The Impact of Photopigment Bleaching on the Human Rod Photoreceptor Subretinal Space Measured Via Optical Coherence Tomography.

Purpose: The purpose of this study was to investigate rod photopigment bleaching-driven intrinsic optical signals (IOS) in the human outer retina and its measurement repeatability based on a commercial optical coherence tomography (OCT) platform.

Methods: The optical path length of the rod photoreceptor subretinal space (SRS), that is, the distance between signal bands of rod outer segment tips and retinal pigment epithelium, was measured in 15 healthy subjects in ambient light and during a long-duration bleaching white-light exposure.

Results: On 2 identical study days (day 1 and day 2 [D1 and D2]), light stimulation resulted in a significant decrease in rod SRS by 21.

Classification of Tear Film Lipid Layer En Face Maps Obtained Using Optical Coherence Tomography and Their Correlation With Clinical Parameters.

Purpose: The purpose of this study was to investigate the correlation between the pattern of optical coherence tomography (OCT) en face maps of the tear film lipid layer (TFLL) and lipid layer thickness (LLT), fluorescein breakup time (FBUT), and Schirmer I test values in healthy subjects.

Methods: Measurements from four clinical data sets were retrospectively analyzed, and TFLL patterns were classified into 3 categories: homogeneous (HOM), wavy (WAV), or dotted (DOT) appearance. Linear mixed model analyses were performed.

Quantification of intrinsic optical signals in the outer human retina using optical coherence tomography.

Intrinsic optical signals constitute a noninvasive biomarker promising the objective assessment of retinal photoreceptor function. We employed a commercial optical coherence tomography (OCT) system and an OCT signal model for evaluation of optical path length (OPL) changes in the temporal outer retina of five healthy subjects during light adaptation. Data were acquired at 30 time points, in ambient light and during long duration stimulation with white light, and analyzed, employing a signal model based on the sum of seven Gaussian curves corresponding to all relevant anatomical structures of the outer retina.

The Association between Tear Film Thickness as Measured with OCT and Symptoms and Signs of Dry Eye Disease: A Pooled Analysis of 6 Clinical Trials.

Purpose: To determine the association between tear film thickness (TFT) as measured with ultra-high resolution optical coherence tomography (UHR-OCT) and signs and symptoms of dry eye disease (DED).

Methods: A total of 450 eyes from 225 patients with DED from six different randomized clinical trials were included in this pooled analysis. In all subjects, TFT was measured with a custom-built UHR-OCT system.

Deep learning segmentation for optical coherence tomography measurements of the lower tear meniscus.

The tear meniscus contains most of the tear fluid and therefore is a good indicator for the state of the tear film. Previously, we used a custom-built optical coherence tomography (OCT) system to study the lower tear meniscus by automatically segmenting the image data with a thresholding-based segmentation algorithm (TBSA). In this report, we investigate whether the results of this image segmentation algorithm are suitable to train a neural network in order to obtain similar or better segmentation results with shorter processing times.

Influence of Perfluorohexyloctane Eye Drops on Tear Film Thickness in Patients with Mild to Moderate Dry Eye Disease: A Randomized Controlled Clinical Trial.

The aim of this mechanistic clinical study was to explore the effect of water-free perfluorohexyloctane eye drops on tear film thickness (TFT) in patients with dry eye disease (DED). Forty-eight patients with mild to moderate DED participated in this randomized, single-masked, observer-blinded parallel group study in a 1:1 ratio to receive either perfluorohexyloctane or unpreserved 0.9% saline solution (Hydrabak, Thea, France) eye drops 4 times daily in both eyes for 4 weeks.

corneal endothelium imaging using ultrahigh resolution OCT.

We investigate the influence of optical coherence tomography (OCT) system resolution on high-quality corneal endothelial cell images of the monkey eye, to allow for quantitative analysis of cell density. We vary the lateral resolution of the ultrahigh resolution (UHR) OCT system (centered at 850 nm) by using different objectives, and the axial resolution by windowing the source spectrum. By suppressing the motion of the animal, we are able to obtain a high-quality corneal endothelial cell map using UHR OCT for the first time with a lateral resolution of 3.

Characterization of dry eye disease in a mouse model by optical coherence tomography and fluorescein staining.

A custom-built ultrahigh-resolution optical coherence tomography (UHR-OCT) system and fluorescein staining were employed for investigation of a scopolamine induced dry eye mouse model. Acquired data was used to evaluate common and complementary findings of the two modalities. Central corneal thickness as measured by UHR-OCT increased significantly over the study period of 24 hours, from 89.

