to prove a meaningful benefit in patients’ lives and the creation of objective patient-centred endpoints in clinical trials. In this review, we will discuss wearable devices collecting different aspects of visual behaviour, visual field, central vision, and functional vision, as well as their potential implementation as outcome measures in research/clinical trial settings. The healthcare landscape is facing a paradigm shift. Clinicians have a key role of collaborating with the development and fine-tuning of digital health innovations, as well as identifying opportunities where they can be leveraged to enhance our understanding of retinal diseases and improve patient outcomes.

AI-Powered Neural Network Verification: System Verilog Methodologies for Machine Learning in Hardware

This research focuses on verifying neural network models using System Verilog, with two primary applications: visual edge detection and neuron behavior modeling. In modern chip design, hardware verification plays a crucial role in ensuring that complex neural models perform as expected. A neuron model based on Hubel and Wiesel’s feed-forward network architecture was proposed and tested using integrator and threshold modules implemented in Verilog. The proposed verification methodology employs self-checking test benches, supported by functional coverage and simulation, for comprehensive validation. The results demonstrate efficient verification with high coverage, paving the way for future advancements in hardware neural networks.

The Effects of Layout Order on Interface Complexity: An Eye-Tracking Study for Dashboard Design.

This study investigated the effect of layout order on the complexity of the dashboard interface based on screen-based eye trackers. By simplifying and abstracting dashboard interfaces and incorporating subjective ratings (symmetry and unity calculations), we successfully manipulated the levels of complexity and layout order of the interface materials. Using four types of eye movement data (total fixation count, total gaze duration, scanning paths, and hotspot maps) and behavioral data, we compared participants' visual search behavior on interfaces with different layout orders and complexity levels. Experiment 1 revealed a significant interaction between layout order and interface complexity, with participants performing significantly better in the high-level layout order condition. Experiment 2 confirmed that the position of the core chart plays a crucial role in users' visual search behavior and that the optimal layout order for the dashboard is to place the core chart on the left side of the interface's horizontal axis, with partial symmetry in the no-core chart areas. This study highlights the effectiveness of eye-tracking techniques in user interface design research and provides valuable insights into optimizing dashboard interface design. Designers should adopt the design principle of "order is more" in addition to "less is more" and consider designing the core chart in the left-center position.

The mediating role of visual behavior in perceived walkability evaluation

ABSTRACT Past studies used street-view images to directly analyze the effect of visual environments on perceived walkability. There is a gap in understanding how eye movement mediates the results of perceived walkability evaluations. The study proposed a method to transform the vector coordinates of gaze into the coordinates of panoramic photos. Then, we used mixed linear regressions and a simple mediation model to reveal the mediating role of visual behavior on perceived walkability evaluations. The results showed that: (1) Fixation has an incomplete mediating role in the impact of visual information on perceived walkability. (2) Most streetscape elements with long fixation duration impacted perceived walkability. (3) In the visual information model, the tree and streetlight negatively impacted perceived walkability. And the gutter positively impacted perceived walkability. However, in the fixation model, the tree and streetlight positively impacted perceived walkability. The gutter negatively impacted perceived walkability. This study offers scholars and policymakers a novel perspective on understanding perceived walkability.

Shining new light on naupliar eyes: A novel molecular phylogeny for Pleuromamma (Family: Metridinidae) and the characterization of luciferase and opsin expression

Pleuromamma (Giesbrecht, 1898) is a cosmopolitan genus of metridinid copepods, with species that perform remarkable diel vertical migrations (DVM) and emit a bioluminescent secretion when disturbed that varies both spectrally and kinetically. Copepod bioluminescence is autogenic and uses luciferase enzymes that catalyze a luciferin, coelenterazine, to produce light. Pleuromamma possess naupliar eyes, relatively simple photosensitive structures used for many visually-guided behaviors. Yet the fundamental molecular unit for vision, the opsin protein, has not been previously described for the family. The light producers and detectors are important to study because DVM is a behavior that mediates significant active elemental fluxes between the upper ocean and midwaters across vast stretches of oceanic habitat, and DVM is guided by visual behaviors, with animals tracking an isolume. Here we provide the first fully resolved molecular phylogeny for Pleuromamma (Family: Metridinidae) and describe the luciferase and opsin gene diversity and expression using de novo assembled transcriptomes. We successfully sequenced and assembled transcriptomes for 10 of 11 described species of Pleuromamma as well as two other metridinid species: Metridia longa and Gaussia princeps. In all species, we obtained coding sequences of one putative rhabdomeric middle wavelength sensitive visual opsin gene, as well as several non-visual opsins – a c-type pteropsin and a tetra-opsin type peropsin. Furthermore, Pleuromamma express luciferases from each of two main evolutionary clades (Luc1 and Luc2), and a single paralog (Luc2a) dominates expression throughout the group. The variation in luciferase number, sequence, and expression among species could lead to different spectral and kinetic properties of bioluminescence and aid in congener recognition.

