Gaze Parameters Research Articles

Impact of Texting-Induced Distraction on Driving Behavior Based on Field Operation Tests

Driver distraction has proven to be among the top contributory factors in road crashes worldwide. The involvement of drivers in secondary activities, such as phone usage, conversation with co-passengers, reaching for objects, eating, and so forth, have been shown to be significant causes of in-vehicle driver distraction. Text messaging using mobile phones while driving can be detrimental to the primary driving task as it invokes manual, visual, and cognitive distractions. Numerous studies in the past have analyzed the effect of texting on driver distraction using driving simulators. This study followed a field operation test–based approach to simulate real road conditions and evaluate the impact of texting on driving behavior. The study was conducted at the connected autonomous vehicle testbed at the Indian Institute of Technology Hyderabad, using an instrumented test vehicle. Data on gaze parameters and vehicle kinematics were recorded using eye-tracker glasses and a high-end global positioning system (GPS) data logger. Thirty-one participants drove on the pre-defined path at the testbed under baseline and texting conditions. The findings demonstrated that the texting task significantly affected fixation count, mean speed, and lateral acceleration. The texting task led to a reduction in mean fixation counts, mean speed, and mean lateral acceleration by 44.37%, 34%, and 46.72%, respectively. The age and driving experience of the participants had a significant effect on their behavior. The results indicate the critical potential of texting-based driver distraction and suggest the enforcement of stringent rules for texting while driving to create a safer road environment.

Tests of abnormal gaze behavior increase the accuracy of mild cognitive impairment assessments

Tests to detect mild cognitive impairment (MCI) should have high sensitivity and accuracy. Previously, we reported on a cognitive composition test (CCT) that we developed to detect MCI. In this study, we compared gaze behavior parameters, namely, gaze fixation duration and gaze-shift frequency, during the CCT in participants with MCI and healthy controls (HC) to determine whether these parameters would accurately detect MCI in older adults. Participants performed CCT-A, -B, and -C tasks with varying difficulty levels while wearing eye-tracking devices. Performance time, gaze fixation duration, and gaze-shift frequency were analyzed. Receiver operating characteristic curve analysis was performed to assess the identification accuracy. The MCI group was significantly slower in completing the CCT-C task and had a higher gaze-shift frequency into both the sample object space and workspace than the HC group. Gaze fixation duration in the sample object space increased in the MCI group as the CCT became difficult. Our findings indicated that combining the CCT with performance time and gaze pattern improved the accuracy of distinguishing between individuals with and without MCI and that patients with MCI have abnormal gaze behavior during cognitive tasks. Therefore, evaluation of gaze parameters may improve the accuracy of identifying patients with MCI.

Gaze-contingent adaptation of VR stereo parameters for cybersickness prevention

Extended exposure to virtual reality displays has been linked to the emergence of cybersickness, characterized by symptoms such as nausea, dizziness, fatigue, and disruptions in eye movements. The main objective of our study is to examine the effects of real-time fine-tuning of stereo parameters and blurriness in virtual reality on the discomfort level of users who are experiencing motion sickness triggered by the display. Our hypothesis proposes that by dynamically correcting the rendering settings, the symptoms of motion sickness can be relieved and the overall VR user experience can be improved. Our methodology commences with a prediction model for the comfort level of the viewer based on their gaze parameters, such as pupil diameter, blink count, gaze position, and fixation duration. We then propose a method to dynamically adapt the stereoscopic rendering parameters by considering the predicted comfort level of the viewer.

Why did Rubens add a parrot to Titian's The Fall of Man? A pictorial manipulation of joint attention.

Almost 400 years ago, Rubens copied Titian's The Fall of Man, albeit with important changes. Rubens altered Titian's original composition in numerous ways, including by changing the gaze directions of the depicted characters and adding a striking red parrot to the painting. Here, we quantify the impact of Rubens's choices on the viewer's gaze behavior. We displayed digital copies of Rubens's and Titian's artworks-as well as a version of Rubens's painting with the parrot digitally removed-on a computer screen while recording the eye movements produced by observers during free visual exploration of each image. To assess the effects of Rubens's changes to Titian's composition, we directly compared multiple gaze parameters across the different images. We found that participants gazed at Eve's face more frequently in Rubens's painting than in Titian's. In addition, gaze positions were more tightly focused for the former than for the latter, consistent with different allocations of viewer interest. We also investigated how gaze fixation on Eve's face affected the perceptual visibility of the parrot in Rubens's composition and how the parrot's presence versus its absence impacted gaze dynamics. Taken together, our results demonstrate that Rubens's critical deviations from Titian's painting have powerful effects on viewers' oculomotor behavior.

