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The fovea centralis is a small, central pit composed of closely packed cones in the eye.It is located in the center of the macula lutea of the retina. [1] [2]The fovea is responsible for sharp central vision (also called foveal vision), which is necessary in humans for activities for which visual detail is of primary importance, such as reading and driving.
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. [2] The anatomical macula at a size of 5.5 mm (0.22 in) is much larger than the clinical macula which, at a size of 1.5 mm (0.059 in), corresponds to the anatomical fovea. [3] [4] [5]
At the low end of the range is the absolute threshold of vision for a steady light across a wide field of view, about 10 −6 cd/m 2 (0.000001 candela per square meter). [23] [24] The upper end of the range is given in terms of normal visual performance as 10 8 cd/m 2 (100,000,000 or one hundred million candelas per square meter). [25]
The center of the foveola is sometimes referred to as the umbo, a small (150-200μm) center of the floor of the foveola; features elongated cones. The umbo is the observed point corresponding to the normal light reflex but not solely responsible for this light reflex. The anatomy of the foveola was recently reinvestigated. [2]
In clinical usage the central part of the fovea is typically referred to simply as the fovea. [7] [8] [9] In terms of visual acuity, "foveal vision" may be defined as vision using the part of the retina in which a visual acuity of at least 20/20 (6/6 metric or 0.0 LogMAR; internationally 1.0) is attained. This corresponds to using the foveal ...
A 2007 Cochrane review found that laser photocoagulation of new blood vessels in the choroid outside of the fovea is an effective and economical method, but that the benefits are limited for vessels next to or below the fovea. [92] Photodynamic therapy has also been used to treat wet AMD. [93]
Photograph of the retina of the human eye, with overlay diagrams showing the positions and sizes of the macula, fovea, and optic disc. 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.
However the thickness of the RNFL also decreases with age and not visual acuity. [3] The sparing of this layer is important in the treatment of the disease as it is the basis for connecting retinal prostheses to the optic nerve, or implanting stem cells that could regenerate the lost photoreceptors.