Advanced Optical Analysis of Divergence Between the Foci of the Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) and Aiming Beam Lasers.

Purpose: To evaluate the divergence between the neodymium-doped yttrium aluminum garnet (Nd:YAG) surgical laser and the aiming diode laser beams foci.

Design: Optical analysis and measurements were performed using a Volk Goldmann 3-mirror lens with a Nidek YC-1800 Nd:YAG laser apparatus.

Subjects: None.

Feasibility Study of Scanning Spectral Imaging Based on a Birefringence Flat Plate.

Hyper-spectral imaging (HSI) systems can be divided into two main types as follows: a group of systems that includes a dedicated dispersion/filtering component whose role is to physically separate the different wavelengths and a group of systems that sample all wavelengths in parallel, so that the separation into wavelengths is performed by signal processing (interferometric method). There is a significant advantage to systems of the second type in terms of the integration time required to obtain a signal with a high signal-to-noise ratio since the signal-to-noise ratio of methods based on scanning interferometry (Windowing method) is better compared to methods based on dispersion. The current research deals with the feasibility study of a new concept for an HSI system that is based on scanning interferometry using the "push-broom" method.

The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation.

Adequate oxygen delivery to a tissue depends on sufficient oxygen content in arterial blood and blood flow to the tissue. Oximetry is a technique for the assessment of blood oxygenation by measurements of light transmission through the blood, which is based on the different absorption spectra of oxygenated and deoxygenated hemoglobin. Oxygen saturation in arterial blood provides information on the adequacy of respiration and is routinely measured in clinical settings, utilizing pulse oximetry.

Tear film imager for dynamic mapping of the human tear film.

Dry eye (DE) disease is a multifactorial disease of the outer ocular surface characterized by several ocular symptoms and mainly by tear film instability. We have developed an optical imaging system, the tear film imager (TFI), which is the first instrument that can directly image the muco-aqueous tear layer physical dimension in vivo and evaluate its parameters in a noninvasive mode with nanometer axial resolution. This instrument provides quantified information about many attributes of the tear film, including muco-aqueous layer thickness, lipid layer thickness, thickness change rate, and the break-up time.

Mapping the Lipid Layer of the Human Tear Film.

Purpose: To describe a new method to distinguish between normal versus lipid-deficient dry eye using a Tear Film Imager (TFI).

Methods: Two groups of study subjects, controls versus lipid-deficient dry eye, were tested using the TFI. This instrument provides an accurate measurement of the thickness and spatial distribution of the muco-aqueous and lipid layers of the tear film.

Enhanced depth imaging in swept-source optical coherence tomography: Improving visibility of choroid and sclera, a masked study.

Purpose: To compare enhanced depth imaging in swept-source optical coherence tomography and non-enhanced depth imaging optical coherence tomography in their ability to capture choroidal and scleral details.

Methods: Averaged foveal B-Scans were obtained from 40 eyes of 20 healthy volunteers by swept-source optical coherence tomography with and without enhanced depth imaging. Visibility and contrast of vascular details within the choroid, choroidoscleral junction, and sclera were evaluated by masked readers using an ordinal scoring scale.

Dynamic assessment of the tear film muco-aqueous and lipid layers using a novel tear film imager (TFI).

Purpose: The objective of the study was to assess a new technology, the tear film imager (TFI), which can dynamically image the muco-aqueous and lipid layers.

Methods: Prospective pilot case series of individuals with and without dry eye (DE). Two sequential images were obtained with the TFI.

Manipulations of Wavefront Propagation: Useful Methods and Applications for Interferometric Measurements and Scanning.

Phase measurements obtained by high-coherence interferometry are restricted by the 2 ambiguity, to height differences smaller than /2. A further restriction in most interferometric systems is for focusing the system on the measured object. We present two methods that overcome these restrictions.

Hyperspectral imaging camera using wavefront division interference.

