Pupil Shape Research Articles

Elaborate pupils in skates may help camouflage the eye.

The skate Leucoraja erinacea is a bottom-dweller that buries into the substrate with its eyes protruding, revealing elaborately shaped pupils. It has been suggested that such pupil shapes may camouflage the eye, yet this has never been tested. Here, we asked whether skate pupils dilate or constrict depending on background spatial frequency. In experiment 1, the skates' pupillary response to three artificial checkerboards of different spatial frequencies was recorded. Results showed that pupils did not change in response to spatial frequency. In experiment 2, in which skates buried into three natural substrates of different spatial frequencies, such that their eyes protruded, pupils showed a subtle but statistically significant response to changes in substrate spatial frequency. Although light intensity is the primary factor determining pupil dilation, our results show that pupils also change depending on the spatial frequency of natural substrates, which suggests that pupils may aid in camouflaging the eye.

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.

Comparing safety and efficiency of two closed-chamber techniques for iridodialysis repair - a retrospective clinical study

BackgroundThis study aims to compare the safety and effectiveness of two closed-chamber techniques for repairing iridodialysis.MethodsSeventy five patients with iridodialysis undergoing surgery from February 2008 to October 2017 were included in this study. Patients were divided into two Groups, Group A (32 eyes) and Group B (35 eyes), with Group A using a 26-gauge hypodermic needle guided 10–0 nylon suture, and Group B using a double-armed polypropylene suture. Before operation and 1, 3, and 6 months after the operation, pupil shape, best corrected visual acuity (BCVA), intraocular pressure (IOP), the rate of endothelial cell loss, and intra- and postoperative complications were compared between two Groups during the follow-up period.ResultsIridodialysis was repaired with pupil shape restored in all cases. IOP was normalized in all eyes except 2 eyes (6.3%) in Group A and 3 eyes (8.6%) in Group B. Postoperative rate of endothelial cell loss was not significantly different between two Groups (P > 0.05). The percentage of complicated cataract was not significantly different in Group A (2 eyes, 6.3%) compared to Group B (2 eyes, 5.7%) (χ2 = 0.009, P = 0.658).ConclusionsBoth techniques for repairing iridodialysis not only were safe but also effective in improving visual function and cosmetic recovery. However, double-armed polypropylene suture might be less invasive than 26-gauge hypodermic needle guided suture.

Retinal specializations and visual ecology in an animal with an extremely elaborate pupil shape: the little skate Leucoraja (Raja) erinacea Mitchell, 1825.

Investigating retinal specializations offers insights into eye functionality. Using retinal wholemount techniques, we investigated the distribution of retinal ganglion cells in the Little skate Leucoraja erinacea by (a) dye-backfilling into the optic nerve prior to retinal wholemounting; (b) Nissl-staining of retinal wholemounts. Retinas were examined for regional specializations (higher numbers) of ganglion cells that would indicate higher visual acuity in those areas. Total ganglion cell number were low compared to other elasmobranchs (backfilled: average 49,713 total ganglion cells, average peak cell density 1,315 ganglion cells mm-2 ; Nissl-stained: average 47,791 total ganglion cells, average peak cell density 1,319 ganglion cells mm-2 ). Ganglion cells fit into three size categories: small (5-20 µm); medium (20-30 µm); large: (≥ 30 µm), and they were not homogeneously distributed across the retina. There was a dorsally located horizontal visual streak with increased ganglion cell density; additionally, there were approximately three local maxima in ganglion cell distribution (potential areae centrales) within this streak in which densities were highest. Using computerized tomography (CT) and micro-CT, geometrical dimensions of the eye were obtained. Combined with ganglion cell distributions, spatial resolving power was determined to be between 1.21 and 1.37 cycles per degree. Additionally, photoreceptor sizes across different retinal areas varied; photoreceptors were longest within the horizontal visual streak. Variations in the locations of retinal specializations appear to be related to the animal's anatomy: shape of the head and eyes, position of eyes, location of tapetum, and shape of pupil, as well as the visual demands associated with lifestyle and habitat type.

The pupillary light responses of animals; a review of their distribution, dynamics, mechanisms and functions.

