Issolio Luis

• PhD
• Professor (Associate) at National Scientific and Technical Research Council

Objetivo: Conocer la valoración de los oftalmólogos sobre las metodologías disponibles para el diagnóstico temprano de glaucoma de ángulo abierto (GAA), y evaluar la necesidad de nuevos métodos para la exploración funcional de la retina. Métodos: Se realizó un estudio transversal basado en una encuesta dirigida a oftalmólogos residentes en Argentin...

Objective This study aims to analyze the effect of correlated color temperature from LED glare sources on driving performance. The evaluation includes assessing the effect of disability glare on visual reaction time and rating discomfort glare using a standardized scale. Background LED technology is widely incorporated into various lighting system...

Purpose: To assess spatial contrast sensitivity (CS) in suspected primary open-angle glaucoma (POAG) patients. Methods: CS was measured using sinusoidal gratings of 4 cycles/degree. First, foveal and peripheral CS were assessed in 34 suspected POAG patients and compared with 71 and 28 age-matched healthy individuals for foveal and peripheral condit...

A review of the mathematical models that predict visual quality of intraocular lenses as a function of the optical quality parameters that characterize them, and a review of the methodologies used for the simulation of vision with intraocular lenses are presented. It is shown that the existing simulation techniques could be useful to evaluate the d...

Purpose To assess contrast sensitivity (CS) for detecting visual changes in suspected POAG patients. Methods CS was measured foveally at photopic conditions and peripherally at mesopic conditions using sinusoidal gratings of 4 cycles/degree. In experiment 1, foveal and peripheral CS were assessed in suspected POAG patients and age-matched healthy c...

Objetivo: El reflejo pupilar a luces de distintos colores (pupilometría cromática) puede usarse como biomarcador del estado funcional de la retina. En este trabajo se evalúa la respuesta pupilar parpadeante a estímulos de color en pacientes con sospecha de glaucoma primario de ángulo abierto. Materiales y métodos: Participaron en este estudio 41 vo...

The modulation transfer function (MTF) is one of the most complete tools to study the optical performance of the eye. We present the average radial MTF profiles measured in 68 subjects grouped in six age ranges (from 20 to 80 years) and a general formula to estimate the radial profile of human MTF as a function of pupil size and age. The mean MTF f...

The pupil reacts to the amount of light reaching the eye. It reduces its size when the light is high and dilates at low light levels to allow the entrance of more photons. This behavior is called pupil light reflex (PLR). Recent investigations in humans were conducted to understand how the photoreceptor signals are combined to drive the pupil light...

The pupil light reflex (PLR) can serve as a biomarker of the photoreceptor function. Protocols for chromatic PLR consider mostly pulsed stimulation. A more sophisticated and promising technique is based on the PLR to flickering stimulation. Our aim was to compare flickering PLR (fPLR) and pulsed PLR (pPLR) parameters to validate the fPLR paradigm....

This chapter describes the most common setups that scientists use for generating light stimulation, from lab-made approaches to commercially available technologies. The studied optical stimulation systems are divided into nonimage-forming and image-forming arrangements. Two classical systems widely used are among the first: the Maxwellian view syst...

Protocols for chromatic pupil light reflex (PLR) testing considered mostly pulsed stimulation (pPLR). A more sophisticated and promising technique is based on the PLR to flickering stimulation (fPLR). Our aim was to compare fPLR and pPLR parameters in order to validate fPLR paradigm. Two different experiments were carried out in young participants...

Purpose A previous work has reported a methodology to quantify intraocular scattering using a high sensitivity double-pass instrument with a robust index, the frequency scatter index. The purpose of our study was to evaluate an adaptation of the frequency scatter index for use in clinical double-pass systems. Methods A prospective observational st...

En este trabajo se presenta el desarrollo de un diseño metodológico para la evaluación de la relación entre la dirección de la mirada y la atención de los visitantes con: 1) la museografía existente, 2) mediciones fotométricas realizadas in situ en los museos (patrones de luminancia) y 3) la valoración del ambiente iluminado por parte del visitante...

Purpose: To develop a methodology based on a double-pass system to obtain information about the transmittance of ocular media. Methods: The procedure consists of recording double-pass images at different powers of a laser diode of 780 nm and determining the scattering in an area between 25–35 arcmin of each image. The scattering showed linear behav...

