Edge Of Pupil Research Articles

Initial Outcome of Subconjunctival Bevacizumab for Corneal Neovascularization - a Case Series

Introduction : Corneal neovascularization (CNV) has a variety of causes and threatens corneal clarity, thus optimal visual acuity. Conventional medical management includes topical steroids and matrix metalloproteinase inhibitors like doxycycline. Anti-vascular endothelial growth factor (anti-VEGF) agents have demonstrated promise but remain off-label for this indication.
 Case Illustration : We present three patients with corneal neovascularization varied in etiology who underwent subconjunctival injection of Bevacizumab . Case 1: a-female-69 years old came with blurred vision after had Stephen Johnson Syndrome which affect her cornea. The examination revealed opacification of cornea accompanied by neovascularization at 5 until 9 o’clock position up to edge of pupil in the left. Case 2: a-male-47 years old presented corneal haze with neovascularization almostin all corneal region on background of fungal keratitis. Case 3: a-male-63 years old who underwent penetrating keratoplasty of indication corneal lekoma following an episode of fungal keratitis. There was opacity in all corneal region and neovascularization in 360 degree of limbus. All of these patients showed regression of neovessel after first injection of bevacizumab.
 Discussion : Corneal neovascularization is a condition caused by disruption homeostasis in which proangiogenic balanced by antiangiogenic, thereby maintaining avascularity. Bevacizumab as VEGF-A-binding proteins could prevent VEGF-A from binding cell surface receptors.
 Conclusion : Subconjunctival injection of Bevacizumab can be considered as a treatment for corneal neovascularization. It has shown promising effects in recess neovascularization in cornea regardlessthe etiology.

Gradient myopic defocus causes scleral tissue reinforcement and structural scleral remodelling

Aims/Purpose: To determine histological effects of lens induced refractive change on scleral remodelling in chicks.Methods: 18 Ross‐Ross chicks were raised for 14 days on a 14 hr light/10 hr dark cycle. 6 chicks were allowed to develop normally. 6 chicks wore conventional ‐10D lenses for the full 14 days. 6 chicks wore conventional ‐10D lenses for the first 7 days and myopia progression control (MPC) lenses or the next 7 days. MPC lenses had a central power of ‐10D and a gradient power rise at pupil edge (+ 2.75D). Birds were euthanized after 14 days and eyes were routinely processed for histopathological evaluation. Whole mount H&E‐stained tissue sections were microscopically analysed using bright field microscopy.Results: All lens treated birds developed significant myopia as expected Total scleral thickness was significantly reduced in the group wearing conventional ‐10 lenses (p < 0.05), but remained comparable to the normal control group for the MPC lenses treated birds. New appositional growth of the cartilaginous sclera was observed in all MPC lenses treated eyes and only in those eyes. The thickness of the cartilaginous component of the sclera was 135 ± 6, 153 ± 5, 125 ± 8 μm for conventional myopic, MPC lenses treated, and control birds respectively. There was a significant increase in the cartilaginous scleral thickness in the MPC lenses treated birds compared to the other two groups (p < 0.03), but not between the conventional ‐10D lens treated and control birds (p > 0.05).Conclusions: It is possible to induce appositional growth in hyaline cartilage in the chick sclera. In our study, this has only been achieved by using MPC lenses to reverse previously induced experimental myopia with conventional minus lenses. Our finding suggests that gradient decrease in peripheral lens power and the resulting differential level of defocus it causes could be a potential trigger of scleral reinforcement through stimulation of cartilage growth in the chick sclera.