Light-induced changes of the subretinal space of the temporal retina observed via optical coherence tomography.

Photoreceptor function is impaired in many retinal diseases like age-related macular degeneration. Currently, assessment of the photoreceptor function for the early diagnosis and monitoring of these diseases is either subjective, as in visual field testing, requires contact with the eye, like in electroretinography, or relies on research prototypes with acquisition speeds unattained by conventional imaging systems. We developed an objective, noncontact method to monitor photoreceptor function using a standard optical coherence tomography system.

Relationship Between the Parameters of Corneal and Fundus Pulse Signals Acquired With a Combined Ultrasound and Laser Interferometry Technique.

Purpose: To estimate the relationship between the characteristics of the corneal pulse (CP) signal and those of the fundus pulse (FP) signal measured with a combined noncontact ultrasonic and laser interferometry technique in healthy subjects.

Methods: Twenty-two healthy subjects participated in experiments that included measurements of intraocular pressure, ocular pulse amplitude, ocular biometry, blood pressure, and heart rate. Additionally, simultaneous recordings of CP and FP signals were acquired with a noncontact ultrasonic device combined with laser interferometry.

Automatic assessment of tear film and tear meniscus parameters in healthy subjects using ultrahigh-resolution optical coherence tomography.

Many different parameters exist for the investigation of tear film dynamics. We present a new tear meniscus segmentation algorithm which automatically extracts tear meniscus area (TMA), height (TMH), depth (TMD) and radius (TMR) from UHR-OCT measurements and apply it to a data set including repeated measurements from ten healthy subjects. Mean values and standard deviations are 0.

Automated segmentation of dermal fillers in OCT images of mice using convolutional neural networks.

We present a system for automatic determination of the intradermal volume of hydrogels based on optical coherence tomography (OCT) and deep learning. Volumetric image data was acquired using a custom-built OCT prototype that employs an akinetic swept laser at ~1310 nm with a bandwidth of 87 nm, providing an axial resolution of ~6.5 μm in tissue.

CorneaNet: fast segmentation of cornea OCT scans of healthy and keratoconic eyes using deep learning.

Deep learning has dramatically improved object recognition, speech recognition, medical image analysis and many other fields. Optical coherence tomography (OCT) has become a standard of care imaging modality for ophthalmology. We asked whether deep learning could be used to segment cornea OCT images.

Ultrahigh-resolution anterior segment optical coherence tomography for analysis of corneal microarchitecture during wound healing.

Purpose: To employ ultrahigh-resolution (UHR) optical coherence tomography (OCT) for investigation of the early wound healing process in corneal epithelium.

Methods: A custom-built UHR-OCT system assessed epithelial healing in human keratoconic cornea after epi-off crosslinking (CXL) procedure and a wound healing model in rabbits with iatrogenic corneal injury. 3D OCT data sets enhanced obtaining epithelial thickness maps and evaluation of reepithelization stage.

[Cornea Imaging by Optical Coherence Tomography - Historical Aspects and Most Recent Technical Developments].

Since its introduction for retinal imaging in the early 1990s, optical coherence tomography (OCT) has undergone rapid development and has revolutionised ophthalmology. Although OCT was initially used mainly for the examination of the retina, numerous systems for the assessment of the anterior segment of the eye have now been developed. OCT is based on the detection and processing of the light back-scattered and back-reflected by the tissue, and provides completely new possibilities for the ophthalmologist to examine the structures of the anterior eye segment.

Effect of Single Instillation of Two Hyaluronic Acid-Based Topical Lubricants on Tear Film Thickness in Patients with Dry Eye Syndrome.

Purpose: This study investigated the effect of single administration of 2 different hyaluronic acid-based topical lubricants on tear film thickness (TFT) in patients with moderate-to-severe dry eye disease (DED).

Methods: Sixty patients were randomized to receive eye drops containing unpreserved sodium hyaluronate, triglycerides, and phospholipids (HTP), unpreserved sodium hyaluronate (HA), or unpreserved sodium chloride (NaCl). TFT and lipid layer thickness (LLT) were assessed before and at defined time points after single instillation with a custom-built ultrahigh-resolution optical coherence tomography system and a white light interferometer.

Anterior segment optical coherence tomography.