Purpose To develop a methodology based on a double-pass system to obtain useful information about the transmission of ocular media, performing noninvasive measures in vivo . Methods This noninvasive procedure consists of recording double-pass images at different voltages of a laser diode of 780 nm and the determination of the scattering in an area...

The ability of the human visual system to detect stimuli at low illumination levels provides awareness of potential risks. The influence of age and spectral power distribution on mesopic spectral sensitivity is analyzed. Two typical light sources are used, a high-pressure sodium lamp (HPS), with a higher content of long wavelengths, and a metal hal...

Biological adaptation to sunlight evolved over millions of years. The intrusion of artificial lighting has disrupted this relationship with the natural environment. On the other hand the discovery of the photopigment melanopsin poses new challenges for lighting designers. We studied melanopsin excitation under natural and artificial illumination co...

Since glaucoma is one of the worldwide leading causes of irreversible blindness, is important to develop tools for early detection. In this work, we explored the ability of the contrast sensitivity (CS) to early detect open-angle glaucoma. We measured CS in patients with mild glaucoma, at two age ranges (20-49 and 50-69 y.o.) and for two light leve...

The visual response in mesopic adaptation depends strongly not only on the level of luminance but also on the relative weight of the response of the cones and rods system. This highlights the importance of knowing the spectral power distribution (SPD) of radiation, when evaluating the functional vision. For this reason, this work proposes the measu...

We explored the complexity of the light adaptation process, assessing adaptation recovery (Ar) at different eccentricities and light levels. Luminance thresholds were obtained with transient background fields at mesopic and photopic light levels for temporal retinal eccentricities (0°–15°) with test/background stimulus size of 0.5 ° / 1 ° using a s...

A set of autofocus operators (AFO) are assessed for their ability to determine the optimal double-pass image as well as their potential to detect the focus lines and the disc of least confusion in astigmatic eyes. Eight AFO and three optical quality parameters (OQP) often used to analyze double-pass aerial images were considered. To quantify the di...

Purpose: To measure the sensitivity of small retinal areas by reducing the influence of the adaptation state of the rest of the retina. To assess the functional behaviour of the retina of several patients affected by different types of retinitis pigmentosa (RP). Methods: A prospective study was performed. Five eyes of patients with retinal disease...

Mechanisms of light adaptation have been traditionally explained with reference to psychophysical experimentation. However, the neural substrata involved in those mechanisms remain to be elucidated. Our study analyzed links between psychophysical measurements and retinal physiological evidence with consideration for the phenomena of rod-cone intera...

The purpose of this study is to determine the pupillary dynamics with periodical flashes from a peripheral glare source, in similar conditions to night driving, while focusing on dependence with age. We measured two groups of people: youth and adults. Maximum pupil size decreases due to periodic flashes. Latency does not present significant differe...

Purpose: To measure log(s) and OSI parameters, both related to forward light scattering in the eye, in subjects with different kinds of early cataracts-nuclear or posterior subcapsular-and corrected visual acuity (CVA). Methods: 34 eyes of 19 patients ranged between 50 and 75 years old with diagnosed nuclear (14 eyes) or posterior subcapsular ca...

The understanding of the mechanisms involved in light adaptation is a challenge not completely solved. Here, we present a model based on visual mechanisms described in the physiological and psychophysical literature able to fit psychophysical data in several stimuli conditions. We propose that the study of changes in the different mechanism and phe...

The solar bottle bulb has become a very important source of light in poor regions and/or in those that have difficult access to power. Its extended use results in the need to have a more rational knowledge of its performance. In this work, we carried out the photometry of the solar bottle bulb considering the sky models that simulate cloudy and sun...

We determined the visual efficiency and visual discomfort for users of a typical transitional space in luminous climates. The subject moves from a brighter exterior to a dimmer interior, facing an abrupt change in the level of lighting as a potential functional vision barrier, mainly for ageing people. We measured suprathreshold visual efficiency i...

This work discusses the relative significance of optical and neural mechanisms in letter contrast sensitivity under different conditions of environmental lighting. A study was carried out on 26 eyes with normal ocular health. Sixteen lighting conditions were obtained by combining different test luminances (from 10cd/m(2) to 600cd/m(2)) and surround...

Purpose: The aim of this article is to propose a quantitative methodology for determining a criterion to discriminate the nonsurgical nuclear cataract from the surgical one taking into account objective measures of intraocular scattering in patients with good visual acuity (>0.6). Methods: Two groups of subjects were taken into account: a contro...

