Pupil Radius Research Articles

Refractive extended depth-of-focus lens design based on periodic power profile for presbyopia correction.

Limitations of existing diffractive multifocal designs for presbyopia correction include discrete foci and photic phenomena such as halos and glare. This study aimed to explore a methodology for developing refractive extended depth-of-focus (EDoF) lenses based on a periodic power profile. The proposed design technique employed an optical power profile that periodically alternated between far, intermediate and near distances across the pupil radius. To evaluate the lens designs, optical bench testing was conducted. The impact on visual performance was assessed using a spatial light modulator-based adaptive optics vision simulator in human subjects. Additionally, the effects of pupil size change and lens decentration on retinal image quality were examined. A comparative performance analysis was carried out against a typical diffractive trifocal design and a monofocal lens. The proposed design method was found to be effective in uniformly distributing light energy across all object distances within the desired depth of focus (DoF). While trade-offs between overall image quality and DoF still exist, the EDoF lens design, when tested in human subjects, provided a continuous DoF spanning over 2.25 D. The results also revealed that the EDoF design had a slightly higher dependence on changes in pupil size and lens decentration than the diffractive trifocal design. The proposed design method showed significant potential as an approach for developing refractive EDoF ophthalmic lenses. These lenses offer a continuous DoF but are slightly more susceptible to variations in pupil size and decentration compared with the diffractive trifocal design.

Eye detection and coarse localization of pupil for video-based eye tracking systems

A video-based eye tracking system generally captures NIR images, each of which contains one or two eyes of a subject. The subject’s point of gaze is then determined using 3D eye model and pupil centre corneal reflection technique. Eye detection and pupil localization play significant roles in video-based eye tracking systems. However, face rotation, wearing glasses, eye-shape variation and illumination variation make it difficult to detect an eye and localize a pupil accurately in the images captured by video-based eye tracking systems. In this paper, we proposed an eye detector that adopts a coarse-to-fine strategy. The eye detector consists of three classifiers: an ATLBP-THACs feature-based cascade classifier, a branch CNN and a multi-task CNN. We also proposed a method for coarse pupil localization. Coarse localization is an important step for pupil localization since it can provide initial pupil coordinates for a fine pupil localization method. Given a downscaled eye image, a shallow CNN is used to estimate the location of seven landmarks. On this basis, pupil center and radius are estimated. A method for small dim target enhancement is used to increase the contrast between pupil and background. The main goal of pupil enhancement is to make it easier to binarize an eye image. At last, component filtering is made by utilizing the estimated pupil center and radius. We collected a dataset named neepuEYE dataset that consists of 5500 NIR eye images from 109 people. The images can be used to generate augmented samples for training an eye detector since they contain eyes with different shape, orientation and pupil localization. Experimental results show that our eye detector is a fast and robust detector. Furthermore, our method for coarse pupil localization can obtain not only high detection rate but also high localization speed.

Handheld chromatic pupillometry can reliably detect functional glaucomatous damage in eyes with high myopia

Background/aimsTo assess pupillary light responses (PLRs) in eyes with high myopia (HM) and evaluate the ability of handheld chromatic pupillometry (HCP) to identify glaucomatous functional loss in eyes with HM.MethodsThis...

Using a video-based eye tracker to analyse the binocular near-reflex dynamics response.

This study presents a novel video-based eye-tracking system for analysing the dynamics of the binocular near-reflex response. The system enables the simultaneous measurement of convergence, divergence and pupillary size during accommodation and disaccommodation to aid the comprehensive understanding of the three-component near-reflex. A high-speed (90 Hz) video-based eye tracker was used to capture changes in eye gaze and pupil radius in 15 participants in response to altering stimulus conditions. An offline analysis involved separating the gaze vector components and pupil radius, which were fitted to a hyperbolic tangent function to characterise the dynamics of the near-reflex process. Significant differences in the temporal parameters of the pupil radius were observed between the near-to-far and far-to-near vision changes, with faster miosis compared with mydriasis. Additionally, differences in response times were found between gaze angle components, with longer convergence times compared to changes in the vertical direction (saccades). The steady-state values of the gaze components and pupil radius were in line with theoretical expectations and previous reports. The proposed system provides a non-invasive, portable and cost-effective method for evaluating near-reflex dynamics under natural viewing conditions using a video-based eye tracker. The sampling rate ensures the accurate assessment of vergence eye movements and pupillary dynamics. By simultaneously measuring eye convergence, divergence and pupil size, the system offers a more comprehensive assessment of the near-reflex response. This makes it a valuable tool for clinical diagnosis, research studies and investigating the effects of near work on the visual system.