The correlation of anterior segment structures in primary congenital glaucoma by ultrasound biomicroscopy with disease severity and surgical outcomes

PurposeTo evaluate the anterior segment structures using ultrasound biomicroscopy (UBM) in primary congenital glaucoma (PCG) and explore their correlation with disease severity and surgical outcomes.MethodsClinical information of PCG patients who underwent UBM prior to their first glaucoma surgeries from September 2014 to March 2021 were reviewed. The study included 214 UBM images of 154 PCG eyes and 60 fellow unaffected eyes. Anterior segment characteristics were analyzed. UBM parameters, including the iris thickness (IT) at variant distances from the pupil edge and iris root, anterior chamber depth (ACD), and pupil diameter (PD), were compared between two groups and their relationship with clinical factors and surgical outcomes were analyzed in PCG eyes.ResultsPCG eyes had unclear scleral spur, thin iris, wide anterior chamber angle, deep anterior chamber, rarefied ciliary body, elongated ciliary processes, and abnormal anterior iris insertion. ITs were thinner, ACD was deeper, and PD was larger in PCG eyes than fellow unaffected eyes (all P < 0.001). In PCG eyes, thinner ITs correlated with bilateral involvement and earlier age at presentation, and larger PD correlated with earlier age at presentation (P = 0.030) and higher intraocular pressure (P < 0.001). Thinner IT2 (P = 0.046) and larger PD (P = 0.049) were identified as risk factors for surgical failure.ConclusionUBM is a powerful technique to exam anterior segment structures in PCG. The anatomical features are associated with disease severity and surgical outcomes, providing essential clinical insights.

Ridge operator-assisted delineation of capsulorhexis border for cataract surgery.

With the continuous development of machine vision and imaging technology and its application in computer-aided diagnosis, it is clinically important to use computer technology to assist physicians in accurate cataract surgery. The capsulorhexis directly affects the outcome of cataract surgery, therefore, we design a method to automatically determine the virtual boundary of capsulorhexis for cataract surgery planning and tracking in-vivo to help surgeons achieve a more ideal capsulotomy geometry. In this study, an effective method was proposed to detect and display the location of capsulorhexis in cataract videos in-vivo. The initial step was locating the entire eye area by analyzing the connected components of the mirror reflective points in the image in the cataract surgery video. Then, an operator was designed for ridge edge variation and used to extract pupil edge features. Lastly, circular Hough transform was used to detect the pupillary margin and calculate the boundary between the scleral limbus and the virtual capsulorhexis border in accordance with the pupillary margin and finally displayed it in-vivo during cataract surgery. The method was tested on eight videos of cataract surgery and the results showed that 98.52% accuracy was achieved in the localization of the specular reflection point. We compared the proposed operator with the Sobel, Scharr, Laplace and Canny operators and the results showed that our operator achieved the smallest mean square error with the greatest structural similarity. The analysis demonstrated that the proposed operator outperformed other operators in detection and achieved satisfactory results in the videos of actual cataract surgeries.

Curvature Sensing-Based Pupil Alignment Method for Large-Aperture Telescopes

In optical systems, pupil alignment is an important component of wavefront sensing, closed-loop feedback, and imaging vignetting control because it directly affects the detection limit of the system and thus the realization of scientific goals. This study proposes the use of the energy transfer characteristics of the pupil edge to determine the misalignment of each pupil. The mechanism involves decoupling the influence of each pupil from the final exit pupil energy distribution by using aperture coding without the addition of other optical paths. The degree to which the pupil is aligned is characterized by the normalized point source sensitivity (PSSn). The pupil misalignment PSSn increased from 0.75 to 0.83. The results of this study can be used to perform tomographic detection of pupil alignment and obtain high-quality telescopic images.

Filterable sample consensus based on angle variance for pupil segmentation

Pupil segmentation is a first and important topic of iris recognition, identity recognition and eye movement information extraction for mental analysis. However, due to the negative effects of eyelash occlusion, eyelid occlusion and off-gaze deflection, making a precise pupil segmentation is a difficult task. Therefore, we propose a precise and robust algorithm for pupil segmentation, namely Angle Variance based Filterable Sample Consensus (AVBFSC), which is composed of an outlier filter and a boundary locator. The outlier filter can eliminate negative effects mentioned above, and also a best pupil segmentation is performed with our boundary locator, which learns a circular mathematical equation by selecting sub-samples from pupil edge pixels randomly. Experiment results in comparison with state-of-the-art methods on CASIA-Iris-V4-Interval dataset, indicate that our algorithm achieved best performance, that is, Accuracy of 98.99%, False Acceptance Rate (FAR) of 2.09% and Genuine Acceptance Rate (GAR) of 98.54%. In addition, it also has robust results under the condition of specific non-ideal scenes from CASIA-Iris-V4-Lamp dataset and Indian Institute of Technology Delhi (IITD) dataset including dark light conditions, eyelash occlusion, eyelid occlusion and off-gaze deflection.

