Nanoporous silicon-based surface patterns fabricated by UV laser interference techniques for biological applications

The fabrication of selectively functionalized micropatterns based on nanostructured porous silicon (nanoPS) by phase mask ultraviolet laser interference is presented here. This single-step process constitutes a flexible method for the fabrication of surface patterns with tailored properties. These surface patterns consist of alternate regions of almost untransformed nanoPS and areas where nanoPS is transformed into Si nanoparticles (Si NPs) as a result of the laser irradiation process. The size of the transformed areas as well as the diameter of the Si NPs can be straightforwardly tailored by controlling the main fabrications parameters including the porosity of the nanoPS layers, the laser interference period areas, and laser fluence. The surface patterns have been found to be appropriate candidates for the development of selectively-functionalized surfaces for biological applications mainly due to the biocompatibility of the untransformed nanoPS regions.Postprint (author's final draft

Estudio óptico de la cinética de obtención de óxidos de semiconductor y semimetal en lámina delgada por ablación e irradiación láser

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de Materiales, leída el 30-04-1993El trabajo presenta un estudio de la cinética de obtención de óxidos de semiconductor y semimetal en lámina delgada. Se utilizan dos procedimientos experimentales, la deposición de láminas por ablación láser y la irradiación de materiales con láser, ambos en atmósfera reactiva de oxígeno. El trabajo establece una unión entre la cinética del proceso de obtención de los óxidos y sus propiedades ópticas y de estegniometría. Se han utilizado medidas ópticas en tiempo real para seguir "dinámicamente" el proceso de formación y crecimiento del óxido y medidas ópticas y de haces de iones (rbs,nra) para caracterizar sus propiedades. Los resultados muestran los mecanismos responsables de las propiedades observadas en los procesos de obtención y en los óxidos: presencia de especies energéticas, relación de flujos de átomos en el substrato, activación en fase liquida y cambio dinámico de propiedades ópticas.Depto. de Física de MaterialesFac. de Ciencias FísicasTRUEpu

Extended depth of focus intraocular lens: Chromatic performance

We describe a first-and-second-diffractive-order intraocular lens ((1st,2nd)DIOL) within the class of hybrid refractive-diffractive designs for intraocular lenses (IOLs) and analyse its properties of focus extension and compensation of longitudinal chromatic aberration (LCA), particularly for lenses with low addition. Power, energy efficiency and their wavelength dependence are extended from monofocal IOL and conventional bifocal zeroth-and-first-diffractive-order IOL ((0th,1st)DIOL) to (1st,2nd)DIOL of low addition. Compensation of LCA is experimentally assessed in optical bench through the through-focus energy efficiency of three Tecnis IOLs with red, green and blue illuminations: ZA9003 (monofocal), ZKB00 (bifocal (0th,1st)DIOL with + 2.75 D add) and Symfony ZXR00. We prove Tecnis Symfony ZXR00 IOL can be considered an example of (1st,2nd)DIOL design of low addition, with LCA compensation in both the distance and intermediate foci, whereas the bifocal (0th,1st)DIOL does not compensate in the distance focus. However, the energy efficiency of (1st,2nd)DIOL for wavelengths other than the design wavelength is markedly more asymmetric.Postprint (published version

Multidisciplinary Ophthalmic Imaging Visible Versus Near-Infrared Optical Performance of Diffractive Multifocal Intraocular Lenses

