Martial H Geiser

Martial H Geiser
HES-SO Valais-Wallis | HES-SO · Institut für Systemtechnik

physicist

About

72
Publications
3,689
Reads
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1,008
Citations
Introduction
Broad experience in the field of first-order lens design, ophthalmic instruments, ocular blood flow measurement, bioluminescence and fluorescence measurement within microfluidic systems for water and food quality assessment, all with an emphasis on systems design.
Additional affiliations
January 1995 - December 2001
Institut de recherche en ophtalmologie
Institut de recherche en ophtalmologie
Position
  • Senior Researcher
Description
  • http://www.irovision.ch/
October 1994 - present
HES-SO Valais

Publications

Publications (72)
Article
For any given set of light sources stimulating the photoreceptors of the retina, the theoretical levels of illumination producing the smallest and the largest expression of one photoreceptor with fixed stimulation for the others are analytically computed. The cases of four, five, and more light sources are studied. We show that, for contrast optimi...
Article
Purpose: To investigate choroidal blood flow changes after isometric exercise in patients with chronic central serous chorioretinopathy nontreated or treated with mineralocorticoid receptor antagonists (MRA). Methods: Foveolar choroidal laser Doppler flowmetry parameters - velocity (ChVel), volume (ChVol) and blood flow (ChBF) - of 22 eyes of 22...
Article
Full-text available
One way to study the specific response of the non-visual melanopsin photoreceptors of the human eye is to silence the response of cones and rods. Melanopsin photoreceptors (ipRGC), highlighted in the early 2000s, are intimately linked to the circadian rhythm and therefore to our sleep and wakefulness. Rest and sleep regulation, health and cognitive...
Article
Significance: The development of a technique allowing for non-invasive measurement of retinal blood flow (RBF) in humans is needed to understand many retinal vascular diseases (pathophysi-ology) and evaluate treatment with potential improvement of blood flow. Aim: We developed and validated an absolute laser Doppler velocimeter (LDV) based on an ad...
Article
Significance: The development of a technique allowing for non-invasive measurement of retinal blood flow (RBF) in humans is needed to understand many retinal vascular diseases (pathophysiology) and evaluate treatment with potential improvement of blood flow. Aim: We developed and validated an absolute laser Doppler velocimeter (LDV) based on an...
Poster
A novel device has been developed that is capable of measuring anti-oxidant activity with a cost-efficient measurement method, in-line with HPLC. The device is based on a microfluidic chip that mixes the HPLC eluent stream with an antioxidant marker and integrates the analysis by conventional UV/VIS photonic sensors. The results enable assessment o...
Article
This study introduced the research and development of a portable and miniaturized system for the measurement of the refractive index of sub-microliter liquid based on a microfluidic chip. A technical method of double-beam interference, was proposed for use in the measurement. Based on this, by using a laser diode as a light source, changes in the r...
Article
Purpose To analyse choroidal blood flow (ChBF) changes after the first intravitreal ranibizumab injection in naïve, age‐related macular degeneration (ARMD) patients. Methods Subfoveal ChBF was assessed by laser Doppler flowmetry (LDF) in newly diagnosed ARMD patients. Both treated and untreated eyes were assessed in each subject at each visit befo...
Article
The Laser Doppler Flowmetry (LDF) is a non-invasive technique used to evaluate blood perfusion of various human tissues like the skin or the fundus of the eye. It is based on the scattering of light on moving red blood cells in tissue. Frequency shifted scattered light is detected and provide an electrical signal. Physical models for LDF use the DC...
Article
Purpose: To investigate the impact of different gas mixtures (hyperoxia, hypoxia, and hypercapnia) on the optic nerve head (ONH) and choroidal (Ch) hemodynamics. Methods: Twenty-three healthy subjects (28 ± 6 years) took part in the study. Variations in inspired oxygen and carbon dioxide fraction were produced by a gas mixing device. Arterial ox...
Article
Full-text available
Living bacteria or yeast cells are frequently used as bioreporters for detection of specific chemical analytes or conditions of sample toxicity. In particular bacteria or yeast equipped with synthetic gene circuitry that allows production of a reliable non-cognate signal (e.g., fluorescent protein or bioluminescence) in response to a defined target...