The timecourse and extent of changes in pupil area in response to light are reviewed in all classes of vertebrate and cephalopods. Although the speed and extent of these responses vary, most species, except the majority of teleost fish, show extensive changes in pupil area related to light exposure. The neuromuscular pathways underlying light-evoked pupil constriction are described and found to be relatively conserved, although the precise autonomic mechanisms differ somewhat between species. In mammals, illumination of only one eye is known to cause constriction in the unilluminated pupil. Such consensual responses occur widely in other animals too, and their function and relation to decussation of the visual pathway is considered. Intrinsic photosensitivity of the iris muscles has long been known in amphibia, but is in fact widespread in other animals. The functions of changes in pupil area are considered. In the majority of species, changes in pupil area serve to balance the conflicting demands of high spatial acuity and increased sensitivity in different light levels. In the few teleosts in which pupil movements occur they do not serve a visual function but play a role in camouflaging the eye of bottom-dwelling species. The occurrence and functions of the light-independent changes in pupil size displayed by many animals are also considered. Finally, the significance of the variations in pupil shape, ranging from circular to various orientations of slits, ovals, and other shapes, is discussed.

Additions to the description of Paroplocephalus atriceps (Serpentes: Elapidae) with a discussion on pupil shape in it and other Australian snakes.

Morphometric data on an additional twelve individuals of Paroplocephalus atriceps Storr are included enlarging Keogh et al.'s 2000 description of the genus and further verifying its affinities with Hoplocephalus. Included are comments on its venom and observations confirming arboreality and although primarily nocturnal, it includes some diurnal activity. Various authors have erroneously suggested it has vertically elliptic pupils but they are round. During an examination of snake's eyes, it was found that several additional species have pupils that require re-describing, especially Suta fasciata Rosen, S. punctata Boulenger and Echiopsis curta Schlegel, all of which include individuals with round pupils. A standardised description is suggested for each of the three common pupil shapes in snakes as narrow elliptic where dilation and constriction is lateral or vertical only, wide elliptic where dilation and constriction is both lateral and vertical, and round where any dilation and constriction is equidistant from the centre around the pupil's circumference.

Eye for positive signs: A practical approach to childhood eye disease.

Eye for positive signs: A practical approach to childhood eye disease.

Pupil Segmentation of Abnormal Eye using Image Enhancement in Spatial Domain

Segmentation is one of the important elements in image processing. There are various types of algorithms that have been developed by researchers, for segmenting the interesting area for classification and identification purposes. This paper, presents the pupil segmentation using logarithmic transformation (LT) and power law transformation (PLT). It is obviously seen in most of the work on pupil segmentation where assumption is made that the pupil has a homogeneous circular. However, there are cases where the shape of pupil is inhomogeneous, for instance, in synechia case. Therefore, the use of circumference equation such as circular Hough transforms (CHT) and Daugman’s Integra-differential operator (DIDO) for section the non-uniform pupil will produce inaccurate segmentation. We propose a new method for pupil segmentation using the combination of LT and PLT algorithm in order to enhance the pupil segmentation. The morphological operators and black white (BW) removal are used the segmentation of pupil. The proposed system uses CASIA V1, CASIAV3 Interval and MMU1 iris database. The results show his method gives accurate segmentation compared to CHT or DIDO technique.

The Correction of Aphakia Using Anterior Chamber Intraocular Lens.

Senile cataract is the leading cause of severe vision loss and blindness worldwide, affecting approximately 20 million people. Anterior chamber intraocular lens (AC IOLs) remain a surgical option for visual rehabilitation required after surgical extraction of the cataract lens. Relevant publications in the PUBMED database were searched for articles regarding the types, visual outcomes and the complications followed the surgical implantation of AC IOLs. AC IOLs, which can be iris- (iris-claw) or angle-supported, increase visual acuity in most patients. However, complications, such as raised intraocular pressure, hyphaema, distorted pupil shape, iris pigment precipitates, endothelial cell loss, corneal oedema, neovascular glaucoma, retinal detachment and cystoid macular oedema, can unfavorably affect the surgical outcome. Although AC IOLs have been found to improve the visual acuity of patients with cataract, they have been also implicated in several complications.

More than meets the eye: change in pupil shape by a mock viper

More than meets the eye: change in pupil shape by a mock viper

Spectral discrimination in color blind animals via chromatic aberration and pupil shape.

We present a mechanism by which organisms with only a single photoreceptor, which have a monochromatic view of the world, can achieve color discrimination. An off-axis pupil and the principle of chromatic aberration (where different wavelengths come to focus at different distances behind a lens) can combine to provide "color-blind" animals with a way to distinguish colors. As a specific example, we constructed a computer model of the visual system of cephalopods (octopus, squid, and cuttlefish) that have a single unfiltered photoreceptor type. We compute a quantitative image quality budget for this visual system and show how chromatic blurring dominates the visual acuity in these animals in shallow water. We quantitatively show, through numerical simulations, how chromatic aberration can be exploited to obtain spectral information, especially through nonaxial pupils that are characteristic of coleoid cephalopods. We have also assessed the inherent ambiguity between range and color that is a consequence of the chromatic variation of best focus with wavelength. This proposed mechanism is consistent with the extensive suite of visual/behavioral and physiological data that has been obtained from cephalopod studies and offers a possible solution to the apparent paradox of vivid chromatic behaviors in color blind animals. Moreover, this proposed mechanism has potential applicability in organisms with limited photoreceptor complements, such as spiders and dolphins.

