Overlay of conventional angiographic and en-face OCT images enhances their interpretation

Enface vitreous OCT 'worm holes': A novel finding in a patient with diffuse unilateral subacute neuroretinitis (DUSN)

Purpose

To describe a case of diffuse unilateral subacute neuroretinitis (DUSN), a rare condition that causes progressive vision loss following infection by a nematode using enface vitreous imaging.

Observations

We present the clinical findings of a 37-year-old female, clinically diagnosed with DUSN after a non-invasive multimodal imaging approach that included MultiColor scanning laser imaging and enface vitreous OCT, which revealed the nematode body and lacunae created by worm migration, respectively.

Conclusion and importance

To our knowledge, this is the first reported case of lacunae visualized using enface vitreous optical coherence tomography (OCT), potentially marking the migration path of the nematode.

En-face optical coherence tomography in the diagnosis and management of age-related macular degeneration and polypoidal choroidal vasculopathy

Optical coherence tomography (OCT) is a noninvasive imaging modality providing high-resolution images of the central retina that has completely transformed the field of ophthalmology. While traditional OCT has produced longitudinal cross-sectional images, advancements in data processing have led to the development of en-face OCT, which produces transverse images of retinal and choroidal layers at any specified depth. This offers additional benefit on top of longitudinal cross-sections because it provides an extensive overview of pathological structures in a single image. The aim of this review was to discuss the utility of en-face OCT in the diagnosis and management of age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy (PCV). En-face imaging of the inner segment/outer segment junction of retinal photoreceptors has been shown to be a useful indicator of visual acuity and a predictor of the extent of progression of geographic atrophy. En-face OCT has also enabled high-resolution analysis and quantification of pathological structures such as reticular pseudodrusen (RPD) and choroidal neovascularization, which have the potential to become useful markers for disease monitoring. En-face Doppler OCT enables subtle changes in the choroidal vasculature to be detected in eyes with RPD and AMD, which has significantly advanced our understanding of their pathogenesis. En-face Doppler OCT has also been shown to be useful for detecting the polypoid lesions and branching vascular networks diagnostic of PCV. It may therefore serve as a noninvasive alternative to fluorescein and indocyanine green angiography for the diagnosis of PCV and other forms of the exudative macular disease.

ENHANCED DEPTH IMAGING FEATURES OF A CHOROIDAL MACROVESSEL

PURPOSE

To report a case of a choroidal macrovessel imaged using enhanced depth imaging spectral domain optical coherence tomography (EDI-OCT) and describe the choroidal features.

METHODS

CASE REPORT

a 42-year-old man presented with metamorphopsia. Multimodal imaging, including color fundus photography, near-infrared reflectance, and EDI-OCT was used to describe a choroidal macrovessel.

RESULTS

Initial ophthalmic examination revealed a serpentine-shaped subretinal pattern deep to the retina near the fovea. When the color image was subjected to a red filter, a large diameter vessel could be seen coursing from the fovea to the temporal macula. EDI-OCT of the choroidal macrovessel revealed a thickened choroid and mild deformation of both the ellipsoid zone and the choroidal-scleral junction. En face spectral domain optical coherence tomography at the level of the choroid demonstrated the anomalous vessel.

CONCLUSION

EDI-OCT and en face optical coherence tomography, used in conjunction with other imaging modalities, can be used to demonstrate the presence and pattern of a choroidal macrovessel. A thickened choroid and overlying outer retinal indentation was observed in association of the choroidal macrovessel. These imaging tools can help distinguish this condition from other diagnoses with a similar appearance, such as ophthalmomyiasis.

En face OCT in Stargardt disease

PURPOSE

To evaluate the structural features of the macular region by enface OCT imaging in patients with clinical diagnosis of Stargardt disease, confirmed by the detection of ABCA4 mutations.

METHODS

Thirty-two STGD patients were included in the study for a total of 64 eyes. All patients received a comprehensive ophthalmological examination, color fundus photography, fundus auto-fluorescence imaging and OCT. Five OCT scans were considered: ILM and RPE scans (both automatically obtained from the instrument), above-RPE slab, photoreceptor slab and sub-RPE slab (these last three manually obtained).

RESULTS

ILM scans showed evident radial folds on the retinal surface in 8/64 eyes (12.5 %). In 6 of the 7 patients, these vitreo-retinal interface abnormalities were unilateral. The photoreceptor slab showed some macular alterations ranging from dis-homogeneous, hypo-reflective abnormalities (7/64 eyes, 11 %) to a homogeneous, well-defined, roundish, hypo-reflective area (17/64 eyes, 27 %) in all the eyes. The sub-RPE slab showed a centrally evident, hyper-reflective abnormality in 58/64 eyes (90.6 %). Superimposing the sub-RPE slab over the images corresponding to the photoreceptor slab, the area of the photoreceptor atrophy sharply exceeded that of the RPE atrophy (44/46 eyes, 96 %).