Article
The exact pathophysiology of glaucoma is not fully understood. Understanding of the vascular pathophysiology of glaucoma requires: knowing the techniques for measuring ocular blood flow and characterizing the topography of vascular disease and the mechanisms involved in this neuropathy. A decreased mean ocular perfusion pressure and a loss of vascu...
Article
Full-text available
Purpose: Noninvasive techniques for ocular blood perfusion assessment are of crucial importance for exploring microvascular alterations related to systemic and ocular diseases. However, few techniques adapted to rodents are available and most are invasive or not specifically focused on the optic nerve head (ONH), choroid or retinal circulation. He...
Article
Full-text available
Purpose Noninvasive techniques for ocular blood perfusion assessment are of crucial importance for exploring microvascular alterations related to systemic and ocular diseases. However, few techniques adapted to rodents are available and most are invasive or not specifically focused on the optic nerve head (ONH), choroid or retinal circulation. Her...
Article
This presentation deals with the ocular vasoreactivity to acute hypoxia and hyperoxia in young healthy subjects (n=16). The protocol consisted in a 15-min inhalation of 100% O2 (hyperoxia) or 10.5% O2 + N2 (for a stable SpO2 of 85%, hypoxia) in normocapnic conditions. Blood flow was measured using laser Doppler flowmetry in the subfoveal choroid or...
Article
We present a compact fundus camera designed to measure the blood flow in small animals based on laser Doppler flowmetry (LDF). The small animal is immobilized on a modified stereotaxic table and the pupil of the LDF device is superposed by translation to the pupil’s eye of the animal. Then rotation centered at the pupil is used to point the probing...
Article
A progressive decrease of the choroidal blood flow related to macular degeneration was observed with glaucoma and aging. Abnormal regulation of the choroidal blood flow in patients suffering from neovascular AMD or Diabétic microangiopathy was also reported. Recent clinical studies have shown a decrease of the choroidal thicknessof in high myopia,...
Article
We present a compact portable biosensor to measure arsenic As(III) concentrations in water using Escherichia coli bioreporter cells. Escherichia coli expresses green fluorescent protein in a linearly dependent manner as a function of the arsenic concentration (between 0 and 100 μg/L). The device accommodates a small polydimethylsiloxane microfluidi...
Article
Full-text available
Purpose: This study investigates the effect of increased ocular perfusion pressure (OPP) on optic nerve head (ONH) hemodynamics. Methods: In 21 healthy subjects, the increase in arterial blood pressure (BP), measured continuously using a pneumatic transcutaneous sensor, was produced by isometric exercise consisting of 2 minutes of hand-gripping....
Article
Full-text available
We describe a device to measure blood perfusion for the human optic nerve head (ONH) based on laser Doppler flowmetry (LDF) with a flicker stimuli of the fovea region. This device is self-aligned for LDF measurements and includes near-infrared pupil observation, green illumination, and observation of the ONH. The optical system of the flowmeter is...
Article
Full-text available
This study presents the design and development of an interferometer for the measurement of the refractive index or concentration of a sub-microliter volume of aqueous solution in a microfluidic chip. This proposed interferometer is manifested by the successful measurement of the refractive index of a sugar–water solution, using a He–Ne laser as a l...
Article
The design and development of the miniaturized interferometer for measurement of the refractive index or concentration of sub-microliter volume aqueous solution in microfludic chip is presented. It is manifested by a successful measurement of the refractive index of sugar-water solution, by utilizing a laser diode for light source and the small rob...
Article
A wide variety of whole cell bioreporter and biosensor assays for arsenic detection has been developed over the past decade. The assays permit flexible detection instrumentation while maintaining excellent method of detection limits in the environmentally relevant range of 10–50 μg arsenite per L and below. New emerging trends focus on genetic rewi...
Article
Obstructive sleep apnea (OSA) syndrome generates hypertension, atherosclerosis, and endothelial and autonomic dysfunction, which may mutually interact with ocular vascular regulation. Exercise and posture changes can be used to manipulate blood pressure, ocular perfusion pressure (OPP), or both. It was hypothesized that choroidal vascular reactivit...
