choroids

The choroid is a vascular layer of the eye located between the retina and the sclera. It is the middle layer of the three layers of the eyeball. This layer is rich in blood vessels and provides nourishment to the outer layers of the retina. The choroid also contains pigment cells that absorb scattered light, which helps to improve the clarity of vision.

The choroid extends from the iris to the ciliary body. It is divided into four layers: Bruch's membrane, the choriocapillaris, the vascular layer, and the suprachoroidal layer. Bruch's membrane is the innermost layer and is a basement membrane that separates the choroid from the retina. The choriocapillaris is a network of capillaries that supplies oxygen and nutrients to the retina. The vascular layer contains larger blood vessels, and the suprachoroidal layer is the outermost layer, connecting the choroid to the sclera.

The choroid plays a crucial role in maintaining the health and function of the retina. Its rich blood supply is essential for the metabolic needs of the photoreceptor cells, which are responsible for detecting light. The pigment within the choroid also absorbs stray light, preventing internal reflections that could blur vision. Diseases affecting the choroid can lead to various vision impairments, including decreased visual acuity and field loss.