Head Rotation Research Articles

Kinematic response of floating piles in a saturated soil layer subjected to seismic S-wave propagation

A mathematical formulation for the seismic analysis of floating piles embedded in a saturated soil layer to vertically propagating S waves is presented in this paper. Pivotal to the formulation is the establishment of a closed-form expression for the lateral soil reaction to pile displacement, and results from expressions for the free-field and scattered soil displacements obtained from Biot’s governing equations. Subsequently the pile is analysed as Euler-Bernoulli beam and the soil column between the pile tip and the bedrock is analysed as one-dimensional shear beam. This results in expressions for the kinematic response factors, that provide the frequency-dependent pile head displacement and rotation as function of the free-field soil movement. Validation of the developed model is followed by a discussion on the sensitivity of pile response to the two-phase nature of soil, focused on informing researchers and practitioners on the uncertainties introduced in conventional seismic analysis, where the foundation soil is modelled as single-phase medium.

Three-dimensional analysis of per-rotational nystagmus

BackgroundHead rotation produces a vestibulo-ocular reflex (VOR). In horizontal rotation, not only lateral semicircular canals but also posterior semicircular canals are stimulated, because posterior canals cupulae are not horizontal in the sitting position. Therefore, theoretical nystagmus is horizontal and torsional. Convection of endolymph does not occur, because the centre of head rotation is a dens of the second cervical vertebra, not the center of lateral canal. Although per-rotational nystagmus is a result of VOR, whether it could be explained by the movement of cupula remains undetermined. To answer this question, we analysed per-rotational nystagmus using three-dimensional video-oculography. ObjectiveTo clarify whether per-rotational nystagmus is the same as the physical movement of cupula (theoretical nystagmus). Materials and methodsFive healthy human were evaluated. The participant's head was rotated (sinusoidal yaw rotation) manually (frequency, 0.33 Hz; amplitude, 60°). The experiment was performed in a dark, with the participant's eyes open. Nystagmus was recorded and converted into digital data. ResultsIn all participants, the direction of nystagmus was rightward on rightward rotation and leftward on leftward rotation. In all participants, nystagmus was purely horizontal. ConclusionsPractical per-rotational nystagmus differs completely from the theoretical nystagmus. Therefore, VOR is strongly influenced by the central nervous system.

Design Considerations Including Rotating Head Technique for Shingled Heat-Assisted Magnetic Recording

Predictions for Signal-to-Noise Ratio (SNR) and User Density (UD) are presented for a large variety of shingled Heat Assisted Magnetic Recording (HAMR) systems. Calculations are performed using a micromagnetic simulation that treats the heated media cells using renormalized spin blocks. Varied parameters include grain pitch, heat spot Full Width Half Maximum, reader width, and shield to shield spacing. Results are optimized with respect to bit length and grain pitch. Unlike previous work, the base condition feature systems already available experimentally (to allow for comparison), extending to media and heads that allow greatly extended capacities. We also discuss the benefits of a rotated read head for these geometries.

Mask dependency of the lacrimal gland dose under whole brain radiotherapy when the six-degrees of freedom couch is not available.

Dry eye syndrome has been recently reported in patients who underwent whole brain radiotherapy (WBRT). WBRT based on a couch with three-degrees of freedom (3D) can occasionally be performed in which the rotational head motion is not corrected. This study assessed the dependency of the rotational errors on the mask and the dose variation of the lens and lacrimal gland in WBRT patients. Translational and rotational setup errors were obtained at the first treatment with cone-beam CT (CBCT) for patients under WBRT and frameless stereotactic radiosurgery (SRS) (n=20 each) immobilized using a conventional WB mask and an SRS mask with a bite block, respectively. For the CT sets of SRS cases, WBRT plans were generated for the study. To simulate the rotational error, rotated CT images were created with each rotational error, on which initial WBRT plans were copied and doses were recalculated. The lens and lacrimal gland doses with and without rotation errors were compared. Despite similar translational setup errors for the two masks, the SRS mask showed a dramatic reduction in rotational errors compared to those of the WB mask. The errors varied within -2.9° to 2.9° and -1.2° to 0.7° for the WB and SRS masks, respectively. Accordingly, the SRS mask confined the change in the maximum lens dose, mean dose of the lacrimal gland, and lacrimal volume receiving 15Gy to one-third of those using the WB mask. When the six-degrees of freedom (6D) couch is not available, the frameless SRS mask is beneficial to WBRT for the faithful treatment as it was planned.