PURPOSE. The purpose of this study was to compare the optical performance of diffractive multifocal intraocular lenses (DMIOLs) with visible (VIS) illumination with that of near infrared (NIR) illumination, the latter being used to test pseudophakic eyes in clinical aberrometers and double-pass systems. METHODS. Two DMIOLs of different design (Tecnis þ2.75 D ZKB00 and AcrySof þ2.5 D SV25T0) were tested in vitro in a model eye under both VIS (k ¼ 530 nm) and NIR (k ¼ 780 nm) illumination, and variations in the add power of the lenses were determined. Moreover, for the two wavelengths, the energy efficiency and modulation transfer function at the DMIOLs' far and near foci were measured with pupils of 3.0 and 4.5 mm. Two counterpart monofocal IOLs (Tecnis ZA9003 and AcrySof SN60WF) were included as references in the comparison. RESULTS. With VIS light, the two DMIOLs produced relatively well-contrasted images at their near and far foci. Under NIR illumination, the add power increased, whereas the energy efficiency of the near focus decreased and that of far focus increased. Hence, the DMIOLs tended to behave like monofocal lenses because they generated good quality well-contrasted images only at their far foci. CONCLUSIONS. In addition to changes in add power, the optical performances of the DMIOLs measured under either VIS or NIR illumination are considerably different. Whereas they show two distinct (near and far) foci under VIS light, their optical performances under NIR illumination are clearly biased in favor of their far focus. These results may help prevent a misleading use of NIR-based clinical instruments for the assessment of eyes implanted with DMIOLs. Keywords: aberrometers, cataract surgery, diffractive multifocal intraocular lens, intraocular lens, pseudophakic eye, visual function testing R emoval of the crystalline lens followed by implantation of a multifocal intraocular lens (MIOL) is presently a surgical procedure primarily aimed at providing pseudoaccommodation to patients after cataract surgery. Diffractive MIOLs (DMIOLs) have proven to provide reliable and better clinical outcomes than their refractive MIOL counterparts or accommodating IOLs, 1 so there is a growing interest in assessing their optical performance in vivo. To objectively determine the imaging quality of DMIOLs in patients, several authors have recently used both wavefront aberrometers 2,3 and double-pass-based systems. Because the wavelengths of NIR testing are quite different from the wavelength corresponding to the maximum value of the photopic sensitivity of the eye under VIS spectrum (approximately 550 nm), for which DMIOLs are designed, there is a mismatch between the NIR and VIS wavelengths, which gives rise to the following issues: -A change in add power of the DMIOL between VIS and NIR (the larger the NIR wavelength, the larger the measured add power), 12 which in turn, has an effect on halo formation and size. 14,15 -A change in distribution of energy between the foci of the DMIOL. METHODS DMIOL Characteristics The Tecnis ZKB00 DMIOL, with þ2.75 diopter (D) add power, has an aspheric anterior surface. The diffractive profile covers the full aperture of the lens and consists of 15 diffractive rings with step boundaries of the same height, intended for approximately equal light distribution between the far and near foci, independent of pupil size. The wavefront-designed aspheric optics of this DMIOL produce a maximum spherical aberration (SA) of À0.27 lm for a 6.0-mm pupil. On the other hand, the AcrySof ReSTOR SV25T0 DMIOL with þ2.5 D add power has an anterior apodized diffractive surface (3.4-mm diameter) within which there is a central refractive zone (1.0 mm diameter approximately). The outer region of the lens to the 6-mm edge is purely refractive, and thus, the central and outer refractive parts of the lens are intended for distance vision. In addition, the diffractive area presents seven concentric rings with step boundaries of decreasing height, which allows for an asymmetrical and pupil-dependent light distribution between the far and near foci that benefits the far focus for large pupils. Additionally, the reference monofocal Tecnis ZA9003 (AMO Groningen) and AcrySof SN60WF (Alcon Laboratories) IOLs were included in our study. We emphasize that each monofocal IOL shares the same aspherical design and the same material, with its diffractive counterpart. Thus, the lenses of each pair (DMIOL and monofocal counterpart) have similar characteristics regarding the compensation for high order aberration (mainly SA) and the spectral variation of the refractive index. All studied lenses had a base optical power of 20 D, which in the case of the DMIOLs corresponded to distance focus. Experimental Setup for Optical Imaging Quality Assessment Assessment of the optical imaging quality of the IOLs was made using an optical test bench with a model eye (artificial cornea plus wet cell) that has been described in detail elsewhere. 26,27 Instead, we used a double convex lens that provided a level of SA at the IOL plane of þ0.27 lm for a 6.0-mm pupil, 28 similar to the one induced by the human cornea on average. Energy Assessment and MTF Measurements by Image Analysis The method of characterizing the energy distribution at the focal planes of a DMIOL has been reported in detail elsewhere Briefly, the image in a given focal plane consisted of the core sharp image of the pinhole object surrounded by a blurred halo-shaped background. This background is principally formed from an out-of-focus image produced by the other focus of the MIOL but may have additional contributions from a variety of factors such as the energy expended in higher diffraction orders, 13 scattering produced by the diffractive steps of the lens

Energy Distribution between Distance and Near Images in Apodized Diffractive Multifocal Intraocular Lenses

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Energy balance in apodized diffractive multifocal intraocular lenses

Postprint (published version

Halos and multifocal intraocular lenses: origin and interpretation

Preprin

Clinical assessment of chromatic aberration in phakic and pseudophakic eyes using a simple autorefractor

We describe a psychophysical method and a simple setup – an autorefractor with a Scheiner disc, sequentially illuminated with red and blue lights – for the clinical assessment of the longitudinal chromatic aberration (LCA) in phakic and pseudophakic patients. This method applies to the unaccommodated eye, even in the presence of positive or negative refractive errors and astigmatism. It measures the chromatic difference of refraction as an estimate of LCA. We built a proof of concept from inexpensive and off-the-shelf optomechanical components with which we obtained the preliminary clinical results presented in the paper. We considered one control group of phakic patients and three groups of pseudophakic patients with monofocal implants of different designs and materials. The results, satisfactory and consistent with those reported by other researchers in related works, demonstrate the method and system feasibility.Peer ReviewedPostprint (published version