Quantitative changes in iris vasculature and blood flow in patients with different refractive errors.

To evaluate the association between microvascular changes in the iris and refractive errors. A cross-sectional case study. Seventy eyes from 70 patients with refractive errors were enrolled. Iris microvasculature was analyzed using optical coherence tomography angiography (OCTA). We divided the iris images into three regions and calculated the vessel area density (VAD) and vessel skeleton density (VSD) of the inner one-third, inner two-thirds, and the entirety of the iris. The VADs and VSDs of the different regions were significantly different. The VAD and VSD of the inner one-third of the iris were higher than those of the other regions. The iris blood vessels were denser near the pupil margin, and blood vessels from the iris root to the pupil edge were radially distributed. The VAD and VSD of patients with mild hyperopia and emmetropia were higher than those of patients with moderate and high myopia. As the spherical equivalent increased, the VAD and VSD of the iris increased. Neither age nor sex contributed to significant differences in VAD and VSD. Quantitative changes in iris microvasculature may indicate the development of myopia.

The spectrally modulated self-coherent camera (SM-SCC): Increasing throughput for focal-plane wavefront sensing

Context. The detection and characterization of Earth-like exoplanets is one of the major science drivers for the next generation of telescopes. Direct imaging of the planets will play a major role in observations. Current direct imaging instruments are limited by evolving non-common path aberrations (NCPAs). The NCPAs have to be compensated for by using the science focal-plane image. A promising sensor is the self-coherent camera (SCC). An SCC adds a pinhole to the Lyot stop in the coronagraph to introduce a probe electric field. The pinhole has to be separated by at least 1.5 times the pupil size to separate the NCPA speckles from the probe electric field. However, such a distance lets through very little light, which makes it difficult to use an SCC at high speed or on faint targets. Aims. A spectrally modulated self-coherent camera (SM-SCC) is proposed as a solution to the throughput problem. The SM-SCC uses a pinhole with a spectral filter and a dichroic beam splitter, which creates images with and without the probe electric field. This allows the pinhole to be placed closer to the pupil edge and increases the throughput. Combining the SM-SCC with an integral field unit (IFU) can be used to apply more complex modulation patterns to the pinhole and the Lyot stop. A modulation scheme with at least three spectral channels can be used to change the pinhole to an arbitrary aperture with higher throughput. This adds an additional degree of freedom in the design of the SM-SCC. Methods. The performance of the SM-SCC is investigated analytically and through numerical simulations. Results. Numerical simulations show that the SM-SCC increases the pinhole throughput by a factor of 32, which increases the wavefront sensor sensitivity by a factor of 5.7. The reconstruction quality of the sensor is tested by varying the central wavelength of the spectral channels. A smaller separation between the wavelength channels leads to better results. The SM-SCC reaches a contrast of 1 × 10−9 for bright targets in closed-loop control with the presence of photon noise, phase errors, and amplitude errors. The contrast floor on fainter targets is photon-noise-limited and reaches 1 × 10−7. The SM-SCC with an IFU can handle randomly generated reference field apertures. For bright targets, the SM-SCC-IFU reaches a contrast of 3 × 10−9 in closed-loop control with photon noise, amplitude errors, and phase errors. Conclusions. The SM-SCC is a promising focal-plane wavefront sensor for systems that use multiband observations, either through integral field spectroscopy or dual-band imaging.

Hybrid FPGA-CPU pupil tracker.

