Maciej Wojtkowski

• Doctor of Philosophy
• Professor (Full) at Institute of Physical Chemistry

In this study, we used an inhibitor of phosphodiesterase 6 (PDE6) to examine the impact of changes in the conformation of the PDE6 protein on the light-induced process responsible for altering the length of the outer segments of photoreceptor cells in both human and rodent eyes. We employed a imaging method called spatiotemporal optical coherence t...

Significance Microcirculation and neurovascular coupling are important parameters to study in neurological and neuro-ophthalmic conditions. As the retina shares many similarities with the cerebral cortex and is optically accessible, a special focus is directed to assessing the chorioretinal structure, microvasculature, and hemodynamics of mice, a v...

Two-photon vision is a new and developing field in vision science. The phenomenon is based on visual perception of pulsed infrared lasers (800-1300 nm) due to the isomerization of visual pigments caused by two-photon absorption, with color perception corresponding to a wavelength about one-half of the stimulating wavelength in the near-infrared spe...

One of the possible applications of two-photon vision is its implementation in retinal displays. This study aims to investigate the effect of defocusing on contrast sensitivity for two-photon vision, enabling a better assessment of the potential application of the phenomenon in Augmented Reality (AR) technology.

Flicker electroretinography (ERG) has served as a valuable noninvasive objective tool for investigating retinal physiological function through the measurement of electrical signals originating from retinal neurons in response to temporally modulated light stimulation. Deficits in the response at certain frequencies can be used as effective biomarke...

In this work, we present a pipeline for processing data acquired during in vivo optoretinography measurements of human photoreceptors' response to light with Spatio-Temporal Optical Coherence Tomography (STOC-T) setup.

We report on Spatio-Temporal Optical Coherence Tomography (STOC-T) applied to detection of pulsatile blood flow frequency, blood pulse wave propagation and other hemodynamic parameters from retinal and choroidal vessels in the mouse eye.

We introduce a modified experimental STOC-T system with an increased lateral resolution of ~3 µm and a high-speed phase modulator that optimizes illumination. The integration of this rapid phase modulator with a numerical averaging process facilitates a noticeable improvement in the signal-to-noise ratio (SNR). This enhancement's effects have been...

We demonstrate that spatio-temporal optical coherence tomography (STOC-T) supported by computational aberration correction provides neuronal-level imaging of the human retina. We show en face images depicting the amacrine cells, the multipolar retinal neurons.

In clinical settings, precise biomechanical assessments of the cornea are crucial for early detection of keratoconus. Our study introduces the clinical application of a breakthrough multi-meridian technique that enables simultaneous 3-D deformation measurements, enhancing the diagnostic capabilities of standard air-puff swept-source OCT systems. By...

The guest editors introduce a feature issue commemorating the 30th anniversary of Optical Coherence Tomography.

In this contribution, we present experimental results of in vivo characterization of the photoreceptor's response to a chirped flickering white light stimulating the retina. We acquire the ORG signal with Spatio-Temporal Optical Coherence Tomography (STOC-T) setup, which combines both temporal and coherence gating to overcome limitations present in...

The contrast sensitivity function for two-photon vision (2phCSF) has not yet been thoroughly characterized. First attempts have been made to measure contrast sensitivity for two-photon vision (IOVS (63)(2022) pp.2234 – F0442). This study aims to extend the research, complete the data on 2phCSF and compare it to standard, one-photon CSF (1phCSF).

This report presents the results of measurements of the two-photon vision threshold for various pulse trains. We employed three pulsed near-infrared lasers and pulse stretchers to obtain variations of the pulse duty cycle parameter over three orders of magnitude. We proposed and extensively described a mathematical model that combines the laser par...

Noninvasive imaging of endogenous retinal fluorophores, including vitamin A derivatives, is vital to developing new treatments for retinal diseases. Here, we present a protocol for obtaining in vivo two-photon excited fluorescence images of the fundus in the human eye. We describe steps for laser characterization, system alignment, positioning huma...

The eye is an ideal organ for imaging by a multi-photon excitation approach, because ocular tissues such as the sclera, cornea, lens and neurosensory retina, are highly transparent to infrared (IR) light. The interface between the retina and the retinal pigment epithelium (RPE) is especially informative, because it reflects the health of the visual...

We developed and applied spatio-temporal optical coherence tomography (STOC-T), which supported by computational aberration correction enables high resolution imaging of the human and mouse retina in vivo .

We used the flicker ORG method with a variable frequency stimulus to measure the frequency characteristics of photoreceptor activity. Data are collected using a Spatio-Temporal Optical Coherence Tomographic (STOC-T) system. We use a white-light LED for stimulation, which is driven by a linear chirped signal (5 Hz to 45 Hz). This approach allows muc...

We present an optical imaging system, termed STOC-T, for in vivo imaging of chorioretinal complex that uses an optimized multimode fiber for crosstalk noise reduction in OCT images.

