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Most persons with obesity who have undergone gastric bypass surgery present depressive symptoms. Depression and anxiety have been associated with tear film disorders. This study aimed to investigate whether there is a correlation between tear film conditions and depression symptoms in patients subjected to bariatric surgery. The participants completed a Patient Health Questionnaire to detect depression symptoms. The break-up time and Schirmer test were subsequently applied; the measurements were performed three times, and the average time was subsequently recorded. The results revealed that the Schirmer test score and PH-9 score were negatively correlated, but this was not the case for the break-up time test. Depression symptoms may correlate with lower tear production from the principal tear gland, but they may not have the same effect on meibomian gland production in adults undergoing bariatric surgery. In addition to routine control, bariatric surgery patients should be periodically evaluated by an ophthalmologist and/or psychologist who is aware of potential comorbidities. Furthermore, the observed association between depression symptoms and tear deficiencies highlights the importance of further investigations to gain a better understanding of these mechanisms.

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Two-dimensional Bessel beams, both vectorial and scalar, have been extensively studied to date, finding many applications. Here we mimic a vectorial axicon to create one-dimensional scalar Bessel beams embedded in a two-dimensional vectorial field. We use a digital micro-mirror device to interfere orthogonal conical waves from a holographic axicon, and study the boundary of scalar and vectorial states in the context of structured light using the Arago-Fresnel laws. We show that the entire field resembles a vectorial combination of parabolic beams, exhibiting dependence on solutions to the inhomogeneous Bessel equation and asymmetry due to the orbital angular momentum associated rotational diffraction. Our work reveals the rich optical processes involved at the interplay between scalar and vectorial interference, opening intriguing questions on the duality, complementarity, and non-separability of vectorial light fields.

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RESUMEN Objetivo: Comparar la sensibilidad al contraste evaluada en un grupo de mexicanos con diabetes mellitus contra uno sin diabetes como control. Métodos: Un total de 31 voluntarios, 14 participantes con DM con un tiempo de diagnóstico entre 2 y 20 años (sin retinopatía diabética), y 17 en el grupo control iniciaron el estudio; 4 diabéticos y 5 no diabéticos fueron excluidos por no cumplir con los criterios de inclusión. Por lo tanto, los datos analizados fueron de un grupo de 10 diabéticos (52 ± 10 años) y otro de 12 no diabéticos (52 ± 6 años). Se evaluó la sensibilidad al contraste con la cartilla Vector Vision CSV1000E a una distancia de 2,5 metros con una iluminación de 85 cd/m2. Resultados: Un mayor porcentaje de ojos diabéticos alcanzaron un mejor umbral de contraste en 3, 6 y 18 ciclos por grado en comparación con el grupo control. En 12 ciclos por grado solamente en los umbrales 1 y 5. Conclusiones: La sensibilidad al contraste de la población mexicana con diabetes mellitus presenta mejor percepción de contraste en las frecuencias evaluadas que el grupo control(AU)

ABSTRACT Objective: Compare contrast sensitivity as measured in a group of Mexican diabetes mellitus patients versus a control non-diabetic group. Methods: A group of 31 volunteers, 14 participants with DM with a diagnosis time between 2 and 20 years (without diabetic retinopathy), and 17 in the control group started the study; 4 diabetics and 5 non-diabetics were excluded because they did not meet the inclusion criteria. Therefore, the data analyzed were from a group of 10 diabetics (52 ± 10 years) and another of 12 non-diabetics (52 ± 6 years). Contrast sensitivity was evaluated with a Vector Vision CSV1000E chart at a distance of 2.5 meters and a luminance of 85 cd/m2. Results: A higher percentage of diabetic eyes reached a better contrast threshold at 3, 6 and 18 cycles per degree in comparison with the control group. At 12 cycles per degree only at thresholds 1 and 5. Conclusions: Contrast sensitivity in the Mexican population with diabetes mellitus displays better contrast perception at the frequencies evaluated than the control group(AU)

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Bariatric surgery patients have deficiencies of macro- and micronutrients that may be related to ophthalmic complications, for example consequences on tear film layers (lipid, aqueous, and mucosa). In this work, we associated protein diet and tear film layers in bariatric patients of a Mexican hospital. We measured characteristics of tear film by the Schirmer and tear break up time (TBUT) tests under three different protein percentage diets: 10, 15, and 25%. TBUT values were low in our study, and therefore, bariatric patients may have high possibilities to suffer dry eye or modifications in lipid tear layer. Bariatric patients, additional to the routine control, periodically should have an extensive eye examination.