The Role of Population Receptive Field Sizes in Higher-Order Visual Dysfunction.

Population receptive field (pRF) modeling is an fMRI technique used to retinotopically map visual cortex, with pRF size characterizing the degree of spatial integration. In clinical populations, most pRF mapping research has focused on damage to visual system inputs. Herein, we highlight recent work using pRF modeling to study high-level visual dysfunctions. Larger pRF sizes, indicating coarser spatial processing, were observed in homonymous visual field deficits, aging, and autism spectrum disorder. Smaller pRF sizes, indicating finer processing, were observed in Alzheimer's disease and schizophrenia. In posterior cortical atrophy, a unique pattern was found in which pRF size changes depended on eccentricity. Changes to pRF properties were observed in clinical populations, even in high-order impairments, explaining visual behavior. These pRF changes likely stem from altered interactions between brain regions. Furthermore, some studies suggested that pRF sizes change as part of cortical reorganization, and they can point towards future prognosis.

Perceptual-Cognitive Skills of Basketball Referees: On-The-Court Visual Search Behavior.

Perceptual-cognitive skills are crucial in successfully managing information and decision-making in sports, particularly in high-pressure environments. We examined 16 basketball referees' on-the-court visual search behavior by comparing referees of different experience levels (experienced, n = 8; and novice, n = 8) and different court positions. Participants' visual search behavior was analyzed during 20 live gameplay situations using eye-tracking technology. Dependent variables were the number of eye fixations, mean fixation time, and total fixation time on selected areas of interest; and independent variables were the referees' experience and visual angles (lead and trail referee positions). Experienced referees exhibited significantly lower total fixation time than novice referees (p = .009). Referees in the trail position showed more fixations of shorter duration and a greater focus on the basket than those in the lead position. Our findings suggest that the visual search behavior of basketball referees varies with their court position and experience. These data provide valuable insights into referees' complex visual search patterns in the real-game context, and they highlight the importance of considering viewing angle and experience in future research.

Virtual reality to characterize anticipation skills of top-level 4 x 100m relay athletes.

One marker of expertise in sport is athletes' ability to anticipate future events. In the 4×100m relay, these anticipation skills are an essential asset for initiating their run at the right time. However, no study has focused on describing the underlying perceptual-motor processes involved. Virtual reality provides powerful tools to describe and understand these processes, overcoming the drastic constraints encountered in the real world. Nineteen athletes from the French national teams were immersed in a digital replica of the Stade de France and confronted with digital twins of potential partners based on motion capture. Their task was to initiate their run exactly when their virtual partner passed over a go-mark placed on the ground. The timing of different body motor events and visual behavior were measured and analyzed. Results showed that the execution of this highly constrained task is the result of a significant reduction in the variability of motor events preceding the start. These findings reveal the implementation of a perceptual-motor dialog until the initiation of the run. This study is a first step toward understanding the mechanisms underlying anticipation skills in the 4×100m relay; it constitutes a preliminary step to the deployment of VR training protocols.

Slc4a7 Regulates Retina Development in Zebrafish.