An off-axis monocular pupil tracker designed for eventual integration in ophthalmoscopes for eye movement stabilization is described and demonstrated. The instrument consists of light-emitting diodes, a camera, a field-programmable gate array (FPGA) and a central processing unit (CPU). The raw camera image undergoes background subtraction, field-flattening, 1-dimensional low-pass filtering, thresholding and robust pupil edge detection on an FPGA pixel stream, followed by least-squares fitting of the pupil edge pixel coordinates to an ellipse in the CPU. Experimental data suggest that the proposed algorithms require raw images with a minimum of ∼32 gray levels to achieve sub-pixel pupil center accuracy. Tests with two different cameras operating at 575, 1250 and 5400 frames per second trained on a model pupil achieved 0.5-1.5 μm pupil center estimation precision with 0.6-2.1 ms combined image download, FPGA and CPU processing latency. Pupil tracking data from a fixating human subject show that the tracker operation only requires the adjustment of a single parameter, namely an image intensity threshold. The latency of the proposed pupil tracker is limited by camera download time (latency) and sensitivity (precision).

Decreased iris thickness on swept-source optical coherence tomography in patients with primary open-angle glaucoma.

To investigate the iris thickness (IT) of patients with primary open-angle glaucoma (POAG) and older adults using anterior segment swept-source optical coherence tomography (SS-OCT). In this comparative cross-sectional study, 154 participants were enrolled, including 40 patients with POAG and 114 healthy individuals. Nasal-angle SS-OCT images were analysed using callipers to measure the thickness of the iris, including the anterior border layer, stromal, and pigmented epithelial layer, at 1 and 2 mm from the pupil edge. The relationship between IT and glaucoma severity was analysed, and receiver operating characteristic curves were constructed to assess the ability of each IT parameter to distinguish patients with glaucoma from healthy controls. The IT parameters and iris area were lower in the POAG group than in the age-matched control group (p< 0.05). In the POAG group, the thickness of the pigmented epithelial layer at 1 and 2 mm was significantly correlated with the severity of glaucoma (p< 0.05). Iris area, with a cut-off of 1.43 mm2, exhibited the highest sensitivity (85%) and specificity (64.81%; area under the curve=0.783) for distinguishing patients with POAG from healthy controls. Older adults tended to have the thinnest IT, children had the smallest iris area (p< 0.05). In patients with POAG, the severity of iris atrophy was associated with glaucoma severity. The results of IT measurements by SS-OCT may help in the clinical evaluation of POAG.

EPS: Robust Pupil Edge Points Selection with Haar Feature and Morphological Pixel Patterns

Pupil parameters are the essential foundation for many applications, such as cognitive science and human–machine interaction. Existing approaches are still affected by various challenges. We propose a novel pupil detection pipeline (known as Edge Points Selector “EPS”) which is suitable even for partial occlusion, lighting, and specular reflection. EPS consists of pupil area detection, edge selection, and ellipse fitting. For the first time, we find the suitable Haar-like feature of 2D-pupil and a new pupil edge feature in the local pupil area, and integrate them into the proposed pipeline. EPS was compared with two state-of-art methods on 130[Formula: see text]856 images in this work. Within an error threshold of 5 pixels, our method outperforms the comparison algorithms by 33.8% and 19.4%, respectively, on overage.

Research on Image Preprocessing Algorithm and Deep Learning of Iris Recognition

With the development of information society, biometrics technology has been paid more and more attention. Iris recognition is considered as the most promising biometric authentication technology in the 21st century because of its uniqueness, stability and non-creativity. However, due to the high cost of iris recognition equipment and some defects of the algorithm, iris recognition cannot be applied in real life on a large scale. In this paper, a fast localization iris recognition algorithm is proposed, which combines the iris segmentation algorithm with deep learning to quickly extract the iris region for recognition. Firstly, the pupil edge was extracted by dynamic threshold analysis and contour extraction, and then iris was located by edge detection and gray calculation. Finally, features of normalized images were learned by deep learning network. Experiments show that the method can guarantee the accuracy and efficiency of iris segmentation and has a high degree of recognition and matching.