The ability to perform multi-meridian, simultaneous measurements of air-induced corneal deformation is expected to highly improve the accuracy of assessing corneal biomechanics. We propose a simplified method targeting 3-D deformation measurements that could be introduced to any swept-source OCT system. We utilize a spatial-depth-encoded multiplexi...

Despite the rapid development of optical imaging methods, high-resolution in vivo imaging with penetration into deeper tissue layers is still a major challenge. Optical coherence tomography (OCT) has been used successfully for non-invasive human retinal volumetric imaging in vivo, advancing the detection, diagnosis, and monitoring of various retina...

Optical coherence tomography (OCT) is a non-contact method for imaging the topological and internal microstructure of samples in three dimensions. OCT can be configured as a conventional microscope, an ophthalmic scanner or endoscopes and small-diameter catheters for accessing internal biological organs. In this Primer, the principles underpinning...

Purpose : The perceived brightness of different visible light sources can be compared with photometric units based on the standardized luminosity curves (300-780nm range). As reported previously (PNAS 111(50), pp. E5445-E5454 (2014)), near-infrared (NIR) radiation can cause isomerization of visual pigments by one- or two-photon absorption. The perc...

We demonstrate in vivo imaging of the ischemic area in the mouse brain after photostroke using a custom prototype Gaussian‑beam optical coherence tomography (OCT) setup in which the near infrared imaging beam and the green photoinducing light pass through the same objective lens. The goal of our research was analysis of vascularity of the ischemic...

For many years electroretinography (ERG) has been used for obtaining information about the retinal physiological function. More recently, a new technique called optoretinography (ORG) has been developed. In one form of this technique, the physiological response of retinal photoreceptors to visible light, resulting in a nanometric photoreceptor opti...

We report the development of a widely-tunable femtosecond fiber laser system and its application for two-photon vision studies. The source is based on an Er-doped fiber laser with spectral shift up to 2150 nm, followed by a second harmonic generation module to generate a frequency-doubled beam tunable from 872 to 1075 nm. The source delivers sub-23...

Fourier-domain full-field optical coherence tomography (FD-FF-OCT) is an emerging tool for high-speed eye imaging. However, cross-talk formation in images limits the imaging depth. To this end, we have recently shown that reducing spatial coherence with a fast deformable membrane can suppress the noise but over a limited axial range and with substa...

We report on a novel human retina imaging system based on Spatio-Temporal Optical Coherence Tomography (STOC-T). We present structural images and spatially-resolve functional responses of the retinal tissue to white light stimulation.

Background: Noninvasive assessment of metabolic processes that sustain regeneration of human retinal visual pigments (visual cycle) is essential to improve ophthalmic diagnostics and to accelerate development of new treatments to counter retinal diseases. Fluorescent vitamin A derivatives, which are the chemical intermediates of these processes, a...

One of the greatest needs in modern ophthalmology is access to the eye choroid in vivo. Without it, it is difficult to introduce new therapies and to understand most of the pathological changes in the eye, because of the total blood flow in the eye is caused by the choroidal circulation. It is entirely responsible for the metabolism of photorecepto...

Purpose : Two-photon vision is associated with the perception of short pulses of near-infrared (NIR) laser radiation as a visible (VIS) light. It is caused by the nonlinear process of two-photon absorption by visual pigments. The longer wavelength of the stimulating radiation suggests that this phenomenon may be beneficial for functional visual exa...

Fourier-domain full-field optical coherence tomography (FD-FF-OCT) has recently emerged as a fast alternative to point-scanning confocal OCT in eye imaging. However, when imaging the cornea with FD-FF-OCT, a spatially coherent laser can focus down on the retina to a spot that exceeds the maximum permissible exposure level. Here we demonstrate that...

Pulsed near-infrared (NIR) light sources can be successfully applied for both imaging and functional testing of the human eye, as published recently. These two groups of applications have different requirements. For imaging applications, the most preferable is invisible scanning beam while efficiently visible stimulating beam is preferable for func...

Spatiotemporal optical coherence (STOC) manipulation is a new method for crosstalk-free, aberration-free, high-speed, high-resolution imaging of the human eye in vivo . Here, we apply STOC for deep blood flow imaging of the human retina in vivo .

OCT imaging of dynamic samples can give rise to significant misleading axial motion artifacts, depending on system specifications. Here, we investigate the axial shift phenomena in low-cost swept-source OCT dynamic measurements and simulations.

The two- and one-photon visual sensitivities (2phS and 1phS) of cataract patients were tested before and after IOL surgery. Mean change in 2phS was twice smaller than 1phS indicating that 2phS is less affected by cataract.

We developed and applied spectral laser doppler holography (SLDH) to Fourier-Domain Full-Field Optical Coherence Tomography (FD-FF-OCT) enabling visualization and quantification of the human retinal blood flow at high speeds and high transverse resolution in vivo .

We present an optimized Fourier-domain full-field optical coherence tomography system for corneal in vivo imaging that uses a line camera for real-time cross-sectional preview and a multimode fiber for preventing retinal damage.