Inherited retinal degenerations (IRDs) are a group of genetic disorders characterized by the progressive degeneration of retinal cells, leading to irreversible vision loss. SLC4A7 has emerged as a candidate gene associated with IRDs, yet its mechanisms remain largely unknown. This study aims to investigate the role of slc4a7 in retinal development and its associated molecular pathogenesis in zebrafish. Morpholino oligonucleotide knockdown, CRISPR/Cas9 genome editing, quantitative RT-PCR, eye morphometric measurements, immunofluorescent staining, TUNEL assays, visual motor responses, optokinetic responses, rescue experiments, and bulk RNA sequencing were used to assess the impact of slc4a7 deficiency on retinal development. Our results demonstrated that the knockdown of slc4a7 resulted in a dose-dependent reduction in eye axial length, ocular area, and eye-to-body-length ratio. The fluorescence observations showed a significant decrease in immunofluorescence signals from photoreceptors and in mCherry fluorescence from RPE in slc4a7-silenced morphants. TUNEL staining uncovered the extensive apoptosis of retinal cells induced by slc4a7 knockdown. Visual behaviors were significantly impaired in the slc4a7-deficient larvae. GO and KEGG pathway analyses reveal that differentially expressed genes are predominantly linked to aspects of vision, ion channels, and phototransduction. This study demonstrates that the loss of slc4a7 in larvae led to profound visual impairments, providing additional insights into the genetic mechanisms predisposing individuals to IRDs caused by SLC4A7 deficiency.

A study of attention allocation mode in clinical decision-making in nurses with different professional titles: An eye-tracking experiment

Abstract Objective: The aim of this experiment was to investigate the way in which attention is allocated in the clinical decision-making process of nurses of different professional ranks and titles and associated factors. Methods: Seventy-six subjects from the emergency departments of 3 hospitals in Beijing were recruited in this experiment using the convenience sampling method, including 28 junior nurses, 24 senior nurses, and 24 supervisor nurses. Subjects were required to complete clinical decision tasks, and data on subjects’ visual behavior were recorded and analyzed using a Tobii Pro eye-tracker during the decision-making process. Results: Nurses with high professional titles had a higher correct response rate in the nursing diagnosis and ranking of nursing diagnoses part (P < 0.05), and it was found that nurses with high professional titles would pay attention to pathophysiological mechanisms of illness earlier when making decisions (F = 3.808, P = 0.024). The heat maps showed differences in the attention allocation modes of nurses with different titles during the decision-making process. Conclusions: Lower-titled nurses focused more on the symptoms and signs section when making clinical decisions and paid less attention to the auxiliary examination results section, demonstrating a poorer level of active attention. Nurses with higher titles were relatively more comprehensive in their distribution of attention to patient disease information when making decisions and paid attention to the information in the patient’s auxiliary examination section earlier.

Assessing driver distraction from in-vehicle information system: an on-road study exploring the effects of input modalities and secondary task types

In-vehicle information system (IVIS) use is prevalent among young adults. However, their interaction with IVIS needs to be better understood. Therefore, an on-road study aims to explore the effects of input modalities and secondary task types on young drivers' secondary task performance, driving performance, and visual glance behavior. A 2 × 4 within-subject design was undertaken. The independent variables are input modalities (auditory-speech and visual-manual) and secondary task types (calls, music, navigation, and radio). The dependent variables include secondary task performance (task completion time, number of errors, and SUS), driving performance (average speed, number of lane departure warnings, and NASA-TLX), and visual glance behavior (average glance duration, number of glances, total glance duration, and number of glances over 1.6 s). The statistical analysis result showed that the main effect of input modalities is significant, with more distraction during visual-manual than auditory-speech. The main impact of secondary task types was also substantial across most metrics, aside from average speed and average glance duration. Navigation and music were the most distracting, followed by calls, and radio came in last. The distracting effect of input modalities is relatively stable and generally not moderated by the secondary task types, except radio tasks. The findings practically benefit the driver-friendly human–machine interface design, preventing IVIS-related distraction.

