THE MULTIFUNCTIONAL CHOROID
By D. Nickla, Josh Wallman. Progress in retinal and eye research, 2009
1,862 citations recorded by the source corpus.
The choroid of the eye is primarily a vascular structure supplying the outer retina. It has several unusual features: It contains large membrane-lined lacunae, which, at least in birds, function as part of the lymphatic drainage of the eye and which can change their volume dramatically, thereby changing the thickness of the choroid as much as four-fold over a few days (much less in primates). It contains non-vascular smooth muscle cells, especially behind the fovea, the contraction of which may thin the choroid, thereby opposing the thickening caused by expansion of the lacunae. It has intrinsic choroidal neurons, also mostly behind the central retina, which may control these muscles and may modulate choroidal blood-flow as well. These neurons receive sympathetic, parasympathetic and nitrergic innervation. The choroid has several functions: Its vasculature is the major supply for the outer retina; impairment of the flow of oxygen from choroid to retina may cause Age-Related Macular Degeneration. The choroidal blood flow, which is as great as in any other organ, may also cool and warm the retina. In addition to its vascular functions, the choroid contains secretory cells, probably involved in modulation of vascularization and in growth of the sclera. Finally, the dramatic changes in choroidal thickness move the retina forward and back, bringing the photoreceptors into the plane of focus, a function demonstrated by the thinning of the choroid that occurs when the focal plane is moved back by the wearing of negative lenses, and, conversely, by the thickening that occurs when positive lenses are worn. In addition to focusing the eye, more slowly than accommodation and more quickly than emmetropization, we argue that the choroidal thickness changes also are correlated with changes in the growth of the sclera, and hence of the eye. Because transient increases in choroidal thickness are followed by a prolonged decrease in synthesis of extracellular matrix molecules and a slowing of ocular elongation, and attempts to decouple the choroidal and scleral changes have largely failed, it seems that the thickening of the choroid may be mechanistically linked to the scleral synthesis of macromolecules, and thus may play an important role in the homeostatic control of eye growth, and, consequently, in the etiology of myopia and hyperopia.
Subfields: Molecular Biology, Ophthalmology
View Paper: https://www.semanticscholar.org/paper/70b93a862c86cd83af553d9ddc9581b71c598aaa
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Citations in the corpus
- The complex interactions of retinal, optical and environmental factors in myopia aetiology. (2012, background): “…discovery that transient alterations in choroidal thickness, a structure previously considered solely as a vascular layer, precede changes in axial length/vitreous chamber enlargement attributable to changes in the sclera (Nickla and Wallman, 2010; Wallman et al., 1995; Wildsoet and Wallman, 1995).”
- Cellular and physiological mechanisms underlying blood flow regulation in the retina choroid in health disease (2012, neutral): “For a comprehensive review on structure and function of the choroid see Nickla and Wallman (2010).”
- Optical coherence tomography angiography (2017, background): “Blood is collected by postcapillary venules, which anastomose creating medium-sized vessels in Sattler’s layer and larger vessels in Haller’s layer (Nickla and Wallman, 2010).”