Two-photon vision is a phenomenon associated with the perception of short pulses of near-infrared radiation (900-1200 nm) as a visible light. It is caused by the nonlinear process of two-photon absorption by visual pigments. Here we present results showing the influence of pulse duration and repetition rate of short pulsed lasers on the visual thre...

Droplet microfluidics disrupted analytical biology with the introduction of digital polymerase chain reaction and single-cell sequencing. The same technology may also bring important innovation in the analysis of bacteria, including antibiotic susceptibility testing at the single-cell level. Still, despite promising demonstrations, the lack of a hi...

Corneal biomechanics play a fundamental role in the genesis and progression of corneal pathologies, such as keratoconus; in corneal remodeling after corneal surgery; and in affecting the measurement accuracy of glaucoma biomarkers, such as the intraocular pressure (IOP). Air-puff induced corneal deformation imaging reveals information highlighting...

Corneal biomechanics plays a fundamental role in the genesis and progression of corneal pathologies, such as keratoconus. It also contributes to corneal remodelling after corneal surgery, and it affects the measurement accuracy of glaucoma biomarkers, such as the intraocular pressure (IOP). Air-puff induced corneal deformation imaging reveals infor...

Ultrafast volumetric (3D) human retina imaging with Fourier-domain Full-Field Optical Coherence Tomography

Significance Two-photon excitation (TPE) of retinal fluorophores with infrared light allows monitoring metabolic transformation of the retina. TPE imaging can provide information about biochemical events that precede structural damage to the retina and thereby accelerate the development of therapies against blinding diseases. While subcellular TPE...

We present in-vivo imaging of the mouse brain using custom made Gaussian beam optical coherence microscopy (OCM) with 800nm wavelength. We applied new instrumentation to longitudinal imaging of the glioblastoma (GBM) tumor microvasculature in the mouse brain. We have introduced new morphometric biomarkers that enable quantitative analysis of the de...

Purpose To investigate the effect of short‐term scleral lens wear on the corneal stroma at a macroscopic (thickness) and microscopic (within tissue) level, including regional variations. Methods Fourteen young, healthy participants wore a rotationally symmetric, 16.5 mm diameter, scleral lens for 8 h. Scheimpflug images were captured before, and i...

A femtosecond frequency-doubled erbium-doped fiber laser with an adjustable pulse repetition rate is developed and applied in two-photon excited fluorescence microscopy. The all-fiber laser system provides the fundamental pulse at 1560 nm wavelength with 22 fs duration for the second harmonic generation, resulting in 1.35 nJ, 60 fs pulses at 780 nm...

Purpose: To introduce a new approach for keratoconus detection based on corneal microstructure observed in vivo derived from a single Scheimpflug image. Methods: Scheimpflug single-image snapshots from 25 control subjects and 25 keratoconus eyes were analyzed; from each group, five subjects were randomly selected to provide out-of-sample data. E...

Purpose : Ocular biomechanical simulations show that air-puff induced corneal deformation imaging (APCDI) can reveal pathological asymmetric responses, as in eccentric keratoconus. Such asymmetries often go undetected when monitoring deformation on only one meridian (Birkenfeld et al., IOVS, 2019), as is the case with commercial instruments. We pre...

A femtosecond frequency-doubled Erbium-doped fiber laser with adjustable pulse repetition rate is developed and applied in two-photon excited fluorescence microscopy. The all-fiber laser system provides the fundamental pulse at 1560 nm wavelength with 22 fs duration for the second harmonic generation, resulting in 1.35 nJ, 60 fs pulses at 780 nm. T...

Corneal evaluation in ophthalmology necessitates cellular-resolution and fast imaging techniques that allow for accurate diagnoses. Currently, the fastest volumetric imaging technique is Fourier-domain full-field optical coherence tomography (FD-FF-OCT), which uses a fast camera and a rapidly tunable laser source. Here, we demonstrate high-resoluti...

Corneal evaluation in ophthalmology necessitates cellular-resolution and fast imaging techniques allowing accurate diagnoses. Currently, the fastest volumetric imaging technique is Fourier-domain full-field optical coherence tomography (FD-FF-OCT) that uses a fast camera and a rapidly tunable laser source. Here, we demonstrate high-resolution, high...

Spatiotemporal optical coherence (STOC) imaging is a new technique for suppressing coherent cross talk noise in Fourier-domain full-field optical coherence tomography (FD-FF-OCT). In STOC imaging, the time-varying inhomogeneous phase masks modulate the incident light to alter the interferometric signal. Resulting interference images are then proces...

We used a new multimodal imaging system that combines optical coherence microscopy and brightfield microscopy. Using this in vivo brain monitoring approach and cranial window implantation, we three-dimensionally visualized the vascular network during thrombosis, with high temporal (18 s) and spatial (axial, 2.5 μ m ; lateral, 2.2 μ m ) reso...

We present a crosstalk-free Fourier-domain full-field optical coherence tomography system that uses a fast deformable membrane for spatial coherence reduction. It enables the visualization of the choroids and helps to better delineate the retinal layers.