Tocotrienol-rich fraction (TRF) protects against retinal cell apoptosis and preserves visual behavior in rats with streptozotocin-induced diabetic retinopathy

BackgroundTocotrienol is a vitamin E analogue that is known to exert anti-inflammatory and antioxidant effects. Hence, in the current study, the effects of TRF on the expression of pro- and anti-apoptotic proteins in the streptozotocin-induced diabetic rat retinas were investigated. The effect of TRF on the visual behaviour of rats was also studied.MethodsDiabetes was induced in rats by intraperitoneal injection of streptozotocin and was confirmed by a blood sugar level of at least 20 mmol/L, 48 h, post-injection. Diabetic rats were divided into a group treated with vehicle (DV) and the other treated with TRF (100 mg/kg; DT). A group of non-diabetic rats treated with vehicle (N) served as the control group. All treatments were administered orally for 12 weeks. Rats were then subjected to an assessment of general behaviour in an open field arena and a two-chamber mirror test to assess their visual behaviour. At the end of the experimental period, rats were sacrificed, and their retinas were isolated to measure the expression of pro- (Casp3, Bax) and anti-apoptotic (Bcl2) markers using RT-qPCR and ELISA. TUNEL staining was used to detect the apoptotic retinal cells.ResultsTreatment with TRF lowered the retinal expression of Casp3 protein by 2.26-folds (p < 0.001) and Bax protein by 2.18-fold (p < 0.001) compared to vehicle-treated rats. The retinal anti-apoptotic protein Bcl2 expression was 1.87-fold higher in DT compared to DV rats (p < 0.001). Accordingly, the Bax/Bcl2 ratio in the TRF-treated group was significantly greater in DT compared to DV rats. Retinal Casp3, Bax, and Bcl2 gene expression, as determined by RT-qPCR, also showed changes corresponding to protein expression. In the open field test, DV rats showed greater anxiety-related behaviour than group N, while the behaviour of DT rats was similar to the N group of rats. DT rats and group N rats preferred the inverse mirror chamber over the mirror-containing chamber in the two-mirror chamber test (p < 0.01).ConclusionOral TRF therapy for 12 weeks lowers retinal cell apoptosis by decreasing pro- and increasing anti-apoptotic markers. The preservation of visual behaviour in a two-chamber mirror test supported these retinal molecular alterations in diabetic rats.

AI can see you: Machiavellianism and extraversion are reflected in eye-movements.

Recent studies showed an association between personality traits and individual patterns of visual behaviour in laboratory and other settings. The current study extends previous research by measuring multiple personality traits in natural settings; and by comparing accuracy of prediction of multiple machine learning algorithms. Adolescent participants (N = 35) completed personality questionnaires (Big Five Inventory and Short Dark Triad Questionnaire) and visited an interactive museum while their eye movements were recorded with head-mounted eye tracking. To predict personality traits the eye-movement data was analysed using eight machine-learning methods: Random Forest, Adaboost, Naive Bayes, Support Vector Machine, Logistic Regression, k Nearest Neighbours, Decision Tree and a three-layer Perceptron. Extracted eye movement features introduced to machine learning algorithms predicted personality traits with above 33% chance accuracy (34%-48%). This result is comparable to previous ecologically valid studies, but lower than in laboratory-based research. Better prediction was achieved for Machiavellianism and Extraversion compared to other traits (10 and 9 predictions above the chance level by different algorithms from different parts of the recording). Conscientiousness, Narcissism and Psychopathy were not reliably predicted from eye movements. These differences in predictability across traits might be explained by differential activation of different traits in different situations, such as new vs. familiar, exciting vs. boring, and complex vs. simple settings. In turn, different machine learning approaches seem to be better at capturing specific gaze patterns (e.g. saccades), associated with specific traits evoked by the situation. Further research is needed to gain better insights into trait-situation-algorithm interactions.

A Physiological Marker for Deep Brain Ultrasonic Neuromodulation

ObjectivesTranscranial ultrasound neuromodulation (TUSN) is a noninvasive and spatially specific therapy that promises to deliver treatments tailored to the specific needs of individuals. To fulfill this promise, each treatment must be modified to adequately correct for variation across individual skulls and neural anatomy. This study examines the use of ultrasound-induced voltage potentials (measured with electroencephalography [EEG]) to guide TUSN therapies. Materials and MethodsWe measured EEG responses in two awake nonhuman primates during sonication of 12 targets surrounding two deep brain nuclei, the left and right lateral geniculate nucleus. ResultsWe report reliable ultrasound evoked potentials measured with EEG after the deep brain ultrasonic modulation in nonhuman primates. Robust responses are observed after just ten repetitions of the ultrasonic stimuli. Moreover, these potentials are only evoked for specific deep brain targets. Furthermore, a behavioral study in one subject shows a direct correspondence between the target with maximal EEG response and ultrasound-based modulation of visual choice behavior. Thus, this study provides evidence for the feasibility of EEG-based guidance for ultrasound neuromodulation therapies.