Intrafield overlay correction for illumination-based distortion

The use of different illumination source shapes and multipatterning processes used to generate sub–40-nm images can create image placement errors level to level, resulting in significant intrafield overlay errors. These errors arise because of the impact of the different pupil shapes on lens aberrations resolving into image placement errors as well as because different tools will react differently to the same pupil shapes. We compare the impact of two extreme illumination sources on intrafield image placement and its effect on overall pattern overlay. We also discuss a method to empirically isolate and measure the amount of intrafield overlay distortion relative to a reference illumination source and then use the results to correct the resultant image placement errors.

Method of pupil shaping for off-axis illumination in optical lithography

Off-axis illumination is one of the key resolution enhancement technologies in projection lithography systems. Phase type diffractive optical elements are adopted by most of the lithography machine manufacturers to realize off-axis illumination. In this paper, a method of pupil shaping for off-axis illumination in optical lithography is introduced which contains a zoom beam expander, circularly symmetric diffractive optical elements, and a Fourier lens. The method could produce the required illumination pattern for off-axis illumination at the pupil plane. Compared with the conventional method of off-axis illumination, the method in this paper could eliminate deterioration of the pupil thoroughly and reduces the difficulty of the optical design of the zoom lens. Based on this method, several circularly symmetric diffractive optical elements are designed for experiments, and a remarkable improvement in eliminating deterioration of the pupil is observed compared with the conventional method.

Exact two-dimensional zonal wavefront reconstruction with high spatial resolution in lateral shearing interferometry

A novel zonal method is proposed for exact discrete reconstruction of a two-dimensional wavefront with high spatial resolution for lateral shearing interferometry. Four difference wavefronts measured in the x and y shear directions are required. Each of the two shear directions is measured twice with different shear amounts. The shear amounts of the second measurements of the x and y directions are Sx+1 pixels and Sy+1 pixels, where Sx pixels and Sy pixels are the shear amounts of the first measurements in the x and y directions, respectively. The shear amount in each direction can be chosen freely, provided that it is below a maximum value determined by the pupil shape and the number of samples N in that direction; thus, the choices are not limited by the more stringent condition required by previous methods, namely, that the shear amounts must be divisors of N. This method can exactly reconstruct any wavefront at evaluation points up to an arbitrary constant if the data is noiseless, and high spatial resolution can be achieved even with large shear amounts. The method is applicable not only to square pupils, but also to general pupil shapes if a sufficient number of Gerchberg iterations are employed. In this study, the validity and capability of the method were confirmed by numerical experiments. In addition, the experiments demonstrated that the method is stable with respect to noise in the difference wavefronts.

Interrater Reliability of Pupillary Assessments

Subjective scoring of pupil reactivity is a fundamental element of the neurological examination for which the pupillometer provides an objective measure. This single-blinded observational study examined interrater reliability of pupil exam findings between two practitioners and between practitioners and a pupillometer. From 2329 paired assessments, the interrater reliability between practitioners was only moderate for pupil size (k = 0.54), shape (k = 0.62), and reactivity (k = 0.40). Only 33.3% of pupils scored as non-reactive by practitioners were scored as non-reactive by pupillometry. Despite the strong emphasis placed on the traditional pupil examination, especially for patients with a neurological illness, there is limited interrater reliability for subjective scoring of pupillary assessments. Thus, the use of automated pupillometers should be examined as a potential method to increase the reliability of measuring of pupil reactivity.

Why do animal eyes have pupils of different shapes?

There is a striking correlation between terrestrial species' pupil shape and ecological niche (that is, foraging mode and time of day they are active). Species with vertically elongated pupils are very likely to be ambush predators and active day and night. Species with horizontally elongated pupils are very likely to be prey and to have laterally placed eyes. Vertically elongated pupils create astigmatic depth of field such that images of vertical contours nearer or farther than the distance to which the eye is focused are sharp, whereas images of horizontal contours at different distances are blurred. This is advantageous for ambush predators to use stereopsis to estimate distances of vertical contours and defocus blur to estimate distances of horizontal contours. Horizontally elongated pupils create sharp images of horizontal contours ahead and behind, creating a horizontally panoramic view that facilitates detection of predators from various directions and forward locomotion across uneven terrain.

