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A green filter ~540–570 nm is used to block out red wavelengths of light. This allows a better contrast for viewing retinal blood vessels and associated hemorrhages, pale lesions such as drusen and exudates, and subtle characteristics such as nerve fibre layer defects and epiretinal membranes. [12]
The quality of vision expected from a retinal implant is largely based on the maximum spatial resolution of the implant. Current prototypes of retinal implants are capable of providing low resolution, pixelated images. "State-of-the-art" retinal implants incorporate 60-100 channels, sufficient for basic object discrimination and recognition tasks.
Drusen, from the German word for node or geode (singular, "Druse"), are tiny yellow or white accumulations of extracellular material that build up between Bruch's membrane and the retinal pigment epithelium of the eye. The presence of a few small ("hard") drusen is normal with advancing age, and most people over 40 have some hard drusen. [1]
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.
The macula (/ˈmakjʊlə/) [1] or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around 5.5 mm (0.22 in) and is subdivided into the umbo, foveola, foveal avascular zone, fovea, parafovea, and perifovea areas.
Perifovea is a region in the retina that circumscribes the parafovea and fovea and is a part of the macula lutea. [1] The perifovea is a belt that covers a 10° radius around the fovea and is 1.5 mm wide. [2] [3] The perifovea ends when the Henle's fiber layer disappears and the ganglion cells are one-layered. [4]
Age-Related Macular Degeneration is a degenerative maculopathy associated with progressive sight loss. It is characterised by changes in pigmentation in the Retinal Pigment Epithelium, the appearance of drusen on the retina of the eye and choroidal neovascularization. AMD has two forms; 'dry' or atrophic/non-exudative AMD, and 'wet' or ...
Bruch's membrane thickens with age, slowing the transport of metabolites. This may lead to the formation of drusen in age-related macular degeneration. [4] There is also a buildup of deposits (Basal Linear Deposits or BLinD and Basal Lamellar Deposits BLamD) on and within the membrane, primarily consisting of phospholipids.