#retinal disorders

[retinahealthcenter]

Understanding Retinal Disorders Through Advanced Imaging and Diagnosis

When it comes to eye health, the retina plays a crucial role. It’s the part of the eye responsible for converting light into signals that th

Explore retinal disorders, their symptoms, and treatment options like advanced imaging techniques and retinal detachment treatment. Learn the importance of early diagnosis, various causes, and prevention tips.

Consult a retina specialist in Fort Myers for expert guidance on protecting your vision and eye health. 

[ijcmcrjournal]

Optical Coherence Tomography Angiography in Retinal Disorders by Richa R

Abstract

Optical coherence tomography angiography (OCTA) is a new non-invasive imaging technique that employs motion contrast imaging. It generates high-resolution volumetric blood flow information through angiographic images. Fluorescein and indocyanine green angiography are still the gold standard angiographic procedures but OCTA is slowly becoming an essential clinical investigation since the past few years. This article will cover the principle and clinical applications of OCTA.

Keywords: OCTA; Retinal Disorders; CNVM

Introduction

Optical coherence tomography (OCT) is a non-invasive, depth-resolved imaging technique based on low-coherence interferometry. Optical coherence tomography generates structural images of the anatomy of the eye based on back-reflected light [1].Coherence tomography angiography (OCTA) is a new technology which provides high-sensitivity, high-resolution and in depth visualization of retinal and ocular microstructures without contact. It is based on the en-face OCT technique that reconstruct scans performed multiple times in a vertical plane into a single image shown on a horizontal plane [2].

OCTA compares the decorrelation signal which are the differences in the backscattered OCT signal intensity or amplitude, between sequential OCT b-scans taken precisely at the same cross-section in order to construct a blood flow map. Axial bulk motion from patient movement is eliminated so areas of motion between repeated OCT b-scans strictly represent erythrocyte movement in retinal blood vessels [3-6].

Comparing OCTA with Conventional Angiography Methods

Fluorescein angiography (FA) and indocyanine green angiography (ICGA) both are invasive test that require administration of dye intravenously and imaging up to 10–30 minutes [7-11]. They provide two-dimensional images that allow a wide field view of the dynamic visualization of the blood flow. Therefore, patterns of dye leakage, staining and pooling can be appreciated and are well-documented in the literature [12].

FA is typically used to visualize the retinal vasculature, while ICGA is used to see the choroidal vasculature. While useful, they require injection of an intravenous dye, which is time consuming and can have adverse side effects, like nausea, vomiting, headache, hypotension, hypersensitivity reaction and in rare cases cardiac arrest [13-14]. In addition, dye staining and leakage, blur the boundaries of capillary dropout or neovascularization. These imaging modalities being two-dimensional, are not depth resolved. As a result, segmentation of different ocular layers is not routinely possible with FA or ICGA. Therefore, identification of the axial location of any pathology requires an understanding of patterns of blockage and leakage of the dye [12]. OCTA offers a benefit over the conventional imaging techniques as being non-invasive, less time consuming and segmentation of different layers thus providing the axial location of the pathology. Table 1 shows the difference between FA and OCTA.

Principle of OCT-A

OCT-A technology uses laser light reflectance of the surface of moving red blood cells to accurately depict vessels through different segmented areas of the eye, thus eliminating the need for intravascular dyes [15]. OCT-A is based on the principle of diffractive particle movement detection of the red blood cells, on sequential OCT B-scans performed multiple times at the same retina location, therefore showing the presence of blood vessels [2]. OCT-A requires higher imaging speeds than most currently available devices are able to provide for a sufficiently dense volume.

To construct the image of the retinal microvascularization, each B-scan of the examination area is repeated several times consecutively. The contrast comparisons on consecutive B-scans at the same location reveal some areas with a constant contrast over time and some areas with a contrast change. The temporal change in the contrast in a specific area is attributed to the movement of erythrocytes, which therefore indicates the location of the blood vessels. After correcting for the gross eye movements (by either using motion tracking or software processing), the only differences remaining between OCT images of the same location in the eye would represent blood flow.

Longer wavelengths have a deeper tissue penetrance, with a slightly lower axial resolution. Light is emitted either through a spectral domain OCT (SD-OCT), with a wavelength of near 800 nm or a swept-source OCT (SS-OCT), which utilizes a longer wavelength, close to 1050 nm. OCT-A employs two methods for motion detection which are amplitude decorrelation or phase variance. The former detects differences in amplitude between two different OCT B-scans. Phase variance is related to the emitted light wave properties, and the variation of phase when it intercepts a moving objects. To improve visualization and reduce background noise from normal small eye movements, two averaging methods which are split spectrum amplitude decorrelation technique (SSADA)  and volume averaging were developed [16,17]. These OCT-A algorithms produce an image (3mm2 to 12mm2) that is by standard segmented into four zones: the superficial capillary plexus, the deep capillary plexus, the outer retina and the choriocapillaris.

