Jakub J. Kaluzny

Spectral optical coherence tomography: a novel technique for cornea imaging.

Purpose: Spectral optical coherence tomography (SOCT) is a new, noninvasive, noncontact, high-resolution technique that provides cross-sectional images of the objects that weakly absorb and scatter light. SOCT, because of very short acquisition time and high sensitivity, is capable of providing tomograms of substantially better quality than the conventional OCT. The aim of this paper is to show the application of the SOCT to cross-sectional imaging of the cornea and its pathologies. Methods: Eleven eyes with different corneal pathologies were examined with a slit lamp and the use of a prototype SOCT instrument constructed in the Institute of Physics, Nicolaus Copernicus University, Toruń, Poland. Results: Our SOCT system provides high-resolution (4 μm axial, 10 μm transversal) tomograms composed of 3000-5000 A-scans with an acquisition time of 120-200 ms. The quality of the images is adequate for detailed cross-sectional evaluation of various corneal pathologies. Objective assessment of the localization, size, shape, and light-scattering properties of the changed tissue is possible. Corneal and epithelial thickness and the depth and width of lesions can be estimated. Conclusion: SOCT technique allows acquiring clinically valuable cross-sectional optical biopsy of the cornea and its pathologies.

Correlation of spectral optical coherence tomography with fluorescein and indocyanine green angiography in multiple evanescent white dot syndrome

Aims: To determine the spatial location of lesions in multiple evanescent white dot syndrome (MEWDS) with the aid of spectral optical coherence topography (SOCT), fluorescein angiography (FA) and indocyanine green angiography (ICGA). Methods: A novel method of three-dimensional SOCT data analysis called reflectivity maps was introduced. The reflectivity maps display the distribution of a back-reflected intensity taken only from individual retinal layers located at specific distance from the reference plane. Reflectivity maps of the inner retina, the junction between photoreceptor inner and outer segments (IS/OS), retinal pigment epithelium and choroid of the patient with MEWDS were created and correlated with FA and ICGA. Results: During the acute stage of MEWDS, the reflectivity map of the IS/OS junction displayed areas of reduced reflectivity that showed a strong positive correlation with hypofluorescent ICGA spots and a weaker but positive correlation with hyperfluorescent FA dots. SOCT examination did not reveal any pathological changes involving either any other retinal layers or the inner choroid. Conclusion: Disseminated disruptions of the IS/OS junction seen on SOCT cross-sectional images in the acute stage of MEWDS form the pattern of spots that can be correlated with those revealed by ICGA. This suggests that hypofluorescent ICGA spots indicate alternations in the retinal pigment epithelium–photoreceptor complex and do not represent inflammatory choroidal lesions.

Spectral optical coherence tomography: a new imaging technique in contact lens practice

Purpose:  Spectral optical coherence tomography (SOCT) is a new non‐invasive, non‐contact, high‐resolution technique, which provides cross‐sectional images of objects that weakly absorb and scatter light. The aim of this article is to demonstrate the application of SOCT to imaging of eyes fitted with contact lenses.

Analysis of posterior retinal layers in spectral optical coherence tomography images of the normal retina and retinal pathologies

We present a computationally efficient, semiautomated method for analysis of posterior retinal layers in three-dimensional (3-D) images obtained by spectral optical coherence tomography (SOCT). The method consists of two steps: segmentation of posterior retinal layers and analysis of their thickness and distance from an outer retinal contour (ORC), which is introduced to approximate the normal position of external interface of the healthy retinal pigment epithelium (RPE). The algorithm is shown to effectively segment posterior retina by classifying every pixel in the SOCT tomogram using the similarity of its surroundings to a reference set of model pixels from user-selected area(s). Operator intervention is required to assess the quality of segmentation. Thickness and distance maps from the segmented layers and their analysis are presented for healthy and pathological retinas.

Comparison of reflectivity maps and outer retinal topography in retinal disease by 3-D Fourier domain optical coherence tomography

We demonstrate and compare two image processing methods for visualization and analysis of three-dimensional optical coherence tomography (OCT) data acquired in eyes with different retinal pathologies. A method of retinal layer segmentation based on a multiple intensity thresholding algorithm was implemented in order to generate simultaneously outer retinal topography maps and reflectivity maps. We compare the applicability of the two methods to the diagnosis of retinal diseases and their progression. The data presented in this contribution were acquired with a high speed (25,000 A-scans/s), high resolution (4.5 microm) spectral OCT prototype instrument operating in the ophthalmology clinic.

A study of macular hole formation by serial spectral optical coherence tomography

Background:  The purpose of this paper is to evaluate changes of the vitreoretinal interface in fellow eyes of eyes with a macular hole and to study early stages of macular hole formation by spectral optical coherence tomography (SOCT).

Coherent noise-free ophthalmic imaging by spectral optical coherence tomography

In this contribution we examine a methodology to avoid parasitic cross-correlation terms in spectral optical coherence tomography (SOCT) images. The optimal conditions of optical power and exposure time are found theoretically and confirmed experimentally to ensure that parasitic images are hidden under the shot noise. An upper limit on useful exposures may then be estimated. In a case of SOCT imaging of the retina this limit is below the ANSI safety limit.