Dynamical Modulation of Transverse Orbital Angular Momentum in Highly Confined Spatiotemporal Optical Vortex

Spatiotemporal optical vortices (STOVs) have attracted numerous attention from researchers in recent years due to their intriguing characteristics with transverse orbital angular momentum (OAM) in the spatiotemporal domain. In this work, we numerically analyze the tightly focusing characteristics of higher-order STOVs and present a method to dynamically modulate the transverse OAM in highly confined STOVs. Richards–Wolf vectorial diffraction theory was employed to simulate the three-dimensional spatiotemporal distribution of the focused STOV corresponding to the incident wave packet of topological charge of −2. The simulation results show that the higher-order spatiotemporal vortices in the transversely polarized components of the focused wave packets split into two first-order vortices with topological charge of −1 when the waist radius of the incident wave packet was larger than 40% of the pupil radius of the focusing lens, and the spacing of the two split vortices could be tailored by adjusting the waist radius of the incident wave packet. Meanwhile, the incident spatial waist radius also affected the tilt angle of the phase singularity trace in the z-polarized component of the focused field. The presented method provides a flexible way to dynamically engineer the spatiotemporal vortices in the tightly focused wave packet and may find potential applications in nanophotonics, light–matter interaction, quantum information processing, etc.

New biomarkers for the assessment of fatigue evoked by long-term sleep deprivation based on pupillary light reflex using rheological models

BackgroundThe pupillary reflex (PLR) can be used to describe the function of individual segments of the visual pathway. It is modulated by the autonomic nervous system (ANS) and clinical disorders. The results of the research on the PLR parameterization methods presented in the article show that it is possible to use the phenomenon of pupil contraction as a result of light stimulation to assess the level of sleepiness. Currently, the PLR reflex is mainly used as the primary tool to study the integrity of the sensory and motor functions of the eye. Emergency medicine physicians routinely test the pupil light reflex to assess brainstem function. MethodsThe study utilized a method for estimating the fatigue level caused by 48-hour sleep deprivation under standardized and controlled conditions through the development and implementation of the Kelvin-Voigt rheology model (KV), explaining the dynamics of the pupillary light reflex. The baseline parameters for the model were as follows: parasympathetic force (fp), sympathetic force (fs), pupil radius in rest conditions (r0), onset time: parasympathetic system (tp), onset time: sympathetic system (ts), product fp × tp and product fs × ts. These parameters were subject to a statistical analysis of variance and compared with the parameters determined by the pupillographic assessment system by AmTech, such as contraction velocity (CV), relative amplitude (RA), pupil diameter (DDil1-fast), pupil diameter (DDil2-slow), latency (Lat), time of minimum diameter (TMD), contraction time (CT), redilation time (RT). ResultsThe statistical analysis involved the data obtained in the research experiment on a group of 18 healthy volunteers enrolled in our study (range 26–32 years, fifty percent of the study group were female). Based on the parameters from the KV model developed, the statistical significance for the model indicators was determined, i.e, fp, r0, tp, ts and fp × ts, compared at different levels of sleep deprivation of 48 h. In addition, analysis of the determined indicators, via the AmTech pupillographic system, demonstrated that an increased level of sleep deprivation does not only result in a change in the slope and amplitude of the curve of the pupil diameter in the contraction phase, which is visualized by the CV, RA, CT parameters, but also in the pupil dilation curve shape (Dil1-fast, Dil2-slow, RT). Sleep deprivation was observed to cause an increase of TMD and Lat. Correlation analysis presented the strongest correlations between fp and the contraction velocity r = 0.73 (p < 0.05) and the minimum pupil diameters as expressed by the RA values: 0.66 (p < 0.05). The force fp, originating from the parasympathetic system, was correlated with redilation time – i.e., the larger the force, the shorter the time: −0.52 (p < 0.05). It also affected the value of the pupil diameter at the end of dilatation (DDil2-slow) r = 0.49 (p < 0.05).The delay in the force tp, originating from the parasympathetic nervous system (PNS), increased the duration of pupil contraction time. In this case, the correlation coefficient was r = 0.73 (p < 0.05). This was also facilitated by a delay (ts) on the part of the sympathetic nervous system (SNS), leading to a delay in dilatation and thus facilitating unrestrained pupil constriction. The correlation coefficient was r = 0.7 (p < 0.05).The controlled level of sleepiness, assessed via the Stanford Sleepiness Scale (SSS) test, had increased by about 150% by the end of the experiment. ConclusionThe results of the studies indicate that the fatigue biomarkers, as determined during the pupil dilation phase (DDil1-fast, DDil2-Slow), as well as the new method for describing the dynamics of the PLR, can provide an effective and specific indicator of sleepiness levels. These results are also confirmed by an analysis of the Stanford Sleepiness Scale assessment results.In addition, the use of the KV rheological model to describe the curve of the pupillary reflex makes it possible, through the designated parameters of the model, to independently assess the sympathetic (fs, ts) and parasympathetic (tp, tp) activation of the autonomic nervous system.