Gendered Disparities in Quality of Cataract Surgery in a Marginalised Population in Pakistan: The Karachi Marine Fishing Communities Eye and General Health Survey.

BackgroundMarine fishing communities are among the most marginalised and hard-to-reach groups and have been largely neglected in health research. We examined the quality of cataract surgery and its determinants, with an emphasis on gender, in marine fishing communities in Karachi, Pakistan, using multiple indicators of performance.Methods and Findings The Karachi Marine Fishing Communities Eye and General Health Survey was a door-to-door, cross-sectional study conducted between March 2009 and April 2010 in fishing communities living on 7 islands and in coastal areas in Keamari, Karachi, located on the Arabian Sea. A population-based sample of 638 adults, aged ≥ 50 years, was studied. A total of 145 eyes (of 97 persons) had undergone cataract surgery in this sample. Cataract surgical outcomes assessed included vision (presenting and best-corrected with a reduced logMAR chart), satisfaction with surgery, astigmatism, and pupil shape. Overall, 65.5% of the operated eyes had some form of visual loss (presenting visual acuity [PVA] < 6/12). 55.2%, 29.0%, and 15.9% of these had good, borderline, and poor visual outcomes based on presenting vision; with best correction, these values were: 68.3 %, 18.6%, and 13.1%, respectively. Of 7 covariates evaluated in the multivariable generalized estimating equations (GEE) analyses, gender was the only significant independent predictor of visual outcome. Women’s eyes were nearly 4.38 times more likely to have suboptimal visual outcome (PVA<6/18) compared with men’s eyes (adjusted odds ratio 4.38, 95% CI 1.96-9.79; P<0.001) after adjusting for the effect of household financial status. A higher proportion of women’s than men’s eyes had an irregular pupil (26.5% vs. 14.8%) or severe/very severe astigmatism (27.5% vs. 18.2%). However, these differences did not reach statistical significance. Overall, more than one fourth (44/144) of cataract surgeries resulted in dissatisfaction. The only significant predictor of satisfaction was visual outcome (P <0.001).ConclusionsThe quality of cataract surgery in this marginalised population, especially among women, falls well below the WHO recommended standards. Gender disparities, in particular, deserve proactive attention in policy, service delivery, research and evaluation.

Wavefront reconstruction for lateral shearing interferometry based on difference polynomial fitting

The wavefront reconstruction method for shearing interferometry using difference Zernike polynomial fitting has been the easiest algorithm to implement up to now. The method is extended to using general basis functions in this paper. Simulations and experiments verify that highly accurate reconstructions can be achieved based on difference polynomial fitting regardless, of the pupil shape and the orthogonality of the basis functions. The reconstruction accuracy mainly depends on whether the used terms of the polynomials are enough to represent the wavefront. When the used terms cannot perfectly represent the wavefront, the reconstruction accuracy of Taylor monomials is a little higher than that of Zernike polynomials. It is also presented and proved that the reconstruction accuracy can be estimated using the deviation between the reconstructed difference fronts and the measured difference fronts.

Radially Polarized Light for Detection and Nanolocalization of Dielectric Particles on a Planar Substrate

A fast noninvasive method based on scattering from a focused radially polarized light to detect and localize subwavelength nanoparticles on a substrate is presented. The technique relies on polarization matching in the far field between scattered and spurious reflected fields. Results show a localization uncertainty of ≈10^{-4}λ^{2} is possible for a particle of area ≈λ^{2}/16. The effect of simple pupil shaping is also shown.

An approach to increase efficiency of DOE based pupil shaping technique for off-axis illumination in optical lithography.

Off axis illumination (OAI) is one of the key resolution enhancement technologies in projection lithography system. Recently, phase type diffractive optical elements (DOEs) are adopted by most of the lithography machine manufactures to realize OAI. In general, the efficiency of the OAI unit is the main consideration compared with uniformity. However, the main goal of the traditional constraint of iterative Fourier transformation algorithm (IFTA) is used to optimize the SNR, while diffraction efficiency is the secondary consideration. Therefore a constraint for IFTA is well designed to increase the efficiency of DOE in this paper. This constraint can guarantee the pole balance at the same time. The main idea of this constraint is to apply amplitude and phase freedoms in the signal window and to control the total energy of each pole. Based on the proposed constraint several DOEs are designed for high NA lithography illumination system. And remarkable improvement in the efficiency is observed compared with the traditional constraint. Furthermore, the efficiency and uniformity could be weighted by adjusting the parameter with extending this constraint to general case. To demonstrate the proposed constraints, experiments are carried out where a spatial light modulator is utilized to represent DOEs.