Clinical Applications

OCTA of Normal Eyes

The most widely available prototype OCTA system is the AngioVue software of the RTVue XR Avanti spectral-domain OCT (SD-OCT) (Optovue, Inc, Fremont, CA). The device uses a SSADA algorithm and obtains volumetric scans of 304 × 304 A-scans at 70,000 A-scans per second in approximately 3.0 seconds. The software offers an option of 2 × 2 mm, 3 × 3 mm, 6 × 6 mm, and 8 × 8 mm OCT angiograms and automated segmentation of these full-thickness retinal scans into the superficial and deep inner retinal vascular plexuses, outer retina, and choriocapillaris. The superficial inner retina contains a projection of the vasculature of the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL). The deep inner retina segmentation shows a composite of the vascular plexuses at the border of the inner plexiform layer (IPL) and inner nuclear layer (INL) and the border of the INL and outer plexiform layer (OPL) (Figure 1).

OCTA in Eyes with Pathology

As a non-invasive, safe and fast procedure to assess the chorioretinal microvasculature, OCT-A has increasingly been used in the diagnosis and management of retinal diseases such as diabetic retinopathy, dry and wet age related macular degeneration, vascular occlusions, macular telangiectasia and choroidal neovascular membranes secondary to various pathologies like myopia, central serous chorioretinopathy etc. It is an extraordinary tool for visualizing abnormal choroidal vasculature and it also provides information on the plane in which these choroidal neovascularization (CNV) develop: below retinal pigment epithelium (RPE) (Type 1 CNV), above RPE (Type 2 CNV) and intraretinal (Type 3 CNV). It helps in determining the location of CNV, along with its morphology and response to Anti-Vascular Endothelial Growth Factor (anti-VEGF) therapy. Visualizing a neovascular network does not necessarily mean neovascular activity. Indeed, new vessels may be present but maybe inactive either spontaneously (quiescent occult neovascularization) or after suitable treatment. Thus, the analysis of OCTA should always include an analysis of a more conventional OCT with B-scans. Comparing both examinations allows an assessment of the anatomical location of new vessels and their activity, evidenced by exudative manifestations.

OCTA finds its utility in vascular disorders of retina such as Macular Telangiectasia, Retinal Vascular Occlusion and Diabetic Retinopathy. It delineates the superficial and deep retinal capillary plexus clearly and also can precisely demarcate the vessels surrounding the foveal avascular zone (FAZ), whereas FA only delineates the superficial vascular plexus with blurry FAZ due to perifoveal leakage. Neovascularisation of disc (NVD) and neovascularization elsewhere (NVE) in Diabetic Retinopathy can be detected by viewing the inner retina/optic nerve surface at the most superficial level [2]. Figure 2 shows the OCTA images of different retinal pathologies.

Limitations & Artefacts

As a light source dependent device, some limitations arise for OCTA technology. Projection artifact is inevitable and is related to the light which traverses the blood vessels and is reflected back by deeper layers (e.g. pigment retinal epithelium), which will appear in the final image with a similar vascular pattern as the overlying vessels [18].

Media opacities can lead to shadowing artifact and signal attenuation [6]. Also, abnormalities in the deeper vessels of the retina may be obscured by superficial blood vessels [17].

OCTA examination is extremely motion-sensitive and requires patient cooperation, which may be difficult in visually impaired [19].

Automated segmentation of structurally abnormal retinas is also a limitation of OCTA. In cases of PED, one should not relay on automated segmentation rather  manually edit layers for the correct interpretation [20].

Imaging of the peripheral retina is another limitation of OCTA [19].

Lastly, as OCTA detects "motion", and thus very low amounts of blood flow near the device threshold may be left undetected [21].

Conclusion

OCTA is a new technology that has great potential for use in the clinical setting. Advantages of OCTA over the current gold standard angiographic procedures include being non-invasive, less time consuming, determines exact size and location of the pathology and visualizes both the retinal and choroidal vasculature. Disadvantages of OCTA include inability to view leakage of neovascular membranes, limited field of view, increased potential for artifacts and inability to detect blood flow below the lowest threshold flow. More studies are needed to determine OCTA’s utility in the clinical setting and to determine if this technology may offer a non-invasive option for visualizing the retinal vasculature in detail.