In a previous work (Opt. Appl. 39(2), 2009, pp. 415-428) we established the characteristics that a computer-based contrast sensitivity function (CSF) measurement system has to be used in the opthalmological clinic. In order to obtain a generalized use of CSF in clinics and as a screening tool, the necessity to incorporate a normality range by age w...

Purpose: The aim of this article is to propose a quantitative methodology for determining a criterion to discriminate the nonsurgical nuclear cataract from the surgical one taking into account objective measures of intraocular scattering in patients with good visual acuity (40.6). Methods: Two groups of subjects were taken into account: a control g...

A glare source in the visual field modifies the brightness of a test patch surrounded by a mesopic background. In this study, we investigated the effect of two levels of transient glare on brightness perception for several combinations of mesopic reference test luminances (Lts) and background luminances (Lbs). While brightness perception was affect...

Light originated at a glare source and entering the eye, produces a veiling luminance that causes contrast decrease in retinal images and this effect could differ if the subject wears lenses or not. In this work the glare effects in subjects wearing lenses is studied inducing ammetropies in emmetropes. Contrast thresholds of sinusoidal patterns of...

In this work we introduce a new category of barriers that we call "functional vision barriers." This expression refers to lighting and visual elements that may complicate or hinder functional vision and may make life even more difficult for people with visual defects. These barriers appear as a consequence of certain negative effects caused by the...

The presence of a glare source in the visual field produces a veiling luminance ( L v ), which generates a brightness reduction that can be expressed in terms of the glare index ( V ). The relation between the veiling luminance caused by glare and the apparent brightness reduction of a reference target has already been established for steady condit...

There is a growing interest in studying mesopic since in this range rods and cones are simultaneously active. It has been suggested that rods cone interactions could be responsible for alterations in temporal and spatial visual response. By employing a two-channel Maxwellian view optical system we measured thresholds luminance at a steady adapting...

The influence of lighting of different spectral power distribution on letter contrast sensitivity has been studied. The different spectral power distributions were obtained by filtering or dimming tungsten halogen lamps. Measurements were made on 20 young and healthy individuals (25 eyes) whose monocular contrast sensitivities were measured with a...

In this study we present the comparison of the performance of two systems to measure intraocular scattering. Measurements were made by using a psychophysical system based on a brightness comparison method that provides a glare index and a physical system based on the double-pass technique, which gives an objective scatter index by measuring the opt...

Background / Purpose: A Transitional Space (TS) – from exterior to interior – becomes a “lighting barrier” due to the extreme lighting conditions involved. Considering the increase in the adaptation time with ageing, strong illumination change effects will dependon peoples age.An experiment was performed to test this dependency. We measured the t...

Night driving is a complex visual task with important ramifications for driver and pedestrian safety. It is usually performed under mesopic or scotopic conditions and frequently, in the presence of transient glare sources that can adapt parts of the central retina. The objective of this work was to analyze the time response of adaptation for the ce...

The purpose of this study was to compare the performance of two psychophysical contrast sensitivity tests, one based on a computerized system – FVC 100 – and the other based on printed charts – VCTS 6500, both using the discrimination of sinusoidal grating orientation under photopic adaptation. Altogether, 45 eyes of 23 people with ages ranging fro...

We have shown that, in the mesopic range, glare reduces the perceived brightness of a foveal test patch in a non-linear fashion (Colombo, Barraza, Issolio, LR&T, 32(2), 2000). Here we report the effects of glare measured under a variety of different contrast conditions obtained by modifying the background luminance. The experiment was carried out u...

Purpose. It was shown previously that a peripheral glare source reduces the brightness of a foveal test. This reduction of brightness cannot be explained by a luminance match. In this work we performed an experiment to test the hypothesis that our brightness evaluation task is affected by lightness intrusion. Methods. Using a magnitude comparison m...

Purpose: Previous results have shown the influence of glare on the brightness evaluation of a foveal test in the mesopic range depends on the test luminance as well as the surround luminance. In this work we perform new experiments in order to find which variable determines lightness constancy. Methods: Patches subtending 1.2 degrees placed on the...

Purpose: When the grey target of a White's display overlaps a pair of adjacent black and white stripes, an illusory contour appears as the continuation of the border between the stripes, but with the contrast polarity reversed. This effect accounts the hypothesis that when two aligned contours undergo a discontinuous change in the magnitude of cont...