How body postures affect gaze control in scene viewing under specific task conditions

Gaze movements during visual exploration of natural scenes are typically investigated with the static picture viewing paradigm in the laboratory. While this paradigm is attractive for its highly controlled conditions, limitations in the generalizability of the resulting findings to more natural viewing behavior have been raised frequently. Here, we address the combined influences of body posture and viewing task on gaze behavior with the static picture viewing paradigm under free viewing as a baseline condition. We recorded gaze data using mobile eye tracking during postural manipulations in scene viewing. Specifically, in Experiment 1, we compared gaze behavior during head-supported sitting and quiet standing under two task conditions. We found that task affects temporal and spatial gaze parameters, while posture produces no effects on temporal and small effects on spatial parameters. In Experiment 2, we further investigated body posture by introducing four conditions (sitting with chin rest, head-free sitting, quiet standing, standing on an unstable platform). Again, we found no effects on temporal and small effects on spatial gaze parameters. In our experiments, gaze behavior is largely unaffected by body posture, while task conditions readily produce effects. We conclude that results from static picture viewing may allow predictions of gaze statistics under more natural viewing conditions, however, viewing tasks should be chosen carefully because of their potential effects on gaze characteristics.

Attention Level Evaluation in Children With Autism: Leveraging Head Pose and Gaze Parameters From Videos for Educational Intervention

Attention Level Evaluation in Children With Autism: Leveraging Head Pose and Gaze Parameters From Videos for Educational Intervention

Driver’s gaze behaviour before, during and after take-over manoeuvres: Influence of agentivity associated with different automation solutions

In the context of progressive automation of the driving activity, an alternation of automated driving phases and manual driving phases is becoming a reality. The problem of regaining manual control of the vehicle after a period of automated control (i.e., take-over) is critical, particularly concerning visual exploration during the transition phase. A driving simulator experiment was designed to investigate the impact of the level of agentivity manipulated by different levels of motor engagement on gaze parameters during the different temporal stages of a non-critical take-over situation (i.e., overtaking collision zone). The level of motor engagement decreased according to the increase in the level of automation; eye tracking data were collected, and gaze distribution over functional areas of interest was analysed across several periods of interest. Results revealed an influence of the degree of motor engagement on the gaze parameters linked to the integration and processing of visual information for a nominal driving period (i.e., automation activated) as well as during the take-over preparation period. During the period of effective resumption of manual control, most of the ocular parameters went back to their initial values, except for the higher motor disengagement modes (i.e., lowest levels of agentivity). These automation levels seem to show a residual influence of take-overs on manual driving, particularly in the ocular exploration of areas carrying the information useful for the fine regulation of the vehicle trajectory.

Gaze behaviour during multiple object tracking is dependent on binocular vision integrity.

Despite the critical importance of binocular vision integrity in daily activities, there exists limited understanding of how alterations in binocular vision integrity impact gaze behaviour during dynamic, complex psychomotor skills. This study aimed to measure how alterations in binocular vision integrity, created by Bangerter filters (BF), affect gaze behaviour during multiple object tracking (MOT). During the experiment, 22 volunteers completed the MOT task under three different visual conditions. The first condition involved natural binocular viewing, while the second and third conditions used 0.4 and 0.2 neutral density BF, respectively, resulting in monocular blur in the sensorially dominant eye. During the MOT task, participants were instructed to track three of eight balls for 10 s, and the speed was adjusted using a staircase procedure. Throughout the task, the following gaze parameters were recorded: fixation duration, saccade duration, amplitude and frequency as well as blink rate. During MOT execution, participants employed three gaze strategies regardless of viewing conditions: saccadic movements were predominant, followed by maintaining fixation on a central location throughout the trial and to a lesser extent, smooth pursuit eye movements. There was a significant effect of manipulating viewing conditions on the MOT scores (p = 0.046, η2 = 0.09). As the viewing conditions became more difficult, we observed a decrease in fixation duration (p = 0.004, η2 = 0.16) and blink rate (p < 0.001, η2 = 0.20) and an increase in saccadic amplitude (p < 0.001, η2 = 0.29). The results support the notion that perceptual-cognitive skills depend on the integrity of binocular vision, underscoring the sensitivity of gaze behaviours to any impairment of binocular function.