Perceiving the Spectrum of Pain: Wavelength-Sensitive Visual Nociceptive Behaviors in Monolayer MoS2-Based Optical Synaptic Devices

Perceiving the Spectrum of Pain: Wavelength-Sensitive Visual Nociceptive Behaviors in Monolayer MoS₂-Based Optical Synaptic Devices

Evolutionary novelty in chemical signalling is linked with chemosensory behaviour in close Liolaemus lizard species (Iguania: Liolaemidae)

AbstractEvolutionary changes, associated with the gain or loss of traits, can occur in signal‐emitting and signal‐detecting organs. Related functionality generally accompanies these changes; however, in some cases there are mismatches and evolutionary innovations do not show an indication of functional advantages. Due to this, the relationship between evolutionary changes and the functionality of sensory organs remains unclear. Lizard species belonging to Liolaemus lineomaculatus section present fast evolutionary state transitions associated with the gain or loss of precloacal pores (chemical signalling glands). In this group, precloacal pores configuration includes species where only males have pores (Liolaemus attenboroughi‐ancestral state), where both sexes lack of them (L. kolengh male‐loss), and species where both sexes have pores (L. zullyae, representing a female‐gain). Here, we test the relationships between evolutionary changes of signal‐emitting glands with different chemical and visual behaviours. We conducted behavioural trials in three species belonging to the Liolaemus lineomaculatus section: L. attenboroughi, L. kolengh, and L. zullyae. We measured individuals' chemical and visual responses to different social scents and to conspecific visual stimuli. Results showed the presence of different social scents recognition ability in both male‐only and female‐gain species, whereas male‐loss species showed no behavioural differences among the chemical trials. Lizards exhibited few responses in the visual trials, although the species with pores used chemo‐sensorial sense in the visual trials, while male‐loss species showed differences in visual displays in the presence of conspecific visual stimuli. These results suggest a link between evolutionary novelties of chemical secretory glands and chemical recognition.

Do Children with High Callous-Unemotional Traits Have Attentional Deficits to Emotional Stimuli? Evidence from a Multi-Method and Multi-Informant Study.

Callous-unemotional (CU) traits in children and adolescents are linked to severe and persistent antisocial behavior. Based on past empirical research, several theoretical models have suggested that CU traits may be partly explained by difficulties in correctly identifying others' emotional states as well as their reduced attention to others' eyes, which could be important for both causal theory and treatment. This study tested the relationships among CU traits, emotion recognition of facial expressions and visual behavior in a sample of 52 boys referred to a clinic for conduct problems (Mage = 10.29years; SD = 2.06). We conducted a multi-method and multi-informant assessment of CU traits through the Child Problematic Traits Inventory (CPTI), the Inventory of Callous-Unemotional (ICU), and the Clinical Assessment of Prosocial Emotions-Version 1.1 (CAPE). The primary goal of the study was to compare the utility of these methods for forming subgroups of youth that differ in their emotional processing abilities. An emotion recognition task assessed recognition accuracy (percentage of mistakes) and absolute dwell time on the eyes or mouth region for each emotion. Results from repeated measures ANOVAs revealed that low and high CU groups did not differ in emotion recognition accuracy, irrespective of the method of assessing CU traits. However, the high CU group showed reduced attention to the eyes of fearful and sad facial expressions (using the CPTI) or to all emotions (using the CAPE). The high CU group also showed a general increasein attention to the mouth area, but only when assessed by the CAPE. These findings provide evidence to support abnormalities in how those elevated on CU traits process emotional stimuli, especially when assessed by a clinical interview, which could guide appropriate assessment and more successful interventions for this group of youth.