Article
Purpose Autoregulation in ocular tissues allows a constant blood flow despite variations in ocular perfusion pressure and may be impaired in ocular diseases. The purpose of this study was to investigate the effect of increased blood pressure (BP) and ocular perfusion pressure (OPP) during isometric exercise on the optic nerve head blood flow (FONH)...
Article
A portable choroidal laser Doppler flowmeter (LDF) with enhanced sensitivity based on a scattering plate is developed. The portable LDF is weighted 2 kg operated at center wavelength of 780 nm, leading to a better penetration into the eye fundus in contrast to the previous LDF operated at center wavelength of 670 nm. Enhancement of number of detect...
Article
Full-text available
This observational study is conducted to demonstrate optic nerve head (ONH) blood flow alterations during extracorporeal circulation (ECC) in routine on-pump cardiovascular operations in order to evaluate the perfusion status of important autoregulatory tissue vascular beds during moderate hypothermia. Twenty-one patients free from eye disease were...
Article
Acta Ophthalmol. 2010: 88: 622–629 This article describes the technique of continuous laser Doppler flowmetry (LDF) as applied to the measurement of the flux of red blood cells in the optic nerve head, iris and subfoveal choroid. Starting with the exposition of the physical principles underlying LDF, we first describe the various devices developed...
Article
Purpose Obstructive sleep apnea syndrome (OSA) has been reported to be associated with ischemic and glaucomatous optic neuropathy (especially normal tension glaucoma). OSA per se is able to generate hypertension, atherosclerosis and autonomic dysfunction, all conditions possibly interacting with ocular vascular regulation. The aim of our study was...
Article
Purpose Obstructive sleep apnea syndrome (OSA) has been recently reported to be associated with ischemic and glaucomatous optic neuropathy. The physiopathology of these diseases includes an abnormal regulation in the optic nerve head vasculature. The aim of our study was to characterize the choroidal vascular reactivity to acute increase in ocular...
Article
Full-text available
Obstructive sleep apnea (OSA) impacts on macrovasculature and autonomic function and may therefore interfere with ocular microvascular regulation. We hypothesized that choroidal vascular reactivity to hyperoxia and hypercapnia was altered in patients with OSA compared with matched control subjects and would improve after treatment with continuous p...
Article
To evaluate the effect of hemodilution on subfoveal choroidal blood flow in the human eye with or without retinal vein occlusion. Choroidal blood flow was measured using laser Doppler flowmetry in 28 patients with retinal vein occlusion in 1 eye. Isovolemic hemodilution was performed when hematocrit was >35%. Laser Doppler flowmetry parameters, vel...
Article
Purpose this review aims to summarize studies which assessed the effect of treatment on choroidal blood flow.Methods this presentation will focus on studies using the laser Doppler flowmeter for the analysis of choroidal blood flow parameters (velocity, volume and flow) before and after treatment. Therapies have been assessed in different ocular di...
Article
Purpose Obstructive sleep apnea syndrome (OSA) is associated with ischemic and glaucomatous optic neuropathy. The physiopathology of these diseases includes an abnormal regulation in the optic nerve head vasculature. The aim of our study was to characterize the choroidal vascular reactivity to hyperoxia and 8% CO2 breathing in OSA patients, as comp...
Article
Full-text available
To assess the short-term changes in choroidal blood flow (ChBF) after photodynamic therapy (PDT) in patients with neovascular age-related macular degeneration (AMD). Fourteen patients with exudative AMD were included after a complete ophthalmological examination, fluorescein and indocyanine green angiography and optical coherence tomography. Subfov...
Article
Introduction La mesure du flux sanguin de la tête du nerf optique est très importante dans certaines pathologies du nerf optique (ischémie, glaucome). La quantification du flux sanguin est également nécessaire pour mieux connaître les capacités de régulation au niveau du nerf optique. Objectifs et Méthodes L’objectif de cette expérimentation était...