Distribution of angle lambda and pupil offset as measured by combined Placido Scheimpflug Topography

BackgroundAngle lambda is the angle between the pupillary axis and the line of sight. It is important for accurate centration during anterior segment surgery. The purpose of this study is to identify the distribution of angle lambda and pupil center offset as measured by a combined placido disc Scheimpflug topography system.MethodsA prospective non-randomized study was performed on 2178 eyes in Eye World Hospital, Giza, Egypt. Sirius device (CSO, Costruzione Strumenti Oftalmici, Florence, Italy, version 3.2.1.60) was used to measure average keratometry (K), anterior chamber depth (ACD), central corneal thickness (CCT), horizontal visible iris diameter (HVID), pupil radius (PR), pupil center intercept x-component (PCI-x), and pupil center intercept y-component (PCI-y). Axial length (AL) was measured by immersion A-scan Eyecube Ultrasonography device (Ellex, Adelaide, South Australia, Australia). Angle lambda was calculated by a trigonometrical equation. Pearson correlation was used to analyze the correlation between angle lambda and age and refraction.ResultsAverage angle lambda in all eyes was 3.32° ± 1.99. Mean angle lambda was significantly smallest in myopia and largest in hyperopia. Age correlation to angle lambda was insignificant. Average PCI-x and PCI-y in all eyes was − 0.047 mm and + 0.091 mm, respectively.ConclusionsAngle λ is significantly larger in hyperopia than myopia, and the effect of age is insignificant. Pupil center offset was horizontally greater in hyperopia than in myopia. We therefore encourage the preoperative assessment of angle λ to avoid decentered ablation, especially when treating hyperopia.

Retinal neural dysfunction in diabetes revealed with handheld chromatic pupillometry.

To evaluate the ability of handheld chromatic pupillometry to reveal and localise retinal neural dysfunction in diabetic patients with and without diabetic retinopathy (DR). This cross-sectional study included 82 diabetics (DM) and 93 controls (60.4 ± 8.4 years, 44.1% males). DM patients included those without (n=25, 64.7 ± 6.3 years, 44.0% males) and with DR (n=57, 60.3 ± 8.5 years, 64.9% males). Changes in horizontal pupil radius in response to blue (469 nm) and red (640 nm) light stimuli were assessed monocularly, in clinics, using a custom-built handheld pupillometer. Pupillometric parameters(phasic constriction amplitudes [predominantly from the outer retina], maximal constriction amplitudes [from the inner and outer retina] and post-illumination pupillary responses [PIPRs; predominantly from the inner retina]) were extracted from baseline-adjusted pupillary light response traces and compared between controls, DM without DR, and DR. Net PIPR was defined as the difference between blue and red PIPRs. Phasic constriction amplitudes to blue and red lights were decreased in DR compared to controls (p < 0.001; p < 0.001). Maximal constriction amplitudes to blue and red lights were decreased in DR compared to DM without DR (p < 0.001; p=0.02), and in DM without DR compared to controls (p < 0.001; p=0.005). Net PIPR was decreased in both DR and DM without DR compared to controls (p=0.02; p=0.03), suggesting a wavelength-dependent (and hence retinal) pupillometric dysfunction in diabetic patients with or without DR. Handheld chromatic pupillometry can reveal retinal neural dysfunction in diabetes, even without DR. Patients with DM but no DR displayed primarily inner retinal dysfunction, while patients with DR showed both inner and outer retinal dysfunction.

