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Ocular OCT retinal thickness map, right eye Time-domain OCT of the macular area of a retina at 800 nm, axial resolution 3 μm Spectral-domain OCT macula cross-section scan. Optical coherence tomography (OCT) is a technique for obtaining sub-surface images of translucent or opaque materials at a resolution equivalent to a low-power microscope.
Occult macular dystrophy (OMD) is a rare inherited degradation of the retina, characterized by progressive loss of function in the most sensitive part of the central retina , the location of the highest concentration of light-sensitive cells (photoreceptors) but presenting no visible abnormality.
Scanning laser ophthalmoscopy developed as a method to view a distinct layer of the living eye at the microscopic level. The use of confocal methods to diminish extra light by focusing detected light through a small pinhole made possible the imaging of individual layers of the retina with greater distinction than ever before. [4]
The Heidelberg Retinal Tomography is a diagnostic procedure used in ophthalmology. The Heidelberg Retina Tomograph (HRT) is an ophthalmological confocal point scanning laser ophthalmoscope [ 1 ] for examining the cornea and certain areas of the retina using different diagnostic modules (HRT retina, HRT cornea, HRT glaucoma).
A short scan time prevents too much patient movement during signal acquisition. With the development of Fourier-domain OCT, spectral-domain OCT, and swept source signal acquisition time was greatly improved making OCTA possible. [40] OCTA scan time is now around three seconds, however, saccadic eye movement still causes a low signal-to-noise ratio.
This is a noninvasive procedure where patients rest their chin and focus on a green light within the machine. [11] Eye dryness and fatigue are the limited risks associated with this scan. [11] Other diseases that can be diagnosed using OCT are glaucoma, macular degeneration, and diabetes-related retinopathy. [11]
OCT can be used to capture functional images of blood flow, a technique known as optical coherence tomography angiography (OCT-A). SV-OCT is one method for OCT-A that uses the variance of consecutively acquired images to detect flow at the micron scale. SV-OCT can be used to measure the microvasculature of tissue.
Colour, where the retina is illuminated by white light and examined in full colour. Red free fundus photography utilizes a filter in order to better observe superficial lesions and some vascular abnormalities within the retina and surrounding tissue. A green filter ~540–570 nm is used to block out red wavelengths of light.