虹膜、睫状体和脉络膜由胚胎的中胚叶发育分化,它们互相连续,富含血管,贴附在巩膜内面,对眼内的组织结构供应血液,携带必需的营养成分,利于眼的物质与液体的代谢和转运等各种生理功能。又因这些组织含有一些色素,便与神经外胚叶发育形成的视杯外层分化而来的视网膜外层的单层色素上皮,睫状体后表面的无色素与有色素的两层上皮,以及虹膜后表面两层均有色素的上皮,共同将眼内围成一个暗房,使眼球接受从瞳孔进入眼内的外环境光线,在视网膜上构成视觉系统清晰感知的影像。因此,虹膜、睫状体和脉络膜一起,对视觉系统的眼内终端组织行使营养生化与物理蔽光等视觉生理活动的重要辅助功能。这一参与构成眼球壁三层组织中介于外层巩膜与内层视网膜之间的中层组织 The iris, ciliary body and choroid develop and differentiate from the mesoderm of the embryo, which are continuous and vascular, attached to the inner sclera, supplying blood to the tissue within the eye, carrying the necessary nutrients, substances beneficial to the eye, Liquid metabolism and transport and other physiological functions. And because these organizations contain some pigment, it will form with the development of neuroectodermal outer layer of the outer layer of the retina differentiated monolayer pigment epithelium, the posterior surface of the ciliary body pigmented and pigmented two epithelial, And the iris posterior surface of the two layers of pigmented epithelium together to form a dark room around the eye, so that the eye to accept the pupil into the eye outside the ambient light, the retina to form a clear visual system vision image. Therefore, the iris, ciliary body, and choroid work together with important auxiliary functions of visual physiology such as nutrition biochemistry and physical ophthalmology for the intraocular terminal tissues of the visual system. This involvement constitutes the middle of the three layers of the eyeball tissue between the outer sclera and the inner retina