EVO+ Implantable Collamer Lens KS-aquaPORT Location, Stability, and Impact on Quality of Vision and Life.

To determine the longitudinal variation in the KS-aquaPORT central hole location of the phakic EVO+I Implantable Collamer Lens (ICL) (STAAR Surgical) and analyze its influence on visual performance, quality of vision (QoV), and quality of life (QoL). A prospective study was performed including 36 patients who had EVO+ ICL implantation. The KS-aquaPORT central hole location (Cartesian and polar coordinates) was determined with respect to the pupil center and visual axis. The effect of time (6-month follow-up) on central hole location was analyzed using linear mixed models. The effect of the KS-aquaPORT location on visual performance, QoV, and QoL parameters was assessed with multivariate regression models. With respect to the visual axis, no significant changes in KS-aquaPORT location were found during follow-up. With respect to the pupil center, the X-coordinate and radius of KS-aquaPORT location showed modest, but significant (P ≤ .05) differences between 1-week and 3-month postoperative visits, and between 1-week and 6-month visits. X-coordinate variation was significant (P = .022) between 1-and 6-month visits. With respect to the visual axis, greater KS-aquaPORT decentration was associated with worse visual acuity (X-coordinate: P = .004; radius: P = .006), and inferior decentration with longer xenon-type glare photostress recovery time (P = .021). With respect to the pupil center, a lower radius was associated with better QoV scores (P ≤ .01) and temporal decentration produced higher ring-shaped dysphotopsia (P = .007). EVO+ ICL KS-aquaPORT location appears to be clinically stable up to 6 months postoperatively. A central location of the EVO+ ICL KS-aquaPORT hole is preferred because it allows reduced perception of dysphotopic phenomena that can result in better QoV. [J Refract Surg. 2022;38(3):177-183.].

Modelling the refractive and imaging impact of multi-zone lenses utilised for myopia control in children's eyes.

PurposeTo develop an optical model of a child's eye to reveal the impact of target distance and accommodative behaviour on retinal image quality when fitted with multi‐zone lenses.MethodsPupil size, aberration levels and accommodative lag were adjusted for models viewing stimuli at 400, 100, 33 and 20 cm. Distributions of defocus across the pupil and simulated retinal images were obtained. An equivalent 16‐point letter was imaged at near viewing distances, while a 0.00 logMAR (6/6) letter was imaged at 400 cm. Multi‐zone lenses included those clinically utilised for myopia control (e.g., dual‐focus, multi‐segmented and aspherical optics).ResultsViewing distance adjustments to model spherical aberration (SA) and pupil radius resulted in a model eye with wider defocus distributions at closer viewing distances, especially at 20 cm. The increasing negative SA at near reduced the effective add power of dual‐focus lenses, reducing the amount of myopic defocus introduced by the centre‐distance, 2‐zone design. The negative SA at near largely compensated for the high positive SA introduced by the aspheric lens, removing most myopic defocus when viewing at near. A 0.50 D accommodative lag had little impact on the legibility of typical text (16‐point) at the closer viewing distances.ConclusionsAll four multi‐zone lenses successfully generated myopic defocus at greater viewing distances, but two failed to introduce significant amounts of myopic defocus at the nearest viewing distance due to the combined effects of pupil miosis and negative SA. Typical 16‐point type is easily legible at near even in presence of the multi‐zone optics of lenses utilised for myopia control and accommodative lag.

Human Eye Pupil Detection System for Different IRIS Database Images

The pupil detection system plays a vital role in ophthalmology diagnosis equipments because pupil has a center place of human eye to locate the exact position. To identify the exact human eye pupil region in near infrared (NIR) images, this work proposes the Center of gravity method and its real time FPGA hardware implementation. The proposed work involves global threshold method to segment the pupil region from human eye and the bright spot suppression process removes the light reflections on the pupil due to the IR (Infra red) rays then the morphology dilation process removes unnecessary black pixels other than pupil region on the image. Finally, center of gravity (COG) method provides the exact pupil center coordinate and radius of the human eye. CASIA IRIS V4 and UBIRIS iris database images used in this work and achieved 90-95% of recognition rate.

