Temporal change of retinal nerve fiber layer reflectance speckle in normal and hypertensive retinas.

This study investigated temporal change of retinal nerve fiber layer (RNFL) reflectance speckle in retinas with ocular hypertensive (OHT) damage and in control retinas from untreated eyes. Experimental OHT damage to rat retinas was induced by laser photocoagulation of the trabecular meshwork. A series of 660 nm reflectance images was collected from isolated retinas at 10-sec intervals.

Reflectance Spectrum and Birefringence of the Retinal Nerve Fiber Layer With Hypertensive Damage of Axonal Cytoskeleton.

Purpose: Glaucoma damages the retinal nerve fiber layer (RNFL). This study used precise multimodal image registration to investigate the changes of the RNFL reflectance spectrum and birefringence in nerve fiber bundles with different degrees of axonal damage.

Methods: The reflectance spectrum of individual nerve fiber bundles in normal rats and rats with experimental glaucoma was measured from 400 to 830 nm and their birefringence was measured at 500 nm.

Cytoskeletal Alteration and Change of Retinal Nerve Fiber Layer Birefringence in Hypertensive Retina.

Purpose: Glaucoma damages the retinal nerve fiber layer (RNFL). Both RNFL thickness and retardance can be used to assess the damage, but birefringence, the ratio of retardance to thickness, is a property of the tissue itself. This study investigated the relationship between axonal cytoskeleton and RNFL birefringence in retinas with hypertensive damage.

Retinal nerve fiber layer reflectometry must consider directional reflectance.

Recent studies reveal that measurements of retinal nerve fiber layer (RNFL) reflectance provide more sensitive detection of glaucomatous damage than RNFL thickness, but most do not consider directional reflectance of the RNFL, an important source of variability. This study quantitatively compared RNFL directional reflectance, represented by an angular spread function (ASF), measured at different scattering angles, different wavelengths and different distances from the optic nerve head (ONH) and for bundles with different thicknesses (T). An ASF was characterized by its amplitude (A) and width (W).

Reflectance speckle of retinal nerve fiber layer reveals axonal activity.

Purpose: This study investigated the retinal nerve fiber layer (RNFL) reflectance speckle and tested the hypothesis that temporal change of RNFL speckle reveals axonal dynamic activity.

Methods: RNFL reflectance speckle of isolated rat retinas was studied with monochromatic illumination. A series of reflectance images was collected every 5 seconds for approximately 15 minutes.

The shape of the ganglion cell plus inner plexiform layers of the normal human macula.

Purpose: To use surfaces generated by two-dimensional penalized splines (2D P-splines) to characterize the shape of the macular ganglion cell plus inner plexiform layers (GCL+IPL) in a group of normal humans.

Methods: Macular images of the right eyes of 23 normal subjects ranging in age from 18 to 75 years were obtained with spectral-domain optical coherence tomography (SD-OCT). The thickness of GCL+IPL was determined by manual segmentation, areas with blood vessels were removed, and the resulting maps were fit by smooth surfaces in polar coordinates centered on the fovea.

Wavelength-dependent change of retinal nerve fiber layer reflectance in glaucomatous retinas.

Purpose: Retinal nerve fiber layer (RNFL) reflectance is often used in optical methods for RNFL assessment in clinical diagnosis of glaucoma, yet little is known about the reflectance property of the RNFL under the development of glaucoma. This study measured the changes in RNFL reflectance spectra that occurred in retinal nerve fiber bundles with different degrees of glaucomatous damage.

Methods: A rat model of glaucoma with laser photocoagulation of trabecular meshwork was used.

Variance reduction in a dataset of normal macular ganglion cell plus inner plexiform layer thickness maps with application to glaucoma diagnosis.

Purpose: To examine the similarities and differences in the shape of the macular ganglion cell plus inner plexiform layers (GCL+IPL) in a healthy human population, and seek methods to reduce population variance and improve discriminating power.