A Pupil-Positioning Method Based on the Starburst Model

Human eye detection has become an area of interest in the field of computer vision with an extensive range of applications in human-computer interaction, disease diagnosis, and psychological and physiological studies. Gaze-tracking systems are an important research topic in the human-computer interaction field. As one of the core modules of the head-mounted gaze-tracking system, pupil positioning affects the accuracy and stability of the system. By tracking eye movements to better locate the center of the pupil, this paper proposes a method for pupil positioning based on the starburst model. The method uses vertical and horizontal coordinate integral projections in the rectangular region of the human eye for accurate positioning and applies a linear interpolation method that is based on a circular model to the reflections in the human eye. In this paper, we propose a method for detecting the feature points of the pupil edge based on the starburst model, which clusters feature points and uses the RANdom SAmple Consensus (RANSAC) algorithm to perform ellipse fitting of the pupil edge to accurately locate the pupil center. Our experimental results show that the algorithm has higher precision, higher efficiency and more robustness than other algorithms and excellent accuracy even when the image of the pupil is incomplete.

Centroid error due to non-uniform lenslet illumination in the Shack-Hartmann wavefront sensor.

Images formed by individual Shack-Hartmann wavefront sensor lenslets are displaced proportionally to the average wavefront slope over their aperture. This principle fails when the lenslet illumination is non-uniform. Here we demonstrate that the resulting error is proportional to the linear component of the illumination intensity, the quadratic wavefront component, and the lenslet size. For illustrative purposes, we compare the error due to centered Gaussian illumination decaying by 30% at the pupil edge against the error due to assuming the wavefront at the lenslet center being equal to the wavefront average across each lenslet. When testing up to ninth-order Zernike polynomial wavefronts and simulating nine lenslets across the pupil, the maximum centroid errors due to non-uniform illumination and sampling are 1.4% and 21%, respectively, and 0.5% and 6.7% when considering 25 lenslets across the pupil in the absence of other sources of error.

Determination of iris thickness development in children using swept-source anterior-segment optical coherence tomography.

PurposeThe uvea comprises the iris, ciliary body, and choroid. However, the development of the anterior part (iris and ciliary body) in children is not yet fully elucidated. We investigated the iris thickness (IT) in children using swept-source anterior-segment optical coherence tomography (ASOCT).MethodsIn this retrospective, clinic-based study, we enrolled 41 children (mean ± standard deviation: 6.8 ± 3.3 years; range: 3–16; 17 males) with normal or mild refractive error. Horizontal scanning images of swept-source ASOCT were analyzed in temporal and nasal angle areas. The ITs at 1 and 2 mm from the pupil edge were measured using swept-source ASOCT. The association between IT and age, sex, and ocular morphological parameters (i.e., axial length, average corneal curvature, central corneal thickness, inter-scleral spur distance, and anterior chamber depth) was assessed using Pearson’s correlation coefficient (r) and linear regression analysis.ResultsThe average IT (temporal and nasal) at 1 and 2 mm were 0.432 ± 0.060 (0.302−0.569 mm) and 0.337 ± 0.045 (0.229−0.414 mm), respectively. There was a significant correlation between age and average IT (r = 0.45, P = 0.002 at 1 mm and r = 0.31, P = 0.042 at 2 mm). Multiple linear regression analysis revealed that age (coefficient: 0.01), axial length (−0.02), average corneal curvature (0.01), and anterior chamber depth (0.01) at 1 mm as well as age (0.00), average corneal curvature (0.09), anterior chamber depth (0.06), and male (–0.02) at 2 mm were identified as predictors of IT.ConclusionsIT in children increases with age. Additionally, IT was thinner with longer axial length and in males, thicker in eyes with deeper anterior chamber and flatter corneal curvature. Our study may partly explain the development of eyeball structures in children.

Expression of transforming growth factor β and matrix metalloproteinases in the aqueous humor of patients with congenital ectopia lentis.