Optical coherence tomography (OCT) provides non-contact, rapid in vivo imaging of ocular structures, and has become a key part of evaluating the anterior segment of the eye. Over the years, improvements to technology have increased the speed of capture and resolution of images, leading to the increasing impact of anterior segment OCT imaging on clinical practice. In this review, we summarize the historical development of anterior segment OCT, and provide an update on the research and clinical applications of imaging the ocular surface, cornea, anterior chamber structures, aqueous outflow system, and most recently anterior segment vessels.

Ultrahigh-resolution OCT imaging of the human cornea.

We present imaging of corneal pathologies using optical coherence tomography (OCT) with high resolution. To this end, an ultrahigh-resolution spectral domain OCT (UHR-OCT) system based on a broad bandwidth Ti:sapphire laser is employed. With a central wavelength of 800 nm, the imaging device allows to acquire OCT data at the central, paracentral and peripheral cornea as well as the limbal region with 1.

Effect of Diffuse Luminance Flicker Light Stimulation on Total Retinal Blood Flow Assessed With Dual-Beam Bidirectional Doppler OCT.

Purpose: We assess the increase in total retinal blood flow (TRBF) induced by flicker stimulation of the human retina in vivo and investigate the flicker induced hyperemia by means of a vascular flow model of the retinal circulation to study neurovascular coupling (NC).

Methods: In six healthy subjects, TRBF was measured before and during stimulation with diffuse luminance flicker. Blood flow velocities in retinal vessels were measured via dual-beam bidirectional Doppler Fourier-domain optical coherence tomography (FD-OCT), retinal vessel diameters were assessed based on FD-OCT phase data.

Effect of different lubricant eye gels on tear film thickness as measured with ultrahigh-resolution optical coherence tomography.

Purpose: To compare the effect of a single drop of different lubricant eye gels on tear film thickness (TFT) as measured with ultrahigh-resolution optical coherence tomography (UHR-OCT) in patients with mild-to-moderate dry eye disease (DED).

Methods: The study followed a randomized, single-masked, observer-blinded parallel group design. Patients received a single dose of either unpreserved trehalose 3% + hyaluronic acid 0.

Effect of a Matrix Therapy Agent on Corneal Epithelial Healing After Standard Collagen Cross-linking in Patients With Keratoconus: A Randomized Clinical Trial.

Importance: Corneal abrasions are frequent after standard (epithelium-off [epi-off]) corneal collagen cross-linking (CXL) in patients with progressive keratoconus. A new matrix therapy agent (ReGeneraTing Agent [RGTA]) has been developed to promote corneal wound healing.

Objective: To assess the effect of the new type of matrix therapy agent on corneal wound healing after epi-off CXL in patients with keratoconus.

Super-resolved thickness maps of thin film phantoms and in vivo visualization of tear film lipid layer using OCT.

In optical coherence tomography (OCT), the axial resolution is directly linked to the coherence length of the employed light source. It is currently unclear if OCT allows measuring thicknesses below its axial resolution value. To investigate spectral-domain OCT imaging in the super-resolution regime, we derived a signal model and compared it with the experiment.

In vivo tear film thickness measurement and tear film dynamics visualization using spectral domain optical coherence tomography.

Dry eye syndrome is a highly prevalent disease of the ocular surface characterized by an instability of the tear film. Traditional methods used for the evaluation of tear film stability are invasive or show limited repeatability. Here we propose a new non-invasive fully automated approach to measure tear film thickness based on spectral domain optical coherence tomography and on an efficient delay estimator.

Tear film thickness after treatment with artificial tears in patients with moderate dry eye disease.

Purpose: This study was designed to investigate the effect of a single-drop instillation of different lacrimal substitutes on tear film thickness (TFT) assessed with optical coherence tomography in patients with mild to moderate dry eye disease.

Methods: The study was performed in a randomized, double-masked, controlled parallel group design. Patients received a single dose of either unpreserved trehalose 30 mg/mL and sodium hyaluronate 1.

Effect of hyaluronic acid on tear film thickness as assessed with ultra-high resolution optical coherence tomography.

Purpose: The aim of this study was to assess the effect of a single drop of hyaluronic acid on tear film thickness (TFT) in healthy subjects.

Methods: Sixteen healthy subjects (eight male/eight female) aged between 20 and 36 years were included in this randomized, double-masked placebo-controlled study. One eye received a single dose of hyaluronic acid (Olixia pure(®) ; Croma Pharma, Korneuburg, Austria) eye drops, and the fellow eye received physiologic saline solution as placebo control.