Methods: Macular images of the right eyes of 23 healthy subjects were obtained with spectral domain optical coherence tomography. The thickness of GCL+IPL was determined by manual segmentation, areas with blood vessels were removed, and the resulting maps were fit by smooth surfaces in polar coordinates centered on the fovea.

Dual-band spectral-domain optical coherence tomography for in vivo imaging the spectral contrasts of the retinal nerve fiber layer.

The ultimate goal of the study is to provide an imaging tool to detect the earliest signs of glaucoma before clinically visible damage occurs to the retinal nerve fiber layer (RNFL). Studies have shown that the optical reflectance of the damaged RNFL at short wavelength (<560 nm) is reduced much more than that at long wavelength, which provides spectral contrast for imaging the earliest damage to the RNFL. To image the spectral contrast we built a dual-band spectral-domain optical coherence tomography (SD-OCT) centered at 808 nm (NIR) and 415 nm (VIS).

Reflectance decreases before thickness changes in the retinal nerve fiber layer in glaucomatous retinas.

Purpose: Glaucoma damages the retinal never fiber layer (RNFL). RNFL thickness, measured with optical coherence tomography (OCT), is often used in clinical assessment of the damage. In this study the relation between the RNFL reflectance and thickness at early stages of glaucoma was investigated.

Registration of OCT fundus images with color fundus photographs based on blood vessel ridges.

This paper proposes an algorithm to register OCT fundus images (OFIs) with color fundus photographs (CFPs). This makes it possible to correlate retinal features across the different imaging modalities. Blood vessel ridges are taken as features for registration.

Revealing Henle's fiber layer using spectral domain optical coherence tomography.

Purpose: Spectral domain optical coherence tomography (SD-OCT) uses infrared light to visualize the reflectivity of structures of differing optical properties within the retina. Despite their presence on histologic studies, traditionally acquired SD-OCT images are unable to delineate the axons of photoreceptor nuclei, Henle's fiber layer (HFL). The authors present a new method to reliably identify HFL by varying the entry position of the SD-OCT beam through the pupil.

Retinal structure of birds of prey revealed by ultra-high resolution spectral-domain optical coherence tomography.

Purpose: To reveal three-dimensional (3-D) information about the retinal structures of birds of prey in vivo.

Methods: An ultra-high resolution spectral-domain optical coherence tomography (SD-OCT) system was built for in vivo imaging of retinas of birds of prey. The calibrated imaging depth and axial resolution of the system were 3.

Characteristics of optic nerve head drusen on optical coherence tomography images.

Background And Objective: To describe the characteristics of optic nerve head drusen in optical coherence tomography (OCT) images.

Patients And Methods: Cross-sectional images of the optic nerve were obtained in seven patients with optic nerve head drusen with Stratus and spectral-domain OCT (Carl Zeiss Meditec, Dublin, CA). These were compared to optic disc photographs, autofluorescence, and echography images.

Altered F-actin distribution in retinal nerve fiber layer of a rat model of glaucoma.

Glaucoma damages the retinal nerve fiber layer (RNFL). The purpose of this study was to investigate the distribution in RNFL of axonal F-actin, a cytoskeletal component, under the development of glaucoma. Intraocular hypertension was induced in a rat model by translimbal laser photocoagulation of the trabecular meshwork.

Spectral domain optical coherence tomographic imaging of geographic atrophy.

Background And Objective: To compare images of geographic atrophy (GA) obtained using spectral domain optical coherence tomography (SD-OCT) with images obtained using fundus autofluorescence (FAF).

Patients And Methods: Five eyes from patients with dry AMD were imaged using SD-OCT and FAF, and the size and shape of the GA were compared.

Results: GA appears bright on SD-OCT compared with the surrounding areas with an intact retinal pigment epithelium because of increased reflectivity from the underlying choroid.

Spectral domain optical coherence tomography for proliferative diabetic retinopathy with subhyaloid hemorrhage.