It is well known that transforming growth factor β (TGFβ), which is able to stimulate multiple intracellular signaling pathways, exerts an important role in Marfan syndrome, although the effects of TGFβ on congenital ectopia lentis (CEL) have yet to be fully elucidated. In the present study, the expression levels of TGFβ and matrix metalloproteinases (MMPs) were investigated in the aqueous humor of patients with ectopic lentis who differed in terms of the severity of the disease. A total of 17 CEL patients with 21 eyes (aged 12.76±9.37 years) and 12 congenital cataract (CC) patients with 17 eyes (aged 6.82±9.18 years) were randomized in the present study. The levels of active TGFβ and MMPs in the aqueous humor were analyzed with Luminex xMAP® technology by using commercially available Bio-Plex Pro™ Human MMP and TGFβ assays. The distance from the lens edge to the pupil edge and the white to white corneal diameter (i.e. the horizontal distance between the borders of the corneal limbus) were measured, and the ratio was calculated as the degree of lens dislocation. The association between TGFβ and MMP levels and the degree of lens dislocation was analyzed using Spearman's correlation test. Compared with the patients with CC, the level of TGFβ2 in the patients with CEL was increased significantly. Specifically, the level of TGFβ2 in the CEL patients was 855.19 pg/ml (744.33, 1,009.24), whereas it was 557.08 (438.24, 692.71) pg/ml in the CC patients (P<0.001). In addition, it was noted that the levels of MMP-2 and −10 in the aqueous humor of the patients with CEL were higher compared with those in the CC patients, although this increase did not reach the level of statistical significance. Notably, the levels of MMP-8 and −9 in the aqueous humor of patients with CEL were significantly lower compared with those in the CC patients (P=0.014 and P=0.002, respectively). Furthermore, a marginal correlation was identified between the severity of ectopic lentis and the levels of TGFβ2 in the aqueous humor (r2=0.379; P=0.003) of the patients with CEL. Taken together, these results demonstrated that a significant correlation existed between high levels of aqueous humor TGFβ2 and the severity of ectopia lentis in patients with CEL. In addition, aqueous humor TGFβ2 levels in the CEL patients were significantly higher compared with those in CC patients.

Clinical and theoretical substantiation of geometrical, optical and functional features of the pupil of the artificial iris

To validate the optimal biometric parameters of the pupil of artificial iris using methods of clinical and theoretical analysis. Mathematical modeling was used to determine the main criteria characterizing natural aperture diaphragm of the eye (pupil) which were considered in the theoretical substantiation of optimal biometric parameters of the AI's pupil. Parameters determined during the theoretical stage of the study were used in the development of iris-lens diaphragm (ILD) for clinical application. The study included 6 patients (6 eyes) with post-traumatic aniridia and cataract requiring reconstructive surgery. In the course of the surgery, intraocular lens and ILD were sequentially implanted into the capsular bag using injector system. The patients underwent standard and special ophthalmic examination including optical coherence tomography (OCT) of the central retina before the surgery and after 3 months. According to mathematical modeling, optimal shape of the ILD pupil was determined to be a circle. The suggested diameter for the ILD pupil is 3.2 mm. The pupil must be located on the optical axis of the eye. Distortions of the retinal image become minimal with pupil's edge thickness of 0.2 mm and cone-shaped profile. After Implantation of the developed ILD with pupil parameters determined during the theoretical substantiation, patients of the study exhibited increased visual acuity and satisfaction with results of the surgery. The biometric parameters of the ILD pupil determined during the clinical-theoretical study can be used in modern ILD models.

Iris Thickness and Severity of Neovascular Glaucoma Determined Using Swept-Source Anterior-segment Optical Coherence Tomography.