CONCLUSION

Enface OCT proved to be a clinically useful tool for the management of STGD patients, illustrating in vivo the structural abnormalities of the different retinal layers.

En-face optical coherence tomography as a novel tool for exploring the ocular surface: a pilot comparative study to conventional B-scans and in vivo confocal microscopy

PURPOSE

To explore the potential of spectral-domain optical coherence tomography (SD-OCT) using the en-face technology for the imaging of ocular surface diseases and to correlate the findings with in vivo confocal microscopy (IVCM) images.

PATIENTS AND METHODS

113 eyes of 75 subjects with various ocular surface diseases were investigated with the RTVue(®) anterior-segment en face OCT. En face OCT images were compared to B-scan OCT and IVCM images.

RESULTS

Patients with corneal dystrophies, corneal deposits, keratitis, pterygium, conjunctivochalasis, or ocular surface squamous neoplasia and patients who underwent lamellar corneal surgeries were included. En-face OCT images showed ocular surface tissue changes that were not discernible using conventional B-scan OCT. Nevertheless, there was a good correlation with IVCM analysis. Compared with IVCM, the major advantages of en-face OCT included easy operation and rapid image acquisition, with minimal operator experience required. In addition, the non-contact method avoided patient discomfort and external pressure on the globe, which was especially useful in patients with corneal dystrophies, ulcers, or corneal abscesses. Although the resolution of en-face OCT was lower than that of IVCM, it allowed useful overall visualization of corneal lesions due to the larger areas analyzed.

CONCLUSION

En-face SD-OCT is a novel, valuable tool to assess a wide variety of ocular surface diseases. It can provide additional information and new insight into different ocular surface conditions with no corneal contact.

Correlation of pathologic features in spectral domain optical coherence tomography with conventional retinal studies

PURPOSE

To delineate pathologic changes in retinal cross sections obtained with spectral (Fourier) domain optical coherence tomography (SDOCT), so that the findings are maintained when collapsed into a two-dimensional fundus image for comparison with conventional retinal studies.

METHODS

SDOCT of the posterior pole of 12 eyes (5 with neovascular age-related macular degeneration [AMD]; 7 with nonneovascular AMD) produced three-dimensional stacks of scans. Location of pathologic features was delineated with color markings in each scan before the stack was collapsed along the depth axis. This en face image contained retinal vessel shadowing and preserved color markings of delineated pathologic features relative to the vessel pattern and was superimposed onto conventional studies.

RESULTS

For patients with neovascular AMD, location and extent of choroidal neovascularization, macular edema, and subretinal fluid were visible on the two-dimensional summed images and, in some cases, involved sites not suspected with conventional imaging. For patients with nonneovascular AMD, the location of drusen and geographic atrophy were correlated with autofluorescence images. For one eye with drusen and three eyes with neovascular AMD, presence or extent of subretinal fluid identified by SDOCT was not visible using other imaging methods.

CONCLUSIONS

In this pilot AMD study, pathologic features within SDOCT scans were transferred into two-dimensional en face projections, enabling researchers to correlate lateral extent of pathologic features from SDOCT with conventional studies. This integration of SDOCT with other retinal studies is promising and will be useful to study the relationship between local OCT morphology and other parameters of retinal disease or function.

Neue Perspektiven in der Diagnostik

BACKGROUND

Recent advances in optical coherence tomography (OCT) have made it possible to increase resolution and scan velocities so that even greater central areas of the retina can be scanned. The aim of this study is to describe the possibilities offered by this new technology for age-related macular degeneration.

MATERIAL AND METHODS

The study included 20 patients with confirmed active choroidal neovascularization (CNV) as well as pigment epithelial detachment (PED). Three-dimensional imaging was performed with a high-definition raster scanning OCT system (HD-OCT) with an axial resolution of 6 microm and a scan velocity of up to 20,000 A-scans/s. The scanned area measured 6 x 6 mm with a depth of 2 mm. Two-dimensional imaging was carried out with a StratusOCT (Carl Zeiss Meditec).

RESULTS

Comparison of the individual slices showed improved identification of intra- and subretinal structures with the HD-OCT. Demarcation of pathological changes in individual retinal layers is possible with the HD-OCT. Summation images permit accurate localization of a scan. Topographic and volumetric evaluations enable analysis of individual compartments in the entire scanned area and are suitable for monitoring treatment of CNV with anti-VEGF therapy. The raster method decreases the dependence on exploratory methods that have been necessary until now to generate retinal thickness maps.