A prototype 6-microm axial resolution spectral domain optical coherence tomography (SD-OCT) device was used to image the retina of a patient with uncontrolled diabetes mellitus who had proliferative diabetic retinopathy with subhyaloid hemorrhage. A raster scan pattern with 128 B-scans covering a 6 X 6 X 2-mm volume of the retina was obtained. SD-OCT showed the presence of blood localized between the internal limiting membrane and the posterior hyaloid face and allowed visualization of the cross sectional retinal architecture and the vitreoretinal interface at different horizontal levels that could be registered with the color fundus photograph.

Macular thickness measurements in normal eyes using spectral domain optical coherence tomography.

Background And Objective: Knowledge of the macular thickness in a normal population is important for the evaluation of pathological macular change. The purpose of this study was to define and measure macular thickness in normal eyes using spectral domain optical coherence tomography (OCT).

Patients And Methods: Fifty eyes from 50 normal subjects (29 men and 21 women, aged 22 to 68 years) were scanned with a prototype Cirrus HD-OCT system (5 microm axial resolution) (Carl Zeiss Meditec, Inc.

Calibration of fundus images using spectral domain optical coherence tomography.

Background And Objective: Measurements performed on fundus images using current software are not accurate. Accurate measurements can be obtained only by calibrating a fundus camera using measurements between fixed retinal landmarks, such as the dimensions of the optic nerve, or by relying on a calibrated model eye provided by a reading center. However, calibrated spectral domain OCT (SD-OCT) could offer a convenient alternative method for the calibration of any fundus image.

Corneal birefringence mapped by scanning laser polarimetry.

Corneal birefringence affects polarization-sensitive optical measurements of the eye. Recent literature supports the idea that corneal birefringence is biaxial, although with some disagreement among reports and without considering corneas with very low values of central retardance. This study measured corneal retardation in eyes with a wide range of central corneal retardance by means of scanning laser polarimetry (GDx-VCC, Carl Zeiss Meditec, Inc.

Three-dimensional spectral-domain optical coherence tomography images of the retina in the presence of epiretinal membranes.

Purpose: To study the inner surface of the retina in the presence of epiretinal membranes (ERMs) using a prototype spectral-domain optical coherence tomography (SD-OCT) device.

Design: Small case series, performed in the Department of Ophthalmology, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami, from August 2005 through December 2006.

Method: An 8-microm axial-resolution SD-OCT instrument was used to scan the eyes of patients diagnosed with ERM.

Documentation by spectral domain OCT of spontaneous closure of idiopathic macular holes.

An observational case series using an 8-microm axial resolution prototype spectral domain optical coherence tomography (OCT) system was performed in two patients with idiopathic macular holes. Spontaneous closure and visual acuity improvement occurred in both patients. Useful information about morphology and vitreoretinal relationship of the holes was provided by spectral domain OCT.

Documentation of optic nerve pit with macular schisis-like cavity by spectral domain OCT.

The authors report using spectral domain optical coherence tomography (OCT) to observe a patient with an optic nerve pit and macular schisis-like spaces. An 8-microm axial resolution prototype spectral domain OCT and stereo fundus photography were used to observe the patient. A macular schisis-like cavity was present at baseline and additional cystic changes developed in the nerve fiber layer over a period of 16 months; however, the visual acuity remained stable at 20/20.

Microtubule contribution to the reflectance of the retinal nerve fiber layer.

Purpose: The reflectance of the retinal nerve fiber layer (RNFL) arises from light scattering by cylindrical structures oriented parallel to ganglion cell axons. In amphibian retinas, at 440 nm, microtubules (MTs) contribute about one half of RNFL reflectance. In rodent retinas, MTs are the only structure contributing to RNFL birefringence.

Quantifying retinal nerve fiber layer thickness in whole-mounted retina.

In order to relate optical measurement of the retinal nerve fiber layer (RNFL) to the underlying structure, one must have accurate values for RNFL thickness at the locations measured optically. The purpose of this study was to develop a method for measuring RNFL thickness at any location on retinal tissue previously studied by other optical imaging. The method developed used confocal laser scanning microscopy (cLSM) to provide both en face and cross-sectional images of a whole-mounted retina.