Fuzzy proportional–integral–derivative control system of electric drive downhole cutting tool based on genetic algorithm

An electric drive downhole tubing cutting tool is the key equipment for tubing cutting in pressurized gas well workover operation. Cutting force control in radial feed movement of the cutting blade is the key to ensuring the successful cutting of tubing. In this article, the relationship model between cutting blade feed speed and cutting force is established by Matlab. Based on the mathematical model of cutting head rotation and blade feed movement, combined with the relationship between blade feed and cutting force obtained from cutting experiments. To keep the cutting force of the blade constant in the cutting process. Genetic algorithm was used to optimize the fuzzy proportional–integral–derivative control, and the automatic control scheme of the electric drive downhole tubing cutting tool was constructed. Based on Matlab/Simulink, the cutting force control simulation of the tubing cutting process is carried out. The performance of fuzzy proportional–integral–derivative control optimized by the genetic algorithm is compared with that of other standard controllers. The results show that the response speed and stability of the fuzzy proportional–integral–derivative control system are better than other algorithms. The steady-state error of the controller in the steady-cutting stage is < 5% based on the ground-cutting experiment of tubing, which meets the actual engineering needs and verifies the reliability and accuracy of the control system.

Engagement detection and enhancement for STEM education through computer vision, augmented reality, and haptics

STEM (Science, technology, engineering, and mathematics) based education is being revolutionized with the rapid development of the applications of intelligent Haptics. Theoretical knowledge may now be put into practice, and complex ideas can now be presented using three-dimensional models that are enhanced in the actual environment via Augmented Reality (AR) and computer Haptics to enhance the student's interest in concepts and studies. This article presents a novel design and development of an AR and Haptics-based STEM product comprising of World Map with Haptic feedback using Vuforia, Unity 3D, and Open-Haptics to enhance student engagement. To detect students' engagement in online learning, a computer vision-based system is also designed and deployed in the real-time website that uses the features, such as facial emotions, pose estimation, and head rotation. Marker-based augmentation is employed, and a sense of touch is included for an immersive experience for the students with the use of the haptic Touch Omni device. Hence, the proposed approach can improve classroom learning activities by using Augmented reality and Haptics-based STEM product and by its evaluation using a computer vision system. To validate the improvement in engagement, a comprehensive user study is performed and analyzed on the proposed setup.

The dynamics of deglutition during head rotation using dynamic 320-row area detector computed tomography.

We aimed to elucidate the dynamics of deglutition during head rotation by acquiring 320-row area detector computed tomography (320-ADCT) images and analyzing deglutition during head rotation. This study included 11 patients experiencing globus pharyngeus. A 320-ADCT was used to acquire images in two types of viscosity (thin and thick), with the head rotated to the left. We measured the movement time of deglutition-related organs (soft palate, epiglottis, upper esophageal sphincter [UES], and true vocal cords) and pharyngeal volume (bolus ratio at the start of UES opening [Bolus ratio], pharyngeal volume contraction ratio [PVCR], and pharyngeal volume before swallowing [PVBS]). A two-way analysis of variance was performed for statistical analysis, and all items were compared for significant differences in terms of head rotation and viscosity. EZR was used for all statistical analyses (p-value <.05). Head rotation significantly accelerated the onset of epiglottis inversion and UES opening compared with no head rotation. The duration of epiglottis inversion with the thin viscosity fluid was significantly longer. The bolus ratio increased significantly with thick viscosity. There was no significant difference in viscosity and head rotation in terms of PVCR. PVBS increased significantly with head rotation. The significantly earlier start of epiglottis inversion and UES opening due to head rotation could be caused by: (1) swallowing center; (2) pharyngeal volume; and (3) pharyngeal contraction force. Thus, we plan to further analyze swallowing with head rotation by combining swallowing CT with manometry and examine its relationship with pharyngeal contraction force. 3b.

Upper Airway Surgery or Weight Control? Modified Drug-Induced Sleep Endoscopy for Obstructive Sleep Apnea.

