Review of En-Face Choroidal Imaging Using Spectral-Domain Optical Coherence Tomography

Investigations of choroidal vasculature have been of particular interest given choroidal vascular dysfunction are thought to be related with a number pathologic conditions such as central serous chorioretinopathy and various forms of AMD, including polypoidal choroidal vasculopathy. On the other hand, en face imaging of the choroid allows an exceptional alternative to histopathologic evaluation of the choroid, and can be used to quantify choroidal vascular structures. Our former study verified differences in the macular choroid in AMD and control patients previously noted on histopathologic studies. The use of phase-resolved approaches in larger population longitudinal studies reveal the sequence of RPE and choroidal changes in the pathogenesis of various AMD subtypes, which cannot be done using histopathology. Issues with lateral resolution of the OCT system in measuring choriocapillaris size could be solved by incorporating the axial dimension of the choriocapillaris into choriocapilaris diameter assessment (assuming the choriocapillaris are round in vivo), and by correcting for anisometric pixel resolution. Forthcoming studies are required to determine whether areas of choriocapillaris correlate with areas of RPD lesions

Review of En-Face Choroidal Imaging Using Spectral-Domain Optical Coherence Tomography

Investigations of choroidal vasculature have been of particular interest given choroidal vascular dysfunction are thought to be related with a number pathologic conditions such as central serous chorioretinopathy and various forms of AMD, including polypoidal choroidal vasculopathy. On the other hand, en face imaging of the choroid allows an exceptional alternative to histopathologic evaluation of the choroid, and can be used to quantify choroidal vascular structures. Our former study verified differences in the macular choroid in AMD and control patients previously noted on histopathologic studies. The use of phase-resolved approaches in larger population longitudinal studies reveal the sequence of RPE and choroidal changes in the pathogenesis of various AMD subtypes, which cannot be done using histopathology. Issues with lateral resolution of the OCT system in measuring choriocapillaris size could be solved by incorporating the axial dimension of the choriocapillaris into choriocapilaris diameter assessment (assuming the choriocapillaris are round in vivo), and by correcting for anisometric pixel resolution. Forthcoming studies are required to determine whether areas of choriocapillaris correlate with areas of RPD lesions

A combined method to quantify the retinal metabolic rate of oxygen using photoacoustic ophthalmoscopy and optical coherence tomography

Quantitatively determining physiological parameters at a microscopic level in the retina furthers the understanding of the molecular pathways of blinding diseases, such as diabetic retinopathy and glaucoma. An essential parameter, which has yet to be quantified noninvasively, is the retinal oxygen metabolic rate (rMRO(2)). Quantifying rMRO(2) is challenging because two parameters, the blood flow rate and hemoglobin oxygen saturation (sO(2)), must be measured together. We combined photoacoustic ophthalmoscopy (PAOM) with spectral domain-optical coherence tomography (SD-OCT) to tackle this challenge, in which PAOM measured the sO(2) and SD-OCT mapped the blood flow rate. We tested the integrated system on normal wild-type rats, in which the measured rMRO(2) was 297.86 +/- 70.23 nl/minute. This quantitative method may shed new light on both fundamental research and clinical care in ophthalmology in the future

Dark hypopyon in Streptococcus bovis endogenous endophthalmitis: clinicopathologic correlations

# The Author(s) 2010. This article is published with open access at Springerlink.com Purpose The aim of this report is to present a previously unreported causative organism associated with brownpigmented hypopyon in a patient with endophthalmitis. Methods This is a retrospective case report which includes clinicopathologic correlations. Results Vitreous cultures demonstrated Streptococcus bovis infection resulting in a brown-pigmented hypopyon, with uveal pigment found intra- and extracellularly on pathologic examination of the pupillary membrane. Conclusions S. bovis endophthalmitis may be a cause of dark hypopyon, especially in patients with a history of liver disease, and, when identified, warrants colonoscopy and cardiac workup. Keywords Streptococcus bovis. Brown/dark hypopyon

Recovery of macular pigment spectrum in vivo using hyperspectral image analysis

We investigated the feasibility of a novel method for hyperspectral mapping of macular pigment (MP) in vivo. Six healthy subjects were recruited for noninvasive imaging using a snapshot hyperspectral system. The three-dimensional full spatial-spectral data cube was analyzed using non-negative matrix factorization (NMF), wherein the data was decomposed to give spectral signatures and spatial distribution, in search for the MP absorbance spectrum. The NMF was initialized with the in vitro MP spectrum and rank 4 spectral signature decomposition was used to recover the MP spectrum and optical density in vivo. The recovered MP spectra showed two peaks in the blue spectrum, characteristic of MP, giving a detailed in vivo demonstration of these absorbance peaks. The peak MP optical densities ranged from 0.08 to 0.22 (mean 0.15+/−0.05) and became spatially negligible at diameters 1100 to 1760 μm (4 to 6 deg) in the normal subjects. This objective method was able to exploit prior knowledge (the in vitro MP spectrum) in order to extract an accurate in vivo spectral analysis and full MP spatial profile, while separating the MP spectra from other ocular absorbers. Snapshot hyperspectral imaging in combination with advanced mathematical analysis provides a simple cost-effective approach for MP mapping in vivo

Idiopathic multifocal choroiditis/punctate inner choroidopathy with acute photoreceptor loss or dysfunction out of proportion to clinically visible lesions.