CONCLUSIONS

This report presents initial experience in using a raster scanning HD-OCT system in patients with neovascular age-related macular degeneration and describes new evaluation functions that aid in obtaining more precise assessment of treatment effect and its impact on the retinal ultrastructure. The results of this study clearly show that development of high-resolution OCT systems in conjunction with development of novel treatment options for exudative diseases offers promising perspectives.

Recent developments in optical coherence tomography for imaging the retina

Optical coherence tomography (OCT) was introduced in ophthalmology a decade ago. Within a few years in vivo imaging of the healthy retina and optic nerve head and of retinal diseases was a fact. In particular the ease with which these images can be acquired considerably changed the diagnostic strategy used by ophthalmologists. The OCT technique currently available in clinical practice is referred to as time-domain OCT, because the depth information of the retina is acquired as a sequence of samples, over time. This can be done either in longitudinal cross-sections perpendicular to, or in the coronal plane parallel to the retinal surface. Only recently, major advances have been made as to image resolution with the introduction of ultrahigh resolution OCT and in imaging speed, signal-to-noise ratio and sensitivity with the introduction of spectral-domain OCT. Functional OCT is the next frontier in OCT imaging. For example, polarization-sensitive OCT uses the birefringent characteristics of the retinal nerve fibre layer to better assess its thickness. Blood flow information from retinal vessels as well as the oxygenation state of retinal tissue can be extracted from the OCT signal. Very promising are the developments in contrast-enhanced molecular optical imaging, for example with the use of scattering tuneable nanoparticles targeted at specific tissue or cell structures. This review will provide an overview of these most recent developments in the field of OCT imaging focussing on applications for the retina.

Birdshot chorioretinopathy

PURPOSE OF REVIEW

Birdshot chorioretinopathy is the disease with the strongest link to a human leukocyte antigen class I allele. Current research aims at understanding its immunogenetic mechanisms, focusing on the A29 allele, its subtypes, and on other loci of the human leukocyte antigen region. Research criteria can be applied to define birdshot chorioretinopathy. Its heterogeneous presentations and its multiple consequences on visual function are being delineated.

RECENT FINDINGS

HLA-A*2902 is the most frequent subtype in Caucasians and in patients with birdshot chorioretinopathy. The condition has also been observed, however, in a few HLA-A*2901 Caucasian patients, but remains absent or extremely rare in Asia where HLA-A*2901 is the most prevalent subtype. Birdshot chorioretinopathy affects visual acuity, color vision, contrast sensitivity or visual field and pigmentation of birdshot spots could be a marker of disease severity. Electroretinography has been used to monitor the course of the disease; abnormalities may be due to altered outer retinal function or to inner retinal dysfunction. Various therapeutic regimens have been tested and most studies confirm that corticosteroids alone are not a sustainable treatment for patients with birdshot chorioretinopathy.

SUMMARY

Progress has been made in understanding the spectrum of manifestations of birdshot chorioretinopathy. The disease remains of unknown cause and many decisions regarding the management of patients are still empirical.

Evaluation of central serous retinopathy with en face optical coherence tomography

BACKGROUND

The diagnosis of idiopathic central serous retinopathy (CSR) is usually based on biomicroscopy and fluorescein angiography (FA). The optical coherence tomography (OCT) ophthalmoscope produces en face OCT scans (OCT C-scans) and provides additional information not readily available by conventional imaging techniques. The authors describe the characteristic features observed in patients with a clinical diagnosis of CSR using the OCT ophthalmoscope.

METHODS

38 eyes with a clinical diagnosis of CSR, seen at the Academic Medical Centre (Amsterdam, Netherlands) and the New York Eye and Ear Infirmary (New York, USA) between August 2002 and March 2004, were evaluated with standard digital FA and scanned with the OCT ophthalmoscope.

RESULTS

Nine of 38 eyes had no serous neurosensory detachment (inactive CSR) when scanned with the OCT ophthalmoscope. Characteristics for active CSR (n=29) were large neurosensory detachment (23/29), subretinal hyper-reflective depoits (20/29), and pigment epithelial detachment (15/29). One third of the patients, either active or inactive, had multiple small pigment epithelial detachments located both within and outside the neurosensory detachment.

CONCLUSION

The OCT ophthalmoscope provides complementary morphological information on patients with CSR. The presence of more diffuse retinal pigment epithelium (RPE) changes lends further support to the concept that CSR is a diffuse rather than localised RPE anomaly.