To identify the value of head rotation in the supine position and oral appliance (OA) use in drug-induced sleep endoscopy (DISE). Eighty-three sleep apnea adults undergoing target-controlled infusion-DISE (TCI-DISE) were recruited from a tertiary academic medical center. During DISE, 4 positions were utilized: supine position (position 1), head rotation (position 2), mandibular advancement using an OA (position 3), and head rotation with an OA (position 4). Polysomnography (PSG) data and anthropometric variables during DISE were analyzed. Eighty-three patients (65 men and 18 women; mean [standard deviation, SD], 48.5 [11.0] years) who underwent PSG and TCI-DISE were included. The mean (SD) apnea-hypopnea index (AHI) was 35.5 (22.4) events/h. Twenty-three patients had persistent complete concentric velopharyngeal collapse in the supine position, even with concurrent head rotation and OA (position 4). Their mean (SD) AHI was 54.7 (24.6) events/h, significantly higher than that of the 60 patients without such collapse in position 4 (p < .001). Their mean (SD) body mass index (BMI) was 29.0 (4.1) kg/m2 , also significantly higher (p = .005). After adjustment for age, BMI, tonsil size, and tongue position, the degree of velum and tongue base obstruction was significantly associated with sleep apnea severity in positions 2, 3, and 4. We showed the feasibility, safety, and usefulness of using simple edge-to-edge, reusable OA in DISE. Patients who are not responsive to head rotation and OA during TCI-DISE may need upper airway surgery and/or weight control.

Biceps Femoris Fascicle Behavior during Submaximal and Maximal Slow Speed Contractions.

The present study compared the effects of contraction intensity (submaximal vs maximal) and mode (concentric vs eccentric) on biceps femoris long head (BFlh) fascicle lengthening, rotation, and architectural gear ratio at long and short muscle lengths. Data were captured from 18 healthy adults (10 men and 8 women) without history of right hamstring strain injury. BFlh fascicle length ( Lf ), fascicle angle (FA), and muscle thickness (MT) were assessed in real time using two serially aligned ultrasound devices while submaximal and maximal concentric and eccentric isokinetic knee flexions were performed at 30°·s -1 . Ultrasound videos were exported and edited to create a single, synchronized video, and three fascicles were analyzed through the range of motion (10° to 80°). Changes (Δ) in Lf , FA, MT, and muscle gear at long (60° to 80° knee angle; 0° = full knee extension) and short (10° to 30°) muscle lengths and across the full knee flexion range were measured and compared. Greater Δ Lf was observed at long muscle length ( P < 0.001) during both submaximal and maximal eccentric and concentric contractions. When the full length range was analyzed, a slightly greater ΔMT was observed in concentric contractions ( P = 0.03). No significant differences between submaximal and maximal contractions were observed for Δ Lf , ΔFA, or ΔMT. No changes were detected in the calculated muscle gear between muscle lengths, intensities, or conditions ( P > 0.05). Although gear ratio ranged ~1.0 to 1.1 under most conditions, the increased fascicle lengthening observed at long muscle lengths might influence acute myofiber damage risk but also speculatively play a role in chronic hypertrophic responses to training.

Prevalence of cervical postural alterations in oculomotor disturbances: a Brazilian cohort study

The literature suggests that maintaining correct posture depends on a balance between orientation and balance, which is linked to the reflex relationship between the oculomotor system and the superior cervical spine. Any disruption to this relationship can cause postural deviation, as the posture is dependent on head balance and eye horizontality. This study aimed to investigate the prevalence of cervical posture alterations, such as head tilt, rotation, and protrusion, scapular waist changes, scoliosis, kyphosis, and lumbar hyperlordosis, in patients with oculomotor disturbances, including convergent, divergent, and vertical squint, and convergence insufficiency. The study evaluated 24 patients aged between 4 and 39 years old, both male and female, through ocular motility and postural examination. The results showed that all patients with oculomotor disturbances also had postural imbalances, and the percentage of alterations in the posture segments was high. Therefore, oculomotor disturbances can cause postural imbalance, leading to orthopedic and facial asymmetry. The study concluded that patients with oculomotor disturbances should be evaluated to determine the compensatory positions they adopt and set a better visual performance that does not alter their appearance in the long term.

The role of transperineal ultrasonography for perinatal management: A review.