Construction of special multi-mode annular optical vortex

Based on the vector diffraction theory, this paper modulates the tightly focused Bessel beam, constructs the vector optical vortex field of nanoscale and studies its energy transfer characteristics. The results show that the topological charge number can adjust the polarization state of the optical vortex, and the phenomenon of multimodal optical vortex soliton appears. The phase parameter can cause the optical vortex to be angularly deflected and a certain amount of energy transfer occurs. The ratio of pupil radius to beam waist results in significant energy migration of the multi-ring optical vortex solitons. In a word, the three parameters proposed in this paper can change the dimension of optical vortex solitons and give rise to a new form of optical vortex. The research in this paper has a good application prospect in the fields of optical vortex manipulation, particle capture and multiplexing of high density communication system, information security and so on.

Paraxial and tightly focused behaviour of the double ring perfect optical vortex.

In this paper we compare the intensity distributions in the paraxial and tightly focused regimes corresponding to a double ring perfect optical vortex (DR-POV). Using the scalar diffraction theory and the Richards-Wolf formalism, the fields in the back focal plane of a low and high (tight focusing) NA lens are calculated. In the paraxial case we experimentally observed a DR-POV whose rings enclose a dark zone thanks to the destructive interference introduced by a π phase shift. In the tightly focused regime, however, the numerical simulations showed that the intensity near the focus is influenced by the input field polarization and it is not intuitive. In both cases we found that the dark region subtended between the rings has a minimal width that is inversely proportional to the pupil radius of the system, reaching 0.42λ for the radially polarized DR-POV. For the tightly focused case, we calculated the optical forces in the transversal and longitudinal coordinates exerted on a metallic particle. As a result, it is theoretically demonstrated that the circularly polarized DR-POV can trap Au metallic particles in 3D using a light wavelength close to its resonance.

Zernike monomials in wide field of view optical designs.

Zernike polynomials are universal in optical modeling and testing of wavefronts; however, their polynomial behavior can cause a misinterpretation of individual aberrations. Wavefront profiles described by Zernike polynomials contain multiple terms with different orders of pupil radius (ρ). Zernike polynomials are a sum of high and low orders of ρ to minimize the RMS wavefront error and to preserve orthogonality. Since the low-order polynomials are still contained in the net Zernike sum, there is redundancy in individual monomials. Monomial aberrations, also known as Seidel or primary aberrations, are useful in studying an optical design's complexity, alignment, and field behavior. Zernike polynomial aberrations reported by optical design software are not indicative of individual (monomial) aberrations in wide field of view designs since the low-order polynomials are contaminated by higher order terms. An aberration node is the field location where an individual (monomial) aberration is zero. In this paper, a matrix method is shown to calculate the individual monomial aberrations given the set of Zernike polynomials. Monomial aberrations plotted as a function of field angle (H) indicate the field order (Hn) and the location of true aberration nodes. Contrarily, Zernike polynomial versus field (ZvF) plots can indicate false aberration nodes, due to the polynomial mixing of high- and low-order terms. Accurate knowledge of the monomial aberration nodes, converted from Zernike polynomials, provides the link between a ray-trace model or lab wavefront measurement and nodal aberration theory (NAT). This method is applied to two different optical designs: (1) 120° circular FOV fish-eye lens and (2) 120∘×4∘ rectangular FOV, off-axis, freeform four-mirror design.

An Iris Recognition System Using Deep convolutional Neural Network

Machine learning rises in varied areas of computer science. A deep conventional neural network is powerful visual models of machine learning. We tend to present robustness and effective structure for the iris recognition system. The image first pass through these stages: enhancing the image quality, determine the iris and pupil center and radius for iris segmentation, converting the image from the Cartesian coordinates to the polar coordinates to reduce the time of processing. The proposed system is named IRISNet that extracting the feature and classifying them automatically without any domain knowledge. The architecture of IRISNet consists of Convolutional Neural Network layers for extract feature and Softmax layer to classify these features into N classes, for training CNN the backpropagation algorithm and Adam optimization method are used for updating the weights and learning rate, respectively. The performance of the proposed system was evaluated using IITD V1 iris database. The results obtained from the proposed system outperform supervised classification model (SVM, KNN, DT, and NB). The identification rate 97.32% and 96.43% for original and normalized images respectively. The recognition time per person is less than one second.