Article
Introduction Le syndrome d’apnées du sommeil est associé aux neuropathies optiques ischémiques et glaucomateuses, dont la physiopathologie comprend une altération vasculaire de la tête du nerf optique. Nous avons mené une étude prospective afin de rechercher et caractériser une dys-régulation vasculaire au niveau de la choroïde rétrofovéolaire chez...
Article
Purpose To develop a confocal ocular laser Doppler device for the recording of functional optic nerve head (ONH) blood flow responses to various physiological stimuli.Methods The flowmeter consists of a self-aligned confocal system, a fundus illumination (green light) and CCD based observation unit, a target fixation system and a CCD camera to obse...
Article
Purpose To evaluate the effect of 14-day intermittent hypoxia on the response of the sub-foveal choroidal blood flow (ChBF) after gas inhalation, in healthy subjects. Recent studies have emphasized the effect of the obstructive sleep apnea (OSA) on CO2 vasodilatation and O2 vasoconstriction. A human model of OSA has been developed in our laboratory...
Article
An automated optical system is built up to perform goniometric measurement of scattering phase function. Measurements of typical samples including monodisperse polystyrene micro-spheres solution, and mutlidisperse polystyrene micro-spheres solution are carried out in a dark room. The possibility of estimating the average particle size of phantom th...
Article
Dual-wavelength optical low-coherent interferometry is proposed in this paper to measure the oxygen saturation in human retinal blood vessel. Wavelength consideration is made from the standpoint of eye safety and system sensitivity. Principle of oxygen saturation measurement based on dual-wavelength low-coherence interferometer is thoroughly develo...
Article
Full-text available
A new optical device to measure forward scattered light in a range of 3 degrees to 20 degrees has been developed and tested. The scattered light is focused on a plane where its axial position is proportional to the scattered angle theta. A motorized iris diaphragm located at this plane selects the scattered light between 0 degrees and a variable an...
Article
A fundus camera-based instrument to investigate increased retinal neuronal activity effect on optic nerve blood flow is described. It incorporates (a) near infrared fundus illumination and observation, (b) near infrared laser Doppler flowmeter (LDF), (c) pupil position monitoring and (d) delivery of visual stimuli. Two types of stimulation are curr...
Article
To determine the distribution of temperatures between the cornea and retina under various external conditions, such as illumination and external temperature, using a simplified heat exchange model. The human eye is modeled as a water sphere surrounded by different heat sources: choroidal and ciliary body blood flow, tears evaporation, metabolic act...
Article
Full-text available
To evaluate the effect of posture change on subfoveal choroidal blood flow (ChBF) in normal volunteers. The pulsatile, nonpulsatile, and mean ChBF were measured with laser Doppler flowmetry in 11 healthy volunteers with a mean age of 32 +/- 13 (SD) years. The posture of the subjects was changed from standing (90 degrees ), to supine (-8 degrees ),...
Article
Full-text available
The high metabolic rate of the human retina is supported by the choroidal vasculature. Knowledge of the normal choroidal blood flow (ChBF) responses to various physiological stimuli is therefore highly important if the pathophysiology of ocular diseases involving the choroid is to be understood better. In the present study, the hemodynamic response...
Article
A compact laser Doppler flowmeter (35x80x210mm3) for the measurement of subfoveal choroidal blood flow parameters (ChBF) was mounted on a helmet. This device allows the measurement of ChBF during dynamic exercises or in supine position, without the need for pupil dilatation. Its optical system is based on a Schlieren arrangement by which the surfac...
Article
PURPOSE: Arterial carbon dioxide tension and arterial oxygen tension are important determinants of retinal and cerebral blood flow. In the present study the hypothesis that changes in arterial blood gases also influence choroidal blood flow was tested. METHODS: The effect of breathing different mixtures of oxygen (O(2)) and carbon dioxide (CO(2))...
Article
Full-text available
To document the response of subfoveal choroidal blood flow (ChBF) in the human eye induced by light and dark exposures and provide some insight into the mechanism underlying this response. In a group of 12 volunteers (age, 25-60 years), ChBF was measured with a confocal laser Doppler flowmeter. Wavelength of the probing laser beam was 785 nm (90 mi...