Transperineal ultrasound (TPUS) has become an increasingly popular tool in obstetrics due to its objective, non-invasive, and real-time imaging capabilities. This review aims to describe the basic approaches, current utilization, and potential future applications of TPUS. A comprehensive literature review on TPUS was conducted. In addition, discussions at academic meetings and congress focused on TPUS were also considered. TPUS was initially used in prostate biopsies and is currently applied to evaluating fetal head descent in labor, with the angle of progression being the most widely used parameter. It is more tolerated than conventional invasive or expensive methods, such as digital vaginal examinations or MRIs. Additionally, TPUS can assess the internal rotation of the fetal head in the birth canal. Compared to other imaging modalities like MRI and CT scans, TPUS is easier to perform and more cost-effective. It also provides real-time imaging, allowing for quick and accurate assessments. It also help clinicians make critical decisions regarding the mode of delivery and identify patients at high risk for fecal incontinence postpartum. With its many benefits, TPUS has the potential to become a standard tool in urogynecology and obstetrics. Transperineal ultrasound is a non-invasive imaging modality that is well-tolerated and easy to understand for patients and their family and help medical staff support the patients. Transperineal ultrasound can be applied in real-time monitoring of labor progress, helping predict the possibility of vaginal delivery during labor, and further research in this area is warranted.

Enabling saccadic redirection through real‐time saccade prediction

AbstractOur proposed redirected walking technique improves on current solutions by leveraging temporary visual disruption caused by saccades for redirection without requiring additional eye‐tracking hardware and enables saccadic redirection on widely used consumer‐grade hardware, like mobile VR. Using a deep neural network trained on head rotation data, we predict saccades during an apparent head rotation and apply rigid transformations to the virtual environment for redirection. This allows users to infinitely walk in a perceived straight direction from within a physical tracked space of m. The three user studies illustrated in this article validate our approach and demonstrate its efficacy.

Biomechanical comparison of intramedullary versus extramedullary implants for fixation of simple pertrochanteric fractures.

The aim of this study was to evaluate the biomechanical performance of the intramedullary TFN-ADVANCED Proximal Femoral Nailing System (TFNA) versus the extramedullary Femoral Neck System (FNS) for fixation of simple pertrochanteric fractures in a human cadaveric model. Ten femoral pairs were implanted pairwise with TFNA or FNS. A simple pertrochanteric fracture OTA/AO 31-A1 was created and all specimens were biomechanically tested under progressively increasing cyclic loading until failure. Interfragmentary and bone-implant movements were monitored by motion tracking. Axial stiffness was comparable between TFNA and FNS, P=0.34. Similarly, varus deformation, femoral head rotation around neck axis and implant migration remained without significant differences between TFNA and FNS after 3000 cycles (800N peak load), P≥0.10. However, cycles to 15mm leg shortening were significantly higher for TFNA versus FNS, P<0.01. From a biomechanical perspective, with its current design FNS does not seem to be a valid alternative to TFNA for treatment of simple pertrochanteric fractures.

Reduced Vestibulo-Ocular Reflex During Fast Head Rotation in Complete Darkness.

The human vestibulo-ocular reflex (VOR) leads to maintenance of the acuity of an image on the retina and contributes to the perception of orientation during high acceleration head movements. Our objective was to determine whether vision affects the horizontal VOR by assessing and comparing the performance at the boundaries of contribution of: (a) unrestricted visual information and (b) no visual information. Understanding how the VOR performs under both lighted and unlighted conditions is of paramount importance to avoiding falls, perhaps particularly among the elderly. We tested 23 participants (M age = 35.3years, standard error of mean (SEM) = 2.0years). The participants were tested with the video Head Impulse Test (vHIT), EyeSeeCam from Interacoustics™, which assesses whether VOR is of the expected angular velocity compared to head movement angular velocity. The vHIT tests were performed under two conditions: (a) in a well-lit room and (b) in complete darkness. The VOR was analyzed by evaluating the gain (quotient between eye and head angular velocity) at 40, 60 and 80ms time stamps after the start of head movement. Additionally, we calculated the approximate linear gain between 0-100ms through regression. The gain decreased significantly faster across time stamps in complete darkness (p < .001), by 10% in darkness compared with a 2% decrease in light. In complete darkness, the VOR gain gradually declined, reaching a marked reduction at 80ms by 10% (p < .001), at which the head velocities were 150°/second or faster. The approximate linear gain value was not significantly different in complete darkness and in light. These findings suggest that information from the visual system can modulate the high velocity VOR. Subsequently, fast head turns might cause postural imbalance and momentary disorientation in poor light in people with reduced sensory discrimination or motor control, like the elderly.

Quantitative vestibular assessment: The development and validation of a novel, remote video head impulse test against in-clinic measurements.