For more information about Journal : https://ijclinmedcasereports.com/

https://ijclinmedcasereports.com/pdf/IJCMCR-SR-00054.pdf https://ijclinmedcasereports.com/ijcmcr-sr-id-00054/

[mayuryeole28-blog]

Diabetic Retinopathy Market size in 2015 worth USD 6.5 billion is forecast to grow at 6.9% CAGR from 2016 to 2023; anti-VEGF held 90% market share in 2015.

Rising diabetes prevalence and increasing world geriatric population are major driving forces for global diabetic retinopathy market growth. Further growth enhancing factors are government initiatives, abundant R&D activities, and skill set enhancement of healthcare providers.Request for sample @ http://bit.ly/2dWsJ80

[jueekate-blog]

Diabetic Retinopathy Market size was USD 6.5 billion in 2015, with the global industry anticipating 6.9% CAGR growth from 2016 to 2023.

Diabetic Retinopathy Market size to exceed $11bn by 2023

[ziplinetoursz]

Dr. Siddharth Sain - Phacoemulsification And Retina Specialist Contemporary Delhi\NCR

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The ophthalmologist has also earned himself quite a popularity among successfully enactment numerous Phaco and Micro Incision Depriving of sight surgeries.<\p>

Cataract which describes a condition whereupon the nictitating membrane of the eye gets dappled is a major key cause apropos of employment for muzzy envisaging and blindness if stick around untreated for long. At Unmusical Sight Centre we extend a variety of intraocular lens trnasplantation surgeries like multifocal, monofocal, toric, S-MICs, zero shattered mind without stint lens etc. for our patients.<\p>

Retina with respect to the other hand is located at the back as respects the organ of vision which is responsible for displaying the image. Any retinal disorders approximating swelling, tear of retina may cause irreparable damage in various cases of the eye. Diabetic retinopathy is the most dangerous retinal grievance that causes longevous blindness. Macular upheaval and retinal detachment onwards about diabetic retinopathy are some core areas gangway which deep-felt sight centre provides favorable reconstructive surgery options equipped with all the farthest out modern technology and experienced surgeons pendant Dr. Siddharth Sain.<\p>

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[britishlasik-blog]

Common Retinal Disorders In Humans

Retinal disorders have become a leading cause of blindness for many people worldwide. British LASIK Dubai is a leading eye clinic specialising in diagnosis and treatments of retinal conditions and diseases.

Retina of the eye is the thin lining on the back of the eyeball. There are variety of causes that affects the retina of the eye, which eventually leads to poor visions and blindness. Retinal disorders are any conditions that affect the retina of the eye.

Ophthalmologists Dubai provides an array of services and treatments to preserve and improve the vision. The aim of most treatments is to stop the progression of the retinal disease. Visit British LASIK Dubai for early diagnosis, which helps to preserve and reduce substantial impact on the vision.

Some of the common retinal disorders include

Age Related Macular Degeneration (AMD)

This is a common eye disease associated with aging. AMD causes a sharp deterioration of the central vision. A person diagnosed with AMD does not have problems with colour loss or eye pain. However, some of the most prevalent symptoms include visual distortion and blind spots. Dry macular degeneration and wet macular denigration are two types of this chronic eye disease that causes vision loss.

Dry Macular Degeneration A deterioration of the macula, which is in the center of the retina, refers to dry macular degeneration. This is the layer of the tissue, which is inside the back of the eyeball.  Symptoms are developed gradually thus increases the blurred vision that interferes with the day to day activities.

Wet Macular Degeneration Wet macular degeneration is caused by a leaking of blood vessels affecting the macular and results in swelling. Early detection and treatment may help to reduce the degree of vision loss. Rapid worsening of the blurriness and visual distortions are the most common symptoms. Wet macular degeneration can be caused due to abnormal growth of blood vessels or fluid build up in the back of the eye.

Retinal Detachment  This is an occurrence when a layer of the tissue in the retina pulls away from the layer of blood vessels (which provides the nutrients and oxygen). Retinal detachment deprives retinal cells without oxygen and prolonged periods of undiagnosed treatments may lead to blindness. Sudden flashes of light and appearances of floaters are the main reasons to visit an ophthalmologist. Eye surgery Dubai is a popular option among patients especially, laser treatments.

Diabetic Retinopathy This can develop on anyone who has type 1 or type 2 diabetes. Diabetic retinopathy is caused by damages to the blood vessels of the sensitive tissues in the retina. This is a complication of diabetes, which affects the eye.  There is a range of laser treatments available to patients. The treatments can stop or slow down the progression of leakage of blood/ fluid in the eye using a laser or shrink the abnormal blood vessels using a laser. Vitrectomy is another eye surgery Dubai which removes blood from the middle of the eye to treat diabetic retinopathy.

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