Eye movements during motor imagery and execution reveal different visuomotor control strategies in manual interception.

Previous research has investigated the degree of congruency in gaze metrics between action execution (AE) and motor imagery (MI) for similar manual tasks. Although eye movement dynamics seem to be limited to relatively simple actions toward static objects, there is little evidence of how gaze parameters change during imagery as a function of more dynamic spatial and temporal task demands. This study examined the similarities and differences in eye movements during AE and MI for an interception task. Twenty-four students were asked to either mentally simulate or physically intercept a moving target on a computer display. Smooth pursuit, saccades, and response time were compared between the two conditions. The results show that MI was characterized by higher smooth pursuit gain and duration while no meaningful differences were found in the other parameters. The findings indicate that eye movements during imagery are not simply a duplicate of what happens during actual performance. Instead, eye movements appear to vary as a function of the interaction between visuomotor control strategies and task demands.

Eye-tracking paradigms for the assessment of mild cognitive impairment: a systematic review.

Mild cognitive impairment (MCI), representing the 'transitional zone' between normal cognition and dementia, has become a novel topic in clinical research. Although early detection is crucial, it remains logistically challenging at the same time. While traditional pen-and-paper tests require in-depth training to ensure standardized administration and accurate interpretation of findings, significant technological advancements are leading to the development of procedures for the early detection of Alzheimer's disease (AD) and facilitating the diagnostic process. Some of the diagnostic protocols, however, show significant limitations that hamper their widespread adoption. Concerns about the social and economic implications of the increasing incidence of AD underline the need for reliable, non-invasive, cost-effective, and timely cognitive scoring methodologies. For instance, modern clinical studies report significant oculomotor impairments among patients with MCI, who perform poorly in visual paired-comparison tasks by ascribing less attentional resources to novel stimuli. To accelerate the Global Action Plan on the Public Health Response to Dementia 2017-2025, this work provides an overview of research on saccadic and exploratory eye-movement deficits among older adults with MCI. The review protocol was drafted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Electronic databases were systematically searched to identify peer-reviewed articles published between 2017 and 2022 that examined visual processing in older adults with MCI and reported gaze parameters as potential biomarkers. Moreover, following the contemporary trend for remote healthcare technologies, we reviewed studies that implemented non-commercial eye-tracking instrumentation in order to detect information processing impairments among the MCI population. Based on the gathered literature, eye-tracking-based paradigms may ameliorate the screening limitations of traditional cognitive assessments and contribute to early AD detection. However, in order to translate the findings pertaining to abnormal gaze behavior into clinical applications, it is imperative to conduct longitudinal investigations in both laboratory-based and ecologically valid settings.

Clinical availability of eye movement during reading

Eyes provide valuable information for neurological diagnosis. So far, the use of diagnostic devices to analyze eye movement is limited. We explored whether the analysis of eye movements can be efficacious. Patients with Parkinson’s disease (PD) (n = 29), spinocerebellar degeneration (SCD) (21), progressive supranuclear palsy (PSP) (19), and control individuals (19) participated in this study. The patients read aloud two sets of sentences displayed on a monitor: one was displayed horizontally, and the other vertically. Parameters such as eye movement speed, travel distance, and fixation/saccade ratio were extracted, and comparisons between groups were performed. Maneuvers of eye movements were also subjected to image classification using deep learning. Reading velocity and fixation/saccade ratio were altered in the PD group, and the SCD group exhibited ineffective eye movements due to dysmetria and nystagmus. Vertical gaze parameters showed aberrant values in the PSP group. Vertical written sentences were more sensitive than horizontal ones in detecting these abnormalities. In the regression analysis, vertical reading indicated a high accuracy in identifying each group. The machine learning analysis showed more than 90 % accuracy in distinguishing between the control and SCD groups and between the SCD and PSP groups. Analyzing eye movements is useful and easily applicable.

Robotic gaze and human views: A systematic exploration of robotic gaze aversion and its effects on human behaviors and attitudes.