Flashlight model: Integrating attention distribution and attention resources for pilots’ visual behaviour analysis and performance prediction

Pilot performance is almost the last line of defense in aircraft safety. Recent years have seen a surge in research aimed at utilizing eye-tracking technology to predict pilot performance, enhancing aviation safety margins. A decline in pilot performance is often attributed to either misdirected attention towards irrelevant tasks or inefficient information processing owing to limited attention resources. Previous research has shown that eye-tracking data can effectively capture these issues and provide accurate performance predictions. Nevertheless, the existing studies either focus on attention distribution or attention resources separately, neglecting the complex interactions between them. To address this gap, our study proposes a synthesized Flashlight model-based eye-tracking analysis for pilot performance prediction, integrating the two perspectives. Accordingly, the combined AOI-gaze metrics are proposed to offer a more nuanced analysis of information processing across specific Areas of Interest (AOIs), thereby enhancing the analysis of gaze metrics. We examined the efficacy of the combined AOI-gaze metrics in the Gradient-boosted decision trees(GBDT) model for pilot performance prediction and compared them with other widely used eye-tracking metrics in a simulated flight experiment case study. Moreover, we employed the SHapley Additive exPlanations (SHAP) method to identify the most influential eye-tracking measurements for pilots’ performance prediction. The result demonstrated that the selected eye-tracking measurements obtained the highest accuracy in performance prediction.

Preservation of vision by transpalpebral electrical stimulation in mice with inherited retinal degeneration.

The potential neuroprotective and regenerative properties of electrical stimulation (ES) were studied in rhodopsin knockout mice (Rho -/- ), a murine model of inherited retinal degeneration. The study focused on assessing the impact of varying ES frequencies on visual functions and photoreceptor cell survival in Rho -/- mice. To elucidate the impact of electrical stimulation on cone survival, Rho -/- mice received either sham or transpalpebral ES using biphasic ramp or rectangular waveforms at 100µA amplitude, starting at sixweeks of age. The treatment duration spanned from one to three weeks. The optimal treatment frequency of ES sessions was determined by applying ES every one, two, or three days in three separate groups of Rho -/- mice. The sham group received daily treatments without the application of ES. Our study revealed significant improvement of visual function in Rho -/- mice following daily or every-other-day noninvasive transpalpebral ES, as evidenced by electroretinogram and optomotor response-based visual behavior assays. Concurrently, assessment of outer nuclear thickness and immunohistochemistry for the cone photoreceptor cell marker PNA demonstrated pronounced increases in the survival of rods and cones and improvement in the morphology of the inner and outer segments. This study underscores the protective effect of non-invasive ES in rhodopsin knockout-induced retinal degenerative disorders, providing a foundation for developing targeted therapeutic interventions for retinitis pigmentosa.

Testing the Hard to Test: A Pilot Study Examining the Role of Questionnaires in Eliciting Visual Behaviours in Children with Autistic Spectrum Disorder.

There is a higher prevalence of visual problems in children with Autistic Spectrum Disorder (ASD) compared with the neuro-typical population. Issues relating to visual perception can be evident as atypical visual behaviours (ViBes). The aim of the study was to compare findings of parents and eye health professionals using questionnaires to describe visual function in young children with ASD. Parents/Caregivers of patients diagnosed with ASD attending routine hospital eye clinics were invited to participate. A questionnaire to draw out presence of ViBes was completed by the parent prior to attending clinic. The clinician independently completed the same questionnaire and undertook a clinical ocular assessment. 32 children were recruited (mean age 7 years, range 4-11). Most caregivers indicated they had noted at least one atypical ViBe (97%, median 5, range 0-8). Parental-reported ViBe8 scores were higher than clinician-reported scores (p = 0.04). The most commonly reported ViBes by both groups related to use of vision at the same time as other senses, and atypical fixation (e.g. looking away during speech or side viewing). There was weak correlation between visual acuity and parental ViBe8 score (rho = 0.364) and no correlation between refractive error and parental ViBe8 score (rho = 0.047). Clinicians were likely to under-report atypical visual function compared with parent. Refraction and visual acuity alone do not detect all visual problems in children with ASD. A Visual Behaviour (ViBe) questionnaire offers a structured approach and shared language to allow documentation of functional visual assessment for both parents, carers, and educational professionals. Use of the ViBe questionnaire may promote understanding between caregiver and professional and provide a baseline for visual behaviours.