To develop a novel remote head impulse test (rHIT), and to provide preliminary data validating the rHIT vestibular-ocular reflex (VOR) gains against the in-clinic vHIT. A convenience sample of 10 patients referred for vestibular assessment at our institution was recruited. In-clinic vHIT was used to quantify lateral VOR gains. Patients subsequently underwent an rHIT protocol, whereby patients performed active, lateral head rotations while their eyes and heads were recorded using a laptop camera and video-conferencing software. The vHIT and rHIT VOR gains were compared using paired t-tests, and a Pearson correlation coefficient between the gains was calculated. Absolute accuracy, sensitivity, and specificity of the rHIT were additionally calculated. Of the 10 patients recruited, 4 were male, and the average ± standard deviation (SD) age was 61.4 ± 15.3 years. As determined by the vHIT, 2 patients had normal bilateral VOR gains, 6 with unilateral vestibular hypofunction, and 2 with bilateral vestibular hypofunction. The correlation between the rHIT and vHIT gains was 0.73 (p < .001). The rHIT exhibited an absolute accuracy of 75.0%, sensitivity of 70.0%, and specificity of 80.0%. When ears had a vHIT VOR gain less than 0.40, the rHIT exhibited 100.0% accuracy. Conversely, 60.0% of deficient ears with vHIT VOR gains greater than 0.40 were incorrectly categorized by the rHIT. The rHIT may be better suited for detecting more severe vestibular deficiencies. Future iterations of the rHIT should aim to increase the video frame-rate capabilities to detect subtler VOR impairments. 4.

Binaural Listening with Head Rotation Helps Persons with Blindness Perceive Narrow Obstacles.

Orientation and mobility (O&M) are important abilities that people with visual impairments use in their independent performance of daily activities. In orientation, people with total blindness pinpoint nonsounding objects and sounding objects. The ability to perceive nonsounding objects is called obstacle sense, wherein people with blindness recognize the various characteristics of an obstacle using acoustic cues. Although body movement and listening style may enhance the sensing of obstacles, experimental studies on this topic are lacking. Elucidating their contributions to obstacle sense may lead to the further systematization of techniques of O&M training. This study sheds light on the contribution of head rotation and binaural hearing to obstacle sense among people with blindness. We conducted an experiment on the perceived presence and distance of nonsounding obstacles, which varied width and distance, for participants with blindness under the conditions of binaural or monaural hearing, with or without head rotation. The results indicated that head rotation and binaural listening can enhance the localization of nonsounding obstacles. Further, when people with blindness are unable to perform head rotation or use binaural hearing, their judgment can become biased in favor of the presence of an obstacle due to risk avoidance.

Teaching NeuroImages: Vertebral artery compression by head tilt around the roll axis diagnosed by transcranial Doppler

A 59-year-old man reported transient vertigo and diplopia during leftward head tilt around the roll axis. Neurologic examination was unremarkable with the head erect or tilted. Magnetic resonance angiography of the head and neck showed hypoplasia of the right vertebral artery (figure 1). Transcranial Doppler waveform was monitored during leftward head tilt. The left vertebral artery flow velocity decreased with tilt, and abruptly increased after returning to erect posture (figure 2). Vertebral artery can be stretched or kinked by head rotation or tilt,1,2 typically at the C1-2 level.1 Transcranial Doppler could be helpful in diagnosis of such cases.

Realistic CT data augmentation for accurate deep-learning based segmentation of head and neck tumors in kV images acquired during radiation therapy.