Similar to human-human interaction (HHI), gaze is an important modality in conversational human-robot interaction (HRI) settings. Previously, human-inspired gaze parameters have been used to implement gaze behavior for humanoid robots in conversational settings and improve user experience (UX). Other robotic gaze implementations disregard social aspects of gaze behavior and pursue a technical goal (e.g., face tracking). However, it is unclear how deviating from human-inspired gaze parameters affects the UX. In this study, we use eye-tracking, interaction duration, and self-reported attitudinal measures to study the impact of non-human inspired gaze timings on the UX of the participants in a conversational setting. We show the results for systematically varying the gaze aversion ratio (GAR) of a humanoid robot over a broad parameter range from almost always gazing at the human conversation partner to almost always averting the gaze. The main results reveal that on a behavioral level, a low GAR leads to shorter interaction durations and that human participants change their GAR to mimic the robot. However, they do not copy the robotic gaze behavior strictly. Additionally, in the lowest gaze aversion setting, participants do not gaze back as much as expected, which indicates a user aversion to the robot gaze behavior. However, participants do not report different attitudes toward the robot for different GARs during the interaction. In summary, the urge of humans in conversational settings with a humanoid robot to adapt to the perceived GAR is stronger than the urge of intimacy regulation through gaze aversion, and a high mutual gaze is not always a signof high comfort, as suggested earlier. This result can be used as a justification to deviate from human-inspired gaze parameters when necessary for specific robot behavior implementations.

Visual Attention to Novel Products - Cross-Cultural Insights From Physiological Data.

The study aims to investigate visual attention and perceived attractiveness to known versus unknown (novel) products above and beyond self-report applying physiological methods. A cross-cultural exploratory approach allows for comparing results gathered in the United States and China. We collected field data on physiological parameters accompanied by behavioral data. Mobile eye-tracking was employed to capture attention by measuring gaze parameters and electrodermal activity serves as indicator for arousal at an unconscious level. A traditional scale approach measuring perceived attractiveness of known versus novel products provide insights at a conscious level. US-American and Chinese consumers in our sample indeed process novel products differently. This can be observed at an unconscious and conscious level. Different gaze movements and arousal levels are observed at an unconscious level. Regarding behavioral data, the level of vertical orientation shapes the perceived attractiveness of novel products at a conscious level. The study showcases how physiological methods complement behavioral ones when investigating visual attention to products. It underlines varying conscious as well as unconscious visual attention and attractiveness ratings comparing known versus novel products, driven by cultural differences. Data from a field setting further enrich the implications derived for new product development and applied marketing.

Application of eye-tracking systems integrated into immersive virtual reality and possible transfer to the sports sector - A systematic review

In recent years, Virtual Reality (VR) has become a valuable tool in rehabilitation and sports training applications. New technologies offer opportunities to combine various systems and use them for sports-related scientific purposes. For instance, examining the visual perception of athletes within a standardized environment could be helpful to understand the differences between novices and experts in their visual behavior and could further reveal possible training applications for enhancing athletes’ visual attention. The current systematic literature review thematizes the importance of eye-tracking (ET) systems’ usage integrated into head-mounted displays (HMDs) in virtual environments for further inclusion in sports-related usage. An overview of possible implementations is given, and additional recommendations for using the combined technic regarding sports are made. Although only one study examined gaze behavior during sports activity within a standardized virtual environment, 38 relevant papers were identified using the ET systems integrated into the HMDs, which ideas can be transferred to the sports sector. The increased usability and fidelity in the virtual environment enabled through the combined technology were illustrated, and different approaches were listed in using and calculating gaze parameters. This literature review examines the possibility of integrating ET in VR, which can be further used to improve usability, interaction methods, image presentation, and visual perception analyses within future physical training scenarios. The compiled studies have shown that the existing methods are feasible due to the performance of the integrated ET systems but still need to be improved for practical use.

Dual tasking reduces gait asymmetry of trajectory deviation during obstacle circumvention in people with Parkinson's disease.