Drusen with Accompanying Fluid underneath the Sensory Retina

PURPOSE To investigate whether confluent drusen may be accompanied by fluid accumulation underneath the sensory retina and to determine if the detection of subretinal fluid on spectral-domain optical coherence tomography (OCT) in patients with coalescent drusen is indicative of choroidal neovascularization (CNV). DESIGN Prospective, noncomparative case series. PARTICIPANTS Seventy-four eyes of 57 patients with large, confluent drusen. METHODS The retinal structure of patients with coalescent drusen was studied by spectral-domain OCT. Optical coherence tomography reflectivity and outer retina topography maps were created and compared with fluorescein angiography (FA) and indocyanine green angiography (ICGA) images as well as with microperimetry. MAIN OUTCOME MEASURES Optical coherence tomography-derived retinal morphologic features. RESULTS What appears to be fluid beneath the sensory retina was found on spectral-domain OCT in 8 eyes of 7 patients. The outer retina topography maps demonstrated that fluid accumulates only in the concavity between clustering soft drusen, not on their outward slopes. The maps also revealed a reduced distance between the retinal pigment epithelium (RPE) and the photoreceptor inner/outer segment (IS/OS) junction over large drusen and tiny elevations of the IS/OS junction around drusen of all sizes. Microperimetry showed decreased retinal light sensitivity at the site of diminished distance between the RPE and the IS/OS junction. Seven eyes of 6 patients who were followed up were found to have no retinal changes other than confluent drusen along with subretinal fluid during the entire observational period (12-27 months). There was no evidence of CNV on FA or ICGA in any of the patients. CONCLUSIONS Large, confluent drusen may be accompanied by subretinal spaces that appear to be filled with fluid. Specific distribution of the fluid limited to the depression between adjacent drusen may indicate that the cluster of coalescent drusen produces mechanical strain to the outer retinal layers that locally pulls the sensory retina away from its normal position. Consequently, the appearance of fluid within subretinal compartment between coalescent drusen in OCT cross-sectional images may not be a reliable marker for the presence of CNV.

Tear meniscus measurement by spectral optical coherence tomography.

Purpose. To evaluate the use of lower tear meniscus measurements obtained with anterior segment Spectral Optical Coherence Tomography (OCT) in quantitative tear evaluation and diagnosis of dry eye syndrome. To verify sensitivity and specificity of different tear meniscus parameters in diagnosis of dry eye syndrome. Methods. A total of 111 eyes in consecutive patients, mean age 34.35 years (SD, 11.17), were enrolled. Each patient completed a standard Ocular Surface Disease Index questionnaire and general ophthalmic examination. Lower tear meniscus was evaluated using Spectral OCT (RTVue, Optovue) with cornea-anterior segment lens short. Three parameters were measured: tear meniscus cross-section area (TMA, mm2), tear meniscus height (TMH, mm), and tear meniscus depth (TMD, mm). Break-up time and Schirmer tests after instillation of topical anesthetic drops were also evaluated. Results. The highest correlation with Schirmer test results was found with TMA, followed by TMH and TMD. Respective Spearman correlation coefficient values were 0.54, 0.52, and 0.3, respectively. TMA, TMH, and TMD measurements were significantly lower in dry eyes than in controls. Sensitivity and specificity for dry eye diagnosis were 80.56% and 89.33% for TMH, 86.11% and 85.33% for TMA, and 77.78% and 52.7% for TMD, respectively. There was a significant negative correlation between both TMA and TMH and Ocular Surface Disease Index questionnaire scores. Conclusions. Lower tear meniscus parameters measured with Spectral OCT correlate well with the Schirmer test, break-up time, and subjective symptoms. TMA and TMH measurements have high sensitivity and specificity for the diagnosis of dry eye syndrome.

Analysis of the outer retina reconstructed by high-resolution, three-dimensional spectral domain optical coherence tomography.

BACKGROUND AND OBJECTIVE A retrospective cross-sectional study was conducted to demonstrate an analysis of an outer retinal layer reconstructed by the three-dimensional and high-speed spectral domain optical coherence tomography (SD-OCT) instrument. PATIENTS AND METHODS New measurement protocols for SD-OCT and methods of analysis and visualization of the individual segmented retinal layer reconstructed by SD-OCT were proposed. Three contour maps representing mutual distances between the basal part of the retinal pigment epithelium, the junction between the inner and outer segments of photoreceptors, and a reference contour representing the shape of a healthy retina were introduced. RESULTS The analysis of the outer retina was performed on pathological eyes. Three cases of central serous chorioretinopathy, age-related macular degeneration, and acute zonal occult outer retinopathy are demonstrated. CONCLUSION Three contour maps reconstructed for clinical cases demonstrate high variability of observed patterns depending on analyzed pathology. The authors believe this can help to present OCT data simultaneously in a more comprehensive and convenient way to assist in everyday clinical diagnosis.