An approach for performing hyperspectral imaging is introduced. The hyperspectral imaging is based on Fourier transform spectroscopy, where the interference is performed by wavefront division interference rather than amplitude division interference. A variable phase delay between two parts of the wavefront emanating from each point of an object is created by a spatial light modulator (SLM) to obtain variable interference patterns.

Spatial-phase-shift imaging interferometry using a spectrally modulated white light source.

An extension of the white light spatial-phase-shift (WLSPS) for object surface measurements is described. Using WLSPS, surface measurements can be obtained from any real object image without the need of a reference beam, thus achieving inherent vibration cancellation. The surface topography is obtained by acquiring multiple images of an object illuminated by a spectrally modulated white light source and using an appropriate algorithm.

Surface measurements by white light spatial-phase-shift imaging interferometry.

A novel method of common-path imaging interferometry, the White Light Spatial-Phase-Shift (WLSPS) for object surface measurements, is discussed here. Compared to standard White Light Interferometry (WLI), which uses a reference mirror, the interferometry of WLSPS is obtained by creating manipulations to the light wavefront reflected from an object's surface. Using this approach, surface measurements can be obtained from any real object image, and do not need to be taken directly from the object itself.

Effect of intraocular pressure on the hemodynamics of the central retinal artery: a mathematical model.

Retinal hemodynamics plays a crucial role in the pathophysiology of several ocular diseases. There are clear evidences that the hemodynamics of the central retinal artery (CRA) is strongly affected by the level of intraocular pressure (IOP), which is the pressure inside the eye globe. However, the mechanisms through which this occurs are still elusive.

Impaired ocular blood flow regulation in patients with open-angle glaucoma and diabetes.

Background:   To elucidate the potential impact of diabetes mellitus on primary open-angle glaucoma pathology through vascular deficiency.

Design:   Cross-section analysis from a longitudinal, prospective study.

Participants:   Eighty-four open-angle glaucoma patients (20 diabetic open-angle glaucoma patients and 64 non-diabetic open-angle glaucoma patients)

Methods:   Patients were analyzed for ocular structure, ocular perfusion pressure (OPP), retrobulbar blood flow and retinal capillary perfusion.

Endothelin and its suspected role in the pathogenesis and possible treatment of glaucoma.

Purpose: To review the role of endothelin in intraocular pressure control, its effect on the trabecular meshwork (TM) and the outflow facility, effect on ocular blood flow and vascular regulation and the potential role of endothelin-1 (ET-1) antagonism in the therapeutic paradigm of glaucoma.

Methods: A thorough review of the medical literature and a meta-analysis on the level of ET-1 in OAG patients in an attempt to demonstrate the evolving importance of endothelin in glaucoma.

Results: ET-1 has been identified in the plasma in concentrations that are markedly increased in a number of systemic as well as ocular pathologies such as glaucoma where underlying vascular dysfunction and pathology play a role.

Wavefront reconstruction by spatial-phase-shift imaging interferometry.

Common-path imaging interferometers offer some advantages over other interferometers, such as insensitivity to vibrations and the ability to be attached to any optical system to analyze an imaged wavefront. We introduce the spatial-phase-shift imaging interferometry technique for surface measurements and wavefront analysis in which different parts of the wavefront undergo certain manipulations in a certain plane along the optical axis. These manipulations replace the reference-beam phase shifting of existing interferometry methods.

Spatial phase-shift interferometry--a wavefront analysis technique for three-dimensional topometry.

We describe a new wavefront analysis method, in which certain wavefront manipulations are applied to a spatially defined area in a certain plane along the optical axis. These manipulations replace the reference-beam phase shifting of existing methods, making this method a spatial phase-shift interferometry method. We demonstrate the system's dependence on a defined spatial Airy number, which is the ratio of the characteristic dimension of the manipulated area and the Airy disk diameter of the optical system.

Generalized method for wave-front analysis.

We suggest and demonstrate a new method for wave-front analysis based on common-path phase-shift interferometry. We introduce a formalism and an iterative mathematical algorithm in which the wave front is transformed, modified, and inversely transformed. The resulting intensity data are sufficient to reconstruct the entire wave front.