Certain aspects of gait may depend on cognition, and the effects of dual-tasking (DT) on gait asymmetry (GA) during obstacle circumvention in people with Parkinson's disease (pwPD) may be walking phase-dependent. While the approaching phase requires allocating significant cognitive resources to perform the task, outweighing the available resources may increase GA. During the avoiding phase, the obstacle could be used as an external cue, enhancing the attention to the obstacle and, consequently, improving gait control and regulating GA. The study investigated the effects of obstacle circumvention during gait with DT on GA in pwPD, considering the circumvention phase. Thirty participants, 15 pwPD and 15 neurologically healthy individuals, circumvented an obstacle 20 times (in total) according to side (right and left side) and DT (presence and absence). Spatial-temporal stride parameters, medial-lateral and horizontal trajectory deviations from the original path, strategy to obstacle circumvention (lead limb away from or close to the obstacle during the crossing step), and gaze parameters were calculated during the approaching and avoiding phases. The parameters were grouped considering the side that the obstacle was circumvented during each task, and the symmetry index was calculated. The results showed greater asymmetry of time of fixations, width, duration, and velocity during the approaching phase (p<0.02), whereas the avoiding phase decreased asymmetry of medial-lateral and horizontal trajectory deviations parameters (p<0.001) during obstacle circumvention with DT, in both pwPD and control group. The findings offer a basis for considering that goal-directed movement control may regulate GA in pwPD.

Stable Gaze Tracking with Filtering Based on Internet of Things.

Gaze tracking is basic research in the era of the Internet of Things. This study attempts to improve the performance of gaze tracking in an active infrared source gaze-tracking system. Owing to unavoidable noise interference, the estimated points of regard (PORs) tend to fluctuate within a certain range. To reduce the fluctuation range and obtain more stable results, we introduced a Kalman filter (KF) to filter the gaze parameters. Considering that the effect of filtering is relevant to the motion state of the gaze, we design the measurement noise that varies with the speed of the gaze. In addition, we used a correlation filter-based tracking method to quickly locate the pupil, instead of the detection method. Experiments indicated that the variance of the estimation error decreased by 73.83%, the size of the extracted pupil image decreased by 93.75%, and the extraction speed increased by 1.84 times. We also comprehensively discussed the advantages and disadvantages of the proposed method, which provides a reference for related research. It must be pointed out that the proposed algorithm can also be adopted in any eye camera-based gaze tracker.

Vision, cognition, and walking stability in young adults

Downward gazing is often observed when walking requires guidance. This gaze behavior is thought to promote walking stability through anticipatory stepping control. This study is part of an ongoing effort to investigate whether downward gazing also serves to enhance postural control, which can promote walking stability through a feedback/reactive mechanism. Since gaze behavior alone gives no indication as to what information is gathered and the functions it serves, we aimed to investigate the cognitive demands associated with downward gazing, as they are likely to differ between anticipatory and feedback use of visual input. To do so, we used a novel methodology to compromise walking stability in a manner that could not be resolved through modulation of stepping. Then, using interference methodology and neuroimaging, we tested for (1) interference related to dual tasking, and (2) changes in prefrontal activity. The novel methodology resulted in an increase in the time spent looking at the walking surface. Further, while some dual-task interference was observed, indicating that this gaze behavior is cognitively demanding, several gaze parameters pertaining to downward gazing and prefrontal activity correlated. These correlations revealed that a greater tendency to gaze onto the walking surface was associated with lower PFC activity, as is expected when sensory information is used through highly automatic, and useful, neural circuitry. These results, while not conclusive, do suggest that gazing onto the walking surface can be used for purposes other than anticipatory stepping control, bearing important motor-control and clinical implications.

Gaze Exploration Index (GE i)-Explainable Detection Model for Glaucoma

Glaucoma is a type of visual impairment that is caused due to damage in the optic nerve. The vision loss increases from the peripheral vision towards the central vision, leading to blindness if untreated. The proposed approach is a Computer-Aided Detection (CADe) system using deep learning to screen visual field loss in glaucoma patients while performing different day-to-day activities such as searching objects, viewing photographs, etc. Incorporating an eye-tracking device helps to identify eye movements of glaucoma patients while performing different activities. Different day-to-day activities are depicted in the form of visual exploration tasks. CADe system fuses performance parameters and eye gaze parameters during visual exploration tasks onto images, to guide health care professionals of primary eye care centers in glaucoma screening. The pertinent eye gaze and performance parameters are visualized in the form of three fusion maps: Gaze Fusion Map (GFM), Gaze Fusion Reaction Time (GFRT) map, Gaze Convex Hull Map (GCHM), which are the outcomes of different visual exploration tasks. In addition, the explainability techniques applied in CADe generated Gaze Exploration - index (GE-i) that discriminates glaucoma and normal.