Using radiation therapy (RT) to treat head and neck (H&N) cancers requires precise targeting of the tumor to avoid damaging the surrounding healthy organs. Immobilisation masks and planning target volume margins are used to attempt to mitigate patient motion during treatment, however patient motion can still occur. Patient motion during RT can lead to decreased treatment effectiveness and a higher chance of treatment related side effects. Tracking tumor motion would enable motion compensation during RT, leading to more accurate dose delivery. The purpose of this paper is to develop a method to detect and segment the tumor in kV images acquired during RT. Unlike previous tumor segmentation methods for kV images, in this paper a process for generating realistic and synthetic CT deformations was developed to augment the training data, and make the segmentation method robust to patient motion. Detecting the tumor in 2D kV images is a necessary step towards 3D tracking of the tumor position during treatment. In this paper a conditional generative adversarial network (cGAN) is presented that can detect and segment the gross tumor volume (GTV) in kV images acquired during H&N RT. Retrospective data from 15 H&N cancer patients obtained from the Cancer Imaging Archive were used to train and test patient-specific cGANs. The training data consisted of digitally reconstructed radiographs (DRRs) generated from each patient's planning CT and contoured GTV. Training data was augmented by using synthetically deformed CTs to generate additional DRRs (in total 39600 DRRs per patient or 25200 DRRs for nasopharyngeal patients) containing realistic patient motion. The method for deforming the CTs was a novel deformation method based on simulating head rotation and internal tumor motion. The testing dataset consisted of 1080 DRRs for each patient, obtained by deforming the planning CT and GTV at different magnitudes to the training data. The accuracy of the generated segmentations was evaluated by measuring the segmentation centroid error, Dice similarity coefficient (DSC) and mean surface distance (MSD). This paper evaluated the hypothesis that when patient motion occurs, using a cGAN to segment the GTV would create a more accurate segmentation than no-tracking segmentations from the original contoured GTV, the current standard-of-care. This hypothesis was tested using the 1-tailed Mann-Whitney U-test. The magnitude of our cGAN segmentation centroid error was (mean ± standard deviation) 1.1 ± 0.8 millimeters and the DSC and MSD values were 0.90 ± 0.03 and 1.6 ± 0.5 millimeters respectively. Our cGAN segmentation method reduced the segmentation centroid error (p<0.001), and MSD (p = 0.031) when compared to the no-tracking segmentation, but did not significantly increase the DSC (p = 0.294). The accuracy of our cGAN segmentation method demonstrates the feasibility of this method for H&N cancer patients during RT. Accurate tumor segmentation of H&N tumors would allow for intrafraction monitoring methods to compensate for tumor motion during treatment, ensuring more accurate dose delivery and enabling better H&N cancer patient outcomes. This article is protected by copyright. All rights reserved.

Bony Stroke: Ischemic Stroke Caused by Mechanical Stress on Brain Supplying Arteries From Anatomical Bone or Cartilage Anomalies

Bone or cartilage anomalies with affection of brain supplying arteries are a potential structural cause for ischemic stroke. In the following, we termed this entity bony stroke. Due to rarity of their description, there is no standardized workup and therapy for bony strokes. Retrospectively, we extracted diagnostic and therapeutic workup of all patients considered to have had a bony stroke between January 2017 to March 2022 at our comprehensive care center. In total, 6 patients classified as a bony stroke were identified among 4200 acute patients with ischemic stroke treated during the study period. Each patient had recurrent ischemic strokes in the dependent vascular territory before diagnosis. Diagnosis was achieved by a combination of imaging devices, including sonography, computed tomography, and magnetic resonance imaging. In addition to conventional static imaging, the application of dynamic imaging modalities with the patients' head in rotation or reclination confirmed a vessel affection following head movements in 3 patients (50%). Treatment options were interdisciplinary assessed and included the following: conservative treatment (n=1), endovascular stenting (n=2) or occlusion (n=2), surgical removal of bone/ cartilage (n=2), and surgical bypass treatment (n=1). In follow-up (mean 11.7 months), no patient experienced further ischemia. As a differential diagnosis, bony strokes may be considered in patients with recurrent ischemic stroke of unknown cause in one dependent vascular territory. Interdisciplinary evaluation and treatment may eliminate risk of stroke recurrence.

Using a smartphone app in the measurement of posture-related pupil center shift on centration during corneal refractive surgery.

Purpose: Pupil center is an important anchor point in corneal refractive surgery, which may affect by body position. This study investigated the feasibility of using a smartphone application in measurement of posture-related pupil center shifts. Methods: Images of undilated eyes were captured for 25 participants (age: 18-38years) at a distance of 40cm in four body positions (seated, supine, right lateral, and left lateral) under controlled lighting conditions. During taking images, a smartphone application was used to guide positioning without head rotation and tilt. From the images, the location of the pupil center and pupil diameter with respect to the limbus boundary were measured. Results: According to the data obtained by the smartphone application, pupil center was located slightly nasal and superior to the limbus center in the seated position, and it shifted more nasally and superiorly (p < 0.001, OD 0.54 ± 0.11mm, OS 0.57 ± 0.14mm) in the supine position. When body position switched between left and right lateral positions, the pupil centers of both eyes shifted along the direction of gravity (p < 0.05), and no significant shift occurred along the longitudinal axis. Moreover, pupil constriction was observed when the body position changed from seated to supine position (p < 0.001, OD 0.64 ± 0.57mm, OS 0.63 ± 0.58mm). Conclusion: Posture-related pupil center shift may be larger than the error tolerance of centration in corneal refractive surgery, which might be difficult to measure by the existing instruments. An accessible application is necessary for evaluating the shift of pupil center and guiding centration during the surgery.