PURPOSE To report acute/subacute vision loss and paracentral scotomata in patients with idiopathic multifocal choroiditis/punctate inner choroidopathy due to large zones of acute photoreceptor attenuation surrounding the chorioretinal lesions. METHODS Multimodal imaging case series. RESULTS Six women and 2 men were included (mean age, 31.5 ± 5.8 years). Vision ranged from 20/20-1 to hand motion (mean, 20/364). Spectral domain optical coherence tomography demonstrated extensive attenuation of the external limiting membrane, ellipsoid and interdigitation zones, adjacent to the visible multifocal choroiditis/punctate inner choroidopathy lesions. The corresponding areas were hyperautofluorescent on fundus autofluorescence and were associated with corresponding visual field defects. Full-field electroretinogram (available in three cases) showed markedly decreased cone/rod response, and multifocal electroretinogram revealed reduced amplitudes and increased implicit times in two cases. Three patients received no treatment, the remaining were treated with oral corticosteroids (n = 4), oral acyclovir/valacyclovir (n = 2), intravitreal/posterior subtenon triamcinolone acetate (n = 3), and anti-vascular endothelial growth factor (n = 2). Visual recovery occurred in only three cases of whom two were treated. Varying morphological recovery was found in six cases, associated with decrease in hyperautofluorescence on fundus autofluorescence. CONCLUSION Multifocal choroiditis/punctate inner choroidopathy can present with transient or permanent central photoreceptor attenuation/loss. This presentation is likely a variant of multifocal choroiditis/punctate inner choroidopathy with chorioretinal atrophy. Associated changes are best evaluated using multimodal imaging

Recovery of macular pigment spectrum in vivo using hyperspectral image analysis

We investigated the feasibility of a novel method for hyperspectral mapping of macular pigment (MP) in vivo. Six healthy subjects were recruited for noninvasive imaging using a snapshot hyperspectral system. The three-dimensional full spatial-spectral data cube was analyzed using non-negative matrix factorization (NMF), wherein the data was decomposed to give spectral signatures and spatial distribution, in search for the MP absorbance spectrum. The NMF was initialized with the in vitro MP spectrum and rank 4 spectral signature decomposition was used to recover the MP spectrum and optical density in vivo. The recovered MP spectra showed two peaks in the blue spectrum, characteristic of MP, giving a detailed in vivo demonstration of these absorbance peaks. The peak MP optical densities ranged from 0.08 to 0.22 (mean 0.15+/−0.05) and became spatially negligible at diameters 1100 to 1760 μm (4 to 6 deg) in the normal subjects. This objective method was able to exploit prior knowledge (the in vitro MP spectrum) in order to extract an accurate in vivo spectral analysis and full MP spatial profile, while separating the MP spectra from other ocular absorbers. Snapshot hyperspectral imaging in combination with advanced mathematical analysis provides a simple cost-effective approach for MP mapping in vivo

Long-Term Results from an Epiretinal Prosthesis to Restore Sight to the Blind

PurposeRetinitis pigmentosa (RP) is a group of inherited retinal degenerations leading to blindness due to photoreceptor loss. Retinitis pigmentosa is a rare disease, affecting only approximately 100 000 people in the United States. There is no cure and no approved medical therapy to slow or reverse RP. The purpose of this clinical trial was to evaluate the safety, reliability, and benefit of the Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc, Sylmar, CA) in restoring some visual function to subjects completely blind from RP. We report clinical trial results at 1 and 3 years after implantation.DesignThe study is a multicenter, single-arm, prospective clinical trial.ParticipantsThere were 30 subjects in 10 centers in the United States and Europe. Subjects served as their own controls, that is, implanted eye versus fellow eye, and system on versus system off (native residual vision).MethodsThe Argus II System was implanted on and in a single eye (typically the worse-seeing eye) of blind subjects. Subjects wore glasses mounted with a small camera and a video processor that converted images into stimulation patterns sent to the electrode array on the retina.Main Outcome MeasuresThe primary outcome measures were safety (the number, seriousness, and relatedness of adverse events) and visual function, as measured by 3 computer-based, objective tests.ResultsA total of 29 of 30 subjects had functioning Argus II Systems implants 3 years after implantation. Eleven subjects experienced a total of 23 serious device- or surgery-related adverse events. All were treated with standard ophthalmic care. As a group, subjects performed significantly better with the system on than off on all visual function tests and functional vision assessments.ConclusionsThe 3-year results of the Argus II trial support the long-term safety profile and benefit of the Argus II System for patients blind from RP. Earlier results from this trial were used to gain approval of the Argus II by the Food and Drug Administration and a CE mark in Europe. The Argus II System is the first and only retinal implant to have both approvals

An overview of optical coherence tomography angiography and the posterior pole

Optical coherence tomography angiography is a relatively new, noninvasive technology that has revolutionized imaging of the retinal and choroidal microvasculature. This technology is based on the detection of movement or changes that represent moving red cells in sequential optical coherence tomography scans. As with other established imaging technologies, it has unique benefits as well as certain disadvantages, which include a limited field of view and vulnerability to imaging artifacts. However, software and hardware improvements are continually evolving to mitigate these limitations. Optical coherence tomography angiography has been used to gain a better understanding of microvascular changes across a spectrum of ocular diseases including diabetic retinopathy, age-related macular degeneration, glaucoma, and retinal vein occlusions. In this article, we review algorithms and techniques commonly utilized in optical coherence tomography angiography systems and compare optical coherence tomography angiography to fluorescein angiography, the current gold standard for imaging the retinal vasculature. In addition, we provide an overview of important optical coherence tomography angiography findings in a variety of ocular diseases. Although the clinical role of this technology is still poorly defined, optical coherence tomography angiography has the potential to become an invaluable tool in the diagnosis and monitoring of vascular pathologies