To investigate the iris thickness (IT) in neovascular glaucoma (NVG) using swept-source anterior-segment optical coherence tomography (ASOCT). In this retrospective, clinic-based, comparative study, we enrolled 20 NVG patients [11 with 360-degree angle-closure (AC)-NVG and 9 with NVG without AC] and 14 healthy age-matched controls. Horizontal scanning images of swept-source ASOCT were analyzed using software calipers in temporal and nasal angle areas. ITs at 1 and 2 mm from the pupil edge were measured using ASOCT. The relation between IT and the severity of NVG, the effects of intraocular pressure (IOP), intravitreal antivascular endothelial growth factor (anti-VEGF) injection, and panretinal photocoagulation (PRP) were assessed using linear regression analysis based on the corrected Akaike information criteria index. The IT was thinner in 360-degree AC-NVG patients, followed by NVG patients without AC and controls (0.33 vs. 0.48 vs. 0.57 mm at 1 mm and 0.31 vs. 0.43 vs. 0.49 mm at 2 mm; P<0.001 by ANOVA). Multiple linear regression analysis revealed that 360-degree AC-NVG patients-NVG patients without AC and controls (coefficient: -0.16), NVG patients without AC-control (-0.13) and underwent PRP (0.23) at 1 mm, 360-degree AC-NVG patients-NVG patients without AC and controls (-0.12), NVG patients without AC-controls (-0.08), underwent PRP (0.16), received anti-VEGF injection (0.05) and IOP (-0.001) at 2 mm were selected predictors to explain IT. IT decreases with the progression of the NVG stage and is thinnest in 360-degree AC-NVG patients. Our study suggests a new morphologic feature of NVG.

Pupil localization algorithm combining convex area voting and model constraint

Locating the center of the eyes plays a significant role in many computer vision applications and research, such as face alignment, face recognition, human-computer interaction, control devices for disabled people, user attention and gaze estimation. The disturbances such as occlusions by eyelashes or eyelids, uneven spots and spectacle frames of glasses affect the accuracy and stability of eye center location. This paper presents a hybrid eye center locating methodology for infrared eye images. The pupil edge points are extracted by Starburst algorithm, and when we get the position and the gradient of the edge points, the approximate pupil boundary is determined by a convex region voting methods. After that, the boundary edge points are iteratively optimized by fitting an ellipses modeling constraint. Finally, the pupil is located correctly. Experiment shows that this algorithm has performance advantages compared with some state of the art approaches in pupil localization accuracy, iteration times and their performance. This algorithm combining convex area voting and model constraint has strong robustness, high accuracy and speed in real environments with occlusions and distortion pupil.

Myopia progression control lens reverses induced myopia in chicks.

To determine whether lens induced myopia in chicks can be reversed or reduced by wearing myopia progression control lenses of the same nominal (central) power but different peripheral designs. Newly hatched chicks wore -10D Conventional lenses unilaterally for 7 days. The myopic chicks were then randomly divided into three groups: one fitted with Type 1 myopia progression control lenses, the second with Type 2 myopia progression control lenses and the third continued to wear Conventional lenses for seven more days. All lenses had -10D central power, but Type 1 and Type 2 lenses had differing peripheral designs; +2.75D and +1.32D power rise at pupil edge, respectively. Axial length and refractive error were measured on Days 0, 7 and 14. Analyses were performed on the mean differences between treated and untreated eyes. Refractive error and axial length differences between treated and untreated eyes were insignificant on Day 0. On Day 7 treated eyes were longer (T1; 0.44 ± 0.07 mm, T2; 0.27 ± 0.06 mm, C; 0.40 ± 0.06 mm) and more myopic (T1; -9.61 ± 0.52D, T2; -9.57 ± 0.61D, C; -9.50 ± 0.58D) than untreated eyes with no significant differences between treatment groups. On Day 14 myopia was reversed (+2.91 ± 1.08D), reduced (-3.83 ± 0.94D) or insignificantly increased (-11.89 ± 0.79D) in treated eyes of Type 1, Type 2 and Conventional treated chicks respectively. Relative changes in axial lengths (T1; -0.13 ± 0.09 mm, T2; 0.36 ± 0.09 mm, C; 0.56 ± 0.05 mm) were consistent with changes in refraction. Refractive error differences were significant for all group comparisons (p < 0.001). Type 1 length differences were significantly different from Conventional and Type 2 groups (p < 0.001). Myopia progression control lens designs can reverse lens-induced myopia in chicks. The effect is primarily due to axial length changes. Different lens designs produce different effects indicating that lens design is important in modifying refractive error.