The investigation of the visual system produced models based on the neural components of such system, capable of describing the way in which the velocity information contained in a scene with movement is extracted. The fact that these models are sensitive to the size of the stimuli in combination with the distance to which the objects are presented...

To determine the influence of surround luminance on the letter contrast sensitivity function. The binocular contrast sensitivities of 31 young and ocularly healthy individuals were measured with letters of sizes calculated to obtain the targeted fundamental frequencies of 3, 10, 20, and 30 c deg(-1), respectively; with surround luminances from 1 to...

When a myopic or hyperopic eye wearing an ophthalmic lens looks at a stimulus and also receives light from a peripheral point, the lens modifies the eccentricity angle with which light originated at this point reaches the eye. Under paraxial approximation, the lens visual magnification (quotient between the angles subtended at the corneal vertex by...

In this work, we evaluate the feasibility to determine the intraocular scattering by measuring the brightness reduction by glare. A haploscopic system based on the brightness comparison has been developed. This system allows to compare the brightness of a test with a steady glare source in the field of vision, and another one without it. Our goal i...

To study the influence of glare on the visual performance of a subject wearing an ophthalmic lens, it is useful to know how the lens affects the illuminance reaching the eye. In this paper, considering spherical standard ophthalmic lenses and defining the relative illuminance, Er, as the quotient between the illuminance at the cornea with and witho...

To use the double-pass technique to evaluate the in vitro optical quality of foldable monofocal intraocular lenses (IOLs) used to correct aphakia. Universitat Politècnica de Catalunya, Terrassa, and Instituto de Microcirugía Ocular de Barcelona, Barcelona, Spain; Universidad Nacional de Tucumán, Tucumán, Argentina. This study assessed the in vitro...

We discuss the characteristics a system to measure the contrast sensitivity function (CSF) in the ophthalmologic clinic has to have. We propose that this system should be computer based in order to assure flexibility and precision. Besides the original calibration, this equipment needs an auxiliary system to keep the working conditions allowing per...

The effect of intraocular scattering of light generated at a peripheral glare source is quantified using a model empirically formulated in terms of the veiling luminance. This luminance is directly proportional to the illuminance generated at the eye by this source and inversely proportional to the square of the eccentricity angle subtended by the...

The amount of light captured by the eye depends on pupil size. Moreover, one of the factors determining the steady-state pupil size is ambient illumination and sudden increments of light reaching the retina cause a brisk and transient pupil constriction described as the dynamic Pupil Light Reflex response. In experiments where a glare source acts a...

Spatial frequencies are often employed both in Fourier Optics and in Physiological Optics. According to Fourier Optics, any object can be synthesized as a superposition of harmonics of different spatial periods and the spatial frequency, defined as the inverse of the corresponding period, is measured in cycles per millimeter. On the other hand, in...

The evaluation of the intraocular scattering is a current area of investigation and there is not one procedure absolutely accepted in the clinical. In this paper, we compare two psychophysical methods: CSF and RTs using sinusoidal gratings of 1, 2, 4, 8, 12 y 24 c/deg. To measure the discriminative ability we use ectoptic diffusers and photopic ada...

We measured the effect of a transient glare source on t heperceived brightness of astandard luminance (L(STD)) patch (0.5 cd/m2) as a function of the surround luminance (Ls). In the experiment, both increment and decrement stimuli were dependent on the value of the Ls (0.01, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, or 2.0 cd/m2). We adopted a magnitude compar...

It was shown that a peripheral glare source reduces the brightness of a foveal stimulus. We hypothesized that this brightness reduction is governed by an inhibitory effect of the glare source on the test. We reported the results of an investigation of the dynamic of brightness reduction of an incremental stimulus immediately after the onset of a gl...

Transient glare reduces the perceived brightness for stimulus luminances within the scotopic-mesopic range. This work studies this effect in myopic observers with lens and spectacles corrections and in one emmetrope. The task of the subject consists of compare brightness of two uniform luminance fields sequentially displayed, one of which had a ref...

This paper reports a study of the effect of disability glare in the scotopic-mesopic range when there is brief exposure to glare to provide conditions similar to those encountered in night driving. Subjects compare the brightness of two uniform luminance fields that are displayed sequentially, when one of them is presented under glare conditions. T...

This paper proposes a quantitative method for evaluation of disability glare, considering a scotopic-mesopic range and transient glare. Subjects had to compare brightness of two uniform luminance fields sequentially displayed, one of which was presented under glare conditions. The observer reported which field was brighter with respect to one anoth...