Macula
Macula | |
---|---|
Details | |
Part of | Retina of human eye |
System | Visual system |
Identifiers | |
Latin | macula lutea |
MeSH | D008266 |
TA98 | A15.2.04.021 |
TA2 | 6784 |
FMA | 58637 |
Anatomical terminology |
The macula (/ˈmakjʊlə/)
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]
The macula is responsible for the central, high-resolution, color vision that is possible in good light; and this kind of vision is impaired if the macula is damaged, for example in macular degeneration. The clinical macula is seen when viewed from the pupil, as in ophthalmoscopy or retinal photography.
The term macula lutea comes from Latin macula, "spot", and lutea, "yellow".
Structure
The macula is an oval-shaped pigmented area in the center of the retina of the human eye and other animal eyes. Its center is shifted slightly away from the optical axis (laterally, by 5°=1.5 mm).[6] The macula in humans has a diameter of around 5.5 mm (0.22 in) and is subdivided into the
An even smaller central region of highest receptor density (40–80 μm) is sometimes referred to as the foveal bouquet.[7][8][9][10] The anatomical macula at 5.5 mm (0.22 in) is much larger than the clinical macula which, at 1.5 mm (0.059 in), corresponds to the anatomical fovea.[3][4][5]The clinical macula is seen when viewed from the pupil, as in
The fovea is located near the center of the macula. It is a small pit that contains the largest concentration of cone cells. The retina's receptor layer contains two types of photosensitive cells, the rod cells and the cone cells.
Color
Because the macula is yellow in color, it absorbs excess blue and ultraviolet light that enter the eye and acts as a natural sunblock (analogous to sunglasses) for this area of the retina. The yellow color comes from its content of
After death or enucleation (removal of the eye), the macula appears yellow, a color that is not visible in the living eye except when viewed with light from which red has been filtered.[13]
Regions
- Fovea – 1.55 mm (0.061 in)
- Foveal avascular zone (FAZ) – 0.5 to 0.6 mm (0.020 to 0.024 in)
- Foveola – 0.35 mm (0.014 in)
- Umbo– 0.15 mm (0.0059 in)
Function
Structures in the macula are specialized for high-acuity vision. Within the macula are the fovea and foveola that both contain a high density of cones, which are nerve cells that are photoreceptors with high acuity.
In detail, the normal human eye contains three different types of cones, with different ranges of spectral sensitivity. The brain combines the signals from neighboring cones to distinguish different colors. There is only one type of rod, but the rods are more sensitive than the cones, so in dim light, they are the dominant photoreceptors active, and without information provided by the separate spectral sensitivity of the cones it is impossible to discriminate colors. In the fovea centralis, cones predominate and are present at high density. The macula is thus responsible for the central, high-resolution, color vision that is possible in good light; and this kind of vision is impaired if the macula is damaged, for example in macular degeneration.[14]
Clinical significance
The clinical macula is seen when viewed from the pupil, as in ophthalmoscopy or retinal photography.
Whereas loss of peripheral vision may go unnoticed for some time, damage to the macula will result in loss of central vision, which is usually immediately obvious. The progressive destruction of the macula is a disease known as macular degeneration and can sometimes lead to the creation of a macular hole. Macular holes are rarely caused by trauma, but if a severe blow is delivered it can burst the blood vessels going to the macula, destroying it.[14]
Visual input from the macula occupies a substantial portion of the brain's visual capacity. As a result, some forms of
In the case of occipitoparietal ischemia owing to occlusion of elements of either
Additional images
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Afundus photograph showing the macula as a spot to the left. The optic disc is the area on the right where blood vessels converge. The grey, more diffuse spot in the centre is a shadow artifact.
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Time-Domain OCT of the macular area of a retina at 800 nm, axial resolution 3 µm
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Spectral-Domain OCT macula cross-section scan.
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macula histology (OCT)
See also
References
- ^ "MACULA | Meaning & Definition for UK English". Lexico.com. Archived from the original on 3 August 2020. Retrieved 24 August 2022.
- ^ a b "Interpretation of Stereo Ocular Angiography : Retinal and Choroidal Anatomy". Project Orbis International. Archived from the original on 19 December 2014. Retrieved 11 October 2014.
- ^ ISBN 978-0-323-04232-1. Retrieved 7 November 2014.
- ^ ISBN 978-1-85070-584-0. Retrieved 7 November 2014.
- ^ ISBN 978-1-85317-585-5. Retrieved 7 November 2014.
- ^ le Grand, Yves (1957). Light, colour and vision. London: Chapman & Hall. p. 52.
- ^ Oesterberg, G. (1935). "Topography of the layer of rods and cones in the human retina". Acta Ophthalmologica Supplement. 6–10: 11–96.
- ^ Polyak, S. L. (1941). The Retina. Chicago: University of Chicago Press.
- PMID 2338596.
- PMID 32489576.
- ISBN 978-1-4557-2777-3. Retrieved 7 November 2014.
- PMID 25709776.
- ISBN 978-3-7643-7501-0. Retrieved 7 November 2014.
- ^ a b "Macular Degeneration". The Lecturio Medical Concept Library. 6 October 2020. Retrieved 9 August 2021.
- ^ Helseth, Erek. "Posterior Cerebral Artery Stroke". Medscape Reference. Medscape. Retrieved 23 October 2011.
- ISBN 978-0-7817-9121-2.
External links
- Media related to Macula lutea at Wikimedia Commons
- MedlinePlus Encyclopedia: 002252