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We propose a new method to determine topological charge by using an improved Fizeau interferometer. This interferometer is very easy to realize, as well as interference fringes are very distinct. Phases of vortex, Hermite-Gaussian, and elliptical vortex beams are experimentally verified using this method. It provides a convenient way to determine the sign and magnitude of topological charge. This method may have some potential applications in space optical communication.

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In this paper we consider a generalization of standard nondiffracting parabolic beams. The proposed generalized beams have two orders: a continuous parameter a, as in standard beams, and the new parameter is an integer index m. Physically, the last parameter is equal to the number of rotated repetitions of the structure of the original angular spectrum on the total circle in the frequency space. Theoretical investigation shows that for a=0 the beams are real functions and have a symmetry of order 2m. If a≠0 the beams will be real functions only for odd values of m. Moreover, in this case the beams have a symmetry of order m, while for even values of m the order of symmetry is 2m. The results of numerical simulation confirm these conclusions. Examples of generalized traveling parabolic waves, which are formed on the basis of generalized static parabolic beams, are also given.

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We introduce a simple method to characterize the topological charge associated with the orbital angular momentum of a m-order elliptic light beam. This method consists in the observation of the far field pattern of the beam carrying orbital angular momentum, diffracted from a triangular aperture. We show numerically and experimentally, for Mathieu, Ince-Gaussian, and vortex Hermite-Gaussian beams, that only isosceles triangular apertures allow us to determine in a precise and direct way, the magnitude m of the order and the number and sign of unitary topological charges of isolated vortices inside the core of these beams.

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In a recent paper, a method for the generation of a long, narrow needle of light was proposed [J. Opt. Soc. Am. A31, 500 (2014)10.1364/JOSAA.31.000500JOAOD61084-7529]. The authors missed fundamental aspects of the mathematical physics of cylindrical electromagnetic waves described by Bessel functions that are essential to obtain the proposed needle. We provide formal arguments showing that a different initial condition is the proper one for the intended purpose. Based on their proposed method we bring to attention the validity of Huygens' principle for cylindrical waves. Also, we extend their analysis in order to have a component of longitudinal energy flow that is needed for most of the applications they suggest. We quantitatively show that a minor modification produces this component with practically negligible increase of the needle width.

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We present for the first time a comparison under similar circumstances between Laguerre-Gauss beams (LGBs) and Bessel beams (BB), and show that the former can be a better option for many applications in which BBs are currently used. By solving the Laguerre-Gauss differential equation in the asymptotic limit of a large radial index, we find the parameters to perform a peer comparison, showing that LGBs can propagate quasi-nondiffracting beams within the same region of space where the corresponding BBs do. We also demonstrate that LGBs, which have the property of self-healing, are more robust in the sense that they can propagate further than BBs under similar initial conditions.

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In this work, we present a new family of modes of confocal resonators eigenfunctions of the Fraunhofer diffraction integral, the elegant Cartesian Laguerre-Hermite-Gaussian modes. We show that these modes can be single-pass or round-trip eigenmodes of the resonator depending on the focal distance of the mirrors and their separation. We study their properties and compare them to the well known normal and elegant Hermite and Laguerre-Gauss modes of laser resonators. The new family of modes are not structurally stable on propagation as normal Gaussian modes nor present a monotonic intensity evolution as the normal and elegant Gaussian modes. We also demonstrate that on propagation, they present the self-healing property.

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We introduce a new class of paraxial optical beams exhibiting discrete-like diffraction patterns reminiscent to those observed in periodic evanescently coupled waveguide lattices. It is demonstrated that such paraxial beams are analytically described in terms of generalized Bessel functions. Such effects are elucidated via pertinent examples.

