Longitudinal Optical Coherence Tomography Research Articles

Intraobserver variability in optical coherence tomography

Purpose To assess the intraobserver variability of optical coherence tomography (OCT) in patients with clinically stable maculas. Design Retrospective, observational case series using a diagnostic instrument. Methods Retrospective study. setting. Private retina practice. patient population. Twenty-two eyes of 19 patients, each studied twice within 4 months. observation procedure. Optical coherence tomograph measurements of the macula obtained by two photographers. main outcome measures. Ordinary least products (OLP) and Bland-Altman analysis of OCT data. Results No fixed or proportional bias was detected in foveal zone thickness and total macular volume between measurements of either of the OCT operators. The coefficient of repeatability for foveal zone thickness was 37.0 μm for photographer 1 and 34.8 μm for photographer 2. The coefficient of repeatability for total macular volume was 0.29 mm 3 for photographer 1 and 0.10 mm 3 for photographer 2. Conclusion Foveal zone thickness and total macular volume measurements show low intraobserver variability when analyzed by OLP and Bland-Altman techniques. Bounds are given for foveal zone thickness and total macular volume for which longitudinal OCT measurements by the same operator can be considered to reflect natural history or intervention effects rather than intraobserver variability.

Correction of distortions in optical coherence tomography imaging of the eye

Optical coherence tomography (OCT) images are affected by artefacts. These artefacts are the result of different factors such as refraction, curvature of the intermediate layers up to the depth of interest and the scanning procedure. The effect of such errors is different, depending on the way the image is acquired, either en-face or longitudinal OCT. We quantify the distortions by evaluating a lateral and an axial error. These measure the lateral and axial deviations of each image point from the object point inside the tissue. We show that the axial distortion can be larger than the achievable depth resolution in modern OCT systems. We have investigated these errors in imaging different tissue: cornea and retina in vivo and an intraocular lens in vitro.

Three dimensional OCT images from retina and skin

We demonstrate the functionality of an en-face optical coherence tomography (OCT) system with images from the retina and skin. En-face images collected at different depths are subsequently used to reconstruct a 3D volume of the tissue. The reconstruction allows software inferred OCT longitudinal images at any transversal position in the stack. The position in depth in the stack before creating longitudinal OCT images is also adjustable, offering a valuable guidance tool for exploring the 3D volume of the tissue. This is illustrated by Quick time movies showing either depth or lateral exploration along one of two possible different directions in the stack of transversal OCT images. Sufficient accuracy of the volume rendered is obtained in 20 seconds when the system operates at 2 frames a second. The system, equipped with the 3D rendering feature acts as a valuable diagnostic tool allowing "peeling off" of transversal and longitudinal biologic material to investigate different internal features.

Care of the suddenly bereaved.

<h3>Abstract</h3> Age-related macular degeneration (AMD) is a common sight-threatening disease of older adults and treatment options are needed. Abnormalities of retinal pigment epithelium (RPE), supporting cells to photoreceptors and capillaries, are a hallmark. Clinical optical coherence tomography (OCT) imaging reveals hyperreflective foci (HRF) that confer risk for end-stage disease and are attributed to ectopic out-of-layer RPE. Using longitudinal OCT imaging of AMD patients, we demonstrate that the trajectory of one HRF form, RPE plume, parallels the retinal Henle fiber layer. Histology shows fully pigmented cells approaching and contacting retinal capillaries with RPE organelles dispersing along Müller glia columns. We used immunohistochemistry and a system of morphologic phenotypes to assess RPE functional repertoire in AMD. RPE corresponding to HRF loses immunoreactivity for retinoid processing proteins RPE65 and CRALBP, and gains immunoreactivity for immune cell markers CD68 and CD163. Müller glia retain CRALBP immunoreactivity. Gain- and loss-of-function for RPE starts with individual in-layer cells and extends to all abnormal phenotypes. Down-regulated RPE retinoid handling may contribute to slowed rod vision while Müller glia sustain cone vision. Ectopic RPE corresponding to HRF are emblematic of widespread transdifferentiation, motivating treatments targeting AMD pathology earlier than the initiation of atrophy. Data can propel new biomarkers and therapeutic strategies for AMD. <h3>One Sentence Summary</h3> In age-related macular degeneration retinal pigment epithelial cells transdifferentiate and migrate into the retina where they are clinically visible progression risk indicators.