Article
To investigate whether light and dark exposures induce a response of choroidal blood flow (ChBF) in the foveal region in humans. In a group of healthy volunteers (age 25-60 years) ChBF was measured using a new confocal laser Doppler flowmeter (probing laser at 785 nm, power at the cornea = 90 microW). ChBF was recorded at room light, in darkness, a...
Article
PURPOSE: To report on a novel approach to measure the velocity of red blood cells (RBCs) at different retinal vessel depths. METHOD: The technique is an extension of conventional laser Doppler velocimetry using light sources of various coherence lengths (CL). Light scattered by the moving RBCs interferes with that reflected from the anterior vesse...
Article
A compact instrument is described that allows the measurement of the laser Doppler flow parameters, i.e., the velocity, the volume, and flow of blood in the foveal region of the human choroidal vascular system. This new device uses the optical principle of confocality for the delivery of the laser light to the site of measurement and heterodyne det...
Article
A new instrument for the measurement of choroidal blood flow in the fovea is presented. It is based on the laser Doppler method and a confocal optical system with an indirect detection of the Doppler shifted light. The intensity of the laser beam (785 nm) at the cornea is 90 microW. Measurements were obtained from a normal population of 21 subjects...
Article
Previous studies have demonstrated, in the cat, a vasodilatation of retinal vessels in response to neuronal activity induced by diffuse luminance flicker. The aim of this study was to determine whether a similar diameter variation is detectable in humans. Nine normal subjects were exposed to 1 min of sinusoidally varying diffuse luminance flicker (...
Article
To determine retinal vessel diameter variations in response to neuronal activity induced by diffuse luminance flicker. The diameter of retinal arteries and veins was measured in 9 normal subjects by computer analysis of fundus pictures taken in monochromatic light under normal conditions of illumination and after 1 min of sinusoidally varying diffu...
Article
A new hand-held bidirectional ocular laser Doppler system for measurement of red blood cell (RBC) velocity in retinal vessels and blood flow in the optic nerve head tissue and in the choriocapillaris is described. Laser power at the cornea is below the maximum permissible level. The instrument is based on the well-established laser Doppler velocime...
Article
The goal of this work is to allow a precise measurement of bar turning pieces. The dimensions of the pieces under study were smaller than 50mm. We have developed an illumination system which is specifically designed for a telecentric objective. Furthermore a special positioning system, which allows an integration of the measurement in a fabrication...
Article
Full-text available
In this paper we analyze the probability density function of the superheterodyne signal obtained in a two-wavelength interferometer from the beat of a local oscillator laser beam with a speckled return beam from a rough target. Theoretical investigation shows that, by using an increased number of spatially separated detectors, one can improve notic...
Article
The fringe pattern observed in a far field after a laser beam illuminates a fused silica capillary immersed in a refractive-index matching material and filled with an analyte fluid is exploited to develop a sensitive optical detector for capillary chemical analysis. The inner capillary interface splits the laser beam into a reflected beam fan and a...
Article
An interactive CAD system for a computer-generated hologram (CGH) is developed to produce many kinds of CGHs in the form of Postscript files, G-code files for NC machines, and HPGL files. These files can later be sent to a laser printer and also a laser beam lithography system. The laser beam lithography system developed has a writing area of 200 m...
Article
We have produced a high efficient phase-only hologram, of which refractive index distribution is modified by using an ion exchange method. This paper describes an optimum condition of the phase profile of the hologram. In computer simulation, ion density and phase profile generated by ion exchanging is calculated. The diffractiion patterns of the g...
Article
Petzval curvature plays an important role in the design of a triplet. Its value should be defined at the beginning of the design process, and along with the field of view, it will characterize the type of design. For these reasons, a look at the consequences of choosing various Petzval values is interesting. Different image quality criteria versus...

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Projects (2)
Project
We are developing a device for the diagnosis of the non-visual activity of the eye related to blue light. This instrumentation is based on the specific excitation of ipRGCs or melanopsin photoreceptors using the so-called "silent substitution" technique. We aimed at very high contrast excitation (larger than 70%) in an homogeneous field of ±20° using Maxwellian projection.