Eye Tracking Parameters Correlate with the Level of Cerebral Oxygen Saturation in Mild Traumatic Brain Injury: A Preliminary Study.

The aim of this study was to assess the relationship between oculomotor synergies and brain oxygen status at mild traumatic brain injury (mTBI) using simultaneous comparison of eye-tracking (ET) parameters and cerebral oxygen saturation. This non-randomised single-centre prospective study included 77 patients with mTBI (mean age was 36.3±4.8years, 48 men, 29 women, median GCS 13.7±0.7). Cerebral oximetry was used to detect oxygen saturation level (SctO2) in the frontal lobe pole (FLP) region. Eye movements were measured simultaneously using the EyeTracker. Calculated parameters were: vertical and horizontal angular eyeball velocity (AV); left vertical speed (LVS); right vertical speed (RVS); left horizontal speed (LHS); and right horizontal speed (RHS). The indices of vertical and horizontal eye version (version index, Vx) were calculated as the Pearson correlation coefficient between the corresponding AV of the right and left eyes. Significance was pre-set to p<0.05. SctO2 in the FLP varied from 62% to 79%. The average SctO2 values were 69.26±6.96% over the left FLP and 70.25±7.58% over the right FLP (p=0.40). The total analysis of the eye-tracking data revealed the following values of gaze parameters: LVS - 0.327±0.263rad/sec; LHS - 0.201±0.164rad/sec; RVS - 0.361±0.269rad/sec; and RHS - 0.197±0.124rad/sec. The calculated vertical version index (VVx) was 0.80±0.12. The calculated horizontal version index (HVx) was 0.82±0.11. The VVx and HVx were correlated with SctO2 levels in the FLP (p=0.038; r=0.235; p=0.048; r=0.218, respectively p=0.035; r=0.241; p=0.039; r=0.235, respectively). VVx and HVx correlate with the SctO2 level in the FLP (p<0.01) in mTBI. No significant correlation was detected between the level of the SctO2 level and vertical and horizontal AV of the eyeballs. Eye tracking can help quantify the severity of ocular conjugation impairments after mTBI, as well as explore the contribution that cerebral oxygen status disorders make to this process.

Audit and Comparison Between Radiographic Markers of Gaze Direction Using EOS Imaging - An Essential Step to Streamline Existing Methods.

Retrospective cohort study on prospectively implemented EOS protocol. This study aims to audit and compare existing radiological definitions of gaze direction-chin brow vertical angle (CBVA), McGregor slope (McGS), slope of line of sight (SLS), orbital-internal occipital protuberance (OIOP) slope angle, and Tangent to the hard palate (THP) in a neutral, healthy, and asymptomatic cohort. The ability to accurately define direction of gaze is the first step when striving for horizontal gaze restoration in any affected individual with rigid sagittal deformity. Yet, the radiological definition of gaze direction remains poorly standardized. Hundred healthy subjects who could achieve horizontal gaze underwent whole-body standing EOS radiographs taken under a strictly standardized protocol. Radiographic measurements of global spinal sagittal parameters and surrogate measures of horizontal gaze were analyzed and compared. The mean age was 45 ± 15.9 years, with a balanced male-to-female-ratio. Their C7 SVA was -7.7 mm ± 24.8 mm, PI was 51.0o ± 11.4o, PI-LL was -0.9o ± 13.0o and T1-slope was 21.2o ± 9.2o. Measured horizontal gaze parameters were as follows: CBVA (1.07o ± 5.48o), McGS (-3.23o ± 5.63o), SLS (0.45o ± 5.34o), OIOP (5.03o ± 4.66o), THP (-0.17o ± 6.27o). CBVA correlated strongly with McGS (r = 0.679, P < 0.001), SLS (r = 0.592, P < 0.001), OIOP (r = 0.697, P < 0.001), and THP (r = -0.504, P < 0.001). OIOP had the lowest variance amongst all parameters and showed less variability compared to CBVA (SD 4.66 Var 21.69 vs. SD 5.48 Var 30.08, P = .012). Multivariate analysis showed that C2-7 angle was the only parameter found to be associated with OIOP values (P = 0.006). OIOP is the least variable, and most robust radiological method in determining gaze direction. It uses easily recognizable anatomical landmarks and an angular criterion, which makes it advantageous both with x-rays or slot scanners.Level of Evidence: 3.