Three-dimensional isotropic STED microscopy generated by 4[formula omitted] focusing of a radially polarized vortex Laguerre–Gaussian beam

In this study, a method is proposed to generate a three-dimensional (3D) isotropic super-resolution spot using stimulated emission depletion (STED) microscopy. A focused radially polarized Laguerre–Gaussian (LG01) beam is used as the pump beam. A focused depletion spot is produced by a radially polarized vortex Laguerre–Gaussian beam in a 4π focusing system. The influences of the topological charge, the order of LG, the maximum aperture angle, and the ratio of the pupil radius to the beam waist (β) on the spherical symmetry of the fluorescent spot are analyzed in detail. With the optimization parameters, an isotropic fluorescent spot is realized. The full widths at half maximum (FWHM) value of the isotropic fluorescent spot are 0.0348λ in both the r and z directions in a saturated case. The proposed model can provide a useful and simple guideline to obtain the spherical spot in 3D microscopy, which is very useful for trapping specific pathological ultra-structures of spherical shaped molecules and related medical applications.

A longitudinal study of pupillary light reflex in 6- to 24-month children

Pupillary light reflex (PLR) is an involuntary response where the pupil size changes with luminance. Studies have shown that PLR response was altered in children with autism spectrum disorders (ASDs) and other neurological disorders. However, PLR in infants and toddlers is still understudied. We conducted a longitudinal study to investigate PLR in children of 6–24 months using a remote pupillography device. The participants are categorized into two groups. The ‘high risk’ (HR) group includes children with one or more siblings diagnosed with ASDs; whereas the ‘low risk’ (LR) group includes children without an ASD diagnosis in the family history. The participants’ PLR was measured every six months until the age of 24 months. The results indicated a significant age effect in multiple PLR parameters including resting pupil radius, minimal pupil radius, relative constriction, latency, and response time. In addition, the HR group had a significantly larger resting and minimal pupil size than the LR group. The experimental data acquired in this study revealed not only general age-related PLR changes in infants and toddlers, but also different PLRs in children with a higher risk of ASD.

Design of corneal cross-linking system: with real-time positioning of pupil position

This paper presents a design of a corneal cross-linking instrument with the function of tracking and locating the central position of the pupil in real time. According to the application requirements, based on the principle of uniform light of compound eye lens, the optical projection system of the corneal crosslinking instrument with the diameter of the treatment spot being 9mm and the uniformity being greater than 90% was designed. And put forward a kind of the pupil localization algorithm, the acquisition of the pupil image gray processing and calculate the histogram, according to the characters of histogram adaptively to take out the appropriate threshold binarization, again after the binarization of image contour tracking, get accurate boundary, the outline of the final vote based on the sliding arc length increment method to determine the pupil center and radius. Experimental results show that the corneal cross-linking system designed in this paper can not only accurately project the treatment of light spot, but also accurately track the central position of the pupil of the human eye.

Seidel aberration coefficients: an alternative computational method.

An alternative method to compute Seidel aberrations is presented that utilizes real pseudoparaxial skew rays traveling through a rotationally-symmetric lens system as a Taylor series expansion in terms of object height and ray-direction spherical coordinates. Expressions for defocus, lateral magnification, and Seidel primary ray aberration coefficients are obtained in terms of numerically-determined higher-order partial derivatives of rays which are proximate to the optical axis. In contrast to commonly used methods, the new form of the aberration coefficients is related to unit entrance pupil radius and unit object height. The proposed methodology can be extended to derive higher-order ray aberration coefficients.

Wavefront propagation based on the ray transfer matrix and numerical orthogonal Zernike gradient polynomials.

The aberrated wavefront propagates along its normal. Both the magnitude and boundary change after the propagation. Wavefronts characterized by Zernike coefficients and a normalized pupil radius can also be represented by a bundle of feature rays normal to the local surface. A ray transfer matrix parameterized by the pupil radius and propagation distance is proposed to transfer these feature rays to obtain the slope and position data of the propagated feature rays. Numerical orthogonal Zernike gradient polynomials are derived to reconstruct the wavefront from the discrete data by using a numerical method. Two aberrated wavefronts are performed as examples to validate the accuracy and flexibility of the proposed numerical method.