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PURPOSE: We propose the Bessel Circular Functions as alternatives of the Zernike Circle Polynomials to represent relevant circular ophthalmic surfaces. METHODS: We assess the fitting capabilities of the orthogonal Bessel Circular Functions by comparing them to Zernike Circle Polynomials for approximating a variety of computationally generated surfaces which can represent ophthalmic surfaces. RESULTS: The Bessel Circular Functions showed better modelling capabilities for surfaces with abrupt variations such as the anterior eye surface at the limbus region, and influence functions. From our studies we find that the Bessel Circular Functions can be more suitable for studying particular features of post surgical corneal surfaces. CONCLUSIONS: We show that given their boundary conditions and free oscillating properties, the Bessel Circular Functions are an alternative for representing specific wavefronts and can be better than the Zernike Circle Polynomials for some important cases of corneal surfaces, influence functions and the complete anterior corneal surface.

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We investigate the propagation of Airy beams in linear gradient index inhomogeneous media. We demonstrate that by controlling the gradient strength of the medium it is possible to reduce to zero their acceleration. We show that the resulting Airy wave beam propagates in straight line due to the balance between two opposite effects, one due to the inhomogeneous medium and the other to the diffraction of the beam, in a similar way as a solitary wave in a nonlinear inhomogeneous medium. Going even further we were able to invert the sign of the acceleration of the beam.

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It is well known that Bessel beams and the other families of propagation-invariant optical fields have the property of self-healing when obstructed by an opaque object. Here it is shown that there exists another kind of field distribution that can have an analog property. In particular, we demonstrate that a class of caustic wave fields, whose transverse intensity patterns change on propagation, when perturbed by an opaque object can reappear at a further plane as if they had not been obstructed. The physics of the phenomenon is fully explained and shown to be related to that of self-healing propagation invariant optical fields.

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We show that propagation of optical beams in periodic lattices induces power oscillations between the Fourier spectrum peaks, with the indices related by the Bragg resonance condition. In the spatial coordinates, this is reflected in the beam position oscillations. A simple resonant theory explains the phenomenon. The effect can be used for controlled generation of the Floquet-Bloch modes in photonic lattices.

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We discuss a computer generated hologram whose transmittance is defined in terms of the Jacobi-Anger identity. If the hologram is implemented with a continuous phase spatial light modulator it generates integer-order non-diffracting Bessel beams, with a common asymptotic radial frequency, at separated propagation axes. On the other hand, when the hologram is implemented with a low-resolution pixelated phase modulator, it is possible to generate multiple Bessel beams with a common propagation axis. We employ this superposition of multiple Bessel beams to generate non-diffracting periodic and quasi-periodic wave fields.

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We report what we believe to be the first experimental observation of a large spatial lateral shift in the interaction of obliquely oriented spatial dark-soliton stripes. We demonstrate by numerical simulations that this new effect can be attributed to the specific features of optical media with a nonlocal nonlinear response.

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A rigorous analysis of the unstable Bessel resonator with convex output coupler is presented. The Huygens-Fresnel self-consistency equation is solved to extract the first eigenmodes and eigenvalues of the cavity, taking into account the finite apertures of the mirrors. Attention was directed to the dependence of the output transverse profiles; the losses; and the modal-frequency changes on the curvature of the output coupler, the cavity length, and the angle of the axicon. Our analysis revealed that while the stable Bessel resonator retains a Gaussian radial modulation on the Bessel rings, the unstable configuration exhibits a more uniform amplitude modulation that produces output profiles more similar to ideal Bessel beams. The unstable cavity also possesses higher-mode discrimination in favor of the fundamental mode than does the stable configuration.

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We report the first experimental observation of parabolic non-diffracting beams, the fourth fundamental family of propagation-invariant optical fields of the Helmholtz equation. We generate the even and odd stationary parabolic beam and with them we are able to produce traveling parabolic beams. It is observed that these fields exhibit a number of unitary in-line vortices that do not interact on propagation. The experimental transverse patterns show an inherent parabolic structure in good agreement with the theoretical predictions. Our results exhibit a transverse energy flow of traveling beams never observed before.

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A new experimental setup is demonstrated to produce high-order Bessel beams. It is based on the field decomposition of the Bessel beam into its even and odd field components. The implementation is performed over the spectral components with a Mach-Zehnder interferometer that synthesizes the components into the desired Bessel beam. The main advantage of our setup is that the required annular transmittances have only discrete phase changes of pi radians instead of a continuous change of phase.